tree

For other uses, see Tree (disambiguation).

Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree

European larch (Larix decidua), a coniferous tree which is also deciduous

Lepidodendron, an extinct lycophyte tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. In looser senses, the taller palms, the tree ferns, bananas and bamboos are also trees. Trees tend to be long-lived, some reaching several thousand years old. The tallest known tree, a coast redwood named Hyperion, stands 115.6 m (379 ft) high. Trees have been in existence for 370 million years. It is estimated that there are just over 3 trillion mature trees in the world.^[1]

A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development. Flowers and fruit may also be present, but some trees, such as conifers, instead have pollen cones and seed cones; others, such as tree ferns, produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are one of the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.

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Definition

Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots.

Although "tree" is a term of common parlance, there is no universally recognised precise definition of what a tree is, either botanically or in common language.^[2] In its broadest sense, a tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground.^[3] Trees are also typically defined by height,^[4] with smaller plants from 0.5 to 10 m (1.6 to 32.8 ft) being called shrubs,^[5] so the minimum height of a tree is only loosely defined.^[4] Large herbaceous plants such as papaya and bananas are trees in this broad sense.^[2]^[6]

A commonly applied narrower definition is that a tree has a woody trunk formed by secondary growth, meaning that the trunk thickens each year by growing outwards, in addition to the primary upwards growth from the growing tip.^[4]^[7] Under such a definition, herbaceous plants such as palms, bananas and papayas are not considered trees regardless of their height, growth form or stem girth. Certain monocots may be considered trees under a slightly looser definition;^[8] while the Joshua tree, bamboos and palms do not have secondary growth and never produce true wood with growth rings,^[9]^[10] they may produce "pseudo-wood" by lignifying cells formed by primary growth.^[11]

Aside from structural definitions, trees are commonly defined by use, for instance as those plants which yield lumber.^[12]

Overview

The tree growth habit is an evolutionary adaptation found in different groups of plants: by growing taller, trees are able to compete better for sunlight.^[13] Trees tend to be long-lived,^[14] some reaching several thousand years old, as well as tall.^[15] Trees have modified structures such as thicker stems composed of specialised cells that add structural strength and durability, allowing them to grow taller than non-woody plants and to spread out their foliage. They differ from shrubs, which are also woody plants, by usually growing larger and having a single main stem;^[5] but the distinction between a small tree and a large shrub is not always clear,^[16] made more confusing by the fact that trees may be reduced in size under harsher environmental conditions such as on mountains and subarctic areas. The tree form has evolved separately in unrelated classes of plants in response to similar environmental challenges, making it a classic example of parallel evolution. With an estimated 100,000 species, the number of trees worldwide might total twenty-five per cent of all living plant species.^[17] The greatest number of these grow in tropical regions and many of these areas have not yet been fully surveyed by botanists, making tree diversity and ranges poorly known.^[18]

Tall herbaceous monocotyledonous plants such as banana lack secondary growth, and are trees only in a loose sense.

Trees exist in two different groups of vascular or higher plants, the gymnosperms and the angiosperms. The gymnosperm trees include conifers, cycads, ginkgophytes and gnetales; they produce seeds which are not enclosed in fruits, but in open structures such as pine cones, and many have tough waxy leaves, such as pine needles.^[19] Most angiosperm trees are eudicots, the "true dicotyledons", so named because the seeds contain two cotyledons or seed leaves. There are also some trees among the old lineages of flowering plants called basal angiosperms or paleodicots; these include Amborella, Magnolia, nutmeg and avocado,^[20] while trees such as bamboo, palms and bananas are monocots.

Wood gives structural strength to the trunk of a tree; this supports the plant as it grows larger. The vascular system of trees allows water, nutrients and other chemicals to be distributed around the plant, and without it trees would not be able to grow as large as they do. Trees, as relatively tall plants, need to draw water up the stem through the xylem from the roots by the suction produced as water evaporates from the leaves. If insufficient water is available the leaves will die.^[21] The three main parts of trees include the root, stem, and leaves; they are integral parts of the vascular system which interconnects all the living cells. In trees and other plants that develop wood, the vascular cambium allows the expansion of vascular tissue that produces woody growth. Because this growth ruptures the epidermis of the stem, woody plants also have a cork cambium that develops among the phloem. The cork cambium gives rise to thickened cork cells to protect the surface of the plant and reduce water loss. Both the production of wood and the production of cork are forms of secondary growth.^[22]

Trees are either evergreen, having foliage that persists and remains green throughout the year,^[23] or deciduous, shedding their leaves at the end of the growing season and then having a dormant period without foliage.^[24] Most conifers are evergreens but larches (Larix and Pseudolarix) are deciduous, dropping their needles each autumn, and some species of cypress (Glyptostrobus, Metasequoia and Taxodium) shed small leafy shoots annually in a process known as cladoptosis.^[5] The crown is a name for the spreading top of a tree including the branches and leaves,^[25] while the uppermost layer in a forest, formed by the crowns of the trees, is known as the canopy.^[26]A sapling is a young tree.^[27]

Many tall palms are herbaceous^[28] monocots; these do not undergo secondary growth and never produce wood.^[9]^[10] In many tall palms, the terminal bud on the main stem is the only one to develop, so they have unbranched trunks with large spirally arranged leaves. Some of the tree ferns, order Cyatheales, have tall straight trunks, growing up to 20 metres (66 ft), but these are composed not of wood but of rhizomes which grow vertically and are covered by numerous adventitious roots.^[29]

Distribution

Further information: Forest

The number of trees in the world, according to a 2015 estimate, is 3.04 trillion, of which 1.39 trillion (46%) are in the tropics or sub-tropics, 0.61 trillion (20%) in the temperate zones, and 0.74 trillion (24%) in the coniferous boreal forests. The estimate is about eight times higher than previous estimates, and is based on tree densities measured on over 400,000 plots. It remains subject to a wide margin of error, not least because the samples are mainly from Europe and North America. The estimate suggests that about 15 billion trees are cut down annually and about 5 billion are planted. In the 12,000 years since the start of human agriculture, the number of trees worldwide has decreased by 46%.^[1]^[30]^[31]^[32]

The Daintree rainforest

In suitable environments, such as the Daintree Rainforest in Queensland, or the mixed podocarp and broadleaf forest of Ulva Island, New Zealand, forest is the more-or-less stable climatic climax community at the end of a plant succession, where open areas such as grassland are colonised by taller plants, which in turn give way to trees that eventually form a forest canopy.^[33]^[34]

In cool temperate regions, conifers often predominate; a widely distributed climax community in the far north of the northern hemisphere is moist taiga or northern coniferous forest (also called boreal forest).^[35]^[36] Taiga is the world's largest land biome, forming 29% of the world's forest cover.^[37] The long cold winter of the far north is unsuitable for plant growth and trees must grow rapidly in the short summer season when the temperature rises and the days are long. Light is very limited under their dense cover and there may be little plant life on the forest floor, although fungi may abound.^[38] Similar woodland is found on mountains where the altitude causes the average temperature to be lower thus reducing the length of the growing season.^[39]

Where rainfall is relatively evenly spread across the seasons in temperate regions, temperate broadleaf and mixed forest typified by species like oak, beech, birch and maple is found.^[40] Temperate forest is also found in the southern hemisphere, as for example in the Eastern Australia temperate forest, characterised by Eucalyptus forest and open acacia woodland.^[41]

In tropical regions with a monsoon or monsoon-like climate, where a drier part of the year alternates with a wet period as in the Amazon rainforest, different species of broad-leaved trees dominate the forest, some of them being deciduous.^[42] In tropical regions with a drier savanna climate and insufficient rainfall to support dense forests, the canopy is not closed, and plenty of sunshine reaches the ground which is covered with grass and scrub. Acacia and baobab are well adapted to living in such areas.^[43]

Parts and function

A young red pine (Pinus resinosa) with spread of roots visible, as a result of soil erosion

Roots

Main article: Root

The roots of a tree serve to anchor it to the ground and gather water and nutrients to transfer to all parts of the tree. They are also used for reproduction, defence, survival, energy storage and many other purposes. The radicle or embryonic root is the first part of a seedling to emerge from the seed during the process of germination. This develops into a taproot which goes straight downwards. Within a few weeks lateral roots branch out of the side of this and grow horizontally through the upper layers of the soil. In most trees, the taproot eventually withers away and the wide-spreading laterals remain. Near the tip of the finer roots are single cell root hairs. These are in immediate contact with the soil particles and can absorb water and nutrients such as potassium in solution. The roots require oxygen to respire and only a few species such as the mangrove and the pond cypress (Taxodium ascendens) can live in permanently waterlogged soil.^[44]

In the soil, the roots encounter the hyphae of fungi. Many of these are known as mycorrhiza and form a mutualistic relationship with the tree roots. Some are specific to a single tree species, which will not flourish in the absence of its mycorrhizal associate. Others are generalists and associate with many species. The tree acquires minerals such as phosphorus from the fungus while it obtains the carbohydrate products of photosynthesis from the tree.^[45] The hyphae of the fungus can link different trees and a network is formed, transferring nutrients from one place to another. The fungus promotes growth of the roots and helps protect the trees against predators and pathogens. It can also limit damage done to a tree by pollution as the fungus accumulate heavy metals within its tissues.^[46]Fossil evidence shows that roots have been associated with mycorrhizal fungi since the early Paleozoic, four hundred million years ago, when the first vascular plants colonised dry land.^[47]

Some trees such as the alders (Alnus species) have a symbiotic relationship with Frankia species, a filamentous bacterium that can fix nitrogen from the air, converting it into ammonia. They have actinorhizal root nodules on their roots in which the bacteria live. This process enables the tree to live in low nitrogen habitats where they would otherwise be unable to thrive.^[48] The plant hormones called cytokinins initiate root nodule formation, in a process closely related to mycorrhizal association.^[49]

Buttress roots of the kapok tree (Ceiba pentandra)

It has been demonstrated that some trees are interconnected through their root system, forming a colony. The interconnections are made by the inosculation process, a kind of natural grafting or welding of vegetal tissues. The tests to demonstrate this networking are performed by injecting chemicals, sometimes radioactive, into a tree, and then checking for its presence in neighbouring trees.^[50]

The roots are, generally, an underground part of the tree, but some tree species have evolved roots that are aerial. The common purposes for aerial roots may be of two kinds, to contribute to the mechanical stability of the tree, and to obtain oxygen from air. An instance of mechanical stability enhancement is the red mangrove that develops prop roots that loop out of the trunk and branches and descend vertically into the mud.^[51] A similar structure is developed by the Indian banyan.^[52] Many large trees have buttress roots which flare out from the lower part of the trunk. These brace the tree rather like angle brackets and provide stability, reducing sway in high winds. They are particularly prevalent in tropical rainforests where the soil is poor and the roots are close to the surface.^[53]

Some tree species have developed root extensions that pop out of soil, in order to get oxygen, when it is not available in the soil because of excess water. These root extensions are called pneumatophores, and are present, among others, in black mangrove and pond cypress.^[51]

Trunk

Northern beech (Fagus sylvatica) trunk in autumn

Main article: Trunk (botany)

The main purpose of the trunk is to raise the leaves above the ground, enabling the tree to reach the light and survive: the tree can overtop other plants and shade them out. It also performs the task of transporting water and nutrients from the roots to the aerial parts of the tree and to distribute the food produced by the leaves to all other parts including the roots.^[54]

In the case of angiosperms and gymnosperms, the outermost layer of the trunk is the bark and is mostly composed of dead cells. It provides a thick, waterproof covering to the living inner tissue. It protects the trunk against the elements, disease, animal attack and fire. It is perforated by a large number of fine breathing pores called lenticels, through which oxygen diffuses. Bark is continually replaced by a living layer of cells called the cork cambium. The London plane (Platanus × acerifolia) periodically sheds its bark in large flakes. Similarly, the bark of the silver birch (Betula pendula) peels off in strips. As the tree's girth expands, newer layers of bark are larger in circumference, and the older layers develop fissures in many species. In some trees such as the pine (Pinus species) the bark exudes sticky resin which deters attackers whereas in rubber trees (Hevea brasiliensis) it is a milky latex that oozes out. The quinine bark tree (Cinchona officinalis) contains bitter substances to make the bark unpalatable.^[54] Large tree-like plants with lignified trunks in the Pteridophyta, Arecales, Cycadophyta and Poales such as the tree ferns, palms, cycads and bamboos have no true bark, but they do have an outer protective covering of some form.^[55]

A section of yew (Taxus baccata) showing 27 annual growth rings, pale sapwood and dark heartwood

Although the bark functions as a protective barrier, it is itself attacked by boring insects such as beetles. These lay their eggs in crevices and the larvae chew their way through the cellulose tissues leaving a gallery of tunnels. This may allow fungal spores to gain admittance and attack the tree. Dutch elm disease is caused by a fungus (Ophiostoma species) carried from one elm tree to another by various beetles. The tree reacts to the growth of the fungus by blocking off the xylem tissue carrying sap upwards and the branch above, and eventually the whole tree, is deprived of nourishment and dies. In Britain in the 1990s, 25 million elm trees were killed by this disease.^[56]

The innermost layer of bark is known as the phloem and this is involved in the transport of the sap containing the sugars made by photosynthesis to other parts of the tree. It is a soft spongy layer of living cells, some of which are arranged end to end to form tubes. These are supported by parenchyma cells which provide padding and include fibres for strengthening the tissue.^[57] Inside the phloem is a layer of undifferentiated cells one cell thick called the vascular cambium layer. The cells are continually dividing, creating phloem cells on the outside and wood cells known as xylem on the inside.^[58]

The newly created xylem is the sapwood. It is composed of water-conducting cells and associated cells which are often living, and is usually pale in colour. It transports water and minerals from the roots to the upper parts of the tree. The oldest, inner part of the sapwood is progressively converted into heartwood as new sapwood is formed at the cambium. The conductive cells of the heartwood are blocked in some species, and the surrounding cells are more often dead. Heartwood is usually darker in colour than the sapwood. It is the dense central core of the trunk giving it rigidity. Three quarters of the dry mass of the xylem is cellulose, a polysaccharide, and most of the remainder is lignin, a complex polymer. A transverse section through a tree trunk or a horizontal core will show concentric circles or lighter or darker wood - tree rings. These rings are the annual growth rings^[59] There may also be rays running at right angles to growth rings. These are vascular rays which are thin sheets of living tissue permeating the wood.^[60] Many older trees may become hollow but may still stand upright for many years.^[61]

Buds and growth

Dormant magnolia (Magnolia sp.) bud

Main article: Bud

Trees do not usually grow continuously throughout the year but mostly have spurts of active expansion followed by periods of rest. This pattern of growth is related to climatic conditions; growth normally ceases when conditions are either too cold or too dry. In readiness for the inactive period, trees form buds to protect the meristem, the zone of active growth. Before the period of dormancy, the last few leaves produced at the tip of a twig form scales. These are thick, small and closely wrapped and enclose the growing point in a waterproof sheath. Inside this bud there is a rudimentary stalk and neatly folded miniature leaves, ready to expand when the next growing season arrives. Buds also form in the axils of the leaves ready to produce new side shoots. A few trees, such as the eucalyptus, have "naked buds" with no protective scales and some conifers, such as the Lawson's cypress, have no buds but instead have little pockets of meristem concealed among the scale-like leaves.^[62]

When growing conditions improve, such as the arrival of warmer weather and the longer days associated with spring in temperate regions, growth starts again. The expanding shoot pushes its way out, shedding the scales in the process. These leave behind scars on the surface of the twig. The whole year's growth may take place in just a few weeks. The new stem is unlignified at first and may be green and downy. The Arecaceae (palms) have their leaves spirally arranged on an unbranched trunk.^[62] In some tree species in temperate climates, a second spurt of growth, a Lammas growth may occur which is believed to be a strategy to compensate for loss of early foliage to insect predators.^[63]

Primary growth is the elongation of the stems and roots. Secondary growth consists of a progressive thickening and strengthening of the tissues as the outer layer of the epidermis is converted into bark and the cambium layer creates new phloem and xylem cells. The bark is inelastic.^[64] Eventually the growth of a tree slows down and stops and it gets no taller. If damage occurs the tree may in time become hollow.^[65]

Leaves

Buds, leaves, flowers and fruit of oak (Quercus robur)

Buds, leaves and reproductive structures of white fir (Abies alba)

Main article: Leaf

Leaves are structures specialised for photosynthesis and are arranged on the tree in such a way as to maximise their exposure to light without shading each other. They are an important investment by the tree and may be thorny or contain phytoliths, lignins, tannins or poisons to discourage herbivory. Trees have evolved leaves in a wide range of shapes and sizes, in response to environmental pressures including climate and predation. They can be broad or needle-like, simple or compound, lobed or entire, smooth or hairy, delicate or tough, deciduous or evergreen. The needles of coniferous trees are compact but are structurally similar to those of broad-leaved trees. They are adapted for life in environments where resources are low or water is scarce. Frozen ground may limit water availability and conifers are often found in colder places at higher altitudes and higher latitudes than broad leaved trees. In conifers such as fir trees, the branches hang down at an angle to the trunk, enabling them to shed snow. In contrast, broad leaved trees in temperate regions deal with winter weather by shedding their leaves. When the days get shorter and the temperature begins to decrease, the leaves no longer make new chlorophyll and the red and yellow pigments already present in the blades become apparent.^[66] Synthesis in the leaf of a plant hormone called auxin also ceases. This causes the cells at the junction of the petiole and the twig to weaken until the joint breaks and the leaf floats to the ground. In tropical and subtropical regions, many trees keep their leaves all year round. Individual leaves may fall intermittently and be replaced by new growth but most leaves remain intact for some time. Other tropical species and those in arid regions may shed all their leaves annually, such as at the start of the dry season.^[67] Many deciduous trees flower before the new leaves emerge.^[68] A few trees do not have true leaves but instead have structures with similar external appearance such as Phylloclades – modified stem structures^[69] – as seen in the genus Phyllocladus.^[70]

Reproduction

Form, leaves and reproductive structures of queen sago Cycas circinalis

Main article: Plant reproduction

Tree forms are found in a wide range of plants and their reproductive strategies are substantially the same as shrub or herbaceous plant forms. Many trees are wind pollinated which may be an evolutionary adaptation to take advantage of increased wind speeds high above the ground, particularly in the case of those that produce pollen before the leaves emerge.^[71] A vast quantity of pollen is produced because of the low likelihood of any particular grain landing on an appropriate female flower. Wind-pollinated flowers of broad-leaved trees are characterised by a lack of showy parts, no scent and a copious production of pollen, often with separate male and female flowers, or separate male and female trees. The male flowers may be high up in the tree, often in the form of dangling catkins. The female flowers may be lower down the tree. The pollen of pine trees contains air sacs which give it buoyancy and it has been known to travel as far as 800 kilometres (500 mi).^[72] Tree pollen can cause allergies and hay fever.^[73]

Seeds

Main article: Seed

Seeds are the primary way that trees reproduce and their seeds vary greatly in size and shape. Some of the largest seeds come from trees, but the largest tree, Sequoiadendron giganteum, produces one of the smallest tree seeds.^[74] The great diversity in tree fruits and seeds reflects the many different ways that tree species have evolved to disperse their offspring.

The single extant species of Ginkgophyta (Ginkgo biloba) has fleshy seeds produced at the ends of short branches on female trees,^[75] and Gnetum, a tropical and subtropical group of gymnosperms produce seeds at the tip of a shoot axis.^[76] The seeds of conifers, the largest group of gymnosperms, are enclosed in a cone and most species have seeds that are light and papery that can be blown considerable distances once free from the cone.^[77] Sometimes the seed remains in the cone for years waiting for a trigger event to liberate it. Fire stimulates release and germination of seeds of the jack pine, and also enriches the forest floor with wood ash and removes competing vegetation.^[78] Similarly, a number of angiosperms including Acacia cyclops and Acacia mangium have seeds that germinate better after exposure to high temperatures.^[79]

Wind dispersed seed of elm (Ulmus), ash (Fraxinus) and sycamore (Acer pseudoplatanus)

For a tree seedling to grow into an adult tree it needs light and space. If seeds only fell straight to the ground, competition among the concentrated saplings and the shade of the parent would likely prevent it from flourishing. Many seeds such as birch are small and have papery wings to aid dispersal by the wind. Ash trees and maples have larger seeds with blade shaped wings which spiral down to the ground when released. The kapok tree has cottony threads to catch the breeze.^[80] The flame tree does not rely on fire but shoots its seeds through the air when the two sides of its long pods crack apart explosively on drying.^[80] The miniature cone-like catkins of Alder trees produce seeds that contain small droplets of oil that help disperse the seeds on the surface of water. Mangroves often grow in water and some species have propagules, which are buoyant fruits with seeds that start germinating before becoming detached from the parent tree.^[81]^[82] These float on the water and may become lodged on emerging mudbanks and successfully take root.^[80] Other seeds, such as apple pips and plum stones, have fleshy receptacles and smaller fruits like hawthorns have seeds enclosed in edible tissue; animals including mammals and birds eat the fruits and either discard the seeds, or swallow them so they pass through the gut to be deposited in the animal's droppings well away from the parent tree. The germination of some seeds is improved when they are processed in this way.^[83] Nuts may be gathered by animals such as squirrels that cache any not immediately consumed.^[84] Many of these caches are never revisited, the nut-casing softens with rain and frost, and the seed germinates in the spring.^[85] Pine cones may similarly be hoarded by red squirrels, and grizzly bears may help to disperse the seed by raiding squirrel caches.^[86]

Evolutionary history

Palms and cycads as they might have appeared in the middle Tertiary

Further information: Evolutionary history of plants

The earliest tree-like organisms were tree ferns, horsetails and lycophytes, which grew in forests in the Carboniferous period. The first tree may have been Wattieza, fossils of which have been found in New York State in 2007 dating back to the Middle Devonian (about 385 million years ago). Prior to this discovery, Archaeopteris was the earliest known tree.^[87] Both of these reproduced by spores rather than seeds and are considered to be links between ferns and the gymnosperms which evolved in the Triassic period. The gymnosperms include conifers, cycads, gnetales and ginkgos and these may have appeared as a result of a whole genome duplication event which took place about 319 million years ago.^[88] Ginkgophyta was once a widespread diverse group ^[89] of which the only survivor is the maidenhair tree Ginkgo biloba. This is considered to be a living fossil because it is virtually unchanged from the fossilised specimens found in Triassic deposits.^[90]

During the Mesozoic (245 to 66 million years ago) the conifers flourished and became adapted to live in all the major terrestrial habitats. Subsequently, the tree forms of flowering plants evolved during the Cretaceous period. These began to dominate the conifers during the Tertiary era (66 to 2 million years ago) when forests covered the globe. When the climate cooled 1.5 million years ago and the first of four ice ages occurred, the forests retreated as the ice advanced. In the interglacials, trees recolonised the land that had been covered by ice, only to be driven back again in the next ice age.^[91]

Tree ecology

Further information: Forest

Trees are an important part of the terrestrial ecosystem,^[92] providing essential habitats including many kinds of forest for communities of organisms. Epiphytic plants such as ferns, some mosses, liverworts, orchids and some species of parasitic plants (e.g., mistletoe) hang from branches; these along with arboreal lichens, algae, and fungi provide micro-habitats for themselves and for other organisms, including animals. Leaves, flowers and fruits are seasonally available. On the ground underneath trees there is shade, and often there is undergrowth, leaf litter, fallen branches and/or decaying wood that provide other habitat. Trees stabilise the soil, prevent rapid run-off of rain water, help prevent desertification, have a role in climate control and help in the maintenance of biodiversity and ecosystem balance.^[93]

Many species of tree support their own specialised invertebrates. In their natural habitats, 284 different species of insect have been found on the English oak (Quercus robur) ^[94]and 306 species of invertebrate on the Tasmanian oak (Eucalyptus obliqua).^[95] Non-native tree species provide a less biodiverse community, for example in the United Kingdom the sycamore (Acer pseudoplatanus), which originates from southern Europe, has few associated invertebrate species, though its bark supports a wide range of lichens, bryophytes and other epiphytes.^[96]

In ecosystems such as mangrove swamps, trees play a role in developing the habitat, since the roots of the mangrove trees reduce the speed of flow of tidal currents and trap water-borne sediment, reducing the water depth and creating suitable conditions for further mangrove colonisation. Thus mangrove swamps tend to extend seawards in suitable locations.^[97] Mangrove swamps also provide an effective buffer against the more damaging effects of cyclones and tsunamis.^[98]

Uses

Silviculture is the practice of controlling the establishment, growth, composition, health, and quality of forests, which are areas that have a high density of trees. Cultivated trees are planted and tended by humans, usually because they provide food (fruits or nuts), ornamental beauty, or some type of wood product that benefits people. A small wooded area, usually with no undergrowth, is called a grove ^[99] and a small wood or thicket of trees and bushes is called a coppice or copse.^[100] A large area of land covered with trees and undergrowth is called woodland or forest.^[101] An area of woodland composed primarily of trees established by planting or artificial seeding is known as a plantation ^[102] and an area of land planted with fruit or nut trees is an orchard.^[103]

Food

Forest honey

Further information: nut (fruit) and fruit

Trees are the source of many of the world's best known fleshy fruits. Apples, pears, plums, cherries and citrus are all grown commercially in temperate climates and a wide range of edible fruits are found in the tropics. Other commercially important fruit include dates, figs and olives. Palm oil is obtained from the fruits of the oil palm (Elaeis guineensis). The fruits of the cocoa tree (Theobroma cacao) are used to make cocoa and chocolate and the berries of coffee trees, Coffea arabica and Coffea canephora, are processed to extract the coffee beans. In many rural areas of the world, fruit is gathered from forest trees for consumption.^[104] Many trees bear edible nuts which can loosely be described as being large, oily kernels found inside a hard shell. These include coconuts (Cocos nucifera), Brazil nuts (Bertholletia excelsa), pecans (Carya illinoinensis), hazel nuts (Corylus), almonds (Prunus dulcis), walnuts (Juglans regia), pistachios (Pistacia vera) and many others. They are high in nutritive value and contain high-quality protein, vitamins and minerals as well as dietary fibre. Walnuts are particularly beneficial to health and contain a higher level of antioxidants than do other nuts.^[105] A variety of nut oils are extracted by pressing for culinary use; some such as walnut, pistachio and hazelnut oils are prized for their distinctive flavours, but they tend to spoil quickly.^[106]

Many trees have flowers rich in nectar which are attractive to bees. The production of forest honey is an important industry in rural areas of the developing world where it is undertaken by small-scale beekeepers using traditional methods.^[107] The flowers of the elder (Sambucus) are used to make elderflower cordial and petals of the plum (Prunus spp.) can be candied.^[108]

The leaves of trees are widely gathered as fodder for livestock and some can be eaten by humans but they tend to be high in tannins which makes them bitter. Leaves of the curry tree (Murraya koenigii) are eaten, those of kaffir lime Citrus × hystrix (e.g., Thai food)^[109] Ailanthus (e.g., in Korean dishes such as bugak) and those of the European bay tree (Laurus nobilis) and the California bay tree (Umbellularia californica) are used for flavouring food.^[110] Camellia sinensis, the source of tea, is a small tree but seldom reaches its full height, being heavily pruned to make picking the leaves easier.^[111]

Sugar maple (Acer saccharum) being tapped for the production of maple syrup

In temperate climates there is a sudden movement of sap at the end of the winter as trees prepare to burst into growth. In North America, the sap of the sugar maple (Acer saccharum) is most often used in the production of a sweet liquid, maple syrup. About 90% of the sap is water, the remaining 10% being a mixture of various sugars and certain minerals.^[112] The sap is harvested by drilling holes in the trunks of the trees and collecting the liquid that flows out of the inserted spigots. It is piped to a sugarhouse where it is heated to concentrate it and improve its flavour. One litre of maple syrup is obtained from every forty litres of sap and has a sugar content of exactly 66%.^[112] Similarly in northern Europe the spring rise in the sap of the silver birch (Betula pendula) is tapped and collected, either to be drunk fresh or fermented into an alcoholic drink. In Alaska, the sap of the sweet birch (Betula lenta) is made into a syrup with a sugar content of 67%. Sweet birch sap is more dilute than maple sap; a hundred litres are required to make one litre of birch syrup.^[113]

Various parts of trees are used as spices. These include cinnamon, made from the bark of the cinnamon tree (Cinnamomum zeylanicum) and allspice, the dried small fruits of the pimento tree (Pimenta dioica). Nutmeg is a seed found in the fleshy fruit of the nutmeg tree (Myristica fragrans) and cloves are the unopened flower buds of the clove tree (Syzygium aromaticum). Sassafras oil is an important flavouring obtained from distilling bark from the roots of the white sassafras tree (Sassafras albidum).^[110]

Fuel

Main article: Wood fuel

Selling firewood at a market

Wood has traditionally been used for fuel, especially in rural areas. In less developed nations it may be the only fuel available and collecting firewood is often a time consuming task as it becomes necessary to travel further and further afield in the search for fuel.^[114] It is often burned inefficiently on an open fire. In more developed countries other fuels are available and burning wood is a choice rather than a necessity. Modern wood-burning stoves are very fuel efficient and new products such as wood pellets are available to burn.^[115]

Charcoal can be made by slow pyrolysis of wood by heating it in the absence of air in a kiln. The carefully stacked branches, often oak, are burned with a very limited amount of air. The process of converting them into charcoal takes about fifteen hours. Charcoal is used as a fuel in barbecues and by blacksmiths and has many industrial and other uses.^[116]

Wood smoke can be used to preserve food. In the hot smoking process the food is exposed to smoke and heat in a controlled environment. The food is ready to eat when the process is complete, having been tenderised and flavoured by the smoke it has absorbed. In the cold process, the temperature is not allowed to rise above 100 °F (38 °C). The flavour of the food is enhanced but raw food requires further cooking. If it is to be preserved, meat should be cured before cold smoking.^[117]

Timber

Main articles: Wood and Timber

Joinery and roof trusses made from softwood

Timber, "trees that are grown in order to produce wood"^[118] is cut into lumber (sawn wood) for use in construction. Wood has been an important, easily available material for construction since humans started building shelters. Engineered wood products are available which bind the particles, fibres or veneers of wood together with adhesives to form composite materials. Plastics have taken over from wood for some traditional uses.^[119]

Wood is used in the construction of buildings, bridges, trackways, piles, poles for power lines, masts for boats, pit props, railway sleepers, fencing, hurdles, shuttering for concrete, pipes, scaffolding and pallets. In housebuilding it is used in joinery, for making joists, roof trusses, roofing shingles, thatching, staircases, doors, window frames, floor boards, parquet flooring, panelling and cladding.^[120]

Wood is used to construct carts, farm implements, boats, dugout canoes and in shipbuilding. It is used for making furniture, tool handles, boxes, ladders, musical instruments, bows, weapons, matches, clothes pegs, brooms, shoes, baskets, turnery, carving, toys, pencils, rollers, cogs, wooden screws, barrels, coffins, skittles, veneers, artificial limbs, oars, skis, wooden spoons, sports equipment and wooden balls.^[120]

Wood is pulped for paper and used in the manufacture of cardboard and made into engineered wood products for use in construction such as fibreboard, hardboard, chipboard and plywood.^[120] The wood of conifers is known as softwood while that of broad-leaved trees is hardwood.^[121]

Art

Informal upright style of bonsai on a juniper tree

Besides inspiring artists down the centuries, trees have been used to create art. Living trees have been used in bonsai and in tree shaping, and both living and dead specimens have been sculpted into sometimes fantastic shapes.^[122]

Bonsai

Main article: Bonsai

Bonsai (盆栽^?, lit. The art of growing a miniature tree or trees in a low-sided pot or tray) is the practice of hòn non bộ originated in China and spread to Japan more than a thousand years ago, there are similar practices in other cultures like the living miniature landscapes of Vietnam hòn non bộ. The word bonsai is often used in English as an umbrella term for all miniature trees in containers or pots.^[123]

The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower).^[124] Bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container, beginning with a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species^[125] that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai and a miniature deciduous forest can even be created using such species as Japanese maple, Japanese zelkova or hornbeam.^[126]

Tree shaping

Main article: Tree shaping

People trees, by Pooktre

Tree shaping is the practice of changing living trees and other woody plants into man made shapes for art and useful structures. There are a few different methods ^[127] of shaping a tree. There is a gradual method and there is an instant method, the gradual method slowly guides the growing tip along predetermined path ways over time where as the instant method bends and weaves saplings 2 to 3 m (6.6 to 9.8 ft) long into a shape that becomes more rigid as they thicken up.^[128] Most artists use grafting of living trunks, branches, and roots, for art or functional structures and there are plans to grow "living houses" with the branches of trees knitting together to give a solid, weatherproof exterior combined with an interior application of straw and clay to provide a stucco-like inner surface.^[128]

Tree shaping has been practised for at least several hundred years, the oldest known examples being the living root bridges built and maintained by the Khasi people of Meghalaya, India using the roots of the rubber tree (Ficus elastica).^[129]^[130]

Bark

Recently stripped cork oak (Quercus suber)

Cork is produced from the thick bark of the cork oak (Quercus suber). It is harvested from the living trees about once every ten years in an environmentally sustainable industry.^[131] More than half the world's cork comes from Portugal and is largely used to make stoppers for wine bottles.^[132] Other uses include floor tiles, bulletin boards, balls, footwear, cigarette tips, packaging, insulation and joints in woodwind instruments.^[132]

The bark of other varieties of oak has traditionally been used in Europe for the tanning of hides though bark from other species of tree has been used elsewhere. The active ingredient, tannin, is extracted and after various preliminary treatments, the skins are immersed in a series of vats containing solutions in increasing concentrations. The tannin causes the hide to become supple, less affected by water and more resistant to bacterial attack.^[133]

At least 120 drugs come from plant sources, many of them from the bark of trees.^[134] Quinine originates from the cinchona tree (Cinchona) and was for a long time the remedy of choice for the treatment of malaria.^[135] Aspirin was synthesised to replace the sodium salicylate derived from the bark of willow trees (Salix) which had unpleasant side effects.^[136] The anti-cancer drug Paclitaxel is derived from taxol, a substance found in the bark of the Pacific yew (Taxus brevifolia).^[137] Other tree based drugs come from the paw-paw (Carica papaya), the cassia (Cassia spp.), the cocoa tree (Theobroma cacao), the tree of life (Camptotheca acuminata) and the downy birch (Betula pubescens).^[134]

The papery bark of the white birch tree (Betula papyrifera) was used extensively by Native Americans. Wigwams were covered by it and canoes were constructed from it. Other uses included food containers, hunting and fishing equipment, musical instruments, toys and sledges.^[138] Nowadays, bark chips, a by-product of the timber industry, are used as a mulch and as a growing medium for epiphytic plants that need a soil-free compost.^[139]

Alleé of London plane trees (Platanus × acerifolia) in garden

Ornamental trees

Main articles: Forestry and Ornamental trees

Trees create a visual impact in the same way as do other landscape features and give a sense of maturity and permanence to park and garden. They are grown for the beauty of their forms, their foliage, flowers, fruit and bark and their siting is of major importance in creating a landscape. They can be grouped informally, often surrounded by plantings of bulbs, laid out in stately avenues or used as specimen trees. As living things, their appearance changes with the season and from year to year.^[140]

Trees are often planted in town environments where they are known as street trees or amenity trees. They can provide shade and cooling through evapotranspiration, absorb greenhouse gasses and pollutants, intercept rainfall and reduce the risk of flooding. It has been shown that they are beneficial to humans in creating a sense of well-being and reducing stress. Many towns have initiated tree-planting programmes.^[141] In London for example, there is an initiative to plant 20,000 new street trees and to have an increase in tree cover of 5% by 2025, equivalent to one tree for every resident.^[142]

Other uses

Latex collecting from a Rubber tree (Hevea brasiliensis)

Further information: Resin, Latex, and Camphor

Latex is a sticky defensive secretion that protects plants against herbivores. Many trees produce it when injured but the main source of the latex used to make natural rubber is the Pará rubber tree (Hevea brasiliensis). Originally used to create bouncy balls and for the waterproofing of cloth, natural rubber is now mainly used in tyres for which synthetic materials have proved less durable.^[143] The latex exuded by the balatá tree (Manilkara bidentata) is used to make golf balls and is similar to gutta-percha, made from the latex of the "getah perca" tree Palaquium. This is also used as an insulator, particularly of undersea cables, and in dentistry, walking sticks and gun butts. It has now largely been replaced by synthetic materials.^[144]

Resin is another plant exudate that may have a defensive purpose. It is a viscous liquid composed mainly of volatile terpenes and is produced mostly by coniferous trees. It is used in varnishes, for making small castings and in ten-pin bowling balls. When heated, the terpenes are driven off and the remaining product is called "rosin" and is used by stringed instrumentalists on their bows. Some resins contain essential oils and are used in incense and aromatherapy. Fossilised resin is known as amber and was mostly formed in the Cretaceous (145 to 66 million years ago) or more recently. The resin that oozed out of trees sometimes trapped insects or spiders and these are still visible in the interior of the amber.^[145]

The camphor tree (Cinnamomum camphora) produces an essential oil ^[110] and the eucalyptus tree (Eucalyptus globulus) is the main source of eucalyptus oil which is used in medicine, as a fragrance and in industry.^[146]

Care

Dead trees pose a safety risk, especially during high winds and severe storms, and removing dead trees involves a financial burden, whereas the presence of healthy trees can clean the air, increase property values, and reduce the temperature of the built environment and thereby reduce building cooling costs. During times of drought, trees can fall into water stress, which may cause a tree to become more susceptible to disease and insect problems, and ultimately may lead to a tree's death. Irrigating trees during dry periods can reduce the risk of water stress and death. Irrigation can be accomplished by use of a garden hose, soaker hose, sprinkler, or modified five-gallon bucket.^[147]

Mythology

Main article: Tree worship

Yggdrasil, the World Ash of Norse mythology

Trees have been venerated since time immemorial. To the ancient Celts, certain trees, especially the oak, ash and thorn, held special significance^[148] as providing fuel, building materials, ornamental objects and weaponry. Other cultures have similarly revered trees, often linking the lives and fortunes of individuals to them or using them as oracles. In Greek mythology, dryads were believed to be shy nymphs who inhabited trees.

The Oubangui people of west Africa plant a tree when a child is born. As the tree flourishes, so does the child but if the tree fails to thrive, the health of the child is considered at risk. When it flowers it is time for marriage. Gifts are left at the tree periodically and when the individual dies, their spirit is believed to live on in the tree.^[149]

Trees have their roots in the ground and their trunk and branches extended towards the sky. This concept is found in many of the world's religions as a tree which links the underworld and the earth and holds up the heavens. In Norse mythology, Yggdrasil is a central cosmic tree whose roots and branches extend to various worlds. Various creatures live on it.^[150] In India, Kalpavriksha is a wish-fulfilling tree, one of the nine jewels that emerged from the primitive ocean. Icons are placed beneath it to be worshipped, tree nymphs inhabit the branches and it grants favours to the devout who tie threads round the trunk.^[151] Democracy started in North America when the Great Peacemaker formed the Iroquois Confederacy, inspiring the warriors of the original five American nations to bury their weapons under the Tree of Peace, an eastern white pine (Pinus strobus).^[152] In the creation story in the Bible, the tree of life and the knowledge of good and evil was planted by God in the Garden of Eden.^[153]

Sacred groves exist in China, India, Africa and elsewhere. They are places where the deities live and where all the living things are either sacred or are companions of the gods. Folklore lays down the supernatural penalties that will result if desecration takes place for example by the felling of trees. Because of their protected status, sacred groves may be the only relicts of ancient forest and have a biodiversity much greater than the surrounding area.^[154] Some Ancient Indian tree deities, such as Puliyidaivalaiyamman, the Tamil deity of the tamarind tree, or Kadambariyamman, associated with the kadamba tree were seen as manifestations of a goddess who offers her blessings by giving fruits in abundance.^[155]

Superlative trees

The General Sherman Tree is thought to be the world's largest tree by volume.

Main article: List of superlative trees

Trees have a theoretical maximum height of 130 m (430 ft), but the tallest known specimen on earth is believed to be a coast redwood (Sequoia sempervirens) at Redwood National Park, California. It has been named Hyperion and is 115.6 metres (379 ft) tall.^[156] The tallest known broad-leaved tree is a mountain ash (Eucalyptus regnans) growing in Tasmania with a height of 99.8 m (327 ft).^[157]

The largest tree by volume is believed to be a giant sequoia (Sequoiadendron giganteum) known as the General Sherman Tree in the Sequoia National Park in Tulare County, California. Only the trunk is used in the calculation and the volume is estimated to be 1,487 m³ (52,500 cu ft).^[158]

The oldest living tree with a verified age is also in California. It is a Great Basin bristlecone pine (Pinus longaeva) growing in the White Mountains. It has been dated by drilling a core sample and counting the annual rings. It is estimated to currently be 5,066 years old.^[a]^[159]

A little further south, at Santa Maria del Tule, Oaxaca, Mexico, is the tree with the broadest trunk. It is a Montezuma cypress (Taxodium mucronatum) known as Árbol del Tule and its diameter at breast height is 11.62 m (38.1 ft) giving it a girth of 36.2 m (119 ft). The tree's trunk is far from round and the exact dimensions may be misleading as the circumference includes much empty space between the large buttress roots.^[160]

ශාක

විකිපීඩියා, නිදහස් විශ්වකෝෂය වෙතින්

වෙනත් භාවිතා සඳහා, ශාක (වක්‍රෝත්තිහරණය) බලන්න.

Plants Temporal range: Early Cambrian to recent, but see text, 520–0 Ma PreЄ Є O S D C P T J K Pg N

Scientific classification
Domain:	Eukaryota
(unranked):	Archaeplastida
Kingdom:	Plantae Haeckel, 1866^[1]
Divisions
Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular land plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses †Horneophytopsida Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails †Progymnospermophyta Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants †Nematophytes

ශාක යනු ජිවයෙහි විශේෂ ආකාරයක් වන අතර ඒ සඳහා පදුරු, තෘණ වර්ග, පර්නාංග, හරිත ඇල්ගි, පෙද වර්ග, වැල් වර්ග සහ ඖෂධ පැලෑටි අයත්වෙයි. 350000 ප්‍රමාණයක ශාක විශේෂ ප්‍රමාණයක් ඇතැයි මේ වන විට ගණන් බලා ඇත. ඒවා බීජ ශාක, bryophyte සහ පර්නාංග වේ. 2004 දී සොයා ගෙන ඇති ආකාරයට 287,655 ප්‍රමාණයක් විශේෂ හඳුනාගෙන ඇති අතර ඉන් 258,650 ප්‍රමාණයක් මල් හට ගන්නා ශාක වන අතර 15,000 ප්‍රමාණයක් bryophyte වේ. හරිත ශාක ඇතැම් අවස්ථාවලදී metaphytes ලෙස හැඳින්වෙන අතර ප්‍රභාසංස්ලේෂණය මගින් සුර්යය ශක්තිය තිර කරනු ලබති.

පටුන

[සඟවන්න]

වර්ධනය[සංස්කරණය කරන්න]

ශාකයක් සෑදී ඇති ඝණ ද්‍රව්‍යවලින් වැඩි ප්‍රමාණයක් ලබාගෙන ඇත්තේ වායුගෝලයෙනි. ඒ ප්‍රභාසංශ්ලේෂණය නම් වූ ක්‍රියාවලිය හරහාය. ශාක හිරු එළියෙන් ශක්තිය ලබාගෙන වායු ගෝලයෙන් ලබාගත් CO₂ සරල සීනි බවට පත් කරයි. මෙම සීනි එහිදී ගොඩනැංවීමේ කොටස් සේ එකතු වී ශාකයේ ප්‍රධාන ව්‍යුහමය සංරචක ගොඩ නංවනු ලබයි. ශාක පස කෙරෙහි ප්‍රාථමික විශ්වාසය රඳවා ආධාරය සහ (ප්‍රමාණාත්මක වශයෙන්) ජලය ලබා ගනී. නයිට්‍රජන්, පොස්පරස් සහ අනෙකුත් තීරණාත්මක පෝෂක මූල ද්‍රව්‍ය පසේත් අඩංගුවේ.

බොහෝ ශාකවල සාර්ථක වර්ධනය සඳහා ඒවාට වායුගෝලීය ඔක්සිජන් ශ්වසනය සඳහාද මූල පද්ධතිය වටා ඇති ඔක්සිජන් ද අවශ්‍ය වේ. කෙසේ වෙතත් විශේෂිත සනාල පැලෑටි කිහිපයක් (කඩොලාන ශාක වැනි)මූල මණ්ඩලය අවට ඔක්සිජන් හීන වූ පරිසරවල වර්ධනය වේ.

අර්ථ දැක්වීම[සංස්කරණය කරන්න]

ඇරිස්ටෝටල් විසින් සියළුම ජීවි ද්‍රව්‍ය ශාක (සංචරනය කල නොහැකි) සහ සත්ව (සංචරනය කල හැකි සහ ආහාර ද්‍රව්‍ය සොයා ගමන් කල හැකි) ලෙස කොටස් දෙකකට බෙදන ලදී. ලිනේයස්ගේ වර්ගි කරණයේදී ඔහු මේවා ශාක (Metaphyta හෝ Plantae) සහ සත්ව (Metazoa) රාජධානි ලෙසද වර්ගි කරණය කරන ලදී. එතැන් පටන් ශාක රාජධානිය විවිධ ඒහා අදාල නොවන කාණ්ඩ සමගද සම්බන්ධ බවට තොරතුරු අනාවරණය වුණි. ඒවා නම් දිලීර වර්ග සහ ඇතැම් ඇල්ගි විශේෂයි. මේවා පසුකාලීනව අලුත් රාජධානියකට වෙන්කර හරින ලදී. කෙසේ නමුත් මේවා බොහෝ අවස්ථා වලදී තව දුරටත් ශාක රාජධානියට අන්තර්ගත ලෙස සලකනු ලැබේ.

ශාක යන නාමකරණය යම්කිසි විශේෂ අවස්ථාවකදී යොදා ගත හොත් එය සාමාන්‍යයෙන් එකි වර්ග තුනෙන් එකකට අයත්වේ. කුඩාම සිට විශාලතම අවස්ථාව දක්වා මෙකි වර්ගිකරණයන් තුල පහත පරිදි වේ. • ගොඩබිමෙහි ඇති ශාක - මේවා Embryophyta හෝ Metaphyta ලෙසද හැදින්වේ. කුඩාම ශාක වර්ගීකරණ කුලකය පහතින් නිරූපණය කර ඇත. • හරිත ශාක - මේවා Viridiplantae, Viridiphyta හෝ Chlorobionta ලෙසද නම් කෙරෙන අතර ඉහතින් සදහන් කරන ලද Embryophyta, Charophyta සහ Chlorophyta (කොළ පැහැ ඇල්ගි වර්ග) වර්ගයට අයත්වෙයි. • Archaeplastida මේවා ශාක sensu lato ලෙසද හැදින්වේ. Plastida හෝ Primoplantae වලට ඉහති කී කොළ පැහැති ශාක අන්තර් ගත වන අතර Rhodophyta (රතු ඇල්ගි) සහ Glaucophyta වන්ද අයත්වෙයි. පුළුල්ම ශාක වර්ගි කරණයේදී මෙහි බොහෝමයක් වු සුනෂ්ටිකයෙන් අන්තර්ගත වන අතර ඒවා ඔවුන්ගේ chloroplast ලබාගෙන ඇත්තේ සයනෝ බැක්ටිරීයාවන් භක්ෂණය කිරීමෙනි.

වෙනත් ආකාරයකින් කිවහොත් ප්‍රභාසංස්ලේෂණය සිදු කරන වෙනත් ජිවීන්ද ශාක ලෙස හැදින්වෙන අතර ඒවා සම්ප්‍රදායික වර්ගිකරණයට අන්තර්ගත ‍නොවන අතර ඔවුන් සැබෑ ශාක වලට සමීප සම්බන්ධතාවයක් නොපවත්වයි. ශාක විශේෂ 375000 ප්‍රමාණයක් සොයා ගෙන ඇති අතර සෑම වසරකදීම අළුතින් ශාක විශේෂ කිහිපයක් සොයා ගන්නා අතර ඒ පිළිබඳව විග්‍රහ කරනු ලබයි.

ඇල්ගී[සංස්කරණය කරන්න]

අර්නස්ට් හේකල්ගේ‍ කුන්ස්ට්ෆොර්මන් ඩර් නටූර්, 1904 වෙතින් හරිත ඇල්ගි

බොහෝ ඇල්ගි වර්ග ශාක රාජධානිය යටතට වර්ගිකරණය නොකෙරේ. ඇල්ගි වර්ග විවිධ කාණ්ඩ වලට අයත් ඇල්ගි වර්ග ප්‍රභාසංස්ලේශණය මගින් ශක්තිය නිපදවන ජීවින් විශේෂ වේ. මින් එක් එක් ඇල්ගි විශේෂ ප්‍රභාසංස්ලේශණය නොකරන වෙනස් පුර්වජයින්ගෙන් පැවත එයි. මෙම ඇල්ගි අතුරෙන් වඩාත් පැහැදිලි විශේෂය වනුයේ ශාක සමුද්‍ර විශේෂයි. මොවුන් බහු සෛලික ඇල්ගි විශේෂ වන අතර දළ වශයෙන් භෞමික ශාක වලට සමානකම් දක්වයි. නමුත් මේවා කොළ, රතු සහ දුඹුරු ඇල්ගි ලෙසට වර්ගිකරණයක් සිදු කරනු ලබයි. මෙකී එක් එක් ඇල්ගි වර්ගද විවිධ අන්වීක්ෂීය සහ එක් සෛලික විශේෂ ලෙසට වර්ගීකරණය කර ඇත.

ඇල්ගි වර්ග අතරින් වර්ග දෙකක් පමණක් භෞමික ශාක වලට (Emvriophytes) සමීප සම්බන්ධතාවයක් ඇතැයි සැලකේ. මින් මුල්ම කාණ්ඩය වනුයේ Charophyta වන් වන අතර එමගින් embryophyta වන් ඇති වු බවට සැලකේ. Emdryophyte සහ Charophyte යන කාණ්ඩ දෙකෙහි සංකලනයන් හරිත ඇල්ගි වල (Chlorophyta) දක්නට ඇති අතර මෙහි වඩාත් පැහැදිලි නොවු කාණ්ඩය එක්ව ගත් කල හරිත ශාක හෝ viridiplantae ලෙසට හැඳින්වේ. ශාක රාජධානිය මෙකි ඒකවංශික වර්ගි කරණයට අයත්වෙයි. හරිත ඇල්ගි වල ඇති යම්යම් වෙනස්කම් හැරුණු කොට ඉහත කී සියළුම වර්ග වල සෛල බිත්ති සෙලියුලෝස් වලින් සැදුම් ලත් අතර හරිත වර්ණක A සහ B අන්තර්ගත හරිතප්‍රද ඇති අතර ආහාර ද්‍රව්‍ය පිෂ්ඨය ලෙස ගබඩා කරනු ලැබේ. ඔවුන් තර්කුවක් නොමැතිව අනුනන විභාජනයට ලක්වන අතර පැතලි මියර සහිත මයිටකොන්ඩ්‍රියාවන් අන්තර්ගත වේ.

හරිත ශාක වල හරිත ලව පටල දෙකකින් ආස්තරණය වී ඇති අතර එමගින් ඔවුන් සයනෝ බැක්ටිරීයාවන්ගෙන් සම්භවය වී ඇති බවට සාක්ෂි ඇත. මෙය අනෙකුත් ඇල්ගි වර්ග දෙක වන Rhodophyta හෙවත් රතු ඇල්ගි සහ Glaucophyta සදහාද සත්‍යවේ. මෙම සියළුම කාණ්ඩ තුන සදහා පොදු සම්භවයක් අතැයි විශ්වාස කෙරෙන අතර ඔවුන් Archaeplastida නම් වර්ගිකරණයට යටත් වෙයි. මීට අමතරව බොහෝමයක් අනෙකුත් ඇල්ගි වර්ග (උදා - haterokonts, haptophytes, dinoflagellates සහ euglenids) සදහා ද ආස්තරණ පටල තුනකින් හෝ හතරකින් ආවරණය වු හරිත භක්ෂණය පවතී. ඔවුන් හරිත ශාක වල සමීප ඥ‍ාතීන් නොවන අතර එහි හරිත ලව ලබාගෙන ඇත්තේ රක්ෂණය කරන ල හෝ සහජීව චර්යා පෙන්වන ද හරිත හෝ රතු ඇල්ගි වලිනි.

දිලීර[සංස්කරණය කරන්න]

දිලීර කලින් ශාක රාජධානියට ඇතුළත්කර තිබුණද, එය තව දුරටත් ශාක ලෙස නොසැලකේ. කළල ශාක සහ ඇල්ගී මෙන් නොව දිලීර ප්‍රභාසංශ්ලේෂක නොවන අතර මෘතෝපජීවී එනම් අවට පරිසරයේ ඇති ද්‍රව්‍ය බිඳ දමා දේහයට උරාගැනීමෙන් ආහාර ලබාගනී.දිලීර ශාක වර්ගයක් නොවන නමුත් අතීතයෙදී ශාක ලෙස සලකා තිබෙන අතර එය උද්භිද විද්‍යාඥයින්ගේ විෂය ධාරාවට ඇතුළත් යයි සළකා ඇත. දිගුකලක සිට දිලීර පරිණාමිකව ශාකවලට වඩා සතුන්ට සමීපයැයි හඳුනාගෙන තිබිණ.නමුත් ඒවා තවමත් මූලික උද්භිද විද්‍යා පාඨමාලාවල ගැඹුරින්ම ආවරණය කරන අතර සත්ව විද්‍යා මූලික පාඨමාලාවලදී එය අනිවාර්‍ය් නොවේ.බොහෝ දිලීර සෑදී ඇත්තේ දිලීර සූත්‍රකා ලෙස හඳුන්වන අන්වීක්ෂීය ව්‍යුහ වලින් වන අතර ඒවා සෛලවලට බෙදී හෝ නොබෙදී හෝ පැවතුනත් සූන්‍යෂ්ටික න්‍යෂ්ටිදරයි. දිලීරවල ප්‍රජනක ව්‍යුහ වන්නේ ඵලදේහ නොහොත් වඩාත් හුරුපුරුදු ලෙස බිම්මල්ය. මොවුන් කිසිම ප්‍රභාසංශ්ලේෂක කණ්ඩායමකට අයත් නොවන අතර සතුන්ගේ ළඟම නෑයන්වේ. මේ නිසා දිලීරවලට ඔවුන්ගේම රජධානියක් ඇත.

ව්‍යුහය, වර්ධනය හා විකසනය[සංස්කරණය කරන්න]

ශාකයක් සෑදී ඇති ඝණ ද්‍රව්‍යය වලින් වැඩි ප්‍රමාණයක් ලබාගෙන ඇත්තේ වායුගෝලයෙනි. ඒ ප්‍රභාසංස්ලේශණය නම් වූ ක්‍රියාවලිය හරහාය. ශාක හිරු එළියෙන් ශක්තිය ලබාගෙන වායු ගෝලයෙන් ලබාගත් CO2 සරල සීනි බවට පත් කරයි. මෙම සීනි එහිදී ගොඩනැංවීමේ කොටස් සේ එකතු වී ශාකයේ ප්‍රධාන ව්‍යුහමය සංරචක ගොඩ නංවනු ලබයි. ශාක පස කෙරෙහි ප්‍රාථමික විශ්වාසය රඳවා ආධාරය සහ (ප්‍රමාණාත්මක වශයෙන්) ජලය ලබා ගනී. නයිට්‍රජන්, පොස්පරස් සහ අනෙකුත් තීරණාත්මක පෝෂණ මූල ද්‍රව්‍ය පසේත්අඩංගුවේ.

බොහෝ ශාකවල සාර්ථක වර්ධනය සඳහා ඒවාට වායුගෝලීය ඔක්සිජන් ශ්වසනය සඳහා මූල පද්ධතිය වටා ඔනක්සිජන් ද අවශ්‍ය වේ. කෙ‍ෙස් වෙතත් විශේෂිත සනාල පැලෑටි කිහිපයක් (කඩොලාන ශාක වැනි)මූල මණ්ඩලය අවට ඔක්සිජන් හීන වූ පරිසරවලද වර්ධනය වේ .

පාරිසරික විද්‍යාවට අනුව ශාකවල වැදගත්කම[සංස්කරණය කරන්න]

අර්තාපල් ශාකය:-යුරෝපීය ජාතිකයන් 1400 අග සහ 1500යේ මුල භාගයේදී ඇමරිකානුවන් සමඟ සම්බන්ධවීමෙන් පසුව අර්තාපල් ලෝකයේ අනෙකුත් ප්‍රදේශ වෙත ද ව්‍යාප්තවූ අතර එතැන් පටන් එය වැදගත් ක්ෂේත්‍ර බෝගයක් බවට පත් වී ඇත.

මිනිසා විසින් ප්‍රයෝජනයට ගන්නා ශාක පිළිබඳව අධ්‍යයනය කිරීම ආර්ථික උද්භිද විද්‍යාව හෙවත් මානවවංශ උද්භිත විද්‍යාව ලෙස හැඳින්වේ.මේවා බොහෝවිට සමානාර්ථපද ලෙස භාවිත කළත්, ඇතැමුන් ආර්ථික උද්භිත විද්‍යාව ප්‍රධාන වශයෙන් නවීන වගාකල ශාක පිළිබඳ මානව වංශ උද්භිද විද්‍යා අධ‍්‍යයනයන් පාරම්පරික ශාක වර්ග දේශීය ජනයා විසින් භාවිත කිරීම පිළිබඳ යොමුවී ඇතිබව සලකනු ලබයි.මානවයා විසින් ශාක වගාකිරීම මිනිස් ශිෂ්ටාචාරයේ පදනම වූ කෘෂිකර්මයෙහි කොටසකි.ශාක කෘෂිකර්මය,සත්ත්ව විද්‍යාව, උද්‍යාන පාලනය හා වන විද්‍යාව ලෙස කොටස් වලට බෙදී ඇත.

ආහාර අර්ථයෙන් සියළු මානව පෝෂණය කෙළින්ම හෝ වක්‍රව ගොඩබිම් ශාක මත රඳාපවතී.බොහෝ මානව පෝෂණය ධාන්‍ය වර්ග විශේෂයෙන් බඩ ඉරිඟු ,තිරිඟු සහ සහල් මත හෝ වෙනත් ප්‍රධාන ආහාර බෝග වන අර්තාපල් මඤ්ඤොක්කා සහ රනිල මත රඳා පවතී.ශාකවල ආහාරයට ගන්නා වෙනත් කොටස් අතරට පළතුරු, එළවළු, කජු, ඖෂධ, කුළු බඩු සහ ආහාරයට ගතහැකි මල් වර්ග අයත් වේ.ශාක වලින් ලබාගන්නා බීම වර්ග වලට කෝපි,තේ, වයින්, බියර් සහ මධ්‍යසාර අයත්වේ. ප්‍රධාන වශයෙන්ම සීනි ලබාගන්නේ උක් සහ බීට් වළිනි. අහාර පිසින තෙල් සහ මාගරින් ලබාගන්නේ බඩඉරිඟු, සොයා බෝංචි, කැනෝලා, සැෆ් මල් , සූරියකාන්ත, ඔලිව් සහ වෙනත් ශාක වලින්ය.අහාර ආකලන වලට ගම් ඇරබික්, ගුවාගම්, ලොඅකස්ට් බෝංචි ගම්, පිෂ්ඨය සහ පෙක්ටීන් අයත් වේ.

ආහාර නොවන නිෂ්පාදන[සංස්කරණය කරන්න]

දැව දඬු පසුව සැකසීම සඳහා ගබඩාකර ඇති අයුරු.

ගොඩනැගිලි තැනීමට දැව,ලී බඩු,කඩදාසි,කාඩ්බෝඩ්,සංගීත භාණ්ඩ සහ ක්‍රීඩාභාණ්ඩ සෑදීමට උපයෝගී කොට ගනී.බොහෝ විට රෙදි සෑදීමට කපු,තණ හෝ සෙලියුලෝස් වලින් වෙන්කරගත් රෙයෝන් සහ ඇසිටේට් වැනි කෘතිම කෙඳි යොදාගනී.ශාකවලින් ලබාගන්නා පුනර්ජනනය කළ හැකි ඉන්ධන වලට දර, පීට් සහ අනෙකුත් ජෛව ඉන්ධන අයත් වේ. ගල් අඟුරු සහ පෙට්‍රෝලියම් ශාක වලින් ව්‍යුත්පන්නවූ පොසිල ඉන්ධන වලට අයත් වේ. ශාක වලින් ලබාගන්නා ඖෂධ අතරට ඇස්ප්‍රීන්, ටැක්සොඅල්, මොර්ෆීන් ,ක්වීනීන්, රෙසර්පින්, කොල්චිසීන්, ඩිජිටාලිස් සහ වින්ක්‍රිස්ටීන් අයත්වේ. ගින්කෝ, එකිනසියා, ෆීවර්ෆිව් සහ සෙන්ට් ජෝන්ස්වර්ට් වැනි ඖෂධීය පරිපූරක සිය ගණනක් ඇත.ශාක වලින් ලබගන්නා කෘමිනාශක අතරට නිකොටීන්, රොටෙනොඅන්, ස්ට්‍රිච්නීන් සහ පයිරත්‍රීන් අයත්වේ. ශාක වලින් ලබගන්නා මත්ද්‍රව්‍ය වලට ඕපියම්,කොකේන් සහ මරිජුවනා ඇතුලත්වේ. ශාක වලින් ගන්නා විශ අතරට රිසීන්, හෙම්ලොක් ක්‍යුරෙයා අයත්ය.ශාක කෙඳි වර්ග ,සුගන්ධ තෙල්, ඩයි වර්ග, වර්ණක ,ඉටිවර්ග, ටැනින්, ගස් වලින් ගන්නා කිරි වර්ග,ගම්, රෙසින්, ඇල්කොලොයිඩ, ඇම්බර් සහ වල්ක වැනි බොහෝ ස්වාභාවික නිෂ්පාදන වල ප්‍රභවයන් ශාකවේ.ශාක වලින් නිපදවාගන්නා නිෂ්පාදන අතරට සබන්,ආලේප,ෂැම්පු,සුවඳ විළවුන්, රූපලාවන්‍ය ද්‍රව‍ය, ටර්පන්ටයින්,රබර් ,වාර්නිෂ්, ලිහිසි තෙල්,ලිනොලියම්, ප්ලාස්ටික්,තීන්ත,චුයින්ගම්, සහ හණ කඹ අයත් වේ.අපරිමිත ප්‍රමාණයක්වූ කාර්මිකව නිපදවන කාබනික රසායන ද්‍රව්‍ය වල,මූලික රසායනික ද්‍රව්‍යවල ප්‍රාථමික ප්‍රභවය වන්නේද ශාකය මෙම රසායනික ද්‍රව්‍ය විශාල විවිධත්වයකින් යුතු පර්යේෂණ හා අධ්‍යයනයන්ට උපයෝගීකොට ගනී.

ශාක කොටස්වල සෞන්දර්යාත්මක ප්‍රයෝජන[සංස්කරණය කරන්න]

දහස් ගණන් ශාක විශේෂ මිනිසාගේ අවට පරිසරය අලංකාර කිරීමට වගාකරනු ලබන අතර ඒවා සෙවණ ලබාදීම, උෂ්ණත්වය අඩුකර ගැනීමට, සුළඟේ වේගය අඩුකර ගැනීමට, ඝෝෂාව අඩුකිරීමට, පෞද්ගලිකත්වය සලසා ගැනීමට සහ පාංශු ඛාදනය වලක්වා ගැනීම ආදියටද යොදාගනී.මිනිසුන් කැපූමල්, වේලන ලද මල් සහ ගෘහාශ්‍රිත ශාක වර්ග ගෘහස්ථව ප්‍රයෝජනයට ගනී.එළිමහනේදී ඔවුන් තණකොළ පිට්ටනි සැදීම සඳහා තණකොළ , සෙවණ ලබාදෙන ගස්, අලංකරණය සඳහා වූ ගස් වර්ග.පඳුරු , වැල් ,පළාවර්ගයට අයත් බහුවාර්ෂිකයෝ සහ පාත්තිවලට යොදාගන්නා ශාක ආදිය ප්‍රයෝජනයට ගනී.ශාකවල අනුරූ බොහෝ විට චිත්‍ර කලාව ,ගෘහ නිර්මාණ ශිල්පය , රසවින්ධනය,භාෂාව සහ ඡායාරූපකරණයට සහ රෙදිපිළිමත මුදල් ,මුද්දර, කොඩිමත හා වංශවතුන්ගේ ලාංඡන ලෙසද යොදාගනී.ජීවී ශාක කලාවට යොදාගන්නා ක්‍රම අතරට පඳුරු නොයෙක් හැඩ වලට කැපීම, බොන්සායි, ඉකෙබානා සහ විවිධ ආධාරක මත වැවීම අයත් වේ.අලංකාර ශාක ටියුලිප් මේනියාවේදී මෙන් ඇතැම් විට ඉතිහාසයේ ගමන් මඟ වෙනස්කර ඇත.සංචාරක ව්‍යාපාරයේදී ශාක වර්ෂයකට ඩොලර් බිලියන ගණනින් ලබාදෙන පදනම වී ඇත්තේ වෘක්ෂ උද්‍යාන, උද්භිද උද්‍යාන, ඓතිහාසික උද්‍යාන, වන උද්‍යාන, ටියුලිප් සැණකෙළි, වැසිවනාන්තර,වර්ණවත් ශරත් පත්‍ර ඇති වනාන්තර සහ සකුරා මල් පිපෙන කාලයට පවත්වන සැණකෙළි ආදියට සංචාරකයන් අකර්ශනය වන නිසාය.වීනස් ෆ්ලයිට්‍රැප් සංවේදී ශාකය සහ පුනර්ජීවන ශාකය ආදිය ඒවායේ අපූරුබව නිසා විකිණුන ශාකවලට උදාහරණයන්ය.

ශාකවල විද්‍යාත්මක සහ සංස්කෘතිකමය ප්‍රයෝජන[සංස්කරණය කරන්න]

යෙව් ගසක අත්තක වාර්ෂික වර්ධක වළලු 27ක් ලා වර්ණයෙන්ද එළය හා තද වර්ණයෙන් යුතුවද අරටුව සහ මජ්ජාවද (මැද පිහිටි තද පැහැති තිත) දැක්වෙන හරස්කඩක්

වෘක්ෂවල වර්ධක වළලු පුරා විද්‍යාවේදී කාළ නිර්ණය සඳහා සහ අතීතයේ පැවැති දේශගුණය පිළිබඳව දැනගැනීම සඳහා වූ වැදගත් ක්‍රමයකි. මූලික ජීව විද්‍යාත්මක පර්යෙෂණ ශාක යොදාගෙන සිදුකර ඇත.උදාහරණයක් ලෙස ජාන විද්‍යාවේ ග්‍රෙගරි මෙන්ඩල්ගේ නීතිය සොයාගෙන ඇත්තේ පී ශාක උපයෝගී කොටගෙනය. අභ්‍යවකාශ නැවතුම් පොළවල්,අභ්‍යවකාශ ජනපද යම් දිනක ජීවිතය රැකගැනීමට ශාකමත විශ්වාසය තබනු ඇත.ශාක ජාතික හා ජනපද ලාංඡන ලෙස යොදාගන්නා අතර එයට ජනපද පුෂ්පය, ජනපද ගස ඇතුලත් වේ. ඓතිහාසිකව වෘක්ෂවලට ගරුකරනු ලබන අතර බොහෝ ඒවා ජනප්‍රියය.ශාක විසින් ලෝක වර්තා ගණනාවක්ම දරනු ලැබේ.සිහිවටන ත්‍යාග සහ උපත්, මරණ,විවාහ සහ නිවාඩු දින සැමරීමට ශාක සිටුවනු ලැබේ.ශාක පුරාණ ප්‍රවාද වල ,ආගම් වල සහ සාහිත්‍යයේ ප්‍රමුඛ ස්ථානයක් ගනී. මානව උද්භිද විද්‍යා ක්ෂේත්‍රයේ පාරම්පරික සංස්කෘතීන් ශාක භාවිතා කල ආකාරය අධ්‍යයනය කරන අතර එය තර්ජනයට ලක්වූ ශාක සංරක්ෂණයට සහ නව ඖෂදීය ශාක සොයා ගැනීමට උපකාරී වේ. උද්‍යාන කරණය එක්සත් ජනපදයේ වඩාත්ම ජනප්‍රියයි. එරට විවේක කාලයට කරන ක්‍රියකාරකම නම් ශාක සිටුවීමයි.ශාක සමඟ වැඩකිරීම හෙවත් උද්‍යාන විද්‍යා චිකිත්සාව දියවැඩියා රෝගීන් පුනරුප්ථාපනය කිරීමට උපකාරී වේ. දුම්කොළ ,මරිජුවානා සහ ඕපියම් වැනි ශාක මානසික තත්වයට බලපාන රසායන ද්‍රව්‍ය වනඅතර ඒවා නිස්සාරණය කරගනී.

ශාකවල සෘණාත්මක බලපෑම[සංස්කරණය කරන්න]

වල් පැළෑටි යනු මිනිසාට අනවශ්‍ය ස්ථාන වල වැඩෙන ශාකයන්ය.මිනිසුන් විසින් ශාක ඔවුන්ගේ උපන් භූමියට වඩා බොහෝ ඈත ප්‍රදේශ වලට පතුරුවාහරිනු ලබන අතර මෙසේ හඳුන්වාදුන් ශාකවලින් සමහරක් ආක්‍රමණකාරී ශාක බවට පත්ව දේශීය විශේෂ ඉවත්කරමින් පවතින පරිසර පද්ධතියට හානි සිදුකරයි.ආක්‍රමණකාරී ශාක විසින් වගාකල බෝග වර්ග විස්ථාපනය කිරීම නිසා වාර්ෂිකව ඩොලර් මිලියන ගණනින් පාඩු සිදුවේ.ඒවා නිෂ්පාදන වියදම ඉහල දමන අතර විනාශ කිරීමට රසායන ද්‍රව්‍ය භාවිතාකිරීමෙන් පරිසරයට බලපෑම් එල්ලවේ.

පැළෑටි මිනිසාටද හානිදායක වේ. ශාක විසින් නිපදවන සුලඟේ පාවී යන පරාග නිසා පීනස් රෝගීන් හට ආසාත්මිකත ඇතිවේ. විෂ සහිත ශාක වර්ග පුළුළ් විවිධත්වයකින් පැතිර ඇත.විෂ සහිත අයිවි වැනි ශාක වර්ග සමෙහි ගැටුන විට කැසීම් ඇතිකරයි. දුම්කොළ, මරිජුවානා, කොකේන් සහ ඕපියම් වැනි ඇතැම් ශාක වල මානසිකත්වයට බලපාන රසායන ද්‍රව්‍ය උකහා ගැනීම හෝ දුම් පානයෙන් සෞඛ්‍යට හානි සිදුවේ. එමෙන්ම මරණය පවා සිදුවේ.ශාක වලින් උපදවාගන්නා නීත්‍යානුකූල හෝ නීත්‍යානුකූල නොවන මත්ද්‍රව්‍ය ආර්ථිකය කෙරෙහි සෘණාත්මකව බලපාන අතර එය වැඩකරන්නාගේ නිෂ්පාදිත ධාරිතාව හා බලාත්මක කිරීමේ වියදම් අඩුකිරීම කෙරෙහි බලපායි.ඇතැම් ශාක වර්ග ශරීරයට උකහාගත් විට මිනිසාට හා සතුන්ට ආසාත්මික ප්‍රතික්‍රියා ඇතිකරන අතර තවත් ශාක ආහාර අපත්‍ය වීමක් ඇතිකරයි.එය සෘණාත්මක සෞඛ්‍ය බලපෑමකි.

මූලාශ්‍ර[සංස්කරණය කරන්න]

Jump up↑ Haeckel G (1866). Generale Morphologie der Organismen. Berlin: Verlag von Georg Reimer. පිටු vol.1: i–xxxii, 1–574, pls I–II; vol. 2: i–clx, 1–462, pls I–VIII.

ප්‍රවර්ග:

ரம்
https://ta.wikipedia.org/s/6h

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பவோபாப் மரம் தென்னாபிரிக்காவிலுள்ளது

கலிபோர்னியா மாநிலத்தில் வளரும் செம்மரம்.

மரம் என்பதை அளவிற் பெரிய பல்லாண்டுத் தாவரம் என வரைவிலக்கணம் கூறலாம். இது நிலத்தில் (ஒரு விதையிலிருந்து) தோன்றி, இடம் விட்டு இடம் தானே நகராது, நிலைத்து வளரக்கூடிய ஒரு நிலைத்திணை வகை ஆகும். இதற்கான அளவு குறித்த வரையறை எதுவும் கூறப்படாவிடினும், பொதுவாக முதிர்ந்த நிலையில் 4.5 மீட்டர் (15 அடி) உயரமும், ஒரு தனி அடிமரத்தில் தாங்கப்பட்ட கிளைகளையும் கொண்டிருக்கும். மரங்கள், இயற்கை நிலத்தோற்றத்தில் முக்கியமான அம்சமாக இருப்பதுடன் நிலத்தோற்றக்கலையில் ஒரு முக்கியமான கூறுமாகும். ஏனைய வகைகளைச் சேர்ந்த செடி கொடி போன்ற நிலத்திணை வகைகளை விட, மரங்கள் நீண்டகாலம் வாழக்கூடியவை. சிலவகை மரங்கள் 100 மீ. (300 அடி), உயரம் வரை வளரக்கூடியவை, சில ஈராயிரம் ஆயிரம் ஆண்டுகளுக்கு மேலும் வாழக்கூடியவை. அமெரிக்காவில் உள்ள கலிபோர்னியா மாநிலத்தில் உள்ள செம்மரம் என்னும் வகை இப்படிப்பட்டன. இதே போல தமிழ் நாட்டில் தூத்துக்குடி மாவட்டத்தில் குலசேகர பட்டினம் என்னும் ஊரில் கடற்கரை அருகில் அமைந்துள்ள ஆப்பிரிக்காவை பூர்வீகமாக கொண்ட "பவோபாப் மரம்" இன்றும் ஆயிரம் ஆண்டுகளை கடந்து வாழ்ந்துகொண்டு இருக்கிறது..

இந்த மரம் தமிழர்கள் ஆதிகாலத்தில் கடல் வணிகத்தில் உலகின் முன்னோடிகளாக இருந்தனர் என்பதற்கு நல்ல உதாரணமாக கூறலாம்..

காரணம் தமிழர்கள் ஆபிரிக்க நாடுகளுக்கு கப்பல் வழி வணிகம் செய்ய போகும்போது இந்த மரத்தின் விதைகளை அங்கிருந்து எடுத்து வந்து இங்கு விதைத்து இருகின்றனர்..

பொருளடக்கம்

[மறை]

உருவவியல் (Morphology)[தொகு]

வேர்கள், அடிமரம், கிளைகள், சிறுகிளைகள், இலைகள் என்பவை மரத்தின் பகுதிகளாகும். மரத் தண்டு, தாங்குவதற்கானதும், நீர், உணவு முதலியவற்றைக் கடத்துவதற்குமான மென்சவ்வுகளைக் (காழ் (xylem) மற்றும் உரியம் (phloem)) கொண்டது. மரம் (மூலப்பொருள்), காழ்க் கலங்களைக் கொண்டது, மரப்பட்டை முக்கியமாக உரியங்களால் ஆனது. மரம் வளரும்போது இது ஆண்டு வளையங்களை உருவாக்குகின்றது. மிதவெப்ப மண்டலக் (temperate) காலநிலைப் பிரதேசங்களில் இந்த வளையங்களை எண்ணுவதன் மூலம் மரத்தின் வயதைக் கணிக்க முடியும். மரத்தின் வேர்கள் பெரும்பாலும் நிலத்திற்கடியிலேயே காணப்படும். இவை மரம் நிலத்தைப் பற்றிப் பிடித்துக்கொள்ள உதவுவதுடன், மண்ணிலிருந்து நீர் மற்றும் போஷாக்குப் பொருட்களை உறிஞ்சவும் பயன்படுகின்றன. தாவரங்கள் உணவைத் தயாரிப்பதற்குச் சூரிய ஒளி தேவை. இலைகளின் மூலமே இச் செயற்பாடு நடைபெறுகின்றது. மரங்கள் அடர்த்தியாகவுள்ள இடங்களில் ஒளிக்காக மற்றத் தாவரங்களுடன், போட்டியிடவேண்டியுள்ளது. இதற்கு உதவும்பொருட்டுத், தண்டுகள், இலைகளைக் கொண்டுள்ள கிளைகளை உயரத்தில் வைத்திருக்க உதவுகின்றன. பல தாவரங்களில், இலைகள் கூடிய அளவு சூரிய ஒளியைப் பெறத்தக்கவகையில், கிளைகளின் ஒழுங்கு அமைந்திருக்கும்.

எல்லா மரங்களும் முன் கூறிய பாகங்களைக் கொண்டிருக்க வேண்டுமென்பதில்லை. உதாரணமாகப் பன்னங்கள் கிளைகளைக் கொண்டிருப்பதில்லை. வட அமெரிக்காவில் வளரும் சாகுவாரோ கக்டஸ்களுக்குச் செயற்பாடுள்ள இலைகள் இல்லை. மரப் பன்னங்கள் பட்டைகளைக் கொண்டிருப்பதில்லை. அவற்றின் பருமட்டான வடிவத்தையும், அளவையும், அடிப்படையாக வைத்து இவையனைத்தும் மரங்களாகவே கொள்ளப்படுகின்றன. சில சமயம் அளவே முக்கியமாகக் கருதப்படுகின்றது. பல கிளைகள் அல்லது தண்டுகளுடன் கூடிய, மரத்தைப் போலவே வடிவமுடைய தாவரமொன்று, அளவில் மிகவும் சிறிதாக இருக்கக்கூடும். இது செடியென்று அழைக்கப்படுகின்றது. எனினும் மரத்துக்கும், செடிக்கும் இடையில் சரியான வேறுபடுத்தும் எல்லை கிடையாது. சிறியனவாக இருப்பதால் "பொன்சாய்"கள் மரங்கள் என்று கொள்ளப்படமுடியாது, எனினும் மரவகைகளின் வடிவத்தைக் கருதும்போது, தனியொரு specimen இன் வடிவத்தோடு குழப்பிக்கொள்ளக்கூடாது. மூங்கில்கள் மரங்களின் பல இயல்புகளைக் கொண்டிருந்தாலும், அவை மரங்களென அழைக்கப்படுவதில்லை.

ஒன்றாக வளரும் சிறு கூட்டம் மரங்கள் தோப்பு எனப்படுகின்றன, பெரியதொரு நிலப்பரப்பில் மரங்கள் அடர்ந்திருக்கும்போது அது காடு எனப்படுகின்றது. பெரிய ஆனால் ஐதாக இருக்கும் மரங்களையும் இடையில் புல்வெளிகளையும் (வழக்கமாக மேய்ச்சலுக்கு விடப்பட்ட அல்லது எரிக்கப்பட்ட) கொண்ட பகுதி வெப்பப் புல்வெளி (savanna) எனப்படுகின்றது. மேலும்..

முக்கிய மரவகைகள் (genera)[தொகு]

மரங்கள் பல்வேறுபட்ட தாவரக் குடும்பங்களுள் அடங்குகின்றன. அதனால், இவை பல்வேறுவகையான இலை வகைகள், வடிவங்கள், பட்டைகள், பூக்கள், பழங்கள், முதலியவற்றைக் கொண்டவையாக உள்ளன. ஆரம்பகால மரங்கள், பெரிய காடுகளில் வளரும் மரப் பன்னங்களாக இருக்கக்கூடும். பின்னர் ஊசியிலை மரங்கள், கிங்க்கோக்கள், சைக்காட்டுகள் மற்றும் எனைய வித்துமூடியிலிகள் (gymnosperm) போன்றவை தோன்றின. இன்று பெரும்பாலான மரங்கள் பூக்கும் தாவரங்களும், ஊசியிலைத் தாவரங்களுமாகும். கிழேயுள்ள பட்டியல் பெரிதும் அறியப்பட்ட மரங்களின் பெயர்களையும், அவை பொதுவாக எவ்வாறு வகைப்படுத்தப்பட்டுள்ளன என்பதையும் காட்டுகின்றது.

பூக்கும் தாவரங்கள் (Magnoliophyta)[தொகு]

கட்டிடத்தின் மேலே வளர்க்கப்படும் மரங்கள்

இருவித்திலைத் தாவரங்கள் (Magnoliopsida)[தொகு]

அனக்காடியேசியே (மரமுந்திரி குடும்பம்)
- மரமுந்திரி, அனக்காடியம் ஒக்சிடென்தலே
- மா, மங்கிபேரா இந்திகா
- பசுங்கொட்டை, பிஸ்தாசியா வேரா (Pistacia vera)
- Lacquer tree, டொக்சிகோடென்றன் வேர்ணிசிபு(f)ளூவா (Toxicodendron verniciflua)
Aquifoliaceae (Holly குடும்பம்)
- Holly, Ilex வகை
அரலியேசியே (Ivy குடும்பம்)
- Kalopanax, கலோபானக்ஸ் பிக்டஸ் (Kalopanax pictus)
Betulaceae (Birch குடும்பம்)
- Alder, Alnus வகை
- Birch, Betula வகை
பொ(b)ம்பாகேசியே (பெருக்க மரம் குடும்பம்; sometimes included in மால்வேசியே)
- பெருக்க மரம், அடன்சோனியா வகை
- முள்ளிலவு, பொ(b)ம்பா(b)க்ஸ் சீபா(b) (Bombax ceiba)
- Kapok, சீபா பெண்டந்திரா (Ceiba pentandra)
- துரியான், துரியோ ஸிபெத்தினஸ் (Durio zibethinus)
- பல்சா, ஒகுரோமா லகோ(g)பஸ் (Ochroma lagopus)
பர்சரேசியே
- கார்வேம்பு, கரூகா பின்னாட்டா (Garuga pinnata)
கக்டாசியே (கள்ளி குடும்பம்)
- Saguaro, கார்னேஜியே ஜைஜண்டியா (Carnegiea gigantea)
கோர்னாசேசியே (Dogwood குடும்பம்)
- Dogwood, கோர்னஸ் (Cornus) வகை
கோரிலேசியே (ஹஸெல் குடும்பம்)
- Hornbeam, கார்பினஸ் (Carpinus) வகை
- Hazel, கோரிலஸ் (Corylus) வகை
பா(f)பே(b)சியே (பட்டாணி குடும்பம்)
- Honey locust, Gleditsia triacanthos
- Black locust, Robinia pseudoacacia
- Laburnum, லபூர்னம் (Laburnum) வகை
- Pau Brasil, Brazilwood, Caesalpinia echinata
பா(f)கே(g)சியே (பீ(b)ச் குடும்பம் )
- செசுநட், Castanea வகை
- பீ(b)ச், Fagus வகை
- Southern beech, Nothofagus வகை
- Tanoak, Lithocarpus densiflorus
- ஓக், Quercus வகை
Fouquieriaceae (Boojum குடும்பம்)
- Boojum, போர்குவேரியா கொலம்னாரிஸ் (Fouquieria columnaris)
Hamamelidaceae (Witch-hazel குடும்பம்)
- Sweet-gum, லிக்குயிடம்பர் (Liquidambar) வகை
- Persian ironwood, பரோட்டியா பேர்ஸிக்கா (Parrotia persica)
ஜக்லண்டேசியே (Walnut குடும்பம்)
- Walnut, ஜக்லான்ஸ் (Juglans) வகை
- Hickory, Carya வகை
லோரேசியே (Laurel குடும்பம்)
- கறுவா சினமோமம் ஸெலனிக்கம் (Cinnamomum zeylanicum)
- Bay laurel லோரல் நொபிலிஸ் (Laurus nobilis)
- அவகாடோ பேசியா அமெரிக்கானா (Persea americana)
லைத்திரேசியே Loosestrife குடும்பம்
- Crape myrtle Lagerstroemia வகை
மக்னோலியேசியே (Magnolia குடும்பம்)
- Tulip tree, Liriodendron species
- Magnolia, Magnolia வகை
மல்வேசியே (திலியேசியே உள்ளடங்கியது) (Mallow குடும்பம்.)
- Linden (Basswood, Lime), Tilia வகை
மெலியேசியே (மலைவேம்பு குடும்பம்)
- வேம்பு, Azadirachta indica (A. Juss)
- Bead tree, மெலியா அஸெடராச் (Melia azedarach)
- மலை வேம்பு, சுவீதெனியா மககோனி (Swietenia mahagoni)
மோராசியே
- ஆல், பை(f)க்கஸ் பெ(b)ங்காலென்சிஸ் (Ficus benghalensis)
- அரசு, பை(f)க்கஸ் ரிலிஜியோசா (Ficus religiosa)
மைரிஸ்டிகேசியே (சாதிக்காய் மரம் குடும்பம்)
- சாதிக்காய் மரம், மைஸ்ரிஸ்டிகா பி(f)ராகிரன்ஸ் (Mysristica fragrans)
மிர்ட்டேசியே (Myrtle குடும்பம் )
- யுகலிப்டஸ், யுகலிப்டஸ் வகை
- Myrtle, Myrtus வகை
- கொய்யா, சிடியம் குவாஜாவா (Psidium guajava)
- நாவல், Syzygium cumini

நைசாசியே (Nyssaceae):பூத்திருக்கும் ஒரு Dove tree

நைசாசியே (Tupelo குடும்பம்; சிலசமயம் Cornaceaeல் உள்ளடக்கப்படுகின்றது)
- Tupelo, Nyssa வகை
- Dove tree, தாவிதியா இன்வொலுகிராட்டா (Davidia involucrata)
ஒலியேசியே (ஒலிவ் குடும்பம்)
- ஒலிவ், Olea europaea
- Ash, பிரக்ஸினஸ் (Fraxinus) வகை
பப்பிலியோனேசியே
- புங்கை, பொங்கமியா பின்னாட்டா (Pongamia pinnata)
- முருக்கு, முள்முருக்கு, எரித்ரைனா இந்திக்கா (Erythrina indica)
பிளாட்டனேசியே (Plane குடும்பம்)
- Plane, பிளாட்டனஸ் வகை
ரிஸோபோராசியே (அலையாத்தித் தாவரங்கள் குடும்பம்)
- Red Mangrove, ரிஸோபோரா மங்கிள் (Rhizophora mangle)
ரோசேசியே (ரோஜா குடும்பம்)
- Rowan, Sorbus வகை
- Hawthorn, Crataegus வகை
- பேரி, Pyrus வகை
- அப்பிள், Malus வகை
- வாதுமை, புரூணஸ் துல்ஸிஸ் (Prunus dulcis)
- பீச், புரூணஸ் பேர்ஸிக்கா (Prunus persica)
- பிளம், புரூணஸ் டொமெஸ்ட்டிக்கா (Prunus domestica)
- செர்ரி, புரூணஸ் வகை
காஃபி குடும்பம் (தாவரவியல்) (Bedstraw குடும்பம்)
- காப்பி, காபி(f)யா அராபிக்கா
Rutaceae (Rue குடும்பம்)
- தோடை, Citrus aurantium
- எலுமிச்சை, Citrus limon
- Cork-tree, Phellodendron வகை
- Euodia, Tetradium வகை
Salicaceae (Willow குடும்பம்)
- Aspen, Populus வகை
- Poplar, Populus வகை
- Willow, Salix வகை
Sapindaceae (including Aceraceae, Hippocastanaceae) (Soapberry குடும்பம்)
- மேப்பிள், Acer வகை
- Buckeye, Horse-chestnut, Aesculus வகை
- Mexican buckeye, Ungnadia speciosa
- விளச்சிப்பழம், Litchi sinensis
- Golden rain tree, Koelreuteria paniculata
Sapotaceae family
- Tambalacoque, or dodo tree, Sideroxylon grandiflorum, previously Calvaria major
Simaroubaceae குடும்பம்
- Tree of heaven, Ailanthus வகை
Sterculiaceae குடும்பம்
- Cacao (cocoa), Theobroma cacao
Ulmaceae (Elm குடும்பம்)
- Hackberry, Celtis வகை
- Elm, Ulmus வகை

ஒருவித்திலைத் தாவரங்கள் (Liliopsida)[தொகு]

அகாவேசியே (அகாவே குடும்பம்)
- Cabbage palm, கோர்டிலைன் அவுஸ்திரேலிஸ் (Cordyline australis)
- Dragon மரம், ட்றசீனா ட்றாக்கோ (Dracaena draco )
- Joshua மரம், Yucca brevifolia
அரெகேசியே (Palmae) (Palm குடும்பம்)
- கமுகு, அரெக்கா காட்டெச்சு
- தென்னை கோகோஸ் நியூசிபெ(f)ரா
- பேரீந்து Palm, Phoenix dactylifera
- Chusan Palm, Trachycarpus fortunei
போவாசியே (புல் குடும்பம்)
- மூங்கில்கள் Poaceae subfamily Bambusoideae
வாழைகள், மரத்தன்மையற்றதாலும், பல்லாண்டுத் தாவரமல்லாததாலும், உண்மையில் மரங்களல்ல என்பதைக் கவனிக்கவும்.

ஊசியிலை மரங்கள்[தொகு]

கலிபோர்னியா செம்மரம், உலகின் அதி உயரமான மர வகை; ஒரு ஊசியிலை மரம்

Araucariaceae (Araucaria குடும்பம்)
- Araucaria, அரொகேரியா வகை
- Kauri, அகாதிஸ் வகை
குப்பிரசாசியே (சைப்பிரஸ் குடும்பம்)
- சைப்பிரஸ், குப்பிரசெஸ் வகை
- சைப்பிரஸ், Chamaecyparis வகை
- Juniper, Juniperus வகை
- Alerce or Patagonian cypress, Fitzroya cupressoides
- Sugi, Cryptomeria japonica
- கலிபோர்னியா செம்மரம், Sequoia sempervirens
- Giant sequoia, Sequoiadendron giganteum
- Dawn redwood, Metasequoia glyptostroboides
- Bald சைப்பிரஸ், Taxodium distichum
பைனாசியே (பைன் குடும்பம்)
- வெண் பைன், பைனஸ் வகை
- Pinyon பைன், பைனஸ் வகை
- பைன், பைனஸ் வகை
- Spruce, பீசியா வகை
- Larch, லாரிக்ஸ் வகை
- டக்லஸ்-பே(f)ர், Pseudotsuga வகை
- பே(f)ர், Abies வகை
- செடார், Cedrus வகை
Podocarpaceae (Yellow-wood குடும்பம்)
- African yellow-wood, Afrocarpus falcatus
- Totara, Podocarpus totara
Taxaceae (Yew குடும்பம்)
- Yew, Taxus வகை

Ginkgos[தொகு]

Ginkgoaceae (Ginkgo குடும்பம்)
- Ginkgo, Ginkgo biloba

சைக்கட்டுகள் (வித்துமூடியிலித் தாவரங்கள்)[தொகு]

சைக்கடேசியே குடும்பம்
- Ngathu சைக்காட், சைக்கஸ் ஆங்கிலாட்டா (Cycas angulata)
Zamiaceae குடும்பம்
- Wunu cycad, Lepidozamia hopei

பன்னங்கள் (Fern)[தொகு]

Cyatheaceae and Dicksoniaceae families
- மரப் பன்னங்கள், Cyathea, Alsophila, Dicksonia (ஒரு monophyletic கூட்டமல்ல)

வாழ்வுக் கட்டங்கள்[தொகு]

மரங்களின், விசேடமாக ஊசியிலை மரங்களின், வாழ்க்கை வட்டம், காடு வளர்ப்புத் துறையில், கணக்கெடுப்பு மற்றும் ஆவணப்படுத்தும் நோக்கங்களுக்காக பின்வரும் கட்டங்களாகப் பிரிக்கப்படுகின்றது:

விதை
நாற்று: விதையிலிருந்து முளைத்துவரும், முளையத்தின் நிலத்துக்கு மேலுள்ள பகுதி.
Sapling: முளையம் வளர்ந்து 1மீ உயரத்திலிருந்து அதன் தண்டு 7 சமீ விட்டமுள்ளதாக ஆகும் வரையுள்ள கட்டம்.
Pole: 7 தொடக்கம் 30 சமீ விட்டமுள்ள இளம் மரங்கள்.
முதிர்ந்த மரம்: 30 சமீ க்கு மேற்பட்ட விட்டம், இனப்பெருக்கக் காலத்தின் தொடக்கம்.
முதிய மரம்: பழைய வளர்ச்சிக் காடுகளில் அதிகம்; உயர வளர்ச்சி பெருமளவு குறைந்துவிடும், அதிகரித்த விதை உற்பத்தி.
அளவுமீறிய முதிர்ச்சி: dieback மற்றும் பழுதடைதல் சாதாரணம்.
Snag: நிற்கும் இறந்த மரங்கள்
மரக்குற்றி/கழிவு: விழுந்த மரக்குற்றிகள்

மரத்தின் விட்டம், அதன் அடியில், நிலத்தின் அதியுயர்ந்த புள்ளியிலிருந்து 1.3 – 1.5 மீட்டர் உயரத்தில் அளக்கப்படுகின்றது. 7 சமீ விட்ட வரையறை பொருளாதார ரீதியிலானது. இதுவே கடதாசி உற்பத்தி போன்றவற்றுக்காக விற்கப்படக்கூடிய அதி குறைந்த விட்டமாகும். 30 சமீ விட்டமே அரியப்படும் மரங்களுக்கான ஆகக்குறைந்த விட்டம். ஒவ்வொரு கட்டமும் may be uniquely perceptive to different pathogens and suitable for especially adapted arboreal animals.

பண்பாடு[தொகு]

மரங்கள் வழக்கமாக பழங்கதைகளிலும், சமயத்திலும் முக்கிய குறியீடுகளாக இருந்துவருகின்றன. உதாரணமாக நோர்ஸ் பழங்கதைகளில்Yggdrasil, ஜெர்மானிக் பழங்கதைகளிலிருந்து பெறப்பட்ட நத்தார் மரம், யூதாயிசத்தினதும், கிறிஸ்துவத்தினதும் அறிவு மரம், பௌத்தத்தின் போதி மரம் மற்றும் இந்துப் பழங்கதைகள் கூறும் கற்பகதரு என்பவற்றைக் கூறலாம்.

பின்வருவனவற்றையும் பார்க்கவும்[தொகு]

பகுப்புகள்:

Plant

From Wikipedia, the free encyclopedia

(Redirected from Plants)

For other uses, see Plant (disambiguation).

For an explanation of similar terms, see Viridiplantae.

Plants Temporal range: Mesoproterozoic–present Had'n Archean Proterozoic Pha.

Scientific classification
Domain:	Eukaryota
(unranked):	Archaeplastida
Kingdom:	Plantae sensu Copeland, 1956
Divisions
†Nematophytes Chlorophyta Palmophyllales Prasinophyceae Nephroselmidophyceae Pseudoscourfieldiales Pyramimonadophyceae Mamiellophyceae Scourfieldiales Pedinophyceae Chlorodendrophyceae Trebouxiophyceae Ulvophyceae Chlorophyceae Streptophyta s.l. Chlorokybophyta Mesostigmatophyta Klebsormidiophyta Charophyta (stoneworts) Chaetosphaeridiales Coleochaetophyta Zygnematophyta Embryophyta (land plants)
Synonyms
Viridiplantae Cavalier-Smith 1981^[1] Chlorobionta Jeffrey 1982, emend. Bremer 1985, emend. Lewis and McCourt 2004^[2] Chlorobiota Kenrick and Crane 1997^[3] Chloroplastida Adl et al., 2005 ^[4] Phyta Barkley 1939 emed. Holt & Uidica 2007 Cormophyta Endlicher, 1836 Cormobionta Rothmaler, 1948 Euplanta Barkley, 1949 Telomobionta Takhtajan, 1964 Embryobionta Cronquist et al., 1966 Metaphyta Whittaker, 1969

Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae.

The term is today generally limited to the green plants, which form an unranked clade Viridiplantae (Latin for "green plants"). This includes the flowering plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae, and excludes the red and brown algae. Historically, plants formed one of two kingdoms covering all living things that weren't animals, and both algae and fungi were treated as plants; however all current definitions of "plant" exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria).

Green plants have cell walls with cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts, derived from endosymbiosis with cyanobacteria. Their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is also common.

There are about 300–315 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants (see the table below).^[5] Green plants provide most of the world's molecular oxygen^[6] and are the basis of most of Earth's ecologies, especially on land. Plants that produce grains, fruits and vegetables form humankind's basic foodstuffs, and have been domesticated for millennia. Plants play many roles in culture. They are used as ornaments and, until recently and in great variety, they have served as the source of most medicines and drugs. The scientific study of plants is known as botany, a branch of biology.

[show]

Definition

Plants are one of the two groups into which all living things were traditionally divided; the other is animals. The division goes back at least as far as Aristotle (384 BC – 322 BC), who distinguished between plants, which generally do not move, and animals, which often are mobile to catch their food. Much later, when Linnaeus (1707–1778) created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia (later Metaphyta or Plantae) and Animalia (also called Metazoa). Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these organisms are still often considered plants, particularly in popular contexts.

Outside of formal scientific contexts, the term "plant" implies an association with certain traits, such as being multicellular, possessing cellulose, and having the ability to carry out photosynthesis.^[7]^[8]

Current definitions of Plantae

When the name Plantae or plant is applied to a specific group of organisms or taxon, it usually refers to one of four concepts. From least to most inclusive, these four groupings are:

Name(s)	Scope	Description
Land plants, also known as Embryophyta	Plantae sensu strictissimo	"Plants in the strictest sense". This group includes the liverworts, hornworts, mosses, and vascular plants, as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969,^[9]Plantae Margulis, 1971^[10]).
Green plants, also known as Viridiplantae, Viridiphyta or Chlorobionta	Plantae sensu stricto	"Plants in a strict sense". This group includes the green algae, and land plants that emerged within them, including stoneworts. The names given to these groups vary considerably as of July 2011. Viridiplantae encompass a group of organisms that have cellulose in their cell walls, possess chlorophylls a and b and have plastids that are bound by only two membranes that are capable of storing starch. It is this clade that is mainly the subject of this article (e.g., Plantae Copeland, 1956^[11]).
Archaeplastida, also known as Plastida or Primoplantae	Plantae sensu lato	"Plants in a broad sense". This group comprises the green plants above plus Rhodophyta (red algae) and Glaucophyta (glaucophyte algae). This clade includes the organisms that eons ago acquired their chloroplasts directly by engulfing cyanobacteria (e.g., Plantae Cavalier-Smith, 1981^[12]).
Old definitions of plant (obsolete)	Plantae sensu amplo	"Plants in an ample sense". Old classifications, now obsolete, placed diverse algae, fungi or bacteria in Plantae (e.g., Plantae or Vegetabilia Linnaeus,^[13] Plantae Haeckel 1866,^[14] Metaphyta Haeckel, 1894,^[15] Plantae Whittaker, 1969^[9]).

Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships. The evolutionary history of plants is not yet completely settled, but one accepted relationship between the three groups described above is shown below.^[16]^[17]^[18]^[19] Those which have been called "plants" are in bold.

Archaeplastida

Glaucophyta (glaucophyte algae)

Rhodophyta (red algae)

Green plants

Chlorophyta (part of green algae)

Streptophyta

streptophyte algae (part of green algae)

	Charales (stoneworts, often included in green algae)

	land plants or embryophytes

groups traditionally

included in the "algae"

The way in which the groups of green algae are combined and named varies considerably between authors.

Algae

Green algae from Ernst Haeckel's Kunstformen der Natur, 1904.

Main article: Algae

Algae comprise several different groups of organisms which produce energy through photosynthesis and for that reason have been included in the plant kingdom in the past. Most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown, red and green algae. Each of these algal groups also includes various microscopic and single-celled organisms. There is good evidence that some of these algal groups arose independently from separate non-photosynthetic ancestors, with the result that many groups of algae are no longer classified within the plant kingdom as it is defined here.^[20]^[21]

The Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions among green algae, the green plants have the following features in common; cell walls containing cellulose, chloroplasts containing chlorophylls a and b, and food stores in the form of starch contained within plastids. They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria.

Two additional groups, the Rhodophyta (red algae) and Glaucophyta (glaucophyte algae), also have chloroplasts which appear to be derived directly from endosymbiotic cyanobacteria, although they differ in the pigments which are used in photosynthesis and so are different in colour. All three groups together are generally believed to have a single common origin, and so are classified together in the taxon Archaeplastida, whose name implies that the chloroplasts or plastids of all the members of the taxon were derived from a single ancient endosymbiotic event. This is the broadest modern definition of the plants.

In contrast, most other algae (e.g. brown algae/diatoms, haptophytes, dinoflagellates, and euglenids) not only have different pigments but also have chloroplasts with three or four surrounding membranes. They are not close relatives of the Archaeplastida, presumably having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in even the broadest modern definition of the plant kingdom, although they were in the past.

The green plants or Viridiplantae were traditionally divided into the green algae (including the stoneworts) and the land plants. However, it is now known that the land plants evolved from within a group of green algae, so that the green algae by themselves are a paraphyletic group, i.e. a group that excludes some of the descendants of a common ancestor. Paraphyletic groups are generally avoided in modern classifications, so that in recent treatments the Viridiplantae have been divided into two clades, the Chlorophyta and the Streptophyta (or Charophyta).^[22]^[23]

The Chlorophyta (a name that has also been used for all green algae) are the sister group to the group from which the land plants evolved. There are about 4,300 species^[24] of mainly marine organisms, both unicellular and multicellular. The latter include the sea lettuce, Ulva.

The other group within the Viridiplantae are the mainly freshwater or terrestrial Streptophyta, which consists of the land plants together with the Charophyta, itself consisting of several groups of green algae such as the desmids and stoneworts. (The names have been used differently, e.g. Streptophyta to mean the group that excludes the land plants and Charophyta for the stoneworts alone or the stoneworts plus the land plants.)^{[citation
needed]} Streptophyte algae are either unicellular or form multicellular filaments, branched or unbranched.^[23] The genus Spirogyra is a filamentous streptophyte alga familiar to many, as it is often used in teaching and is one of the organisms responsible for the algal "scum" that pond-owners so dislike. The freshwater stoneworts strongly resemble land plants and are believed to be their closest relatives. Growing underwater, they consist of a central stalk with whorls of branchlets, giving them a superficial resemblance to horsetails, species of the genus Equisetum, which are true land plants.

Fungi

Main article: Fungi

The classification of fungi has been controversial until quite recently in the history of biology. Linnaeus' original classification placed the fungi within the Plantae, since they were unquestionably not animals or minerals and these were the only other alternatives. With later developments in microbiology, in the 19th century Ernst Haeckel felt that another kingdom was required to classify newly discovered micro-organisms. The introduction of the new kingdom Protista in addition to Plantae and Animalia, led to uncertainty as to whether fungi truly were best placed in the Plantae or whether they ought to be reclassified as protists. Haeckel himself found it difficult to decide and it was not until 1969 that a solution was found whereby Robert Whittaker proposed the creation of the kingdom Fungi. Molecular evidence has since shown that the most recent common ancestor (concestor), of the Fungi was probably more similar to that of the Animalia than to that of Plantae or any other kingdom.^[25]

Whittaker's original reclassification was based on the fundamental difference in nutrition between the Fungi and the Plantae. Unlike plants, which generally gain carbon through photosynthesis, and so are called autotrophs, fungi generally obtain carbon by breaking down and absorbing surrounding materials, and so are called heterotrophic saprotrophs. In addition, the substructure of multicellular fungi is different from that of plants, taking the form of many chitinous microscopic strands called hyphae, which may be further subdivided into cells or may form a syncytium containing many eukaryotic nuclei. Fruiting bodies, of which mushrooms are the most familiar example, are the reproductive structures of fungi, and are unlike any structures produced by plants.

Diversity

The table below shows some species count estimates of different green plant (Viridiplantae) divisions. It suggests there are about 300,000 species of living Viridiplantae, of which 85–90% are flowering plants. (Note: as these are from different sources and different dates, they are not necessarily comparable, and like all species counts, are subject to a degree of uncertainty in some cases.)

Diversity of living green plant (Viridiplantae) divisions

Informal group	Division name	Common name	No. of living species	Approximate No. in informal group
Green algae	Chlorophyta	green algae (chlorophytes)	3,800–4,300 ^[26]^[27]	8,500 (6,600–10,300)
Green algae	Charophyta	green algae (e.g. desmids & stoneworts)	2,800–6,000 ^[28]^[29]	8,500 (6,600–10,300)
Bryophytes	Marchantiophyta	liverworts	6,000–8,000 ^[30]	19,000 (18,100–20,200)
	Anthocerotophyta	hornworts	100–200 ^[31]
	Bryophyta	mosses	12,000 ^[32]
Pteridophytes	Lycopodiophyta	club mosses	1,200 ^[21]	12,000 (12,200)
Pteridophytes	Pteridophyta	ferns, whisk ferns & horsetails	11,000 ^[21]	12,000 (12,200)
Seed plants	Cycadophyta	cycads	160 ^[33]	260,000 (259,511)
	Ginkgophyta	ginkgo	1 ^[34]
	Pinophyta	conifers	630 ^[21]
	Gnetophyta	gnetophytes	70 ^[21]
	Magnoliophyta	flowering plants	258,650 ^[35]

The naming of plants is governed by the International Code of Nomenclature for algae, fungi, and plants and International Code of Nomenclature for Cultivated Plants (see cultivated plant taxonomy).

Evolution

Further information: Evolutionary history of plants

The evolution of plants has resulted in increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns to the complex gymnosperms and angiosperms of today. Plants in all of these groups continue to thrive, especially in the environments in which they evolved.

An algal scum formed on the land 1,200 million years ago, but it was not until the Ordovician Period, around 450 million years ago, that land plants appeared.^[36] However, new evidence from the study of carbon isotope ratios in Precambrian rocks has suggested that complex photosynthetic plants developed on the earth over 1000 m.y.a.^[37] For more than a century it has been assumed that the ancestors of land plants evolved in aquatic environments and then adapted to a life on land, an idea usually credited to botanist Frederick Orpen Bower in his 1908 book "The Origin of a Land Flora". A more recent alternative view, supported by genetic evidence, is that they evolved from single-celled algae that were already terrestrial.^[38] Primitive land plants began to diversify in the late Silurian Period, around 420 million years ago, and the fruits of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage from the Rhynie chert. This chert preserved early plants in cellular detail, petrified in volcanic springs. By the middle of the Devonian Period most of the features recognised in plants today are present, including roots, leaves and secondary wood, and by late Devonian times seeds had evolved.^[39] Late Devonian plants had thereby reached a degree of sophistication that allowed them to form forests of tall trees. Evolutionary innovation continued after the Devonian period. Most plant groups were relatively unscathed by the Permo-Triassic extinction event, although the structures of communities changed. This may have set the scene for the evolution of flowering plants in the Triassic (~200 million years ago), which exploded in the Cretaceous and Tertiary. The latest major group of plants to evolve were the grasses, which became important in the mid Tertiary, from around 40 million years ago. The grasses, as well as many other groups, evolved new mechanisms of metabolism to survive the low CO₂ and warm, dry conditions of the tropics over the last 10 million years.

A 1997 proposed phylogenetic tree of Plantae, after Kenrick and Crane,^[40] is as follows, with modification to the Pteridophyta from Smith et al.^[41] The Prasinophyceae are a paraphyletic assemblage of early diverging green algal lineages, but are treated as a group outside the Chlorophyta:^[42] later authors have not followed this suggestion.

Prasinophyceae (micromonads)

Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes

Eutracheophytes

Euphyllophytina

Lignophyta

	Spermatophytes (seed plants)

	Progymnospermophyta †

Pteridophyta

	Pteridopsida (true ferns)

	Marattiopsida

	Equisetopsida (horsetails)

	Psilotopsida (whisk ferns & adders'-tongues)

	Cladoxylopsida †

Lycophytina

	Lycopodiophyta

	Zosterophyllophyta †

Rhyniophyta †

Aglaophyton †

Horneophytopsida †

Bryophyta (mosses)

Anthocerotophyta (hornworts)

Marchantiophyta (liverworts)

Charophyta

Chlorophyta

	Trebouxiophyceae (Pleurastrophyceae)

	Chlorophyceae

Ulvophyceae

A newer proposed classification follows Leliaert et al. 2011^[43] and modified with Silar 2016^[44] for the green algae clades and Novíkov & Barabaš-Krasni 2015^[45] for the land plants clade. Notice that the Prasinophyceae are here placed inside the Chlorophyta.

Chlorophyta

?Palmophyllales Zechman et al. 2010

Prasinophyceae Christensen 1962 s.s.

Nephroselmidophyceae Cavalier-Smith 1993

Pseudoscourfieldiales Melkonian 1990 [Pycnococcales]

	Mamiellophyceae Marin & Melkonian 2010

	Pyramimonadophyceae

Picocystis Lewin 2001

Tetraphytina

?Scourfieldiales Moestrup 1991

Pedinophyceae Moestrup 1991

Chlorophytina

Chlorodendrophyceae Massjuk 2006

Trebouxiophyceae Friedl 1995

	Ulvophyceae Mattox & Stewart 1984

	Chlorophyceae Christensen 1994

Streptophyta s.l.

?Chlorokybophyta

Mesostigmatophyta

Klebsormidiophyta

Phragmoplastophyta

Charophyta Rabenhorst 1863 emend. Lewis & McCourt 2004 (Stoneworts)

Chaetosphaeridiales Marin & Melkonian 1999

Coleochaetophyta

Zygnematophyta

Embryophyta

Marchantiophyta (Liverworts)

Stomatophyta

Bryophyta (True mosses)

Anthocerotophyta (Non-flowering hornworts)

Polysporangiophyta

Horneophyta

	Lyonophyta

	Tracheophyta (Vascular Plants)

Green algae

Embryophytes

Main article: Embryophyte

Dicksonia antarctica, a species of tree fern

The plants that are likely most familiar to us are the multicellular land plants, called embryophytes. Embryophytes include the vascular plants, such as ferns, conifers and flowering plants. They also include the bryophytes, of which mosses and liverworts are the most common.

All of these plants have eukaryotic cells with cell walls composed of cellulose, and most obtain their energy through photosynthesis, using light, water and carbon dioxide to synthesize food. About three hundred plant species do not photosynthesize but are parasites on other species of photosynthetic plants. Embryophytes are distinguished from green algae, which represent a mode of photosynthetic life similar to the kind modern plants are believed to have evolved from, by having specialized reproductive organs protected by non-reproductive tissues.

Bryophytes first appeared during the early Paleozoic. They can only survive where moisture is available for significant periods, although some species are desiccation-tolerant. Most species of bryophytes remain small throughout their life-cycle. This involves an alternation between two generations: a haploid stage, called the gametophyte, and a diploid stage, called the sporophyte. In bryophytes, the sporophyte is always unbranched and remains nutritionally dependent on its parent gametophyte. The bryophytes have the ability to secrete a cuticle on their outer surface, a waxy layer that confers resistant to desiccation. In the mosses and hornworts a cuticle is usually only produced on the sporophyte. Stomata are absent from liverworts, but occur on the sporangia of mosses and hornworts, allowing gas exchange while controlling water loss.

Vascular plants first appeared during the Silurian period, and by the Devonian had diversified and spread into many different terrestrial environments. They developed a number of adaptations that allowed them to spread into increasingly more arid places, notably the vascular tissues xylem and phloem, that transport water and food throughout the organism. Root systems capable of obtaining soil water and nutrients also evolved during the Devonian. In modern vascular plants, the sporophyte is typically large, branched, nutritionally independent and long-lived, but there is increasing evidence that Paleozoic gametophytes were just as complex as the sporophytes. The gametophytes of all vascular plant groups evolved to become reduced in size and prominence in the life cycle.

The first seed plants, Pteridosperms (seed ferns), now extinct, appeared in the Devonian and diversified through the Carboniferous. In these the microgametophyte is reduced to pollen and the megagametophyte remains inside the megasporangium, attached to the parent plant. A megasporangium invested in protective layer called an integument is known as an ovule. After fertilisation by means of sperm deposited by pollen grains, an embryo develops inside the ovule. The integument becomes a seed coat, and the ovule develops into a seed. Seed plants can survive and reproduce in extremely arid conditions, because they are not dependent on free water for the movement of sperm, or the development of free living gametophytes.

Early seed plants are gymnosperms, as the ovules and subsequent seeds are not enclosed in a protective structure (carpels or fruit), but are found naked, typically on cone scales. Pollen typically lands directly on the ovule. Four surviving groups remain widespread now, particularly the conifers, which are dominant trees in several biomes.

Fossils

Main articles: Paleobotany and Evolutionary history of plants

A petrified log in Petrified Forest National Park, Arizona

Plant fossils include roots, wood, leaves, seeds, fruit, pollen, spores, phytoliths, and amber (the fossilized resin produced by some plants). Fossil land plants are recorded in terrestrial, lacustrine, fluvial and nearshore marine sediments. Pollen, spores and algae (dinoflagellates and acritarchs) are used for dating sedimentary rock sequences. The remains of fossil plants are not as common as fossil animals, although plant fossils are locally abundant in many regions worldwide.

The earliest fossils clearly assignable to Kingdom Plantae are fossil green algae from the Cambrian. These fossils resemble calcified multicellular members of the Dasycladales. Earlier Precambrian fossils are known that resemble single-cell green algae, but definitive identity with that group of algae is uncertain.

The oldest known fossils of embryophytes date from the Ordovician, though such fossils are fragmentary. By the Silurian, fossils of whole plants are preserved, including the lycophyte Baragwanathia longifolia. From the Devonian, detailed fossils of rhyniophytes have been found. Early fossils of these ancient plants show the individual cells within the plant tissue. The Devonian period also saw the evolution of what many believe to be the first modern tree, Archaeopteris. This fern-like tree combined a woody trunk with the fronds of a fern, but produced no seeds.

The Coal measures are a major source of Paleozoic plant fossils, with many groups of plants in existence at this time. The spoil heaps of coal mines are the best places to collect; coal itself is the remains of fossilised plants, though structural detail of the plant fossils is rarely visible in coal. In the Fossil Grove at Victoria Park in Glasgow, Scotland, the stumps of Lepidodendron trees are found in their original growth positions.

The fossilized remains of conifer and angiosperm roots, stems and branches may be locally abundant in lake and inshore sedimentary rocks from the Mesozoic and Cenozoic eras. Sequoia and its allies, magnolia, oak, and palms are often found.

Petrified wood is common in some parts of the world, and is most frequently found in arid or desert areas where it is more readily exposed by erosion. Petrified wood is often heavily silicified (the organic material replaced by silicon dioxide), and the impregnated tissue is often preserved in fine detail. Such specimens may be cut and polished using lapidary equipment. Fossil forests of petrified wood have been found in all continents.

Fossils of seed ferns such as Glossopteris are widely distributed throughout several continents of the Southern Hemisphere, a fact that gave support to Alfred Wegener's early ideas regarding Continental drift theory.

The earliest fossils attributed to green algae date from the Precambrian (ca. 1200 mya).^[46]^[47] The resistant outer walls of prasinophyte cysts (known as phycomata) are well preserved in fossil deposits of the Paleozoic (ca. 250-540 mya). A filamentous fossil (Proterocladus) from middle Neoproterozoic deposits (ca. 750 mya) has been attributed to the Cladophorales, while the oldest reliable records of the Bryopsidales, Dasycladales) and stoneworts are from the Paleozoic.^[42]^[48]

Structure, growth and development

Further information: Plant morphology

The leaf is usually the primary site of photosynthesis in plants.

Most of the solid material in a plant is taken from the atmosphere. Through a process known as photosynthesis, most plants use the energy in sunlight to convert carbon dioxide from the atmosphere, plus water, into simple sugars. (Parasitic plants, on the other hand, use the resources of its host to grow.) These sugars are then used as building blocks and form the main structural component of the plant. Chlorophyll, a green-colored, magnesium-containing pigment is essential to this process; it is generally present in plant leaves, and often in other plant parts as well.

Plants usually rely on soil primarily for support and water (in quantitative terms), but also obtain compounds of nitrogen, phosphorus, potassium, magnesium and other elemental nutrients. Epiphytic and lithophytic plants depend on air and nearby debris for nutrients, and carnivorous plants supplement their nutrient requirements with insect prey that they capture. For the majority of plants to grow successfully they also require oxygen in the atmosphere and around their roots (soil gas) for respiration. Plants use oxygen and glucose (which may be produced from stored starch) to provide energy.^[49] Some plants grow as submerged aquatics, using oxygen dissolved in the surrounding water, and a few specialized vascular plants, such as mangroves, can grow with their roots in anoxic conditions.

Factors affecting growth

The genotype of a plant affects its growth. For example, selected varieties of wheat grow rapidly, maturing within 110 days, whereas others, in the same environmental conditions, grow more slowly and mature within 155 days.^[50]

Growth is also determined by environmental factors, such as temperature, available water, available light, carbon dioxide and available nutrients in the soil. Any change in the availability of these external conditions will be reflected in the plant's growth.

Biotic factors are also capable of affecting plant growth. Plants compete with other plants for space, water, light and nutrients. Plants can be so crowded that no single individual produces normal growth, causing etiolation and chlorosis. Optimal plant growth can be hampered by grazing animals, suboptimal soil composition, lack of mycorrhizal fungi, and attacks by insects or plant diseases, including those caused by bacteria, fungi, viruses, and nematodes.^[50]

There is no photosynthesis in deciduous leaves in autumn.

Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Other plants may be organized according to their seasonal growth pattern: annual plants live and reproduce within one growing season, biennial plants live for two growing seasons and usually reproduce in second year, and perennial plants live for many growing seasons and continue to reproduce once they are mature. These designations often depend on climate and other environmental factors; plants that are annual in alpine or temperate regions can be biennial or perennial in warmer climates. Among the vascular plants, perennials include both evergreens that keep their leaves the entire year, and deciduous plants that lose their leaves for some part of it. In temperate and boreal climates, they generally lose their leaves during the winter; many tropical plants lose their leaves during the dry season.

The growth rate of plants is extremely variable. Some mosses grow less than 0.001 millimeters per hour (mm/h), while most trees grow 0.025-0.250 mm/h. Some climbing species, such as kudzu, which do not need to produce thick supportive tissue, may grow up to 12.5 mm/h.

Plants protect themselves from frost and dehydration stress with antifreeze proteins, heat-shock proteins and sugars (sucrose is common). LEA (Late Embryogenesis Abundant) protein expression is induced by stresses and protects other proteins from aggregation as a result of desiccation and freezing.^[51]

Effects of freezing

When water freezes in plants, the consequences for the plant depend very much on whether the freezing occurs within cells (intracellularly) or outside cells in intercellular spaces (Glerum 1985).^[52] Intracellular freezing, which usually kills the cell (Lyons et al. 1979)^[53] regardless of the hardiness of the plant and its tissues, seldom occurs in nature because rates of cooling are rarely high enough to support it. Rates of cooling of several degrees Celsius per minute are typically needed to cause intracellular formation of ice (Mazur 1977).^[54]

At rates of cooling of a few degrees Celsius per hour, segregation of ice occurs in intercellular spaces, the “extraorgan ice” of Sakai and Larcher (1987)^[55] and their coworkers. This may or may not be lethal, depending on the hardiness of the tissue.

The process of intercellular ice formation was described by Glerum (1985).^[52] At freezing temperatures, water in the intercellular spaces of plant tissue freezes first, though the water may remain unfrozen until temperatures drop below −7 °C (19 °F). After the initial formation of ice intercellularly, the cells shrink as water is lost to the segregated ice, and the cells undergo freeze-drying. This dehydration is now considered the fundamental cause of freezing injury.

Plant cell

Plant cell structure

Main article: Plant cell

Plant cells are typically distinguished by their large water-filled central vacuole, chloroplasts, and rigid cell walls that are made up of cellulose, hemicellulose, and pectin. Cell division is also characterized by the development of a phragmoplast for the construction of a cell plate in the late stages of cytokinesis. Just as in animals, plant cells differentiate and develop into multiple cell types. Totipotent meristematic cells can differentiate into vascular, storage, protective (e.g. epidermal layer), or reproductive tissues, with more primitive plants lacking some tissue types.^[56]

Physiology

Main article: Plant physiology

Photosynthesis

Main articles: Photosynthesis and Biological pigment

Plants are photosynthetic, which means that they manufacture their own food molecules using energy obtained from light. The primary mechanism plants have for capturing light energy is the pigment chlorophyll. All green plants contain two forms of chlorophyll, chlorophyll a and chlorophyll b. The latter of these pigments is not found in red or brown algae. The simple equation of photosynthesis is as follows:-

6CO₂ + 6H₂O → (in the presence of light and chlorophyll) C₆H₁₂O₆ + 6O₂

Immune system

By means of cells that behave like nerves, plants receive and distribute within their systems information about incident light intensity and quality. Incident light that stimulates a chemical reaction in one leaf, will cause a chain reaction of signals to the entire plant via a type of cell termed a bundle sheath cell. Researchers, from the Warsaw University of Life Sciences in Poland, found that plants have a specific memory for varying light conditions, which prepares their immune systems against seasonal pathogens.^[57] Plants use pattern-recognition receptors to recognize conserved microbial signatures. This recognition triggers an immune response. The first plant receptors of conserved microbial signatures were identified in rice (XA21, 1995)^[58] and in Arabidopsis thaliana (FLS2, 2000).^[59] Plants also carry immune receptors that recognize highly variable pathogen effectors. These include the NBS-LRR class of proteins.

Internal distribution

Main article: Vascular tissue

Vascular plants differ from other plants in that nutrients are transported between their different parts through specialized structures, called xylem and phloem. They also have roots for taking up water and minerals. The xylem moves water and minerals from the root to the rest of the plant, and the phloem provides the roots with sugars and other nutrient produced by the leaves.^[56]

Ecology

Main article: Plant ecology

The photosynthesis conducted by land plants and algae is the ultimate source of energy and organic material in nearly all ecosystems. Photosynthesis radically changed the composition of the early Earth's atmosphere, which as a result is now 21% oxygen. Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively rare anaerobic environments. Plants are the primary producers in most terrestrial ecosystems and form the basis of the food web in those ecosystems. Many animals rely on plants for shelter as well as oxygen and food.

Land plants are key components of the water cycle and several other biogeochemical cycles. Some plants have coevolved with nitrogen fixing bacteria, making plants an important part of the nitrogen cycle. Plant roots play an essential role in soil development and prevention of soil erosion.

Distribution

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Plants are distributed worldwide in varying numbers. While they inhabit a multitude of biomes and ecoregions, few can be found beyond the tundras at the northernmost regions of continental shelves. At the southern extremes, plants have adapted tenaciously to the prevailing conditions. (See Antarctic flora.)

Plants are often the dominant physical and structural component of habitats where they occur. Many of the Earth's biomes are named for the type of vegetation because plants are the dominant organisms in those biomes, such as grasslands and forests.

Ecological relationships

The Venus flytrap, a species of carnivorous plant.

Numerous animals have coevolved with plants. Many animals pollinate flowers in exchange for food in the form of pollen or nectar. Many animals disperse seeds, often by eating fruit and passing the seeds in their feces. Myrmecophytes are plants that have coevolved with ants. The plant provides a home, and sometimes food, for the ants. In exchange, the ants defend the plant from herbivores and sometimes competing plants. Ant wastes provide organic fertilizer.

The majority of plant species have various kinds of fungi associated with their root systems in a kind of mutualistic symbiosis known as mycorrhiza. The fungi help the plants gain water and mineral nutrients from the soil, while the plant gives the fungi carbohydrates manufactured in photosynthesis. Some plants serve as homes for endophytic fungi that protect the plant from herbivores by producing toxins. The fungal endophyte, Neotyphodium coenophialum, in tall fescue (Festuca arundinacea) does tremendous economic damage to the cattle industry in the U.S.

Various forms of parasitism are also fairly common among plants, from the semi-parasitic mistletoe that merely takes some nutrients from its host, but still has photosynthetic leaves, to the fully parasitic broomrape and toothwort that acquire all their nutrients through connections to the roots of other plants, and so have no chlorophyll. Some plants, known as myco-heterotrophs, parasitize mycorrhizal fungi, and hence act as epiparasites on other plants.

Many plants are epiphytes, meaning they grow on other plants, usually trees, without parasitizing them. Epiphytes may indirectly harm their host plant by intercepting mineral nutrients and light that the host would otherwise receive. The weight of large numbers of epiphytes may break tree limbs. Hemiepiphytes like the strangler fig begin as epiphytes but eventually set their own roots and overpower and kill their host. Many orchids, bromeliads, ferns and mosses often grow as epiphytes. Bromeliad epiphytes accumulate water in leaf axils to form phytotelmata that may contain complex aquatic food webs.^[60]

Approximately 630 plants are carnivorous, such as the Venus Flytrap (Dionaea muscipula) and sundew (Drosera species). They trap small animals and digest them to obtain mineral nutrients, especially nitrogen and phosphorus.^[61]

Importance

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Main article: Plants in culture

The study of plant uses by people is termed economic botany or ethnobotany; some consider economic botany to focus on modern cultivated plants, while ethnobotany focuses on indigenous plants cultivated and used by native peoples. Human cultivation of plants is part of agriculture, which is the basis of human civilization. Plant agriculture is subdivided into agronomy, horticulture and forestry.

Foods and beverages

Mechanical harvest of oats.

Main article: Agriculture

Much of human nutrition depends on plants, either directly through foods and beverages consumed by people, or indirectly as feed for animals or the flavoring of foods. The science of agriculture deals with the planting, raising, nutrition, and harvest of food crops, and has played a key role in the history of world civilizations.

Human nutrition depends to a large extent on cereals, especially maize (or corn), wheat, rice, oats, and millet. Large areas of many countries are given over to the cultivation of cereals for local consumption or export to other countries. Livestock animals including cows, pigs, sheep, goats and camels are all herbivores; and most feed primarily or entirely on cereal plants. Cereals are staple crops, meaning that they provide calories (in the form of complex carbohydrates such as starch) that are needed to fuel daily activities, and thus form the foundation of a daily diet. Other staple crops include potatoes, cassava, yams, and legumes.

Human food also includes vegetables, which consist principally of leaves and stems eaten as food. Vegetables are important for the vitamins, minerals, and dietary fiber they supply. Fruits provide a higher quantity of sugars and have a sweeter taste than vegetables. However, whether a particular food is considered a "vegetable" or a "fruit" will depend on context, since the word fruit has a more precise definition in botany than it does in general use. Nuts and seeds, including foods such as peanuts, walnuts, almonds, and pistachios, contain unsaturated fats that are also necessary for a healthy diet. As with fruits, the terms nut and seed have stricter definitions in plant science.

Many plants are used to flavor foods. Such plants include herbs (e.g. rosemary and mint), which come from the green leafy parts of plants, and spices (e.g. cumin and cinnamon), which come from other plant parts. Some plants produce edible flowers, which may be added to salads or used to decorate foods. Sweeteners such as sugar and stevia are derived from plants. Sugar is obtained mainly from sugar cane and sugar beet, and honey is created when bees regurgitate the nectar from flowers. Cooking oils and margarine come from maize, soybean, rapeseed, safflower, sunflower, olive and others. Food additives include gum arabic, guar gum, locust bean gum, starch and pectin.

Plants are also the source of beverages produced either by infusion, such as coffee and tea; by fermentation, such as beer and wine; or by distillation, such as whisky, vodka, rum, and other alcoholic spirits.

Nonfood products

Timber in storage for later processing at a sawmill.

Plants are the source of many natural products such as essential oils, natural dyes, pigments, waxes, resins, tannins, alkaloids, amber and cork. Products derived from plants include soaps, shampoos, perfumes, cosmetics, paint, varnish, turpentine, rubber, latex, lubricants, linoleum, plastics, inks, and gums. Renewable fuels from plants include firewood, peat and many other biofuels. Coal and petroleum are fossil fuels derived from the remains of plants. Olive oil has been used in lamps for centuries to provide illumination.

Structural resources and fibers from plants are used in both the construction of dwellings and the manufacture of clothing. Wood is used not only for buildings, boats, and furniture, but also for smaller items such as musical instruments and sports equipment. Wood also may be pulped for the manufacture of paper and cardboard. Cloth is often made from cotton, flax, ramie or synthetic fibers derived from cellulose, such as rayon and acetate. The thread that is used to sew cloth likewise comes from plant fibers. Hemp and jute are grown for their fibers, which may be woven into rope or rough sacking.

Plants are also a primary source of basic chemicals, both for their medicinal and physiological effects, as well as for the industrial synthesis of a vast array of organic chemicals. Medicines derived from plants include aspirin, taxol, morphine, quinine, reserpine, colchicine, digitalis and vincristine. There are hundreds of herbal supplements such as ginkgo, Echinacea, feverfew, and Saint John's wort. Pesticides derived from plants include nicotine, rotenone, strychnine and pyrethrins. Certain plants contain psychotropic chemicals that are extracted and ingested, including tobacco, cannabis (marijuana), opium, and cocaine. Poisons from plants include ricin, hemlock and curare.

Aesthetic uses

A rose espalier at Niedernhall in Germany.

Capitals of ancient Egyptian columns decorated to resemble papyrus plants. (at Luxor, Egypt)

Thousands of plant species are cultivated for aesthetic purposes as well as to provide shade, modify temperatures, reduce wind, abate noise, provide privacy, and prevent soil erosion. Plants are the basis of a multibillion-dollar per year tourism industry, which includes travel to historic gardens, national parks, rainforests, forests with colorful autumn leaves, and the National Cherry Blossom Festival.

While some gardens are planted with food crops, many are planted for aesthetic, ornamental, or conservation purposes. Arboretums and botanical gardens are public collections of living plants. In private outdoor gardens, lawn grasses, shade trees, ornamental trees, shrubs, vines, herbaceous perennials and bedding plants are used. Gardens may cultivate the plants in a naturalistic state, or may sculpture their growth, as with topiary or espalier. Gardening is the most popular leisure activity in the U.S., and working with plants or horticulture therapy is beneficial for rehabilitating people with disabilities.

Plants may also be grown or kept indoors as houseplants, or in specialized buildings such as greenhouses that are designed for the care and cultivation of living plants. Venus Flytrap, sensitive plant and resurrection plant are examples of plants sold as novelties. There are also art forms specializing in the arrangement of cut or living plant, such as bonsai, ikebana, and the arrangement of cut or dried flowers. Ornamental plants have sometimes changed the course of history, as in tulipomania.

Architectural designs resembling plants appear in the capitals of ancient Egyptian columns, which were carved to resemble either the Egyptian white lotus or the papyrus. Images of plants are often used in painting and photography, as well as on textiles, money, stamps, flags and coats of arms.

Scientific and cultural uses

Barbara McClintock (1902–1992) was a pioneering cytogeneticist who used maize (or corn) to study the mechanism of inheritance of traits.

Basic biological research has often been done with plants. In genetics, the breeding of pea plants allowed Gregor Mendel to derive the basic laws governing inheritance, and examination of chromosomes in maize allowed Barbara McClintock to demonstrate their connection to inherited traits. The plant Arabidopsis thaliana is used in laboratories as a model organism to understand how genes control the growth and development of plant structures. Space stations or space colonies may one day rely on plants for life support.

Ancient trees are revered and many are famous. Tree rings themselves are an important method of dating in archeology, and serve as a record of past climates.

Plants figure prominently in mythology, religion and literature. They are used as national and state emblems, including state trees and state flowers. Plants are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. The arrangement of flowers may be used to send hidden messages.

The field of ethnobotany studies plant use by indigenous cultures, which helps to conserve endangered species as well as discover new medicinal plants.

Negative effects

Weeds are uncultivated and usually unwanted plants growing in managed environments such as farms, urban areas, gardens, lawns, and parks. People have spread plants beyond their native ranges and some of these introduced plants become invasive, damaging existing ecosystems by displacing native species. Invasive plants cause costly damage in crop losses annually by displacing crop plants, they further increase the cost of production and the use of chemicals to control them, which in turn affects the environment.

Plants may cause harm to animals, including people. Plants that produce windblown pollen invoke allergic reactions in people who suffer from hay fever. A wide variety of plants are poisonous. Toxalbumins are plant poisons fatal to most mammals and act as a serious deterrent to consumption. Several plants cause skin irritations when touched, such as poison ivy. Certain plants contain psychotropic chemicals, which are extracted and ingested or smoked, including tobacco, cannabis (marijuana), cocaine and opium. Smoking causes damage to health or even death, while some drugs may also be harmful or fatal to people.^[62]^[63] Both illegal and legal drugs derived from plants may have negative effects on the economy, affecting worker productivity and law enforcement costs.^[64]^[65] Some plants cause allergic reactions when ingested, while other plants cause food intolerances that negatively affect health.

මල්

විකිපීඩියා, නිදහස් විශ්වකෝෂය වෙතින්

ලොව සුවඳ විහිදවමින් ස්වාභාවිකවම හටගන්නා ඒ අපූර්වතම වස්තුව මලයි.

විවිධ කුලයන්ට අයත් පුෂ්ප එකතුවක්

මල් යනු ශාකයන්හි ලිංගික ප්‍රජනන අවයවයකි.ජීව විද්‍යාඥයන්ට අනුව මල්වල පුරුෂ හා ස්ත්‍රී ලිංගික කොටස් දක්නට ලැබේ,පුරුෂ කොටස ලෙස පරාගද ස්ත්‍රී කොටස ලෙස කලංකයද මල් තුල ප්‍රධාන වශයෙන් දක්නට ලැබේ.ස්ත්‍රී හා පුරුෂ කොටස් එක්වීම පරාගනය මගින් සිදුවේ.මෙම පරාගනය මගින් සිදුවන ලිංගික සංසේචනය මගින් නව පරපුරකට උපතදියහැකි බීජ නිපවීම සිදුවේ.මෙම පරාගනය ක්‍රම දෙකකට සිදුවේ ඒ ස්වපරාගනය හා පරපරාගනය වශයෙනි.

මීට අමතරව ශාක වල ප්‍රජනන අවයවය වූ මල් අලංකරණ කටයුතු සදහාද යොදා ගනී.මල් වල ඇති සුන්දරත්වය හා සුගන්දවත්බව එයට හේතුවයි.ඇතැම් මල් ආහාර ලෙසද යොදාගනී.

පටුන

[සඟවන්න]

මල් විශේෂීකරණය හා පරාගනය[සංස්කරණය කරන්න]

මල් සහිත ශාක එහි ඇති මල්වල පරාග පතුරුවාහැරීම සදහා විවිධ ක්‍රම යොදාගනී.මෙම ශාක සුළග මගින් ජලය මගින් මෙන්ම සතුන් මගින්ද පරාගනය සිදුකරයි.ඇතැම් ශාක මෙම ක්‍රමවලින් කිහිපයක්ම යොදා ගනී.

ඇතැම් ශාක ස්වපරාගනය සිදුකරයි .

ඇට්ටේරියා පුෂ්ප.රාත්‍රී කාලයේ පිපෙන ඉතා සුඟන්දවත් පුෂ්පවේ

සපුෂ්පික ශාක තම පරාගන ක්‍රියාවලිය පහසු කරගැනීම විවිධ සැකසුම් සහිතව සකස්වී ඇත.සතුන් මගින් පරාගනය සිදුවන ශාකවල සතුන් ආකර්ෂණය සදහා පරාගධානියට ආසන්නව මල්පැණි පිහිටා ඇත.මල්පැණි ලබාගැනීමට මලවෙත එන සතුන්ගේ සිරුරේ පරාග තැවරීම සිදුවන අතර තවත් මලක පැණි උරාබීමට යන විට කලින් ගෑවී තිබූ පරාග අදාල පුෂ්පයේ කලංකය මත පතිතවීමෙන් මලක පූමාංගී හෙවක් පුරුෂ සෛල හා කලංකයමත ඇති ජායාංගී හෙවත් ස්ත්‍රී සෛල සංසේචනයවීම සිදුවේ.මෙම සතුන් මගින් පරාගනය සිදුවන සපුෂ්පික ශාක සතු මල් ඉතා අලංකාර හා සුගන්දවත්ය.බොහෝවිට දිවා කාලයේ පිපෙන මල් විවිධ වර්ණ රටාවලින් අලංකාර වී ඇති අතර රාත්‍රියේ පිපෙන මල් සුදු පැහැති වන අතර ඉතා මිහිරි සුගන්දයක් විහිදුවයි.උදාහරණ ලෙස පිච්ච කඩුපුල් ඇට්ටේරියා ආදී පුෂ්ප දැක්විය හැක.දිවා කාලයේ පිපෙන මල් විචිත්‍ර වර්ණ සහිත අලංකාරව පිපී තිබීම නිසා මල්පැණි බීමට එන සතුන්ට පහසුවෙන් දැකගැනීමට හැකිවේ.රාත්‍රී කාලයේ පිපෙන මල් සුදු පැහැ වර්ණයෙන් යුක්ත වීමත් ඉතා මිහිරි සුවදක් විහිදීමත් නිසා නිශාචර සතුන්ට පහසුවෙන් ලංවීමට හැකිවේ.

පූමාංගී පුෂ්ප පමණක් ඇති පැපොල් වෘක්ෂයක මල්

ඇතැම් සපුෂ්පිත ශාක තම පරාගනය සිදු කරන්නේ සුළග මගිනි.මේ වර්ගයට තෘණ පවුලට අයත් ශාක,මුර්ජ ශාක,මේපල් ශාක තාල වර්ගයට අයත් ශාක ආදිය ගතහැක.මෙම වර්ගයට අයත් මල් එකවර විශාල සංඛාවක් හටගනී මෙවාහි පරාග ඉතා සැහැල්ලු වන අතර විශාල පරාග ප්‍රමාණයක් නිපදවයි.බොහෝවිට මෙම මල් ස්ත්‍රී හා පුරුෂ වශයෙන් වෙන්වෙන්ව පවතී.පුරුෂ කොටස් පමණක් ඇති පූමාංගී මල් ඉතා විශාල සංඛ්‍යාවක් වරෙකට නිපදවේ.පුරුෂ කොටස් පමණක් ඇති පූමාංගී මල් කුඩා වන අතර ස්ත්‍රී කොටස් පමණක් ඇති ජායාංගී පුෂ්ප තරමක් විශාලව වැඩේ.මෙම සුළග මගින් පරාගනය වන පුෂ්ප වල අලංකාර වර්ණවත් බවක් හෝ සුගන්දවත් බවක් නැත.

රූපාකරය[සංස්කරණය කරන්න]

සපුෂ්ක ශාක වල ප්‍රජනනය සිදුකෙරෙන බීජානු පරාග හා ඩිම්බ වශයෙන් වර්ග දෙකකට බෙදේ.ඒ අනුව ශාකයක ස්ත්‍රී හා පුරුෂ ප්‍රජනන කොටස් ද්විත්වයම ශාක පුෂ්පයක අන්තර්ගතය.කෙසේ වෙතත් ඇතම් ශාක වල පුෂ්ප තුල පුරුෂ කොටස් පමණක්ද තවත් කොටසක ස්ත්‍රී පුෂ්ප කොටසද දක්නට ලැබේ.උදාහරණ ලෙස වට්ටක්කා මලේ ස්ත්‍රී පුෂ්පය හෙවත් ජායාංගී පුෂ්පයත් පුරුෂ කොටස් ඇතුලත් පූමාංගී පුෂ්පත් වෙනවෙනම දක්නට ලැබේ.තවත් ශාකවල ජායාංගි පුෂ්ප එක් ශාකයකත් පූමාංගී පුෂ්ප තව ශාකයකත් වැඩේ.උදාහරණලෙස පැපොල් වෘක්ෂ වල මේආකාර විභේදනයක් දක්නට ලැබේ.

ශාක පුෂ්පයන්හි ව්‍යුහය මීලගට සලකා බලමු.

පුෂ්පයක ව්‍යුහය

An example of a "perfect flower", this Crateva religiosa flower has both stamens (outer ring) and a pistil (center).

මණිපත්‍රය මල් පෙති වලට පිටතින් ඇති කොළ පැහැති ආවරණය.
මුකූටය:මලේ පෙති වලට ඇතුල් පැත්තෙට වෙන්නට ඇති සිහින් සුමුදු දඩුවක ආකාරගත් අංගයකි.මෙහි අග පරාග තැන්පත්ව පවතී.මෙය මල් රේණු නමින්ද හදුන්වයි.මෙහි පාලජම්බුල කිරණවලට සංවේදී පෙදෙසක් පවතී.එමගින් මල් පැණි බීමට එන සංයුක්ත ඇස් ඇති සතුන්ට මල් පැණි ඇති පෙදෙට ගමන් කිරීමට පහසුවේ.(සංයුක්ත ඇස් ඇති සතුන්ට පාලජම්බුල කිරණ සංවේදීවේ).
පූමංගය මුකූටය අග ඇති පරාගධානියයි.මෙය තුල පරාග විශාල ප්‍රමාණයක් නිපදවෙයි.මෙය මලක පුරුෂ කොටසට අයත් ප්‍රධාන උපාංගයයි.
ජායාංගය මෙය පුෂ්පයක ප්‍රධාන ස්ත්‍රී ලිංගික කොටසයි.මෙයට කලංකය ඩිම්බ බිම්බ කෝෂය අයත්වේ.ඇතැම් පුෂ්පවල එක් ඩිම්බකෝෂයක්ය හා එක් ඩිම්බයක් පමණක් පවතී.තවත් පුෂ්පවල ඩිම්බ කෝෂය තුල ඩිම්බ කිහිපයක් දක්නට ලැබේ. .

මලක ව්‍යුහය පොදුවේ ඉහත පරිද් දැක්වුවද එකිනෙකට අසමාන විවිධ වෙනස්කම් මල්තුල දක්නට ලැබේ.මෙම වෙනස්කම් සදහා පරිණාමීය සාධක ප්‍රෙව්ණිගත සාධක පාරිසරික සාධක ආදිය බලපායි.එකම පවුලකට අයත් විශේෂයක වුවද විවිධ වෙනස්කම් දක්නට ලැබේ.

බොහෝ පුෂ්පයන්හි ජායාංගි හා පූමාංගි කොටස් දෙකම එකම පුෂ්පයක දක්නට ලැබේ.මෙවැනි පුෂ්ප ද්වීලිංගික පුෂ්ප යනුවෙන් හදුන්වයි.ඇතම් පුෂ්පවල ජායාංගී කොටස හා පූමාංගී කොටස වෙන වෙනම පිහිටා ඇත.මෙවැනි පුෂ්ප එ්ක ලිංගික පුෂ්ප යනුවෙන් හදුන්වයි.පූමංගී කොටස පමණක් ඇති පුෂ්ප පූමංගී පුෂ්ප ලෙසත් ජායාංගී කොටස් පමණක් ඇති පුෂ්ප ජායාංගී පුෂ්ප ලෙසත් හදුන්වයි.මෙවැනි පුෂ්පයන්ට උදාහරණ ලෙස වට්ටක්කා කරවිල වැටකොළු ආදී පුෂ්ප දැක්විය හැකිය.බොහෝවිට මෙම ජායාංගී හා පූමාංගී පුෂ්ප එකම ශාකයක වර්ධනය වෙයි.එවැනි ලක්ෂණ සහිත ශාක ඒකගෘහී ශාක යනුවෙන් හදුන්වයි.එහෙත් තවත් ශාකයන්හි ජායංගී පුෂ්පය එක ශාකයකත් තවත් ශාකයක පූමංගී පුෂ්ප ලෙසත් වෙන වෙනම වර්ධනයවේ.මෙවන් ශාක ද්වීගෘහි ශාක යනුවෙන් හදුන්වයි.

ඇන්තූරියම් මල

මල් වල හැඩය ප්‍රමාණය විශාලත්වය අනුව එකිනෙකින් වෙනස්වේ.විවිධ පුෂ්පවල මණි පත්‍රෙය් හැඩය හා ප්‍රමාණය ද වෙනස්ය.ඇතැම් පුෂ්පවල මණියට අමතරව උප මණියක්ද දක්නට ලැබේ.විවිධ පුෂ්පවල දල ප්‍රමාණය එකිනෙකට වෙනස්ය.ඇතැම් පුෂ්ප වලට ඇත්තේ එක් දලයක් පමණි.උදාහරණලෙස ඇන්තූරියම් පුෂ්පය දැක්විය හැක.තවත් මල්වල දල දෙකක් තුනක් ආදී වශයෙන්ද දක්වට ලැබේ බහුලව දක්නට ලැබෙන්නේ දල හතරක් හෝ පහක් ඇති පුෂ්පයි.ඇතඅම් පුෂ්පවල දල හයක් අටක් හෝ විශාල දල ප්‍රමාණයක් ඇති පුෂ්පද දැකිය හැකිය.පූමංගය හෙවත් රේණුවල ස්වභාවය අනුවද මල් එකිනෙකට වෙනස්වේ.ඇතුම් පුෂ්පවල රේණු කිහිපයක් දක්නට ලැබේ.රේණුවේ දණ්ඩ හෙවත් සූත්‍රිකා විවිධ දිගින් යුක්තව දක්නට ලැබේ.ඇතැම් මල්වල සූත්‍රිකා කුඩාවට පිහිටා ඇති අතර තවත් මල්වල සූත්‍රිකා දික්ව පිහිටා ඇත.

ඵල හටගැනීම[සංස්කරණය කරන්න]

පුෂ්පයක කලංකයමත ඇලෙනසුලු සීනි ද්‍රාවණයක් පවතී.පරාගකයේ දී කලංකයමත පතිතවන පරාග කංලකයමත ඇති ද්‍රාවණයේ ප්‍රෙරා්හණයවීමට පටන්ගනී.මෙහිදී පරාග බිත්තියේ තුනී ස්ථානයකිත් රාගය තුල ඇති සෛල ප්ලාස්මය නළයක්සේ පිටතට වර්ධනයවේ.මෙය පරාග නාලය නමින් හදුන්වයි.පරාගයේ න්‍යෂ්ටියද පිටතට පැමිනේ.ඉන්පසු මෙය කීලය දිගේ වර්ධනයවී පුෂ්පයේ ඩිම්බ කෝෂය දෙසට ලගාවෙයි.ඩිම්බය තුල පවතින ඩිම්බ අනුද්වාරයනම් සිදුරෙන් ඇතුළුවී පරාගයේ න්‍යෂ්ටියත් ඩිම්බයේ න්‍යෂ්ටියත් සම්බන්ධවී සංසේචනය සිදුවේ.මෙසේ සංසේචනයවූ පුෂ්පයේ දල පරවී වැටේ.මලක අනෙකුත් කොටස් මිය යද්දී ඩිම්බ බීජ බවටත් ඩිම්බ කෝෂය ඵලාවරණය ලෙසත් වර්ධනයවීම ඇරඹේ.

පරාගනය[සංස්කරණය කරන්න]

Grains of pollen sticking to this bee will be transferred to the next flower it visits

Tip of a tulip stamen. Note the grains of pollen

මූලික ලිපිය: මල්

ශාකයක ලිංගික ප්‍රජනනයේ මූලික අවස්තාව පරාගනයයි.ශාකයක ප්‍රධාන ලිංගික අවයවය එහි පුෂ්පයන්ය.පුෂ්පයක ඇති පරාග ඩිමබ හා සංසේචනයවීමේ ක්‍රියාවලිය සරලව පරාගනය ලෙස දැක්විය හැක.පරාග හෙවත් පූමාංගී සෛලවල න්‍යෂ්ටිය හා ඩිමබ වල න්‍යෂ්ටිය හාවීම සංසේචනය යනුවෙන් හදුන්වයි.සමාන්‍යයෙන් පරාග ශාකයකින් ශාකයකට ගමන්කරයි.එහෙත් ඇතැම් ශාක ස්වපරාගනය සිදුකරයි.මේ ආකාරයට ස්වපරාගනය සිදු වන්නේ එකම පුෂ්පයක ස්ත්‍රී හා පුරුෂ කොටස් දෙකම ඇති පුෂ්පයන් ඇති ශාක වලය.සංසේචනය වූ ඩිමබ මගින් පමණක් ඉදිරි පරම්පරාව ගෙනයාහැකි බීජ නිපදවයි. පුෂ්පයන් පරාගනය සදහා විවිධ රූපාකරයන් අනුව හැඩගැසී පවතී.ඇතැම් පුෂ්ප සතුන් මගින් පරාගනය වීමටත් ඇතැම් පුෂ්ප වාතය මගින් පරාගනය වීමටත් තවත් සමහර පුෂ්ප ජලය මගින් පරාගනය වීමටත් හැඩගැසී ඇත.සතුන් මගින් පරාගනය වීමට හැඩගැසී ඇති පුෂ්ප සදහා කෘබීන් කුරුල්ලන් හා වවුලන් වැනි සතුන්ගේ සහය හිමිවේ.

ආකර්ශන උපක්‍රම[සංස්කරණය කරන්න]

මීමැස්සියකගේ වේෂාන්තරය ගත් මී මැසි උඩවැඩියා මලක්.

ශාකයකට එක්තැනක සිට තවත් තැනකට සංචරණය වීමට නොහැකිය.එම නිසා සංචරණය වියහැකි සතුන්ගේ සහය පරාගනය සදහා ශාකයන් විසින් උපයෝගීකරගනී.පරාගනයේ දී ශාකයන්ට වැඩිපුරම සහය ලබා දෙන්නේ කෘබීන්ය.කෘබින් ආදී පරාගනය සදහා සහය දැක්විය හැකි සතුන් ආකර්ශන සදහා මල් වල විශේෂ හැඩගැසීම් පෙන්වයි.සතුන් මගින් පරාගනය සිදුවන මල්වල මධුකොෂයක් පිහිටයි.මෙහි රසවත් මල්පැණි පිරී පවතී.එම මල්පැණි බීමට මීමැස්සන් කෘබීන් කුරුල්ලන් පැමිනේ.මෙම මල්වල පරාගධානියේ සිට මධුකෝෂය දක්වා දෘෂ්‍ය ආලෝකයට සංවේදී නොවන එහෙත් පාරජම්බුල කිරණවලට සංවේදී ගමන් මාර්ගයක් පිහිටා ඇත.මෙම ගමන් මාර්ගය විශේෂයෙන් සංයුත්ත ඇස් ඇති සතුන්ට හොදින් දර්ශනයවේ.දිවා කාලයේ පිපෙන මල් විවිධ වර්ණයන්ගෙන් සමන්විය.මෙම විචිත්‍ර වර්ණ රටා සතුන් ආකර්ශනය කරගැනීමට හැකිය.එහෙත් රාත්‍රී කාලයේ පිපෙන මල් සතුන් ආකර්ශනය කරගැනීම සදහා සුවද විහිදුවීම සිදුකරයි.එසෙම එම මල් බොහෝවිට සුදු පැහැතිය.ඇතැම් මල් වලින් නිකුත් කරන සුගන්දයන් මිනිස් නාසයට සංවේදීවේ නොවේ.තවත් ඇතැම් මල් මිහිරි සවදක් වෙනුවට නිකුත් කරන්නේ අමිහිරි දුර්ගන්ධයන්ය.උදාහරණ ලෙස රැෆ්ලේසියා කිඩාරම් ආදිය දැක්විය හැක.මෙම මල් පරාගනයවීම සිදුවන්නේ වවුලන් සළබයන් ආදී සතුන් මගිනි.

ඇතැම් මල් පරාගනය සදහා අමුතු හැසිරීම් දක්වයි.උදාහරණ ලෙස ඇතැම් ඕකිඩ් මල් ගැහැණු මීමැස්සන්ගේ වර්ණය හැඩය ගැනීම මෙන්ම ගැහැණු මීමැස්සන් ගේ සුවන විහිදුවයි.මෙවිට පිරිමි මීමැස්සන් ගැහැණු මීමැස්සන් යැයි සැකකර සංසර්ගය සදහා පැමිනේ.

පරාගන යාන්ත්‍රණය[සංස්කරණය කරන්න]

පරාගන යාන්ත්‍රණය ශක අනුව වෙනස්වේ.බොහෝ පුෂ්පයන් ප්‍රධාන වශයෙන් කොටස් දෙකකට බෙදේ.

කෘබිකාමී(Entomophilous): මෙම වර්ගයට අයත් මල් පරාගනය සදහා කෘබීන් වවුලන් හෝ වෙනත් සතුන් උපයොගීකරගනී.නිතරම මෙම වර්ගයට අයත් මල් කෘබීන් ආකර්ශනය කරගැනීමට හැඩගැසී ඇත.විචිත්‍ර වර්ණ දැරීම සුගන්දයන් විහිදුවීම මධුකෝෂ පිහිටා තිබීම ඉන් කිහිපයකි.මෙමගින් ස්වපරාගනය වලක්වා පරපරාගනය සිදුවීම පහසු කරවයි.වඩාත් උසස් ඉදිරි පරම්පරාවක් බිහිකිරීමට නම් පරපරාගනය වඩාත් උචිතය.ඇතැම් ශාක ස්වපරාගනය වැළැක්වීමට හැඩගැසී පවතී.

Anthers detached from a Meadow Foxtail flower.

A grass flower head (Meadow Foxtail) showing the plain coloured flowers with large anthers.

වාතකාමී(Anemophilous): ඇතැම් පුෂ්පයන් වාතය මගින් පරාගනයවීමට හැඩගැසී ඇත.තෘණ කුලයට අයත් ශාක හා තාල වර්ගයට අයත් ශාක වැනි විවිධශාක වර්ග මෙම ගණයට අයත්ය. මෙම ශාකවලට කෘබිකාමී ශාක වලට මෙන් කෘබීන් ආකර්ශනය කරගැනීමට අවශ්‍ය නැතතඑබැවින් මෙම පුෂ්ප අලංකාර හෝ සුගන්දවත් බවක් නොපෙන්වයි.මෙම පුෂ්ප බොහෝ විට කුඩාය.පරාග ඉතා සැහැල්ලුය සුළගේ පාවී යන පරාග පුෂ්පයක කලංකය මත පතිතවීමෙන් සංසේචනය සිදුවේ.මෙම පුෂ්පයන් පරාග ඉතා විශාල සංඛාවක් නිපදවයි.

බොහෝ පුෂ්පයන් ස්වපරාගනය සිදු කරන අතර ඇතැම් ශාකවල ස්වපරාගනය වැළැක්වීම සදහා හැඩගැසී පවතී.

පරාගන සම්භන්ධතා[සංස්කරණය කරන්න]

පරාගනයේ දී පුෂ්පයන් හා කෘබීන් ආදී පරාගන කාරක සතුන් අතර විවිධ සම්භන්ධතා දැකිය හැකිය.ඇතැම් පුෂ්පයන් කරා ලගාවන්නේ එක් විශේෂයකට අයත් කෘබීන් පමණය.එබැවින් ඇතැම් ශාක වෙනත් භූගෝලීය කලාපයක සරුවට වැඩුනද ඵල හටගැනීම සිදු නොවේ.එයට හේතුව එම මල් පරාගනය කිරීමට සුදුසු සත්ව විශේෂය එහි නොසිටීමයි.එසෙම පරාගන කාරක සතුන් යම් හෙයකින් වදවී ගියහොත් හෝ ආපදාවකට පත්වු හොත් අදාල ශාකයන්හි ඵල හටගැනීම සිදුනොවේ.උදාහරණ ලෙස මැලේසියාවේ සිදුවූ අධික හිරිගල් ගුහා කඩා දැමීමත් සමග වවුලන් දහස් ගණනකට තම වාසස්ථාන අහිමිවිය.ඒ සමගම එරට දූරියන් ඵලදාව ඉතා විශාල ලෙස අඩුවිය.එයට හේතුව ඩූරියන් පුෂ්ප පරාගනයට වවුලන් දායකවූ බැවිනි.මේ ආකාරයට යම් ශාකයකට අයත් පරාගන කාරක සත්වයින්ට වන හානියත් සමග එම ශාකයන්හි ඵලදාව අඩුවේ.

මේ ආකාරයට ශාක හා පරාගන කාරක සතුන් අතර ඇති සම්භන්ධය වරෙක ඔවුන් දෙකොට්ටාශයේම අවාසියකට හේතුවිය හැක.මන්ද එක් විශේෂයකට සිදුවන හානිය අනෙත් විශේෂයේ පැවැත්මට ඍජුව බලපාන බැවිනි.

සංසේචනය හා ව්‍යාප්තිය[සංස්කරණය කරන්න]

Cassia Fistula. A hermaphrodite flower showing both male and female parts.

ස්ත්‍රී හා පුරුෂ කොටස් දෙකම ඇති ද්ළුීලිංගික පුෂ්ප බොහෝවිට ස්වපරාගනය සිදුකරයි.මෙම ස්වපරාගනය සිදුවන ශාකවල ජානමය වෙනස්වීම් ඉතා අඩුවෙන් සිදුවේ.මෙම හේතුව නිසා පරිසරයට ඔරෝත්තු දියහැකි නව ප්‍රභේදයන් බිහිවීම අවමවේ.ඇතැම් පුෂ්පයන්හි ස්වපරාගනය වැළැක්වීමට විශේෂයෙන් හැඩගැසී ඇති ආකාරය දක්නට ලැබේ.උදාහරණ ලෙස වැල් දොඩම් ශාකය දැක්විය හැක.

පුෂ්පයන්හි ඇති පරාග පුෂ්පයේ කලංකය මතට වැටීමෙන් පසු ප්‍රරෝහනය වන පරාගය ඩිම්බ කෝෂය දක්වා වර්ධනයවී පරාගයේ න්‍යෂ්ටිය හා ඩිම්බයේ න්‍යෂ්ටි හාවීමෙන් සංසේචනය සිදුවේ.පසුව සංසේචනයවූ ඩිම්බ බීජ ලෙසත් ඩිම්බ කෝෂය ඵලාවරණය ලෙසත් වර්ධනය වෙයි.

මෙසේ වර්ධනයවූ ඵලයේ බීජ ව්‍යාප්තිය සදහා ශාක මගින් විවිධ උපක්‍රම භාවිත කරයි.උදාහරණ ලෙස සතුන් මගින් ජලය මගින් හා වාතය මගින් හා ස්ඵෝටනය මගින්ද බීජ ව්‍යාප්තිය සිදුකරයි.

සතුන් මගින්[සංස්කරණය කරන්න]

සතුන් මගින් ව්‍යාප්තවන බීජයන්හි සතුන්ට ආහාරයට ගත හැකි මාංසල කොටසක් දැරීම සිදුකරයි.එසේම ද්වීප්තිමත් වර්ණ දැරීම ආකර්ෂණීය සුවඳක් විහිදුවීම ආදිය මගින් සතුන් ආකර්ෂණය කරගනී.ඇතැම් ඵලයන් සතුව සතුන් ආකර්ෂණය කරගතහැකි මාංසල කොටස් නොදරයි.ඒ වෙනුවට සතුන්ගේ සිරුරේ දැවටියහැකි කෙඳි කොකු වැනි උපාංග දරයි.

වාතය මගින්[සංස්කරණය කරන්න]

වාතය මගින් ව්‍යාප්තවන බීජ සැහැල්ලුය.සුලගේ පහසුවෙන් පාවී යාහැකිවන සේ සැකසුන පියාගත් කෙඳි වැනි උපාංඟ දරයි.උදාහරණ ලෙස මහෝගනී හොර ගම්මාලු වරා අදී දැක්වය හැක.

ජලය මගින්[සංස්කරණය කරන්න]

ජලය මගින් ව්‍යප්තවන බීජ වාතය පිරි කෙඳි සහිත ඵලාවණනයක් දරයි.එසේම සෑහෙන දවසක් බීජය කුණු නොවී ජලයේ රැඳී පැවතිය හැක.උදාහරණ ලෙස පොල් පුවක් ආදී තාල වර්ගයේ ශාක බීජ හා කදුරු නෙළුම් දැක්විය හැක.

ස්ඵොටනය මගින්[සංස්කරණය කරන්න]

ස්ඵොටනය හෙවත් පිපිරීමෙන් ව්‍යාප්තවන බීජ වල ඵලාවරණය වියලීමෙන් පසු වේගයෙන් පිපිරීමට ලක්වේ.එවිට ඵලාවරණයෙහි රැදී තිබුන බීජ වේගයෙන් ඉවතට විසිවේ.රබර් කූඩළු ආදිය මේවාට උදාහරණවේ.

පරිනාමය[සංස්කරණය කරන්න]

Further information: Evolutionary history of plants#Evolution of flowers

Archaefructus liaoningensis, one of the earliest known flowering plants

වසර මිලියන 425 පමණ මල් මුලින්ම ප්‍රජනනය සිදුවූයේ ඉතා සරල ආකාරයටය,මල් වල පරාග ජලයේ පාවීම මගින් පරාගනය සිදුවිය.නමුත් ගොඩබිම බිහිවීමත් සමග ගොඩබිම මතුපිට පැන පැගුන පුෂ්පයන්ට පරාගනය සදහා නව ක්‍රමවේදයන්ට අනුවර්තනය වීමට සිදුවිය.බීජ ආරක්ෂා කිරීමටද නව අනුවර්තනයන් අවශ්‍ය විය,මුල් යුගයේ ශාකවල බීජාවරණයක් නොවීට..

නිව් කැලිෆොනියා ප්‍රදේශයෙන් හමුවූ ඇබොරෙල්ලා ත්‍රිකොපොඩා නම් ශාක විශේෂය සපුෂ්ප ශාකවල මුල් පූර්වජකයන්ට අයත් බවයි^[1]

ගොනුව:Amborella buds.jpg

Amborella buds

The general assumption is that the function of flowers, from the start, was to involve other animals in the reproduction process. Pollen can be scattered without bright colors and obvious shapes, which would therefore be a liability, using the plant's resources, unless they provide some other benefit. One proposed reason for the sudden, fully developed appearance of flowers is that they evolved in an isolated setting like an island, or chain of islands, where the plants bearing them were able to develop a highly specialized relationship with some specific animal (a wasp, for example), the way many island species develop today. This symbiotic relationship, with a hypothetical wasp bearing pollen from one plant to another much the way fig wasps do today, could have eventually resulted in both the plant(s) and their partners developing a high degree of specialization. Island genetics is believed to be a common source of speciation, especially when it comes to radical adaptations which seem to have required inferior transitional forms. Note that the wasp example is not incidental; bees, apparently evolved specifically for symbiotic plant relationships, are descended from wasps.

Likewise, most fruit used in plant reproduction comes from the enlargement of parts of the flower. This fruit is frequently a tool which depends upon animals wishing to eat it, and thus scattering the seeds it contains.

While many such symbiotic relationships remain too fragile to survive competition with mainland animals and spread, flowers proved to be an unusually effective means of production, spreading (whatever their actual origin) to become the dominant form of land plant life.

Lomatium parryi, a plant that used to be consumed by early Native Americans

While there is only hard proof of such flowers existing about 130 million years ago, there is some circumstantial evidence that they did exist up to 250 million years ago. A chemical used by plants to defend their flowers, oleanane, has been detected in fossil plants that old, including gigantopterids^[2], which evolved at that time and bear many of the traits of modern, flowering plants, though they are not known to be flowering plants themselves, because only their stems and prickles have been found preserved in detail; one of the earliest examples of petrification.

The similarity in leaf and stem structure can be very important, because flowers are genetically just an adaptation of normal leaf and stem components on plants, a combination of genes normally responsible for forming new shoots.^[3] The most primitive flowers are thought to have had a variable number of flower parts, often separate from (but in contact with) each other. The flowers would have tended to grow in a spiral pattern, to be bisexual (in plants, this means both male and female parts on the same flower), and to be dominated by the ovary (female part). As flowers grew more advanced, some variations developed parts fused together, with a much more specific number and design, and with either specific sexes per flower or plant, or at least "ovary inferior".

Flower evolution continues to the present day; modern flowers have been so profoundly influenced by humans that many of them cannot be pollinated in nature. Many modern, domesticated flowers used to be simple weeds, which only sprouted when the ground was disturbed. Some of them tended to grow with human crops, and the prettiest did not get plucked because of their beauty, developing a dependence upon and special adaptation to human affection.^[4]

ලක්ෂණ[සංස්කරණය කරන්න]

Lilies are often used to denote life or resurrection

Flowers are common subjects of still life paintings, such as this one by Ambrosius Bosschaert the Elder

Chinese Jade ornament with flower design, Jin Dynasty (1115-1234 AD), Shanghai Museum.

Many flowers have important symbolic meanings in Western culture. The practice of assigning meanings to flowers is known as floriography. Some of the more common examples include:

Red roses are given as a symbol of love, beauty, and passion.
Poppies are a symbol of consolation in time of death. In the UK, New Zealand, Australia and Canada, red poppies are worn to commemorate soldiers who have died in times of war.
Irises/Lily are used in burials as a symbol referring to "resurrection/life". It is also associated with stars (sun) and its petals blooming/shining.
Daisies are a symbol of innocence.

Flowers within art are also representative of the female genitalia, as seen in the works of artists such as Georgia O'Keeffe, Imogen Cunningham, Veronica Ruiz de Velasco, and Judy Chicago, and in fact in Asian and western classical art. Many cultures around the world have a marked tendency to associate flowers with femininity.

The great variety of delicate and beautiful flowers has inspired the works of numerous poets, especially from the 18th-19th century Romantic era. Famous examples include William Wordsworth's I Wandered Lonely as a Cloud and William Blake's Ah! Sun-Flower.

Because of their varied and colorful appearance, flowers have long been a favorite subject of visual artists as well. Some of the most celebrated paintings from well-known painters are of flowers, such as Van Gogh's sunflowers series or Monet's water lilies. Flowers are also dried, freeze dried and pressed in order to create permanent, three-dimensional pieces of flower art.

The Roman goddess of flowers, gardens, and the season of Spring is Flora. The Greek goddess of spring, flowers and nature is Chloris.

In Hindu mythology, flowers have a significant status. Vishnu, one of the three major gods in the Hindu system, is often depicted standing straight on a lotus flower.^[5] Apart from the association with Vishnu, the Hindu tradition also considers the lotus to have spiritual significance.^[6] For example, it figures in the Hindu stories of creation.^[7]

භාවිතයන්[සංස්කරණය කරන්න]

Flower market, Detroit's Eastern Market.

Female hand spreading flowers over a Lingam temple in Varanasi

In modern times, people have sought ways to cultivate, buy, wear, or otherwise be around flowers and blooming plants, partly because of their agreeable appearance and smell. Around the world, people use flowers for a wide range of events and functions that, cumulatively, encompass one's lifetime:

For new births or Christenings
As a corsage or boutonniere to be worn at social functions or for holidays
As tokens of love or esteem
For wedding flowers for the bridal party, and decorations for the hall
As brightening decorations within the home
As a gift of remembrance for bon voyage parties, welcome home parties, and "thinking of you" gifts
For funeral flowers and expressions of sympathy for the grieving
For worshiping goddesses. in Hindu culture it is very common to bring flowers as a gift to temples.

People therefore grow flowers around their homes, dedicate entire parts of their living space to flower gardens, pick wildflowers, or buy flowers from florists who depend on an entire network of commercial growers and shippers to support their trade.

Flowers provide less food than other major plants parts (seeds, fruits, roots, stems and leaves) but they provide several important foods and spices. Flower vegetables include broccoli, cauliflower and artichoke. The most expensive spice, saffron, consists of dried stigmas of a crocus. Other flower spices are cloves and capers. Hops flowers are used to flavor beer. Marigold flowers are fed to chickens to give their egg yolks a golden yellow color, which consumers find more desirable. Dandelion flowers are often made into wine. Bee Pollen, pollen collected from bees, is considered a health food by some people. Honey consists of bee-processed flower nectar and is often named for the type of flower, e.g. orange blossom honey, clover honey and tupelo honey.

Hundreds of fresh flowers are edible but few are widely marketed as food. They are often used to add color and flavor to salads. Squash flowers are dipped in breadcrumbs and fried. Edible flowers include nasturtium, chrysanthemum, carnation, cattail, honeysuckle, chicory, cornflower, Canna, and sunflower. Some edible flowers are sometimes candied such as daisy and rose (you may also come across a candied pansy).

Flowers can also be made into herbal teas. Dried flowers such as chrysanthemum, rose, jasmine, camomile are infused into tea both for their fragrance and medical properties. Sometimes, they are also mixed with tea leaves for the added fragrance.

ගොනුව:Crocus, Yellow.jpg

Crocus angustifolius

මේවාත් බලන්න[සංස්කරණය කරන්න]

මානෙල්

යොමුව[සංස්කරණය කරන්න]

Eames, A. J. (1961) Morphology of the Angiosperms McGraw-Hill Book Co., New York.
Esau, Katherine (1965) Plant Anatomy (2nd ed.) John Wiley & Sons, New York.

Look up flower in

Wiktionary, the free dictionary.

සැකිල්ල:Commons-gallery

විකිමාධ්‍ය කොමන්ස් වෙත මෙය ආශ්‍රිත මාධ්‍ය සතු වෙයි: Flowers

බාහිර සබැදුම්[සංස්කරණය කරන්න]

[සඟවන්න] v t e උද්භිදවේදය (Botany)

උද්භිදවේදයේ උප ක්‍ෂේත්‍ර (Subdisciplines of botany)	Ethnobotany · Paleobotany · Plant anatomy · Plant ecology · Plant evo-devo · Plant morphology · Plant physiology

Plants	Evolutionary history of plants · Algae · Bryophyte · Pteridophyte · Gymnosperm · Angiosperm

Plant parts	Flower · Fruit · Leaf · Meristem · Root · Stem · Stoma · Vascular tissue · Wood

ශාක සෛලය	සෛල බිත්තිය · Chlorophyll · Chloroplast · Photosynthesis · Plant hormone · Plastid · Transpiration

ශාක ප්‍රජනනය	Alternation of generations · Gametophyte · Plant sexuality · Pollen · Pollination · Seed · Spore · Sporophyte

ශාක නාමකරණය	Botanical name · Botanical nomenclature · Morphology and Botanical glossaries · Herbarium · IAPT · ICBN · Species Plantarum

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Flower

From Wikipedia, the free encyclopedia

மலர்
https://ta.wikipedia.org/s/319

கட்டற்ற கலைக்களஞ்சியமான விக்கிப்பீடியாவில் இருந்து.

இக்கட்டுரை கூகுள் மொழிபெயர்ப்புக் கருவி மூலம் உருவாக்கப்பட்டது. இதனை உரை திருத்த உதவுங்கள். இக்கருவி மூலம் கட்டுரை உருவாக்கும் திட்டம் தற்போது நிறுத்தப்பட்டுவிட்டது. இதனைப் பயன்படுத்தி இனி உருவாக்கப்படும் புதுக்கட்டுரைகளும் உள்ளடக்கங்களும் உடனடியாக நீக்கப்படும்

பன்னிரண்டு வகை மலர் தாவரங்கள் அல்லது வெவ்வேறு இனங்களைச் சார்ந்த மலர்களின் கொத்துக்களின் ஒரு தட்டி

முதிர்ச்சி பெற்ற மலரின் உறுப்புகளை விவரிக்கும் வரைபடம்

மலர் (அல்லது பூ) என்பது மலரும் தாவரங்களில் காணப்படும் இனப்பெருக்க அமைப்பு ஆகும். மலர்கள், தாவரங்களின் இனப்பெருக்க உறுப்புகளைக் கொண்டுள்ளன. மலர்களின் பணி விதைகளை உருவாக்குவது ஆகும். உயர்நிலைத் தாவரங்களுக்கு விதைகளே அடுத்த தலைமுறையை உருவாக்குகின்றன. தாவரங்களின் மலர்கள் இனப்பெருக்க அமைப்பாக இருப்பதுடன் அவற்றின் மணம், அழகு ஆகியவற்றுக்காக பன்னெடுங்காலமாக மனிதர்களால் விரும்பி வளர்க்கப்பட்டு வருகின்றன. சில மலர்கள் உணவாகவும் பயன்படுவது உண்டு.

பூக்கும் தாவரங்களின் ஒரு இனப்பெருக்க உறுப்பாக சேவையாற்றுவதோடு, பூக்கள் மனிதர்களால் நெடுங்காலமாக போற்றப்பட்டு முக்கியமாக தங்கள் சுற்றுச்சூழலை அழகுப்படுத்தவும், அதோடு மட்டுமல்லாமல் உணவு ஆதாராமாகவும் பயன்படுத்தப்படுகின்றன.

பொருளடக்கம்

[மறை]

மலர் தனிச்சிறப்பு மற்றும் மகரந்தச் சேர்க்கை[தொகு]

பூக்கும் தாவரங்கள் தங்களின் மகரந்தங்களின் மாற்றத்தைச் சிறப்பாக ஆற்றல்படுத்துவதற்காக வழக்கமாக ஒரு தேர்ந்தெடுப்பிற்கான அழுத்தத்தை எதிர்கொள்கின்றன, மற்றும் இது பூக்களின் உருவவியல் வகை மாற்றத்திற்கு பொருத்தமாக இருக்கின்றன. மகரந்தங்கள் தாவரங்களுக்கிடையே பல்வேறு வகையாக 'எடுத்துச்செல்பவைகளால்' மாற்றப்படுகின்றன. சில தாவரங்கள் காற்று (அனிமாஃபில்லி அல்லது காற்றுவழி மகரந்தச் சேர்க்கை) அல்லது மிகக் குறைந்த அளவு பொதுவாக, நீர் ( ஹைட்ரோஃபில்லி அல்லது நீர்வழி மகரந்தச் சேர்க்கை) மற்றவை பூச்சிகள் (என்டமோஃபிலி அல்லது பூச்சிவழி மகரந்தச் சேர்க்கை), பறவைகள் (ஆர்னிதோஃபிலி அல்லது பறவை வழி மகரந்தச் சேர்க்கை) வெளவால்கள் (சிரோப்டெரோஃபிலி அல்லது வெளவால் வழி மகரந்தச் சேர்க்கை) மற்றும் பிற விலங்குகள் உள்ளிட்ட எடுத்துச்செல்லும் உயிர்களைப் பயன்படுத்துகின்றன. சில தாவரங்கள் பல்வேறு எடுத்துச்செல்பவைகளைப் பயன்படுத்துகின்றன, ஆனால் அவற்றில் பல உயர்ந்த சிறப்புடையனவாகும்.

அலராநிலைப்புணர்ச்சிப் பூக்கள் சுய மகரந்தச் சேர்க்கையை உடையவை, அதற்குப் பின்னர் அவை திறக்கலாம் அல்லது திறக்காமலும் போகலாம். பல வாய்லா மற்றும் சில சால்வியா தாவரவகைகள் இவ் வகையானப் பூக்களைக் கொண்டிருப்பதாக அறியப்படுகிறது.

மகரந்தங்களை எடுத்துச்செல்லும் உயிர்களைப் பயன்படுத்தும் சிலத் தாவரங்கள் பொதுவாக விலங்குகள் மலர்களுக்கு வருகைத் தருவதற்கான ஒரு ஊக்கமாக விளங்கக்கூடிய தேன்சுரப்பிகள் கொண்டிருக்கின்றன. தேனை எங்கே அறிவது என்பதை மகரந்தசேர்ப்பிக்களுக்கு காட்டும் தேன் வழிகாட்டிகள் எனும் முன்மாதிரிகளை சிலத் தாவரங்கள் கொண்டிருக்கின்றன. வாசனை மற்றும் நிறங்களால் மகரந்தசேர்ப்பிக்களை மலர்கள் கவர்கின்றன. அதேநேரம் மகரந்தசேர்ப்பிக்களை கவர்வதற்காக ஒப்புப்போலிப் பண்பினைப் பயன்படுத்துகின்றன. உதாரணத்திற்கு, சில ஆர்ச்சிட்டுகளின் தாவரவகைகள் நிறம், வடிவம் மற்றும் வாசனையால் பெண் தேனிக்களை ஈர்க்கக்கூடியப் பூக்களை உற்பத்தி செய்கின்றன. மலர்கள் வடிவத்திலும் சிறப்பானைவை மற்றும் மகரந்தசேர்ப்பிகள் தம்முடைய கவர்பவைகளைத் (தேன், மகரந்தம் அல்லது ஒரு இணை) தேடி இறங்கும் போது அவற்றின் உடலில் மகரந்தத் துகள்கள் மாற்றப்படுவதை உறுதி செய்வதற்கான மலரிழைகளின் வரிசையைக் கொண்டுள்ளது. ஒரே வகையைச் சார்ந்த பல மலர்களிலிருந்து இந்தக் கவர்பவைகளை பின்தொடர்ந்து செல்வதன் மூலம், தாம் செல்லும் மலர்கள் அனைத்திலும் - துல்லியமாக சமமாக வரிசைப்படுத்தப்பட்டிருக்கும் சூலக முகட்டிற்கு மகரந்தங்களை மகரந்தசேர்ப்பிகள் மாற்றுகின்றன.

காலிஸ்டேமான் சிட்ரினஸ் மலர்கள்

அனிமோஃபிலஸ் மலர்கள் ஒரு பூவிலிருந்து மற்றொரு பூவிற்கு மகரந்தங்களை மாற்றுவதற்கு காற்றைப் பயன்படுத்துகின்றன. புற்கள், பூர்ச்ச மரங்கள், ராக்வீட் மற்றும் மேபில்ஸ் ஆகியவற்றை உதாரணங்களில் உள்ளடக்கலாம். அவற்றிற்கு மகரந்தசேர்ப்பிக்களை கவரவேண்டியதில்லை என்பதால், அவை “பகட்டான” மலர்களாக இருக்க முயற்சிப்பதில்லை. ஆண் மற்றும் பெண் இனப்பெருக்க உறுப்புக்கள் பொதுவாக தனித்தனி மலர்களில் காணப்படுகின்றன, பல நீண்ட இழைகளைக் கொண்டு உள்ளே முடிவடையும் ஆண்மலர்கள் மலரிழைகளுக்கு வெளிப்படுகின்றன மற்றும் நீண்ட இறகு போன்ற சூலக முகடுகளைக் கொண்டிருக்கும். அதே சமயம், விலங்குகளால் மகரந்தச் சேர்க்கை செய்யப்பட்ட மலர்களின் மகரந்தங்கள், அதிக துகள் உள்ளவையாகவும், ஒட்டிக்கொள்பவையாகவும், புரத வளம் (மகரந்தசேர்ப்பிக்களுக்கான மற்றொரு “பரிசு”) கொண்டவையாக இருக்கும், அனேமோஃபிலிஸ் மலரின் மகரந்தம் வழக்கமாக சிறு துகள்களாகவும், மிகவும் லேசானதாகவும், விலங்குகளுக்கு குறைந்த ஊட்டசத்து மதிப்பைக் கொண்டதாகவும் இருக்கும்.

தாவர வடிவ அமைப்பியல்[தொகு]

பூக்கும் தாவரங்கள் ஹெட்ரோஸ்போரான்ஜியேட் (பல்லினவித்துள்ளவை) ஆகும், அவை இரண்டு வகையான இனப்பெருக்க வித்துகளை உற்பத்தி செய்யும். மகரந்தங்கள் (ஆண் வித்துகள்) மற்றும் சூல்வித்துக்கள் (பெண் வித்துகள்) வெவ்வேறு உறுப்புகளால் உருவாக்கப்படுகின்றன, ஆனால் இது போன்ற மலர்கள் இரண்டு உறுப்புகளையும் கொண்டிருப்பதால் இவை பைஸ்பொரான்ஜியேட் ஸ்ட்ரோபிலஸ் ஆகும்.

ஒரு மலரானது குறுக்கப்பட்ட கணுவிடைகள் மற்றும் இலையுடனான மாறுதல் செய்யப்பட்ட தாவரத் தண்டு ஆகும், அதன் கணுக்களில் உள்ள அமைப்புகள் இலைகளாக^[1] மிகவும் மாற்றமடைந்துள்ளன. சுருங்கச்சொன்னால், ஒரு மலரின் கட்டமைப்பு மாறுதல் செய்யப்பட்டத் தளிர்களில் உருவாகிறது அல்லது தொடர்ந்து வளராத (வளர்ச்சி தீர்மானிக்கப்பட்டது) நுனி ஆக்குத்திசுவுடனான ஊடுவரை ஆகும். மலர்கள் தாவரத்துடன் சில வழிகளில் ஒட்டிக்கொண்டிருக்கும். மலர் தண்டினைக் கொண்டிருக்காமல் இலைக் காம்புக்கவட்டில் உருவாகுமானால், அது செஸைல் (காம்பில்லாத பூ) என்றழைக்கப்படும். ஒரு மலர் உருவாக்கப்படும்போது, அந்த மலரை பற்றிக்கொண்டிருக்கும் தண்டு பெடங்கிள் (மஞ்சரித் தண்டு) என்றழைக்கப்படும். பெடங்கிள் மலர்களின் தொகுதியுடன் முடியுமானால், ஒவ்வொரு மலரையும் பற்றிக்கொண்டிருக்கும் தண்டு பெடிக்கிள் (சிறு காம்பு) என்றழைக்கப்படும். பூக்கும் தண்டு ஒரு இறுதி முனையை உருவாக்குகிறது, அது டோரஸ் (பொருமல்) அல்லது மஞ்சரித்தளம் என்று அழைக்கப்படும். மலரின் பாகங்கள் டோரஸின் சுருள்களாக அமைக்கப்பட்டிருக்கும். நான்கு முக்கிய பாகங்கள் அல்லது சுருள்கள் (மலரின் அடிப்பகுதியில் அல்லது கீழ்க்கணுவில் தொடங்கி மேல்நோக்கி பார்ப்பது) பின்வருமாறு:

முதிர்ந்த மலரின் முக்கிய பாகங்களைக் காட்டும் வரைபடம்

"முழுமையான மலருக்கு" ஒரு உதாரணம், இந்த கிரேடேவா ரி லேகோசியா மலர் மகரந்த கோசம் (வெளி வளையம்) மற்றும் யோனி (மையம்) இரண்டையும் கொண்டிருக்கிறது.

கேலிக்ஸ் (புல்லிவட்டம்): புறஇதழ்களின் வெளிச் சுருள்; உதாரணமாக அவை பச்சையாக இருக்கும், ஆனால் அவை சில தாவர வகைகளில் இதழ்களைப் போன்று இருக்கும்.
- கோரோலா (அல்லிவட்டம்): இதழ்களின் சுருள், வழக்கமாக மெல்லியதாக, மென்மையாக மற்றும் மகரந்தச் சேர்க்கை செயல்முறைக்கு உதவுவதற்காக விலங்குகளைக் கவரும் நிறமுடையதாக இருக்கும். நிறமாக்கம் புறஊதாவுக்கு விரிவடையக்கூடும், அவை பூச்சிகளின் பலகூறுகளான கண்களுக்குப் புலப்படுகின்றன, ஆனால் பறவைகளின் கண்களுக்குப் புலப்படுவதில்லை.
- ஆண்ட்ரீசியம் (மகரந்தத் தாள் வட்டம்) (கிரேக்கத்தில் ஆண்ட்ரஸ் ஓய்கியா: மனிதனின் வீடு): மகரந்த கோசத்தின் ஒன்று அல்லது இரண்டு சுருள்கள், ஒவ்வொரு மகரந்தக்கம்பியும் மகரந்தங்களை உற்பத்தி செய்யும் ஒரு மகரந்தப் பையை தலையில் கொண்டிருக்கும். மகரந்தங்கள் ஆண் புணரிக்களைக் கொண்டிருக்கும்.
சூலக வட்டம் (கிரேக்கத்தில் கைனைக்காஸ் ஓய்கியா: பெண்ணின் வீடு): ஒன்று அல்லது அதற்கு மேற்பட்ட யோனிக்கள். கார்பெல் (சூல்வித்திலை) பெண் இனப்பெருக்க உறுப்பாகும்: இது சூல்வித்துக்களுடனான ஒரு சூல்பையைக் கொண்டிருக்கும் (அது பெண் புணரிக்களைக் கொண்டிருக்கும்). ஒரு சூலக வட்டம் நிறைய சூல்வித்திலைகளை ஒன்றாக இணையப் பெற்றிருக்கும், அதே நேரம் ஒரு மலருக்கு ஒரு யோனி இருக்கும் அல்லது ஒரு ஒற்றை சூல்வித்திலையைக் கொண்டிருக்கும் (இந்த மலர் அபோகார்பஸ் (இணையாச் சூலகம்) என்றழைக்கப்படும். சூலகமுடி என்னும் யோனியின் பசையான முனை, மகரந்தங்களைப் பெறுகிறது. அதன் உதவிகரமான சூலகத் தண்டு எனும் காம்பு, சூலகமுடிக்கு ஒத்திசைவாக, சூல்வித்துக்களுக்கு, இனப்பெருக்க பொருட்களைக் கொண்டு சென்று, மகரந்தத் துகள்களிலிருந்து மகரந்த குழல்கள் வளர்வதற்கான ஒரு பாதையாக உருவாகிறது.

மேலே விவரிக்கப்பட்ட மலரமைப்பு ஒரு “உதாரண" அமைப்புத் திட்டமாக இருந்தாலும், தாவரவகைகள் இந்தத் திட்டத்திலிருந்து பரந்த அளவிலான மாற்றங்களைக் காட்டுகின்றன. இந்த மாற்றங்கள் பூக்கும் தாவரங்களின் வளர்ச்சியில் தனிச்சிறப்பானது மற்றும் தாவரவியலாளர்களாலும் தாவர வகைகளில் உறவுமுறையை ஏற்படுத்துவதற்காக விரிவாகப் பயன்படுத்தப்படுகிறது. உதாரணமாக, ஒவ்வொரு சுருளிலிலும் இருக்கும் பூக்கும் உறுப்புகளின் எண்ணிக்கையைப் பொருத்து, இரண்டு துணைப் பிரிவுகள் பிரிக்கப்படலாம்: டைகோடிலேடான்ஸ் (இருவித்துள்ள இலையி), உதாரணமாக ஒவ்வொரு சுருளிலும் 4 அல்லது 5 உறுப்புகளைக் கொண்டிருக்கும் மற்றும் மோனோகாட்டிலைடன்ஸ் (ஒருவித்துள்ள இலையி) மூன்று அல்லது சில மும்மடங்குகளைக் கொண்டிருக்கும். ஒரு கூட்டுச் சூலகத்தில் இருக்கும் சூலக இலையின் எண்ணிக்கை இரண்டாக மட்டுமே இருக்கும் அல்லது மற்றபடி ஒரு வித்து இலையிக்கள் அல்லது இருவித்து இலையிக்களுக்கான பொதுவிதிக்குத் தொடர்புடையதாக இருக்காது.

பெரும்பான்மையான தாவர வகைகளில் தனிப்பட்ட மலர்கள் மேலே விவரிக்கப்பட்டவாறு சூலகத்தையும் மகரந்தத்தாள்களையும் கொண்டிருக்கும். இந்த மலர்கள் தாவரவியலாளர்களால் முழுமையான, இருபாலான அல்லது ஹெர்மாஃப்ரோடைட் (இருபாலானவை) என்று அழைக்கப்படுகிறது. எனினும் சில வகைத் தாவரங்களில் முழுமையற்றவையாக அல்லது ஒரு பாலாக: ஆணாகவோ (மகரந்தத் தாளாகவோ) பெண்ணாகவோ (சூலகமாகவோ) இருக்கும். முந்தைய நிகழ்வில், ஒரு தனிப்பட்ட தாவரம் பெண்ணாகவோ அல்லது ஆணாகவோ இருந்தால் அந்த வகை டையோசியஸாக (இருபால் செடி) என கருதப்படும். எனினும், ஒரு பால் ஆண் மற்றும் பெண் மலர்கள் ஒரே தாவரத்தில் தோன்றும் போது, அந்த வகை மோனோசியஸ் (ஒரு பால் செடியாக) கருதப்படும்.

அடிப்படைத் திட்டத்திலிருந்தான பூக்கும் மாறுதல்கள் குறித்த கூடுதல் விவாதங்கள் மலரின் ஒவ்வொரு அடிப்படை பாகங்கள் மீதான கட்டுரைகளில் வழங்கப்பட்டுள்ளன. ஒரு ஊடுவரையில் ஒன்றுக்கும் மேற்பட்ட மலர்களைக் கொண்டிருக்கும் தாவரவகைகளை காம்போஸிட் ஃப்ளவர்ஸ் (கூட்டு மலர்கள்) என்றழைக்கப்படும் - மலர்களின் தொகுதி இன்ஃப்ளாரசன்ஸ் (பூத்திரள் அல்லது மஞ்சரி) எனப்படும்; இந்தச் சொல் தண்டில் ஒரு குறிப்பிட்ட மலர்வரிசையையும் குறிக்கும். இது தொடர்பாக, ஒரு "மலர்” என்பது என்ன என்பதை கருதுவதற்கு அக்கறை செலுத்தப்படவேண்டும். தாவரயியல் பயனீட்டுச் சொல்படி, உதாரணத்திற்கு ஒரு ஒற்றை டெய்ஸி அல்லது சூரியகாந்திப்பூ ஒரு மலரல்ல ஆனால் ஒரு மலர் தலை யாகும் – ஒரு இன்ஃப்ளாரசன்ஸ் பல்வேறு சிறு சிறு மலர்களின் (சில சமயங்களில் சிறு பூ என்றும் அழைக்கப்படும்) தொகுப்பினைக் கொண்டது. இந்த மலர்களில் ஒவ்வொன்றும் உள்ளமைப்புப்படி மேற்குறிப்பிட்டவாறு இருக்கலாம். பல மலர்கள் சமச்சீரைக் கொண்டிருக்கும், இதழ்வட்டமானது ஒத்த இருபகுதிகளாக ஊடுவரையின் மூலம் எந்தவொருப் புள்ளியிலிருந்தாவது பிரிக்கப்பட்டால், சமச்சீர் அரைவட்டம் உருவாக்கப்படும் - மலர் வழக்கமானது அல்லது அக்டினோமார்ஃபிக் (ஆரை சமச்சீரானது) என்று அழைக்கப்படும், எ.கா: ரோஜா அல்லது ட்ரில்லியம். மலர்கள் இருபகுதிகளாகப் பிரிக்கப்படும்போது ஒரே ஒரு கோடு ஒரு சமச்சீர் அரைவட்டத்தை உருவாக்குமானால் அந்த மலர் ஒழுங்கற்றது அல்லது ஸைகோமாரஃபிக் (இருபக்க சமச்சீரானது) எனப்படும். எ.கா: ஸ்னாப்டிராகன் அல்லது அனேக ஆர்ச்சிட்கள்.

கிறிஸ்மஸ் லில்லியம் (லில்லியம் லாங்கிஃப்ளோரம்). 1சூலகமுடி, 2. வடிவம், 3. மகரந்தகோசங்கள், 4. இழை, 5. அகவிதழ்

பூச்சூத்திரம்[தொகு]

ஒரு பூச்சூத்திரம் என்பது ஒரு மலரின் அமைப்பை குறிப்பிட்ட எழுத்துக்கள், எண்கள் மற்றும் சின்னங்களைப் பயன்படுத்தி உருவகப்படுத்துவதாகும். உதாரணமாக, ஒரு பொதுவான சூத்திரம் ஒரு குறிப்பிட்ட தாவர இனத்தைக் காட்டிலும் ஒரு தாவரக் குடும்பத்தின் மலரமைப்பை உருவகப்படுத்துவதாகும். அதற்கு பின்வரும் உருவகப்படுத்தல்கள் பயன்படுத்தப்படுகின்றன:

Ca = காலிக்ஸ் (புல்லிவட்டம்) (புற இதழ் சுருள்; எ.கா., Ca⁵ = 5 புறஇதழ்கள்)
Co = கரோலா (அகவிதழ் சுருள்; எ.கா., Co^3(x) = அகவிதழ்கள் மூன்றின் மடங்கில் )
Z = ஸைகோமார்ஃபிக் (இருபக்க சமச்சீரானது) சேர்க்கவும் (எ.கா., CoZ⁶ = ஸைகோமார்ஃபிக் (இருபக்க சமச்சீரானது) 6 அகவிதழ்களுடன்)
A = ஆண்டிரிசியம் (மகரந்தத்தாள் வட்டம்) (whorl of stamens; எ.கா., A^∞ = பல மகரந்தத் தாள்கள்)
G = சூலக வட்டம் (சூல்வித்திலை அல்லது சூல்வித்திலைகள்; எ.கா: G¹ = மோனோகார்பஸ் (ஒரு சூல்வித்திலையுள்ளது))

x : ஒரு “மாறியல் எண்ணை" சுட்டுவதற்காக
∞: “பல” என்பதை சுட்டுவதற்காக

ஒரு பூச்சூத்திரம் என்பது இதுபோன்று இருக்கும்:

Ca⁵Co⁵A^{10 - ∞}G¹

பல கூடுதல் சின்னங்களும் சில நேரங்களில் பயன்படுத்தப்படும் (பார்க்கவும் பூச்சூத்திரங்களுக்கான விடைக் குறிப்புகள்).

மேம்பாடு[தொகு]

மலர்வதற்கான இடைமாறுதல்[தொகு]

மலர்வதற்கான இடைமாறுதல் என்பது ஒரு தாவரம் அதன் வாழ்க்கை சுழற்சியில் செய்யும் ஒரு முக்கியமான மாற்றமாகும். கருவுறுதலுக்கும், விதை உருவாக்கத்திற்கும் சாதகமான ஒரு காலத்தில் இந்த இடைமாறுதல் இடம்பெறவேண்டும், அதனால் அதிகபட்ச இனப்பெருக்க வெற்றி உறுதி செய்யப்படும். இந்த வெற்றியை சந்திப்பதற்கு தாவர ஹார்மோன்கள் அளவிலான மாற்றங்கள் பருவகால வெப்பநிலை மற்றும் ஒளிக்கால மாற்றங்கள்^[2] போன்ற முக்கியமாக அகத்தில் தோன்றக்கூடிய மற்றும் சுற்றுச்சூழல் பின்னல்களை தாவரம் இடையீடு செய்யவேண்டியிருக்கும். பல பல்லாண்டுத் தாவரங்கள் மற்றும் அனேக இருபருவத் தாவரங்களுக்கு மலர்களின் வசந்தகால நிலைப்படுத்தல் தேவைப்படுகிறது. இந்த சமிகைகைளின் மூலக்கூறு இடையீடு, கான்ஸ்டன்ஸ், ஃப்ளவரிங் லோகஸ் சி மற்றும் ஃப்ளவரிங் லோகஸ் டி ஆகியவை உள்ளிட்ட பல்வேறு ஜீன்களை உள்ளிடுகின்றன, இது சிக்கலான சமிக்ஞைகள் என்று அறியப்படும் ஃப்ளோரிஜென்கள் மூலமாக செய்யப்படுகிறது. ஃப்ளோரிஜென் இனப்பெருக்கத்திற்குச் சாதகமான சூழ்நிலைகளில் இலைகளில் உருவாக்கப்பட்டு மொட்டுக்களிலும், வளரும் முனைகளிலும் பல்வேறு வாழ்வியல் மற்றும் உருவவியல் மாற்றங்களை ^[3] ஏற்படுத்துவுதற்கு ஃப்ளோரிஜென் உற்பத்தி செய்யப்படுகிறது. பதிய முறையான தண்டு முன்தோன்றலை பூ முன்தோன்றலுக்கு மாற்றுவது முதல் படியாகும். இது ஒரு உயிர் வேதியியல் மாற்றமாக இலை, மொட்டு மற்றும் தண்டு திசுக்களின் உயிரணு மாறுபாட்டை இனப்பெருக்க உறுப்புகளாக வளரக்கூடிய திசுக்களாக மாற்றுவதற்காக நடக்கிறது. தண்டு முனையின் நடுப்பகுதியின் வளர்ச்சி நின்றுவிடுகிறது அல்லது தட்டையாகிறது மற்றும் பக்கங்கள் புடைப்புகளாக வட்டமாக அல்லது சுரண்ட வகையில் தண்டு முனையின் வெளிப்புறப் பகுதியில் உருவாக்குகின்றது. இந்தப் புடைப்புகள் புல்லிகள், அல்லிகள், மகரந்தத் தாள்கள் மற்றும் சூலகமாக உருவாகின்றன. இந்த செயல்முறைத் துவங்கியதும், அனேக தாவரங்களில் இதை மீண்டும் திருப்ப முடியாது மேலும் தண்டு மலர்களை உருவாக்குகிறது, மலர் உருவாக்க நிகழ்வின் துவக்கத்தின் ஆரம்ப நிலையிலும் அது சில சுற்றுச்சூழல் பின்னலைச் சார்ந்துள்ளது.^[4] செயல்முறை துவங்கியதும், பின்னல் நீக்கப்பட்டாலும் தண்டு, மலர்களின் உருவாக்கத்தைத் தொடர்ந்து செய்யும்.

உறுப்பு வளர்ச்சி[தொகு]

மலர் வளர்ச்சியின் ABC வடிவம்

மலர் உறுப்பு அடையாளத்தை தீர்மானித்தலின் மூலக்கூறு கட்டுப்பாடு நல்லமுறையில் புரிந்துகொள்ளப்பட்டுள்ளது. ஒரு எளிய வடிவத்தில், பூவுக்குரிய ஆக்கு திசுவினுள் உறுப்பு முன்தோன்றல் அடையாளங்களைத் தீர்மானிப்பதற்காக மூன்று ஜீன் நடவடிக்கைகள் ஒன்றுடன் ஒன்று கலவையான முறையில் செயல்படுகின்றன. இந்த ஜீன் இயக்கங்கள் A, B மற்றும் C ஜீன் செயல்பாடுகள் என்று அழைக்கப்படும். முதல் பூவுக்குரிய வட்டத்தில், புல்லிகளை முன்னிலைப்படுத்தி A-ஜீன்கள் மட்டும் வெளிப்படுத்தப்படும். இரண்டாம் வட்டத்தில், அல்லிகளின் உருவாக்கத்தை முன்னிலைப்படுத்தி A மற்றும் B ஜீன்கள் வெளிப்படுத்தப்படும். மூன்றாம் வட்டத்தில், B மற்றும் C ஜீன்கள் மகரந்தகோசத்தை உருவாக்குவதற்கு இணைந்து செயல்படுகின்றன மற்றும் மலரின் நடுப்பகுதியில் C-ஜீன்கள் மட்டும் சூலகவித்திலைகளை உருவாக்கச் செய்கின்றன. இந்த மாதிரி வடிவம் அரபிடோப்சிஸ் தாலியானா வில் ஹோமியோடிக் விகாரிகள் மற்றும் ஸ்னாப் ட்ராகன், ஆன்ட்ரினம் மாஜஸ் ஆகியவற்றின் ஆய்வுகளின் அடிப்படையிலானதானகும். உதாரணத்திற்கு B-ஜீன் இயக்கத்தில் இழப்பு ஏற்படும் போது, விகாரி மலர்கள் புல்லிகளுடன் முதல் வட்டத்தில் வழக்கம் போல் உருவாக்கப்படும், ஆனால் இரண்டாவது வட்டத்திலும் சாதாரணமான அல்லி உருவாக்கத்திற்கு பதிலாக வழக்கமாக உருவாக்கப்படும். மூன்றாம் வட்டத்தில் B-ஜீனின் இயக்கத்தின் குறைபாடு காரணமாக ஆனால் C-ஜீன் இயக்கத்தின் நாலாவது வட்டத்தை ஒப்புப் போலியாக்குகிறது, அது சூலகத்தை மூன்றாவது வட்டத்தில் உருவாக்குதவற்கு வழிவகுக்கிறது. மலர் உருவாக்கத்தின் ABC வடிவத்தையும் பார்க்கவும்.

இந்த மாதிரியில் மையப்படுத்தப்பட்டிருக்கும் அனேக ஜீன்கள் MADS-பாக்ஸ் ஜீன்களைக்கு உரியதாக இருக்கிறது மற்றும் படியெடுத்தல் காரணிகளாக ஒவ்வொரு மலருக்குரிய உறுப்புக்கான ஜீன் சார்ந்த வெளிப்பாட்டை ஒழுங்குபடுத்துகிறது.

மகரந்தச் சேர்க்கை[தொகு]

இந்த தேனீயுடன் ஒட்டிக்கொண்டிருக்கும் மகரந்த துகள்கள் அது அடுத்து செல்லும் மலருக்கு மாற்றப்படும்

ஒரு மலரின் முதன்மை நோக்கம் இனப்பெருக்கமாகும். மலர்கள் தாவரத்தின் இனப்பெருக்க உறுப்பாக இருப்பதால், அவை மகரந்தத்திலிருக்கும் விந்துக்களை, சூல்பையிலிருக்கும் சூல்வித்துடன் இணைப்பதன் மூலம் இடையீடு செய்கின்றன. மகரந்தச் சேர்க்கை என்பது மகரந்தப் பையிலிருந்து சூலகமுடிக்கு மகரந்தங்கள் நகர்வதாகும். சூல்வித்துக்களுடன் மகரந்தங்கள் சேர்வதே கருவுறுதலாகும். சாதாரணமாக, மகரந்தம் ஒரு தாவரத்திலிருந்து மற்றொன்றுக்கு நகரும், ஆனால் பல தாவரங்களால் சுய மகரந்தச் சேர்க்கையை செய்யமுடிகிறது. கருவுற்ற சூல்கள் அடுத்த தலைமுறை விதைகளை உருவாக்க முடிகிறது. பாலியல் சம்பந்தப்பட்ட இனப்பெருக்க மரபு முதலில் தனித்துவமான மரபினை, மாற்றியமைத்துக்கொள்ள அனுமதிப்பதற்காக உருவாக்குகிறது. மலர்களுக்கு குறிப்பிட்ட வடிவமைப்பு இருக்கும், அவை மகரந்தத்தை ஒரு தாவரத்திலிருந்து அதே வகையான மற்றொரு தாவரத்திற்கு மகரந்தத்தை மாற்ற ஊக்குவிக்கின்றன. காற்று மற்றும் விலங்குகளை உள்ளிட்டு, பல தாவரங்கள் மகரந்தச் சேர்க்கைக்கு வெளிப்புற காரணிகளைச் சார்ந்திருக்கின்றன, அதுவும் குறிப்பாக பூச்சிகளைச் சார்ந்திருக்கின்றன. பறவைகள், வெளவால்கள் மற்றும் பிக்மி போஸம் போன்ற பெரிய விலங்குகளும் ஈடுபடுத்தப்படலாம். இந்த செயல்முறை நடைபெறும் காலம் (மலர் முழுவதுமாக விரிந்து இயங்கக்கூடியதாக இருப்பது) ஆன்தேசிஸ் (அரும்பவிழ்தல்) என்று அழைக்கப்படுகிறது.

கவர்ச்சி முறைகள்[தொகு]

ஆண் தேனீக்களை மகரந்த சேர்ப்பிக்களாக கவர்வதற்காக ஆர்ச்சிட் மலர் பெண் தேனீ போல் செயல்பட காலப்போக்கில் வளர்ச்சிபெற்றுள்ளது.

தாவரங்கள் ஒரு இடஅமைவிலிருந்து மற்றொன்றுக்கு நகர முடியாது, அதனால் மகரந்தங்களை தனிப்பட்டவற்றிக்கிடையே பரவலான வகையில் மாற்றுவதற்கு விலங்குகளைக் கவர்வதற்காக மலர்கள் அலர்விக்கப் படுகின்றன. பூச்சிகளால் மகரந்தச் சேர்க்கை பெறும் மலர்கள் என்டமோஃபிலஸ் (பூச்சிநாட்டமுள்ளவை) என்று அழைக்கப்படுகின்றன. சரியாக சொல்லவேண்டுமென்றால், இலத்தீனில் "பூச்சிகள் விரும்பி” என்பதாகும். அவை மகரந்தச் சேர்க்கை செய்யும் பூச்சிகளுடன் இணையாக சிறந்து வருவதன் மூலம் உயர்ந்த அளவில் மாற்றியமைக்கப்படுகின்றன. பூக்கள் பொதுவாக தன்சுரப்பிகள் எனும் சுரப்பிக்களை பல்வேறு பாகங்களில் கொண்டிருக்கின்றன, அவை ஊட்டம் மிக்க தேனை தேடிவரும் விலங்குகளைக் கவரும். பறவைகள் மற்றும் வண்டுகளுக்கு நிறப் பார்வை உள்ளதால், அவற்றால் “வண்ணம் நிறைந்த" மலர்களைப் பார்க்க முடியும். சில மலர்கள் "தேன் வழிகாட்டிகள்" எனும் முன் மாதிரிக்களைக் கொண்டிருக்கும், அவை மகரந்த சேர்ப்பிக்களுக்கு தேன் எங்கிருக்கிறது என்பதைக் காட்டும்; அவை புறஊதா ஒளியில் பார்க்கக்கூடியதாக, வண்டுகளுக்கும் இதர சில பூச்சிகளுக்கும் தெரிவதாக இருக்கும். மகரந்த சேர்ப்பிக்களை நறுமணம் மூலமாகவும் மலர்கள் கவருகின்றன மற்றும் சில நறுமணங்கள் நமக்கு இனிமையானவையாக இருக்கின்றன. அனைத்து மலர்களின் நறுமணமும் மனிதர்களுக்கு இனிமையானவையாக இருப்பதில்லை, அழுகிப்போன சதையினால் கவரப்படக்கூடிய பூச்சிகளால் பல்வேறு மலர்களால் மகரந்தச் சேர்க்கை செய்யப்படுகின்றன மற்றும் இந்த மலர்கள் செத்த விலங்குகள் போன்ற வாடையை உடையவை, அவை ரஃப்ளேசியா , டைடன் ஆரம் மற்றும் வட அமெரிக்க பாவ்பாவ் (அஸ்மினா ட்ரிலோபா) உள்ளிட்ட கேரியன் மலர்கள் என்றழைக்கப்படுகின்றன. வெளவால்கள் மற்றும் அந்துப்பூச்சிகள் உள்ளிட்ட, இரவு வருகையாளர்களால் பூக்கள் மகரந்தச் சேர்க்கை செய்யப்படுகின்றன, அவை மகரந்தச் சேர்ப்பிக்களைக் கவருவதற்கு வாசனையில் செறிவாக இருக்கின்றன மற்றும் அத்தகைய மலர்களில் அனேகமானவை வெள்ளையாக இருக்கும்.

இன்னும் பிற மலர்கள் மகரந்தச் சேர்ப்பிகளைக் கவர்வதற்காக ஒப்புப்போலிகளை பயன்படுத்துகின்றன. உதாரணத்திற்கு, சில ஆர்ச்சிட் மலர்களின் வகைகள், நிறம், வடிவம் மற்றும் வாசனையில் பெண் வண்டுகளை ஒத்திருக்கும் மலர்களை உருவாக்குகின்றன. ஒரு இணையைத் தேடி அத்தகைய மலர்களில் ஒன்றிலிருந்து மற்றொன்றுக்கு ஆண் வண்டுகள் செல்லும்.

மகரந்தச் சேர்க்கை நுட்பம்[தொகு]

மகரந்தச் சேர்க்கைத் தொழில்நுட்பம் என்ன வகையான தொழில்நுட்பம் பயன்படுத்தப்படுகின்றன என்பதைப் பொறுத்து மகரந்தச் சேர்க்கை நுட்பம் ஈடுபடுத்தப்படும்.

அனேக மலர்களில் மகரந்தச் சேர்க்கை முறைகள் இரண்டு பெரும் குழுக்களாக பிரிக்கப்படுகின்றன:

என்டோமோஃபிலஸ்: பூச்சிகள், வெளவால்கள், பறவைகள் அல்லது பிற விலங்குளை மலர்கள் கவர்ந்து மகரந்தங்களை ஒரு மலரிலிருந்து இன்னொரு மலருக்கு எடுத்துச்செல்வதற்கு பயன்படுத்துகின்றன. அனேக நேரங்களில் அவை வடிவத்தில் சிறப்பானவையாகவும், மகரந்தசேர்ப்பிகள் அதன் ஈர்ப்பினைத் (தேன், மகரந்தம் அல்லது இணை) தேடி வரும்போது அதன் உடலில் மகரந்த தூள்கள் மாற்றப்படுவதை உறுதி செய்வதற்காக மகரந்தகோசங்களை வரிசையாக கொண்டிருக்கும். இந்த ஈர்ப்பிக்களை ஒரே வகையான தாவரங்களின் பல்வேறு மலர்களில் பின்தொடர்வதில், அது வருகைத் தரும் அனைத்து மலர்களிலும் - வரிசையாக அடுக்கப்பட்டிருக்கும் சூலக முகட்டில் மகரந்தங்களை மாற்றுகின்றன. மகரந்தச்சேர்க்கையை உறுதி செய்வதற்காக மலர் பாகங்களிடையே எளிய இடவகை அண்மையை பல மலர்கள் நம்பியிருக்கின்றன. மற்றவைகள், சாராசேனியா அல்லது லேடி ஸ்லிப்பர் ஆர்ச்சிட் மலர்கள் போன்றவை, சுய மகரந்தச் சேர்க்கையை தவிர்க்கும்போது மகரந்தச் சேர்க்கையை உறுதி செய்வதற்காக நுட்பமான வடிவமைப்பைக் கொண்டுள்ளது.

மகரந்தப் பைகள் ஒரு மிடோ ஃபாக்ஸ் டெயில் மலரிலிருந்து பிரிந்திருக்கிறது

ஒரு புல் மலர் தலை (மிடோவ் ஃபாக்ஸ்டெயில்) நீண்ட மகரந்தபைகளுடன் கூடிய இயல்பான நிறமுடைய மலர்களைக் காட்டுகிறது.

அனேமோஃபிலஸ்: மலர்கள் மகரந்தங்களை ஒன்றிலிருந்து இன்னொன்றுக்கு நகர்த்துவதற்கு காற்றைப் பயன்படுத்துகின்றன, உதாரணங்களில் உள்ளடங்குவன புற்கள் (போவேசியா), பிர்ச் மரங்கள், ராக்வீட் மற்றும் மேபிள்ஸ். அவைகளுக்கு மகரந்தசேர்ப்பிகளைக் கவரவேண்டியத் தேவையில்லை, எனவே அவைகள் “ஆடம்பர” மலர்களைக் கொண்டிருக்கவேண்டிய அவசியமில்லை. அதே சமயம் என்டமோஃபிலஸ் மலர்களின் மகரந்தம் பெரிய துகள்களாகவும், ஒட்டக்கூடியதாகவும் புரத வளம் நிறைந்ததாகவும் (மகரந்தச் சேர்ப்பிகளுக்கு மற்றுமொரு “பரிசு”) இருக்கும், அனேமோஃபிலஸ் மலர் மகரந்தங்கள் பொதுவாக சிறிய துகள்களாகவும், மிகவும் லேசானதாகவும், பூச்சிகளுக்கு குறைந்த ஊட்டமிக்கதாகவும், பஞ்சகாலங்களில் மட்டும் கிடைப்பதாகவும் இருக்கின்றன. தேனீக்களும், பெரியவகை வண்டுகளும் அனேமோஃபிலஸ் கதிர்மணி (மக்காச்சோளம்) மகரந்தங்களை, அவைகளுக்கு அவை குறைந்த மதிப்பினதாக இருந்தாலும், ஆற்றலுடன் சேகரிக்கின்றன்.

சில மலர்கள் சுய மகரந்தச் சேர்க்கை செய்பவை மற்றும் ஒருபோதும் திறவாத மலர்களைப் பயன்படுத்துகிறது அல்லது மலர்கள் திறக்கும் முன்பே மகரந்தச் சேர்க்கை முடிந்துவிடும். இந்த மலர்கள் க்ளேயிஸ்டோகாமஸ் என்று அழைக்கப்படுகின்றன. பல வயோலா தாவர வகைகள் மற்றும் சில சால்வியாக்கள் இந்த வகை மலர்களைக் கொண்டிருக்கும்.

மலர்-மகரந்தசேர்ப்பி உறவுமுறைகள்[தொகு]

பல மலர்கள் ஒன்று அல்லது ஒரு சில குறிப்பிட்ட மகரந்தச் சேர்க்கை செய்யும் உயிர்களுடன் நெருங்கிய உறவு கொண்டுள்ளது. உதாரணத்திற்கு, சில மலர்கள் ஒரே ஒரு குறிப்பிட்ட பூச்சிவகைகளை கவர்கின்றன, எனவே வெற்றிகரமான இனப்பெருக்கத்திற்கு அந்தப் பூச்சியையே சார்ந்திருக்க வேண்டியிருக்கிறது. மலர் மற்றும் மகரந்தபரப்பி இரண்டும், ஒரு நீண்ட காலத்தில் ஒன்றுக்கொன்றின் தேவைகளை எதிர்கொண்டு ஒன்றாக வளர்ச்சியடையவதாகக் கருதப்படுவதால், இந்த நெருக்கமான உறவுமுறை இணைமலர்தலுக்கான ஒரு உதாரணமாக அடிக்கடி கொடுக்கப்படுகிறது.

இந்த நெருக்கமான உறவுமுறை மரபழிவின் எதிர்மறை விளைவுகளை ஒன்று சேர்க்கிறது. இத்தகைய உறவுகளில் எந்த ஒரு உறுப்பினரின் அழிவும் ஏறக்குறைய மற்ற உறுப்பினரின் அழிவும் உறுதியாகிறது. அழிவிலிருக்கும் சில தாவர வகைகள் அவ்வாறு ஏற்படுவதற்கு சுருங்கிவரும் மகரந்த சேர்ப்பிகளின் தொகைகளே காரணமாகும்.

கருவுறுதலும் பரவுதலும்[தொகு]

சில மலர்களில் மகரந்தகோசங்கள் மற்றும் யோனி சுயக் கருத்தரித்தலுக்கான திறனுடன் இருக்கும். அது விதைகளை உருவாக்குவதற்கான வாய்ப்பினை அதிகரிக்கச் செய்கிறது, ஆனால் மரபு மாற்றத்தைக் கட்டுப்படுத்துகிறது. சுயக்கருத்தரித்தலின் அதிகபட்ச நிகழ்வு எப்போதும் சுயக்கருத்தரித்தல் உண்டாகும் மலர்களில் நிகழ்கிறது, பல டான்டேலியன்கள் போன்றவை. சொல்லப்போனால், சுயகருத்தரித்தலைத் தவிர்ப்பதற்கான வழிகளைக் கொண்டிருக்கின்றன. ஒற்றைப் பால் ஆண் மற்றும் பெண் மலர்கள் ஒரே தாவரத்தில் தோன்றாமலோ அல்லது ஒரே நேரத்தில் முதிர்ச்சியடையாமலோ இருக்கலாம், அல்லது ஒரே தாவரத்திலிருந்தான மகரந்தம் அதன் சூல்வித்தை கருத்தரிக்கச் செய்ய இயலாமல் போகும். முந்தைய வகைகள், தங்களின் சொந்த மகரந்தங்களை பெற்றிருக்க இரசாயன தடைகளைக் கொண்டிருக்கும், அவை சுய-மலடு அல்லது சுய-திறனற்றவை என்றும் குறிக்கப்படுகிறது. (தாவரப் பாலியலைப் பார்க்கவும்).

பரிணாமம்[தொகு]

ஆர்கேஃப்ரக்டஸ் லியோனின்ஜெனிசிஸ், அறியப்பட்ட மிகப் பழமையான மலர் தாவரங்களில் ஒன்று

425 மில்லியன் ஆண்டுகளுக்கு முன்னர் தாவரங்கள் இருந்தபோது, முதலாமானவைகள் தங்களின் நீர்சார் இணைகளான வித்துகளிடமிருந்து ஒரு எளிமையான ஏற்பின் மூலம் அதாவது வித்து மூலம் இனப்பெருக்கம் செய்தன. கடலில், தாவரங்கள் -- மற்றும் சில விலங்குகள் -- தங்களின் மரபு குளோன்களை சிதறச் செய்து அவை மிதந்து வேறு எங்காவது வளரச் செய்ய முடியும். இவ்வாறு தான் ஆதி கால தாவரங்கள் வளர்ந்தன. இந்தப் பிரதிகள் காய்ந்துவிடுவதை மற்றும் கடலை விட நிலத்தில் அதிகம் நிகழக்கூடிய பிற கேடுகளை எதிர்கொள்வதற்கான பாதுகாப்பு முறைகளை தோற்றுவித்தன. அது மலராகத் தோன்றாவிட்டாலும், அந்தப் பாதுகாப்பே வித்து ஆனது. ஆரம்ப கால விதைத் தாவரங்கள் ஜின்க்கோ மற்றும் கூம்புத் தாவரங்கள் ஆகியவற்றை உள்ளிடுகின்றன, ஆரம்பகால மலர் தாவரங்களின் புதைப்படிவமானது, 125 மில்லியன் ஆண்டுகளுக்கு முந்தைய, ஆர்கேஃப்ரக்டஸ் லியானின்ஜெனிசிஸ் ஆகும்[13].

ஏலடோச்லடுஸ் பலானா. ஆதிகாலத்தில் அறியப்பட்ட தாவரங்களில் ஒன்று, ஸ்டீபன் அ. என்பவரால் ஸ்ரீபெரும்புதூர் அருகே கண்டெடுக்கப்பட்டது.

மரபழிந்த மூடாவித்துத் தாவரங்களின் (எக்ஸ்டின்க்ட் ஜிம்னோஸ்பேர்ம்ஸ்) பல்வேறு குழுக்கள், குறிப்பாக விதை பன்னங்கள் (சீடு ஃபெர்ன்கள்), மலர் தாவரங்களின் முன்னோடிகளாக முன்வைக்கப்படுகின்றன, ஆனால் எவ்வாறு மலர் தோன்றியது என்பதைக் காட்டுவதற்கான தொடர்ச்சியான புதைப்படிவங்கள் ஏதும் கிடைக்கப் பெறவில்லை. மரபழிந்த மூடாவித்துத் தாவரங்களின் (எக்ஸ்டின்க்ட் ஜிம்னோஸ்பேர்ம்ஸ்) பல்வேறு குழுக்கள், குறிப்பாக விதை பன்னங்கள் (சீடு ஃபெர்ன்கள்), மலர் தாவரங்களின் முன்னோடிகளாக முன்வைக்கப்படுகின்றன, ஆனால் எவ்வாறு மலர் தோன்றியது என்பதைக் காட்டுவதற்கான தொடர்ச்சியான புதைப்படிவங்கள் ஏதும் கிடைக்கப் பெறவில்லை. புதைப்படிவப் பதிவுகளில் தொடர்புடைய நவீன மலர்களின் திடீரென்று வெளிப்பட்ட தோற்றமானது, தோற்ற பரிணாமத்திற்கான கோட்பாட்டிற்கே பெரும் சிக்கலை உண்டாக்கி அதை சார்லஸ் டார்வின் "அருவருப்பான புதிர்" என்று கூறும் அளவுக்குச் சிக்கலானது. சமீபத்தில் கண்டறியப்பட்ட ஆர்கியோஃப்ரக்டஸ் போன்ற மலர் தாவரங்களின் புதைப்படிவம், மூடாத்தாவரப் புதைப்படிவங்களுக்கான மேற்கொண்ட கண்டுபிடிப்புகளுடன், மலர்தாவரங்களின் குணநலன்களை எவ்வாறு தொடர்ச்சியான படிப்படியான வளர்ச்சியை பெற்றிருக்கக்கூடும் என்பதை கருத்துரைக்கின்றன.

சமீபத்திய டிஎன்ஏ பகுப்பாய்வுகள் (மூலக்கூறு முறைப்படுத்தல்கள்)^[5]^[6] பசிபிக் தீவுகளின் நியூ காலடோனியாவில் காணப்படும் “அம்போரெல்லா டிரிக்கோபோடா”, மற்ற இதர மலர் தாவரங்களின் துணைக் குழு என்று காட்டுகின்றன. மேலும் தாவர வடிவமைப்பியல்^[7] அது முந்தைய தாவர மலர்களின் குணநலன்களாக இருப்பவற்றிற்கான அம்சங்களைக் கொண்டிருக்கக்கூடும் என்று கருத்துரைக்கின்றன.

ஆரம்பம் முதலே, மலர்களின் செயல்பாடு என்பது பிற விலங்குகளை இனப்பெருக்க செயல்முறைகளில் ஈடுபடுத்துவது என்ற பொதுவான ஊகமாகும். மகரந்த தூள்கள் பளிச்சென்ற நிறங்கள் மற்றும் நிச்சயமான வடிவம் இன்றி பரப்பப்படலாம், தாவரத்தின் வளங்களை பயன்படுத்துவதன் மூலம், அவை மற்ற சில பலன்களை தராதபட்சத்தில், அது மற்றுமொரு கடப்பாடாக இருக்கக்கூடும். மலர்களின் இந்த திடீரென்ற முழுமையான வளர்ச்சிபெற்றத் தோற்றத்திற்கு முன்வைக்கப்படும் காரணம், அவை ஒரு தீவு அல்லது தீவுகளின் சங்கிலித் தொடர்போன்ற அமைப்புகளில் தோன்றியது என்பதாகும், அவ்விடங்களில் அவற்றைக் கொண்டிருக்கும் தாவரங்கள் மிகவும் சிறப்பான உறவினை சில குறிப்பிட்ட விலங்குகளுடன் (உதாரணத்திற்கு குளவி) உருவாக்கிக்கொள்கின்றன, இந்த வழியில் பல தீவுத் தாவர இனங்கள் இன்றும் வளர்கின்றன. இந்த இணைவாழ்வுத் திடமான உறவுமுறை, குளவியினால் ஒரு தாவரத்திலிருந்து மற்றொரு தாவரத்திற்கு கொண்டு செல்லப்படுவதாகக் கூறப்படும் ஃபிக் குளவிகள் இன்று செய்வது, இரண்டு தாவரங்களிலும் மற்றும் அதன் கூட்டாளிகளிலும் உயர் அளவிலான சிறப்பினை உருவாக்கியிருக்கக்கூடும். தாவர வகைப்படுத்தலுக்கான பொதுவான ஆதாரமாக தீவு மரபியல் நம்பப்படுகிறது, குறிப்பாக அடிப்படை ஏற்புகள் என்று வரும்போது தாழ்வான இடைமாறுபாட்டு மாற்றங்களைக் கொண்டிருப்பதாகப் பார்க்கப்படுகிறது. குளவி உதாரணம், தற்செயலானது அல்ல என்பதை கவனத்தில் கொள்ளவும்; இணைவாழ்வுத் திறன் உறவுமுறைளுக்காக குறிப்பாகத் தெளிவுடன் தோன்றியவை வண்டுகள்; அவை குளவிகளின் மரபுவழித் தோன்றல்களாகும்.

அதேபோன்று, தாவர இனப்பெருக்கத்திற்கு பயன்படுத்தப்படும் அனேகப் பழங்கள் பூக்களின் பாகங்களின் பெரிதாக்கப்படுதலில் இருந்து வருவதாகும். அதை உண்ணவிரும்பும் விலங்குகளைப் பொருத்து அந்தப்பழம் அடுக்கு நிகழ்வுக் கருவியாகிது, மற்றும் அது கொண்டிருக்கும் பழங்கள் அவ்வாறே பரவச் செய்யப்படுகின்றன.

அத்தகைய பல இணைவாழ்வுத் திறமான உறவுகள் முக்கிய நில விலங்குகளுடன் வாழ்வதற்கான போட்டியிலும் பரவுவதிலும் மிகவும் வலுவற்றதாக இருப்பதால், மலர்கள் அசாதாரணமான வகையில் இனப்பெருக்கத்திற்கும், நிலத் தாவர வாழ்வில் முனைப்பானவையாக ஆவதற்காக பரவுவதற்கும் (அவற்றின் அசல் தோற்றம் எதுவாக இருந்தாலும்) ஆற்றல்மிக்கவைகளாக நிரூபணமாயின.

லோமேடியம் பாரீ, ஆதி அமெரிக்கக் குடிகளால் உட்கொள்ளப்பட்ட ஒரு தாவரம்

அத்தகைய மலர்கள் 130 மில்லியன் ஆண்டுகளுக்கு முன் இருந்ததற்கு மிகவும் அரிதான ஆதாரங்கள் இருக்கும்போது, அவை 250 ஆண்டுகளுக்கு முன் வரை இருந்ததற்கு சில சூழ்நிலை சார்ந்த ஆதாரங்களும் இருக்கின்றன. கைகான்டோபெட்ரிட்ஸ்ஸை^[8] உள்ளிட்டு, தங்கள் மலர்களைப் பாதுகாத்துக்கொள்வதற்காக, ஓலியனேன் என்ற இரசாயனத்தைப் பயன்படுத்தும் தாவரம் புதைப்படிவத்தில் அறியப்பட்டுள்ளன, அதே சமயத்தில் வளர்ச்சியடைந்த மற்றும் மலரும் தாவரங்களின் நவீன தனிக்கூறுகளைக் கொண்டிருக்கும் அவை, தாமாகவே மலரும் தாவரங்களாக அறியப்படவில்லை, ஏனென்றால் அவற்றின் தண்டுகள் மற்றும் சிறுமுட்கட்கள் மட்டுமே விவரமாக பாதுகாக்கப்பட்டுள்ளது; கல்லாகச்சமைதலின் உதாரணங்களில் ஒன்றாகும்.

இலை மற்றும் தண்டு அமைப்பிலிருக்கும் ஒத்த தன்மை மிகவும் முக்கியமானது, ஏனென்றால் மரபியல்படி பூக்கள் ஒரு தாவரத்தின் சாதாரண இலை மற்றும் தண்டுக்கூறுகளின் தழுவலாகும், ஒரு புதிய இளந்தளிர் கொம்பின்^[9]உருவாக்கத்திற்கு மரபணுக்களின் கலவை பொறுப்பாகிறது. மிகவும் முற்பட்டக் காலத்திய மலர்கள் பலவேறு மாறுபட்ட மலர்களின் பாகங்களைக் கொண்டிருந்திருக்கலாம் என்று எண்ணப்படுகிறது, அவை அடிக்கடி ஒவ்வொன்றிலிருந்தும் தனித்தனியாக இருக்கும் (ஆனால் தொடர்பிலிருக்கும்). இருபால் வகையாக இருப்பதற்கு (தாவரங்களில், இது ஒரே மலரில் ஆண் மற்றும் பெண் பாகங்கள் இருப்பதாகப் பொருள்படும்) மற்றும் கருவகத்தால் விஞ்சப்பட்டிருப்பதற்கு (பெண் பாகம்), மலர்கள் சுருள் வகையாக வளர்வதற்கு எண்ணப்படுகிறது. மலர்கள் மேலும் நவீனமாக வளர்வதால், மேலும் அதிகமான குறிப்பிட்ட எண்ணிக்கை மற்றும் வடிவத்துடன், ஒரு மலருக்கு அல்லது ஒரு தாவரத்திற்கு, ஏதேனும் ஒரு பாலுடனோ அல்லது குறைந்தது “தாழ்வான கருவகத்துடனோ" சில மாற்றங்களுடனான பாகங்கள் ஒன்றிணைந்திருக்கும்.

மலர் வளர்ச்சி தொடர்ந்து இன்றுவரை இருக்கிறது; நவீன மலர்கள் முழுமையான ஆற்றலுடன் மனிதர்களால் தாக்கமடையச் செய்யப்படுவதால் இயற்கையாக மகரந்தச் சேர்க்கை செய்யமுடிவதில்லை. வீடுகளில் வளர்க்கப்படும் பல நவீன மலர்கள் வெறும் களைகளாக இருந்தன, நிலத்தை களையும்போது மட்டுமே அவை தழைத்தன. அவற்றில் சில மனிதப் பயிர்களுடன் வளர முயற்சித்தன மற்றும் அவற்றில் மிகவும் அழகாக இருந்தவை அவற்றின் அழகுக் காரணமாக, சார்புத்தன்மையை ஏற்படுத்தி மனித பாசத்தை தழுவிக்கொள்வதால் பறிக்கப்படுவதில்லை.^[10].

குறியீட்டு முறைமை[தொகு]

வாழ்க்கை அல்லது உயிர்பித்தலை குறிக்க லில்லிக்கள் அவ்வப்போது பயன்படுத்தப்படுகிறது

ஆம்புரோசியஸ் பாஸ்சேர்ட் தி எல்டர் அவர்களால் உருவாக்கப்பட்ட இது போன்ற, உயிரற்ற தத்ரூபமான படங்களுக்கு மலர்களே பொதுவான அகப்பொருளாக இருந்திருக்கினற்ன.

மலர் வடிவங்களுடன் சீன ஜேடு நகைகள், ஜின் அரசகுலம் (1115-1234 ஆம் ஆண்டுகள்) ஷாங்காய் அருங்காட்சியகம்.

பல மலர்கள் மேற்கத்திய கலாச்சாரத்தில் முக்கியக் குறியீட்டு பொருள்களைக் கொண்டுள்ளன. மலர்களுக்கு பொருள் தரும் நடைமுறைக்கு ஃப்ளோரியோகிராஃபி என்று பெயர். மிகவும் பொதுவான உதாரணங்களில் உள்ளடங்கும் சில:

சிவப்பு ரோஜாக்கள் காதல், அழகு மற்றும் அதி விருப்பங்களின் அடையாளமாக வழங்கப்படுகிறது.
மரணம் ஏற்படும் தருணங்களில் ஆறுதல் வழங்கும் அடையாளமாக பாப்பீக்கள் இருக்கின்றன.இங்கிலாந்து, நியூசிலாந்து, ஆஸ்திரேலியா மற்றும் கனடாவில், சிவப்பு பாப்பீக்கள் போர் தருணங்களில் இறந்த வீரர்களை நினைவுகூர்வதற்காக அணியப்படுகிறது.
இரிஸ்கள்/லில்லி “உயிர்ப்பித்தல்/வாழ்க்கை”யைக் குறிக்கும் ஒரு அடையாளம். அது நட்சத்திரங்கள் (சூரியன்) உடனும் மற்றும் அதன் ஒளிரும்/பளபளக்கும் இதழ்களுடனும் தொடர்புடையதாக இருக்கிறது.
டெய்ஸிக்கள் அப்பாவித் தனத்திற்கான ஒரு அடையாளமாக இருக்கிறது.

ஜியார்ஜிய ஓ’கேஃப்பே, ஈமோஜென் கன்னிங்ஹாம், வெரோனிகா ரூயிஸ் டி வெலாஸ்கோ மற்றும் ஜூடி சிகாகோ போன்ற கலைஞர்களின் படைப்புகளிலும், இன்னும் ஆசிய மேற்கத்திய கலை ஓவியங்களிலும் காணப்படுவதுபோல், மலர்கள் கலையிலும் பெண்ணுறுப்புகளின் அம்சமாக சித்தரிக்கப்படுகிறது. உலகெங்கிலும் பல்வேறு கலாச்சாரங்கள் பெண்மையுடன் தொடர்புடையதாக மலர்களைக் குறித்துள்ளன.

பல்வேறு கவிஞர்களின் படைப்புகள், குறிப்பாக 18-19 ஆம் நூற்றண்டின் காதல் காலத்தில், பெரிய அளவிலான மற்றும் அழகான மலர்களின் தாக்கத்தைக் கொண்டிருந்தன. பிரபலமான உதாரணங்களில் உள்ளடங்குவன, வில்லியம் வேர்ட்ஸ்வொர்த்தின் ஐ வாண்டர்ட் லோன்லி ஆஸ் எ க்ளௌட் மற்றும் வில்லியம் ப்ளேக்கின் ஆ! சன்ஃப்ளவர்

அவற்றின் மாறுபட்ட மற்றும் வண்ணமயமானத் தோற்றம் காரணமாக, மலர்கள் காட்சிச் சார்ந்த கலைஞர்களின் விருப்ப விஷயமாக பல காலமாக இருந்து வருகிறது. வான் காகின் சூரியகாந்தி மலர் வரிசை அல்லது மோனட்டின் நீர் அல்லிகள் போன்ற நன்கு அறியப்பட்ட ஓவியர்களின் பிரபலமான ஓவியங்கள் மலர்களுடனானவை. முப்பரிமான மலர் ஓவியங்களை உருவாக்குவதற்காக, மலர்கள் உலரவைக்கப்படுகின்றன, உறைய வைக்கப்பட்டு உலர வைக்கப்படுகின்றன மற்றும் அழுத்தப்படுகின்றன.

மலர்கள், பூந்தோட்டங்கள் மற்றும் வசந்த காலத்திற்கான ரோமனிய பெண் கடவுள் ஃப்ளோரா. வசந்த காலம், மலர்கள் மற்றும் இயற்கைக்கான கிரேக்க பெண் கடவுள் க்ளோரிஸ்.

இந்து மதப் புராணங்களில், மலர்களுக்கு குறிப்பிடத்தக்க மதிப்பிருக்கிறது. இந்து அமைப்பின் மூன்று கடவுள்களில் ஒருவரான விஷ்ணு, எப்போதும் தாமரை மலர் மீது நேராக நின்றிருப்பது போன்று சித்தரிக்கப்படுகிறார்.^[11] விஷ்ணுவுடன் உள்ளத் தொடர்பு தவிர, இந்து பாரம்பரியம் தாமரையை ஆன்மீக முக்கியத்துவம் வாய்ந்தாகக் கருதுகிறது.^[12]உதாரணத்திற்கு, உருவாக்கத்திற்கான இந்து மதக் கதைகளில் அது சித்தரிக்கப்படுகிறது.^[13]

பயன்பாடு[தொகு]

மலர்க்கோலம்

வாரணாசியில் லிங்கக் கோவிலில் மலர்களை வைக்கும் பெண்ணின் கரம்

நவீன காலங்களில், அவற்றின் ஏற்கத்தக்க தோற்றம் மற்றும் மணம் காரணமாக, ஓரளவு மக்கள் பூக்களை அல்லது மொட்டுக்களை விளைவிக்கவும், வாங்கவும், அணிந்துகொள்ளவும் அல்லது ஏதோ ஒரு வகையில் மலர்களைச் சுற்றியிருக்கவும் விரும்புகிறார்கள். உலகெங்கிலும், மக்கள் மலர்களை பல்வேறு வகையான நிகழ்ச்சிகள் மற்றும் விழாக்களுக்கு பயன்படுத்துகிறார்கள், இது ஒட்டுமொத்தமாக ஒருவரின் வாழ்வினை சூழ்ந்திருக்கிறது:

குழந்தைப் பிறப்பு அல்லது பெயர் வைத்தலில்
சமுதாய விழாக்கள் அல்லது விடுமுறைகளுக்கு அணிந்துகொள்ளப்படும் மலர்கச்சுக்களாக அல்லது சட்டையை அலங்கரிக்கும் மலர்கொத்தாக
அன்பு அல்லது மரியாதையின் அடையாளமாக
திருமணங்களுக்கான பெண்ணழைப்பு விருந்துக்காக மற்றும் அரங்கத்தை அலங்கரிப்பதற்காக
வீட்டினுள் ஒளிரச்செய்யும் அலங்காரமாக
வழியனுப்புவதற்கான விழாக்கள், வரவேற்பு விழாக்களுக்கான நினைவுப் பரிசாக, "நினைவில் வைத்திருப்பதற்கான” பரிசுகளாக
சவ ஊர்வலங்களுக்காக மற்றும் துக்கத்திற்கான அனுதாபங்களை வெளிப்படுத்துவதற்காக
பெண் கடவுள்களை வழிப்படுவதற்காக, கோவில்களுக்கு மலர்களைக் கொண்டு வருவது இந்துக் கலாச்சாரத்தில் மிகவும் பொதுவான ஒன்றாகும்.

எனவே மலர்களை மக்கள் வீட்டைச் சுற்றி வளர்க்கிறார்கள், தங்களின் வாழ்விடம் முழுவதையும் மலர் தோட்டத்திற்காக அர்பணிக்கிறார்கள், காட்டுப்பூக்களைப் பறிக்கிறார்கள் அல்லது மொத்த வர்த்தக மலர் வளர்ப்பவர்கள் மற்றும் அவர்களின் வணிகத்திற்கு உதவும் அனுப்புபவர்களை சார்ந்திருக்கும் மலர் விற்பனையாளர்களிடமிருந்து வாங்குவார்கள்.

தாவரத்தின் மற்ற பாகங்களைவிட (விதைகள், பழங்கள், வேர்கள், தண்டுகள் மற்றும் இலைகள்) குறைவான உணவையே அளிக்கிறது, ஆனால் அவை பல்வேறு முக்கிய உணவுகளையும் நறுமணப் பொருட்களையும் அளிக்கின்றன. ப்ரக்கோலி, காலிஃப்ளவர் மற்றும் ஆர்டிசோக் உள்ளிட்டவை மலர்காய்கள். மிகவும் விலைமதிப்புமிக்க நறுமணப்பொருள், குங்குமப்பூ, க்ராகஸின் காயவைக்கப்பட்ட சூலகங்களைக் கொண்டிருக்கும். பிற மலர் நறுமணப்பொருட்களாவன கிராம்பு மற்றும் கேப்பர். ஹாப்ஸ் மலர்கள் பீரை சுவையூட்டப் பயன்படுத்தப்படுகின்றன. வாடிக்கையாளர்கள் விரும்பக்கூடிய, முட்டையின் மஞ்சள் கரு பொன்நிற மஞ்சளாக இருப்பதற்காக மாரிகோல்டு மலர்கள் கோழிகளுக்குக் கொடுக்கப்படுகினறன. டேன்டேலியன் மலர்கள் ஒயினாக தயாரிக்கப்படுகின்றன. ஆரோக்கியமான உணவாகக் கருதப்படும் சிலரால் தேனீக்களால் சேகரிக்கப்படும் மகரந்தங்கள். தேன் தேனீக்கள் சேகரித்த மலர்த் தேனைக் கொண்டிருக்கும் மற்றும் இது மலரின் வகையைப் பொருத்து பெயரிடப்படுகிறது, எ.கா. ஆரஞ்சுமலர்தேன், க்ளோவர் தேன் மற்றும் டுபேலோ தேன்.

நூற்றுக்கணக்கான மலர்கள் சாப்பிடக்கூடியவையாக இருந்தாலும், மிகக் குறைவானவையே விரிவாக சந்தைப்படுத்தப்படுகின்றன. அவை அடிக்கடி சாலாட்களில் நிறம் மற்றும் சுவையை சேர்க்கப் பயன்படுத்துகின்றன. ஸ்குவாஷ் மலர்கள் பிரட் தூள்களில் நனைக்கப்பட்டு வறுக்கப்படுகின்றன. சாப்பிடக்கூடிய மலர்களில் உள்ளடங்குவன நாஸ்டுர்டியம், கிரிஸான்தமம், கார்னேஷன், காட்டெயில், ஹனிசக்கிள், சிக்கரி, கார்ன்ஃப்ளவர், கன்னா மற்றும் சூரியகாந்தி. சில நேரங்களில் சில சாப்பிடக்கூடிய மலர்களில் டெய்ஸி மற்றும் ரோஜா போன்றவை சர்க்கரைப்பாகினைக் கொண்டிருக்கும் (நீங்கள் சக்கரைப்பாகுள்ள பான்ஸிக்களைப் பார்த்திருக்கலாம்)

மலர்கள் மூலிகை தேனீராகவும் தயாரிக்கப்படலாம். உலரவைக்கப்பட்ட க்ரிஸான்தமம், ரோஜா, ஜாஸ்மின், கமோமைல் தேனீரில் மணத்திற்காகவும் மருத்துவ குணங்களுக்காகவும் ஊறவைக்கப்படுகின்றன. சில நேரங்களில் அவை கூடுதல் மணத்திற்காக தேயிலையுடன் கலக்கப்படுகின்றன.

மலர்களின் பருவநிலைத் தமிழ்ப்பெயர்கள்[தொகு]

அரும்பு - அரும்பும் தோன்றுநிலை

நனை - அரும்பு வெளியில் நனையும் நிலை

முகை - நனை முத்தாகும் நிலை

மொக்குள் - "முகை மொக்குள் உள்ளது நாற்றம்" - திருக்குறள் (நாற்றத்தின் உள்ளடக்க நிலை)

முகிழ் - மணத்துடன் முகிழ்த்தல்

மொட்டு - கண்ணுக்குத் தெரியும் மொட்டு

போது - மொட்டு மலரும்பொழுது காணப்படும் புடைநிலை

மலர்- மலரும் பூ

பூ - பூத்த மலர்

வீ - உதிரும் பூ

பொதும்பர் - பூக்கள் பலவாகக் குலுங்கும் நிலை

பொம்மல் - உதிர்ந்து கிடக்கும் புதுப் பூக்கள்

செம்மல் - உதிர்ந்த பூ பழம்பூவாய்ச் செந்நிறம் பெற்று அழுகும் நிலை

பூக்களின் பட்டியல்[தொகு]

பல்வேறு வண்ணம், வடிவங்களில் மலர்கள்

சங்ககால மலர்கள்

ගස් සහ පැළ සහ මල් Trees and plants and flowers மரங்கள் மற்றும் தாவரங்கள்மற்றும் மலர்கள்

Tree

From Wikipedia, the free encyclopedia

For other uses, see Tree (disambiguation).

Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree

European larch (Larix decidua), a coniferous tree which is also deciduous

Lepidodendron, an extinct lycophyte tree

Contents

[show]

Definition

Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots.

Aside from structural definitions, trees are commonly defined by use, for instance as those plants which yield lumber.[12]

Overview

Tall herbaceous monocotyledonous plants such as banana lack secondary growth, and are trees only in a loose sense.

Distribution

Further information: Forest

The Daintree rainforest

Parts and function

A young red pine (Pinus resinosa) with spread of roots visible, as a result of soil erosion

Roots

Main article: Root

Buttress roots of the kapok tree (Ceiba pentandra)

Some tree species have developed root extensions that pop out of soil, in order to get oxygen, when it is not available in the soil because of excess water. These root extensions are called pneumatophores, and are present, among others, in black mangrove and pond cypress.[51]

Trunk

Northern beech (Fagus sylvatica) trunk in autumn

Main article: Trunk (botany)

A section of yew (Taxus baccata) showing 27 annual growth rings, pale sapwood and dark heartwood

Buds and growth

Dormant magnolia (Magnolia sp.) bud

Main article: Bud

Leaves

Buds, leaves, flowers and fruit of oak (Quercus robur)

Buds, leaves and reproductive structures of white fir (Abies alba)

Main article: Leaf

Reproduction

Form, leaves and reproductive structures of queen sago Cycas circinalis

Main article: Plant reproduction

Seeds

Main article: Seed

Wind dispersed seed of elm (Ulmus), ash (Fraxinus) and sycamore (Acer pseudoplatanus)

Evolutionary history

Palms and cycads as they might have appeared in the middle Tertiary

Further information: Evolutionary history of plants

Tree ecology

Further information: Forest

Uses

Food

Forest honey

Further information: nut (fruit) and fruit

Sugar maple (Acer saccharum) being tapped for the production of maple syrup

Fuel

Main article: Wood fuel

Selling firewood at a market

Timber

Main articles: Wood and Timber

Joinery and roof trusses made from softwood

Wood is pulped for paper and used in the manufacture of cardboard and made into engineered wood products for use in construction such as fibreboard, hardboard, chipboard and plywood.[120] The wood of conifers is known as softwood while that of broad-leaved trees is hardwood.[121]

Art

Informal upright style of bonsai on a juniper tree

Besides inspiring artists down the centuries, trees have been used to create art. Living trees have been used in bonsai and in tree shaping, and both living and dead specimens have been sculpted into sometimes fantastic shapes.[122]

Bonsai

Main article: Bonsai

Tree shaping

Main article: Tree shaping

People trees, by Pooktre

Tree shaping has been practised for at least several hundred years, the oldest known examples being the living root bridges built and maintained by the Khasi people of Meghalaya, India using the roots of the rubber tree (Ficus elastica).[129][130]

Bark

Recently stripped cork oak (Quercus suber)

Alleé of London plane trees (Platanus × acerifolia) in garden

Aside from structural definitions, trees are commonly defined by use, for instance as those plants which yield lumber.^[12]

Some tree species have developed root extensions that pop out of soil, in order to get oxygen, when it is not available in the soil because of excess water. These root extensions are called pneumatophores, and are present, among others, in black mangrove and pond cypress.^[51]

Wood is pulped for paper and used in the manufacture of cardboard and made into engineered wood products for use in construction such as fibreboard, hardboard, chipboard and plywood.^[120] The wood of conifers is known as softwood while that of broad-leaved trees is hardwood.^[121]

Besides inspiring artists down the centuries, trees have been used to create art. Living trees have been used in bonsai and in tree shaping, and both living and dead specimens have been sculpted into sometimes fantastic shapes.^[122]

Tree shaping has been practised for at least several hundred years, the oldest known examples being the living root bridges built and maintained by the Khasi people of Meghalaya, India using the roots of the rubber tree (Ficus elastica).^[129]^[130]