Documents for "Botany: General":

• air plant see epiphyte.

• alpine plants high-altitude representatives of various flowering plants (chiefly perennials) that because of their dwarf habit, profuse blooming, and the preference of many for shady places are cultivated in...

• alternation of generations see gametophyte ; reproduction.

• amitosis see mitosis.

• amyloplast also called leucoplast, a nonpigmented organelle, or plastid, occurring in the cytoplasm of plant cells. Amyloplasts transform glucose, a simple sugar, into starch through the process of...

• angiosperm term denoting seed plants in which the ovules, or young seeds, are enclosed within the ovary (that part of the pistil specialized for seed production), in contrast to the gymnosperms, in which the...

• annual plant that germinates from seed, blossoms, produces seed, and dies within one year. Annuals propagate themselves by seed only, unlike many biennials and perennials. They are thus especially suited...

• annual rings the growth layers of wood that are produced each year in the stems and roots of trees and shrubs. In climates with well-marked alternations of seasons (either cold and warm or wet and dry), the wood cells produced when...

• anther pollen -bearing structure of the stamen of a flower, usually borne on a slender stalk called the filament. Each anther generally consists of two pollen sacs, which open when the pollen is mature. The...

• auxin plant hormone that regulates the amount, type, and direction of plant growth. Auxins include both naturally occurring substances and related synthetic compounds that have similar effects. Auxins...

• bark outer covering of the stem of woody plants, composed of waterproof cork cells protecting a layer of food-conducting tissue—the phloem or inner bark (also called bast). As the woody stem increases...

• bast see bark.

• berry see fruit.

• biennial plant requiring two years to complete its life cycle, as distinguished from an annual or a perennial. In the first year a biennial usually produces a rosette of leaves (e.g., the cabbage) and a...

• botany science devoted to the study of plants. Botany, microbiology, and zoology together compose the science of biology. Humanity's earliest concern with plants was with their practical uses, i.e., for fuel, clothing, shelter, and, particularly, food and drugs. The establishment of botany as an intellectual science...

• bran outer coat of a cereal grain—e.g., wheat, rye, and corn—mechanically removed from commercial flour and meal by bolting or sifting. Wheat bran is extensively used as feed for farm animals. Bran is...

• bud in lower plants and animals, a protuberance from which a new organism or limb develops; in seed plants, a miniaturized twig bearing compressed rudimentary lateral stems (branches), leaves, or...

• bulb thickened, fleshy plant bud, usually formed under the surface of the soil, which carries the plant over from one blooming season to another. It may have many fleshy layers (as in the onion and...

• bur or burr, popular name for fruits that have barbed, pointed, or rough outgrowths. By clinging to the fur or hair of animals and the clothing of man they are transported from the parent plant, often great...

• calyx see sepal.

• cambium thin layer of generative tissue lying between the bark and the wood of a stem, most active in woody plants. The cambium produces new layers of phloem on the outside and of xylem ( wood ) on the inside, thus increasing the diameter of the stem. In herbaceous plants the cambium is almost inactive; in monocotyledonous plants it is usually absent. In regions where there are alternating seasons, each year's growth laid down by the cambium is...

• chlorophyll green pigment that gives most plants their color and enables them to carry on the process of photosynthesis. Chemically, chlorophyll has several similar forms, each containing a complex ring structure and a long hydrocarbon tail. The molecular structure of the chlorophylls is similar to that of the heme portion of hemoglobin, except that the latter contains iron in place of magnesium. Within the photosynthetic cells...

• chloroplast a complex, discrete green structure, or organelle, contained in the cytoplasm of plant cells. Chloroplasts are reponsible for the green color of almost all plants and are lacking only in plants...

• climbing plant any plant that in growing to its full height requires some support. Climbing plants may clamber over a support (climbing rose), twine up a slender support (hop, honeysuckle), or grasp the support...

• cone or strobilus , in botany, reproductive organ of the gymnosperms (the conifers , cycads , and ginkgoes ). Like the flower in the angiosperms (flowering plants), the cone is actually a highly modified branch; unlike the flower, it does not have sepals or petals. Usually separate male (staminate, or...

• cork protective, waterproof outer covering of the stems and roots of woody plants. Cork is a specialized secondary tissue produced by the cork cambium of the plant (see meristem , bark ). The regularly arranged walls of cork cells are impregnated with a waxy material, called suberin, that is almost impermeable to water or gases. Commercial cork, obtained from the cork oak , is buoyant in water because of the presence of trapped air in the cavities of the waterproof dead cells. It is also resilient, light, chemically inert, and, because of the suction cup action of...

• corm short, thickened underground stem, usually covered with papery leaves. A corm grows vertically, producing buds at the upper nodes and roots from the lower surface. Corms serve as organs of food...

• corolla see petal.

• cortex in botany, term generally applied to the outer soft tissues of the leaves, stems, and roots of plants. Cortical cells of the leaves and outer layers of nonwoody stems contain chloroplasts, and are...

• cotyledon in botany, a leaf of the embryo of a seed. The embryos of flowering plants, or angiosperms , usually have either one cotyledon (the monocots) or two (the dicots). Seeds of gymnosperms, such as pines, may have numerous cotyledons. In some seeds the cotyledons are flat and leaflike; in...

• cryptogam in botany, term used to denote a plant that produces spores, as in algae , fungi , mosses , and ferns , but not seeds. The term cryptogam, from the Greek kryptos, meaning "hidden," and gamos, meaning "marriage," was coined by 19th-century botanists because the means of sexual reproduction in these plants was not then apparent. In contrast, in the seed plants the reproductive organs are easily seen; the...

• deciduous plant see tree.

• dioecious plant plant in which the male and female reproductive structures are found in different individuals, as distinct from a monoecious plant (see hermaphrodite ), in which they are found in the same individual....

• drupe see fruit.

• epiphyte or air plant, any plant that does not normally root in the soil but grows upon another living plant while remaining independent of it except for support (thus differing from a parasite ). An epiphyte manufactures its own food (see photosynthesis ) in the same way that other green plants do, but obtains its moisture from the air or from moisture-laden pockets of the host plant, rather than from the soil. Some epiphytes are found in every...

• flower name for the specialized part of a plant containing the reproductive organs, applied to angiosperms only. A flower may be thought of as a modified, short, compact branch bearing lateral appendages...

• fruit matured ovary of the pistil of a flower, containing the seed. After the egg nucleus, or ovum, has been fertilized (see fertilization ) and the embryo plantlet begins to form, the surrounding ovule (see pistil ) develops into a seed and the ovary wall (pericarp) around the ovule becomes the fruit. The pericarp consists of three layers of tissue: the thin outer exocarp, which becomes the "skin" ; the thicker mesocarp; and the inner endocarp, immediately surrounding the ovule. A flower may have one or more simple pistils or a compound pistil made up of two or more fused simple pistils (each...

• gametophyte phase of plant life cycles in which the gametes, i.e., egg and sperm, are produced. The gametophyte is haploid, that is, each cell contains a single complete set of chromosomes, and arises from...

• germination in a seed, process by which the plant embryo within the seed resumes growth after a period of dormancy and the seedling emerges. The length of dormancy varies; the seed of some plants (e.g., most grasses and many tropical plants) can sprout almost...

• gibberellins a group of growth-regulating substances of plants, having complex chemical structure, of which the best known, gibberellic acid, is noted for its promotion of stem growth. In Japan it was long...

• growing season period during which plant growth takes place. In temperate climates the growing season is limited by seasonal changes in temperature and is defined as the period between the last killing frost of...

• gymnosperm see angiosperm.

• halophyte any plant, especially a seed plant, that is able to grow in habitats excessively rich in salts, such as salt marshes, sea coasts, and saline or alkaline semideserts and steppes. These plants have...

• hardwood see wood.

• heartwood the central, woody core of a tree, no longer serving for the conduction of water and dissolved minerals; heartwood is usually denser and darker in color than the outer sapwood. Before the synthesis...

• herb name for any plant that is used medicinally or as a spice and for the useful product of such a plant. Herbs as condiments and seasonings are still important in culinary art; the use of medicinal...

• herbaceous plant plant whose stem is soft and green and shows little growth of wood. The term is used to distinguish such plants from woody plants. Herbaceous plants, or herbs, as they are commonly called, may be annual —that is, the plants die after a year's growth, and the plants are propagated by seed—or they may be produced each year by new shoots from dormant roots. The stems of woody plants, e.g., most shrubs...

• herbarium collection of dried and mounted plant specimens used in systematic botany. To preserve their form and color, plants collected in the field are spread flat in sheets of newsprint and dried, usually...

• isogamy in biology, a condition in which the sexual cells, or gametes, are of the same form and size and are usually indistinguishable from each other. Many algae and some fungi have isogamous gametes....

• kinetin one of a group of chemically similar plant hormones, the cytokinins, that promote cell division. In some instances kinetin acts together with another hormone, indoleacetic acid, or auxin ; in other...

• leaf chief food-manufacturing organ of a plant, a lateral outgrowth of the growing point of stem. The typical leaf consists of a stalk (the petiole) and a blade—the thin, flat, expanded portion...

• leaf mold crumbly brown humus typical of forest floors. It is composed of decayed leaves and other plant material mixed with soil.

• leucoplast see amyloplast.

• liana or liane , name for any climbing plant that roots in the ground. The term is most often used for the woody vines that form a characteristic part of tropical rain-forest vegetation; they are sometimes also...

• lignin a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly...

• meristem a specialized section of plant tissue characterized by cell division and growth. Much of the mature plant's growth is provided by meristems. Apical meristems found at the tips of stems and roots...

• monoecious plant see hermaphrodite.

• mucilage thick, glutinous substance, related to the natural gums, comprised usually of protein, polysaccharides, and uranides. It swells but does not dissolve in water. Mucilage is secreted by the seed...

• nastic movement in botany, the movement of plant parts in response either to certain external stimuli or to internal growth stimuli. Nastic movements, which are generally slow, can be observed by time-lapse...

• nut in botany, a dry one-seeded fruit which is indehiscent (i.e., does not split open along a definite seam at maturity). Among the true nuts are the acorn, chestnut, and hazelnut. Commonly the word nut is used for any seed or fruit having an edible kernel surrounded by a hard or brittle covering. Thus the peanut pod is actually a legume, the Brazil nut is a seed enclosed with others in a capsule,...

• perennial any plant that under natural conditions lives for several to many growing seasons, as contrasted to an annual or a biennial. Botanically, the term perennial applies to both woody and herbaceous plants (see stem ) and thus includes numerous members of the kingdom. In horticulture, however, the term is usually restricted to hardy herbaceous perennials, particularly border plants such as alyssum,...

• petal one of the four basic parts of a flower , next innermost organ from the sepal. The whorl of petals is known collectively as the corolla [Lat.,=little crown]. The number of petals is usually constant within groups (e.g., five in the rose...

• phanerogam see cryptogam.

• phloem see bark ; stem.

• photosynthesis process in which green plants utilize the energy of sunlight to manufacture carbohydrates from carbon dioxide and water in the presence of chlorophyll. Some of the plants that lack chlorophyll,...

• pistil one of the four basic parts of a flower , the central structure around which are arranged the stamens, the petals, and the sepals. The pistil is usually called the female reproductive organ of a flowering plant, although the actual...

• pith in botany, core of the stem of most plants. Pith is composed of large, loosely packed food-storage cells. As the stem grows older the pith usually dries out, and in some it disintegrates and the stem becomes hollow. In trees...

• plant any organism of the plant kingdom, as opposed to one of the animal kingdom or of the kingdoms Fungi , Protista , or Monera in the five-kingdom system of classification. (A more recent system, suggested by genetic sequencing studies, places plants with animals and some other forms in an overarching group, the eukarya,...

• pod or legume, dehiscent fruit of a member of the family Leguminosae ( pulse family). At maturity the pod splits along its two seams and releases the enclosed seeds.

• poisonous plant any plant possessing a property injurious to man or animal. Plants may be poisonous to the touch (e.g., poison ivy, poison sumac), or orally toxic (e.g., poison hemlock, deadly amanita). Many...

• pollen minute grains, usually yellow in color but occasionally white, brown, red, or purple, borne in the anther sac at the tip of the slender filament of the stamen of a flowering plant or in the male...

• pollination transfer of pollen from the male reproductive organ (stamen or staminate cone) to the female reproductive organ (pistil or pistillate cone) of the same or of another flower or cone. Pollination is not to be confused...

• propagation of plants is effected in nature chiefly sexually by the seed and the spore , less often by rhizomes and other methods (see reproduction ). Vegetative means include cutting , layering , grafting , tissue...

• pyrenoid see chloroplast.

• rafflesia any of a genus ( Rafflesia ) of parasitic plants native to the rain forests of the Malay peninsula, Sumatra, Borneo, and the Philippines. The plants have no roots, stems, or leaves, consisting of threadlike growths on the...

• rhizome or rootstock, fleshy, creeping underground stem by means of which certain plants propagate themselves. Buds that form at the joints produce new shoots. Thus if a rhizome is cut by a cultivating tool it does not...

• root in botany, the descending axis of a plant, as contrasted with the stem, the ascending axis. In most plants the root is underground, but in epiphytes the roots grow in the air and in hydrophytes (e.g., cattails and water lilies) they grow in water or marshes. Roots function to absorb water and dissolved minerals from the soil, to anchor the...

• rootstock see rhizome.

• runner or stolon, slender, creeping stem capable of taking root where its nodes touch the ground and thereby producing new shoots. The runner itself usually dies at the end of the season, leaving independent new...

• sap fluid in plants consisting of water and dissolved substances. Cell sap refers to this fluid present in the large vacuole, or cell cavity, that occupies most of the central portion of mature plant...

• saprophyte any plant that depends on dead plant or animal tissue for a source of nutrition and metabolic energy, e.g., most fungi (molds) and a few flowering plants, such as Indian pipe and some orchids...

• sapwood relatively thin, youngest, outer part of the woody stem of a tree, the part that conducts water and dissolved materials. In the cross section of a tree, the sapwood is recognizable by its texture...

• seed fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing them in flowering plants as in the grains and nuts. The seed-bearing plants are the highest in the evolutionary scale; in lower plants (e.g., mosses and ferns) the spore is the agent of...

• sepal a modified leaf, part of the outermost of the four groups of flower parts. The sepals of a flower are collectively called the calyx and act as a protective covering of the inner flower parts in the bud. Sepals are usually green, but in some flowers (e.g., the lily...

• shrub any woody, perennial, bushy plant that branches into several stems or trunks at the base and is smaller than a tree. Shrubs are an important feature of permanent landscape planting, being used for formal decorative groups, hedges, screens, and background plantings, to which they contribute pattern, color,...

• sporophyte see gametophyte.

• stamen one of the four basic parts of a flower. The stamen (microsporophyll), is often called the flower's male reproductive organ. It is typically located between the central pistil and the surrounding petals. A stamen consists of a slender...

• star-of-Bethlehem in botany, low, spring-blooming bulbous plant ( Ornithogalum umbellatum ) of the family Liliaceae ( lily family), native to the Mediterranean region but naturalized in North America and cultivated in gardens. The plant has rather stiff, grasslike leaves and a cluster of white star-shaped flowers...

• stem supporting structure of a plant, serving also to conduct and to store food materials. The stems of herbaceous and of woody plants differ: those of herbaceous plants are usually green and pliant and...

• stigma see pistil.

• style see pistil.

• succulent any fleshy plant that belongs to one of many diverse families, among them species of cactus, aloe, stonecrop, houseleek, agave, and yucca. Most succulents are indigenous to arid or semiarid...

• tendril slender, sensitive structure of many climbing plants that by a response to contact (see auxin ) supports the plant. Tendrils are modified stems, leaves, or leaf parts or roots. Most young tendrils revolve slowly in their natural growth, as do the growing tips of roots and shoots; the...

• terrarium a miniature garden in an artificial environment, in which small plants and animals may be kept as ornament or for educational purposes. Fish bowls, small fish tanks, large bottles, and carboys are...

• thorn sharp-pointed projection on some plants, usually protective in function. Botanically, thorns are distinguished as modified stems (as in the honey locust and hawthorn) from spines, which are...

• timber see lumber ; wood.

• transpiration in botany, the loss of water by evaporation in terrestrial plants. Some evaporation occurs directly through the exposed walls of surface cells, but the greatest amount takes place through the...

• tree perennial woody plant with a single main stem (the trunk, or bole) from which branches and twigs extend to form a characteristic crown of foliage. In general, a tree differs from a shrub in that it has a single trunk, it reaches a greater...

• tree surgery practice of repairing damaged trees to restore their appearance and to arrest disease. Injured or diseased parts are first removed (even small cavities in the bark may harbor injurious fungi and...

• tuber enlarged tip of a rhizome (underground stem) that stores food. Although much modified in structure, the tuber contains all the usual stem parts—bark, wood, pith, nodes, and internodes. The eyes of...

• vascular bundle in botany, a strand of conducting tissue extending lengthwise through the stems and roots of higher plants, including the ferns, fern allies, gymnosperms, and angiosperms. The vascular bundle...

• vegetable term originally used for any plant, now the name for many food plants, most of them annuals, and for their edible parts. There is no clear botanical distinction between vegetables and fruits. Most...

• vegetative propagation the ability of plants to reproduce without sexual reproduction, by producing new plants from existing vegetative structures. Some plants, such as the Canada thistle and most bamboos, send out long...

• vine climbing plant or trailing plant. The grape is often called "the vine." See also liana.

• weed common term for any wild plant, particularly an undesired plant, growing in cultivated ground, where it competes with crop plants for soil nutrients and water. In their natural habitat, wildflowers...

• wood botanically, the xylem tissue that forms the bulk of the stem of a woody plant. Xylem conducts sap upward from the roots to the leaves, stores food in the form of complex carbohydrates, and...

• woody plant see herbaceous plant.

• xylem see stem ; wood.