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A major plant hormone that plays an important role in plant growth and development. Abscisic acid (ABA), with a chemical formula of C15H20O4 (Fig. 1), is one of the most significant hormones found in plants. It is responsible for regulating various…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

The branch of biological science that embraces the study of plants and plant life. Botany is the scientific study of plants (see illustration), encompassing investigations of plant anatomy, physiology, genetics, phylogeny, ecology, pathology, and…

The segment of horticulture concerned with the commercial production, marketing, and sale of plants grown and used for decorative or display purposes. Floriculture is a branch of horticulture, that is, the art and science of growing plants,…

An annual leafy leguminous vine, Pisum sativum (order Fabales), cultivated for its smooth or wrinkled, round edible seeds, which are borne in dehiscent pods. The garden pea (Fig. 1) is one of the world's oldest cultivated crops. It is a native of…

An informal assemblage of predominantly aquatic organisms that carry out oxygen-evolving photosynthesis, but lack specialized water-conducting and food-conducting tissues. Algae (Fig. 1) may be either prokaryotic organisms (lacking an organized…

A natural process in which harmful or beneficial effects are caused by secondary metabolites that spread from a donor organism to a recipient and are produced by plants, algae, bacteria, and fungi. Allelopathy is a key ecological process and has…

A deciduous tree (genus Malus) in the order Rosales, which produces an edible, simple, fleshy, pome-type fruit. Apples (Fig. 1) belong to the family Rosaceae, which includes many other deciduous fruits, including pears, peaches, and cherries. There…

A large tropical plant of the genus Musa and its edible fruit. The banana belongs to the family Musaceae (order Zingiberales). The banana of commerce (Musa acuminata), which is believed to have originated in the Asian tropics, was one of the…

The American beech (Fagus grandifolia) is native to forest regions east of the Mississippi River and is a key tree species in the United States. In particular, it is very abundant from Ohio to the New England states. The tree is also found in the…

A genus comprising yeasts that cause a variety of human diseases referred to as candidiasis. All Candida species are single-celled yeasts (fungal organisms) that are ovoid in shape and 3–5 μm in size, and they multiply by a process called budding.…

A biennial umbellifer (Daucus carota) of Asiatic and Mediterranean origin belonging to the plant order Apiales. The carrot (Daucus carota; Fig. 1) is grown for its edible roots, which are eaten raw or cooked. Cultivated forms of the root vegetable…

A general term for a genus of tall forage grasses, of which the most important species is the deeply rooted perennial Paspalum dilatatum. Dallis grass (see illustration) is widely grown in the southern United States, mostly for pasture, and remains…

An order of green algae (Chlorophyceae) in which the plant body (thallus) is composed of a nonseptate axis, attached by rhizoids and bearing whorls of branches. The walls utilize a partially crystalline mannan (polymer of mannose) as the skeletal…

The date palm, Phoenix dactylifera, which is one of the oldest cultivated tree crops. The date palm provides a staple food for many populations in the Middle East and North Africa and is also highly valued for feed, fiber, and shelter. Beginning in…

A subclass of the true mosses (Bryopsida) largely limited to the South Pacific. The subclass consists of a single genus, Dawsonia, of nine species. The gametophytes are remarkably similar to those of the Polytrichidae, but the origin and structure…

Woody higher plants that regularly lose their leaves at the end of each growing season. Dropping of the leaves occurs at the inception of an unfavorable season characterized by either cold or drought or both. Many woody plants of temperate climates…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order has only a single family, the Diapensiaceae, with about 18 species of herbs and dwarf shrubs in…

A large group of flowering plants (angiosperms) that for many years has been considered one of the two main categories of plants, the other being monocotyledons. Dicotyledons have two seedling leaves as opposed to the single one in most…

A large and diverse order of the true mosses (Bryopsida), containing 13 families. Plants in the Dicranales generally have long, narrow leaves and deeply forked peristome teeth. The plants are erect and simple or merely forked and often woolly…

A genus of the plantain family (Plantaginaceae) or figwort family (Scrophulariaceae), whose dried leaves contain a number of glucosides that can be used as powerful cardiac stimulants and diuretics. The genus Digitalis ranges from the Canary Islands…

An annual culinary herb, genus Anethum, of the carrot family, Apiaceae (Umbelliferae). Dill supplies four products: dill seed oil, dill leaf oil, dill seed, and dill leaf. Although all dill grown in the United States is one species, Anethum…

An order of flowering plants, division Magnoliophyta (Angiospermae), class Magnoliopsida (dicotyledons), subclass Dilleniidae. The order Dilleniales consists of one family: the Dilleniaceae, which comprises about 350 species. (The family Paeoniaceae…

A large subclass of the class Magnoliopsida (dicotyledons) of the division Magnoliophyta (Angiospermae), the flowering plants, consisting of 13 orders, 78 families, and nearly 25,000 species. The subclass is morphologically ill-defined, but most of…

A large and extremely diverse class of biflagellate algae (dinoflagellates) in the chlorophyll a–c phyletic line (Chromophycota). In protozoological classification, these organisms constitute an order, Dinoflagellida, of the class Phytomastigophora.…

A widespread order of lilioid monocotyledons composed of four or five families, the most important of which is Dioscoreaceae (650 species). The families comprising the order Dioscoreales contain some of the most peculiar plants among the monocots.…

An order of flowering plants (angiosperms) in the asterid I group of the eudicotyledons consisting of around 6 families and almost 1000 species. Like many asterids of the asterid II group, Dipsacales have an inferior ovary and opposite leaves. They…

Any of the tree or shrub species in the genus Cornus. The tree, Cornus florida, also known as the flowering dogwood, may reach a height of 40 ft (12 m) and is found in the eastern half of the United States and in southern Ontario, Canada. It has…

The state in which a living plant organ (seed, bud, tuber, and bulb) fails to exhibit growth, even when environmental conditions are favorable. Environmental conditions favorable for growth usually include the presence of water and oxygen, and an…

A large coniferous tree, Pseudotsuga menziesii (formerly, P. taxifolia), known also as red fir, belonging to the pine family (Pinaceae). Douglas-fir is one of the most widespread and most valuable tree species of western North America and ranks…

An order of flowering plants, division Magnoliophyta (Angiospermae) in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order consists of 5 families and about 1750 species, the Sapotaceae (about 800 species) and Ebenaceae…

Any tree of the genus Diospyros of the ebony family, containing more than 250 species. Some species of ebony are important for their succulent fruits, such as date plum, kaki plum, and persimmon, and several are important for timber, particularly…

An obligate association formed between the roots of many plant species, especially trees, and a diverse range of soil fungi. The fungi and the finest, terminal root tips interact to form joint organs called ectomycorrhizas (Fig. 1). In…

Any species of Ulmus, a genus of hardwood trees in the Northern Hemisphere, with simple, serrate, deciduous leaves. The American or white elm (U. americana) is the most important species (Fig. 1). It is a large, typically vase-shaped tree that…

One of the two plant subkingdoms, with the other being the Thallobionta. The Embryobionta (often also called Embryophyta) form a well-marked group with many morphological, anatomical, and physiological features in common, and taxonomists are agreed…

An order of the true mosses (subclass Bryidae) that grow in dull, dark tufts on soil or soil-covered rock, generally in calcareous areas. The Encalyptales consist of a single family and two genera, the better known being Encalypta, the extinguisher…

The single layer of plant cells that is located between the cortex and the vascular (xylem and phloem) tissues (Fig. 1). It has its most obvious development in roots and subaerial stems. In the aerial stem and in leaves it is not always detectable…

The outermost layer (occasionally several layers) of cells on the primary plant body. Its origin and structure are variable. In addition to a general description of the epidermis of plants, this article singles out five structural components of the…

An order of the division Sphenophyta, subkingdom Embryobionta. The Equisetales, commonly known as horsetails, is represented by a single living genus, Equisetum, with about 25 species found in both moist and dry habitats. These plants grow…

Ergot is the seedlike body of fungi (molds) of the genus Claviceps; ergotism is a complex disease of humans and certain domestic animals caused by ingestion of grains and cereals infested with ergot. Ingestion of these long, hard, purplish-black…

An order of flowering plants, division Magnoliophyta (angiosperms), in the large asterid assemblage (often Asteridae in previous systems of classification). Nearly all of the 24 families assigned to the order have previously been considered members…

An order of flowering plants, division Magnoliophyta (Angiospermae), subclass Commelinidae of the class Liliopsida (monocotyledons). The order consists of the single family Eriocaulaceae, with about 1200 species. The Eriocaulales are Commelinidae…

Volatile, fragrant oils obtained from plants. Essential oils are distinguished from those known as fixed oils, which are mainly triglycerides of fatty acids. Essential oils have been obtained from thousands of plants (Fig. 1) and are designated and…

The study of utilization of fungi by common people, as food or medicine, or in crafts, stories, or rituals. Ethnomycology is a subfield of ethnobotany (although, strictly speaking, fungi are not plants) or ethnobiology. Originally, emphasis was on…

A phytohormone (plant hormone) that is an important signaling molecule involved in many plant processes, including, but not limited to, abscission (the physiological process promoted by abscisic acid whereby plants shed a part), leaf and flower…

A large and important Australian forest tree, including about 700 species in the family Myrtaceae. Eucalyptus trees (eucalypts; genus Eucalyptus) occur throughout Australia and are particularly prevalent in eastern areas of the continent. However,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Hamamelidae of the class Magnoliopsida (dicotyledons). The order consists of a single family, genus, and species, Eucommia ulmoides, of China. It is a simple-leaved…

One of the two major types of flowering plants (angiosperms), characterized by possession of three apertures in their pollen; the other major type is magnoliids. Although this difference in pollen development and form has been known for a long time,…

An informal set of flowering plant orders that contains Laurales, Magnoliales, Piperales, and Winterales, plus the monocotyledons, and in total contains roughly one-third of angiosperm species. Formerly, many have equated this group (minus the…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order consists of the large family Euphorbiaceae (about 7500 species) and 3 small satellite families which…

A small class of nonmotile, photosynthetic, unicellular algae, segregated from the class Xanthophyceae (Tribophyceae) on the basis of cytological, ultrastructural, and biochemical features of the vegetative cell and zoospore. Because of their lack…

Plants that retain their green foliage throughout the year. Popularly, needle-leaved trees (pine, fir, juniper, spruce) and certain broad-leaved shrubs (rhododendron, laurel) are called evergreens. In warm regions many broad-leaved trees (magnolia,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order consists of three closely related families (Mimosaceae, Caesalpiniaceae, Fabaceae) collectively called…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the superorder Rosanae (eudicotyledons). The order Fagales consists of 8 families: Betulaceae, Casuarinaceae, Fagaceae, Juglandaceae, Myricaceae, Nothofagaceae, Rhoipteleaceae,…

Foeniculum vulgare, a culinary herb of the parsley family (Apiaceae). Fennel is grown for the dried, ripe fruits or seeds, which are used as a spice in breads, pickles, liqueurs, and meat sauces and dishes. Although similar in odor to anise, fennel…

A process in many plants resulting in the fusion of a female gamete and a male gamete to form a single cell, the zygote. Both vegetative (asexual) reproduction and sexual reproduction occur in plants. Reproduction by gamete fusion is very different…

Plants grown for their fibrous material, which is used for many commercial purposes and for home industry. Many plants are grown as fiber crops because of their content or yield of fibrous material, which is used in the manufacture of textiles,…

A species of deciduous tree, Ficus carica, of the mulberry family (Moraceae). The fig tree is of southwest Asian origin and is now cultivated in the subtropical regions of the world for its edible fruit, especially in Asia, Africa, Europe, and the…

Any tree of the genus Abies, of the pine family, characterized by erect cones, the absence of resin canals in the wood but with many in the bark, and flattened needlelike leaves that lack definite stalks. Fir leaves usually have two white lines on…

An order of the true mosses (subclass Bryidae) consisting of a single family, the Fissidentaceae, and about 800 species in the genus Fissidens plus a few others distributed in four or five segregate genera. Fissidens is the largest genus of…

A large category of natural plant products that derive from γ-pyrone (1). All flavonoid compounds, which are derived from either 2-phenylbenzopyrone (2) or 3-phenylbenzopyrone (3), can be classified into 10 groups (Fig. 1): chalcones,…

A hormone-like protein that controls when a plant will flower in response to the changes in day length associated with the different seasons. Florigen is produced in leaves, where changes in day length are perceived, and migrates through the phloem…

A higher plant's sexual apparatus in the aggregate, including the parts that produce sex cells and closely associated attractive and protective parts (Fig. 1). “Flower” has been used broadly enough by some botanists to include the reproductive…

The application of plant science for purposes of civil or criminal law. Forensic botany has opened aspects of the field of botany to novel avenues within criminal investigations. Today, several subdisciplines of plant science are being applied…

The organic remains, traces, or imprint of seeds and fruits. Seeds, ovules containing a fertilized egg and ready to be shed from the plant, are reproductive organs characteristic of both gymnospermous and angiospermous plants. In angiosperms…

A matured carpel or group of carpels (the basic units of the gynoecium or female part of the flower) with or without seeds, and with or without other floral or shoot parts (accessory structures) united to the carpel or carpels. Carpology is the…

Any edible fruit borne on a tree. Tree fruits include temperate, subtropical, and tropical zone species. Most temperate-zone fruit trees are deciduous, that is, they lose their leaves in the autumn. They are grown principally in regions protected…

A large and diverse order of conspicuous brown algae (class Phaeophyceae), including such well-known seaweeds as Fucus and Sargassum. Definitive features of members of the Fucales include apical growth, production of sex organs in cavities, and a…

An order of the true mosses (subclass Bryidae). The Funariales, often annuals or biennials and sometimes ephemeral, are for the most part characterized by a uniformity of gametophytic structure in contrast to a variability of sporophytic characters…

The application of biotechnological techniques utilizing fungi for agricultural purposes. Fungal biotechnology is applied in agriculture to promote plant vigor, to increase yields, and to reduce impacts of plant diseases, weeds, or invertebrate…

The study of the entire genetic content of fungal organisms. Fungal genomics is a discipline that developed out of advances in automated nucleic acid sequencing and computer technology. In the case of fungal genomics, the objective of the DNA…

The classification of Fungi based on phylogenetic (evolutionary) relationships. Fungi constitute one of the major branches of the tree of life. There are about 100,000 described species in the Fungi, but it has been estimated that there are as many…

An order of flowering plants (angiosperms) in the euasterid I group of the asterid eudicotyledons. The order consists of five families and approximately 17,500 species. The circumscription of Gentianales has been widened to include Rubiaceae,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the superorder Rosanae (eudicotyledons). The order Geraniales consists of 6 families (Francoaceae, Geraniaceae, Greyiaceae, Ledocarpaceae, Melianthaceae, and Vivianiaceae), 15…

Members of a family of diterpenoid carboxylic acids, most of which possess the ent-gibberellane or ent-20-norgibberellane skeletons. Gibberellins occur in some fungal and bacterial species and in all higher plants, in which certain members function…

An order of gymnosperms in the class Ginkgoopsida with only one extant species, Ginkgo biloba (the maidenhair tree). Ginkgo biloba (Fig. 1), also referred to as the ginkgo tree, is native to China. It is cultivated as a shade tree in cities around…

A class of largely extinct gymnosperms. The class Ginkgoopsida contains one order of seed plants: Ginkgoales. Representatives of the Ginkgoales lived predominantly from the Triassic into the Cretaceous, with one species, Ginkgo biloba, persisting to…

The common name for plants of the genus Vitis characterized by climbing stems and grown for the edible, pulpy berries. The common grapevine Vitis vinifera (Fig. 1) has intermittent forked tendrils, a bark that sheds, a diaphragm at the node, and…

Citrus paradisi, an evergreen tree belonging to the order Sapindales and having a well-rounded top cultivated for its edible citrus fruit, which is large, globose, and characterized by a yellow rind and white, pink, or red pulp. The grapefruit…

Members of the family Poaceae (Gramineae) cultivated as forage and grain for consumption. The grasses are the most useful of all the plants that cover the Earth. The cereal grass crops [wheat (Fig. 1), rice, corn (maize), rye, barley, oats, sorghum,…

A glass- or plastic-enclosed structure that is used to grow plants under protected conditions. Greenhouses (also known as glasshouses) are transparent, enclosed, climate-controlled structures (Fig. 1) in which young, tender, or out-of-season plants…

Morphologically distinct cells that are found in the epidermis of terrestrial plant shoots and that function in regulating stoma size. Each pair of specialized guard cells circumscribes and defines a microscopic hole called a stoma (the plural form…

A genus of marine, benthic, green algae (division Chlorophyta) belonging to the family Halimedaceae in the order Bryopsidales. Halimeda plants are attached by a holdfast, generally several centimeters high, and consist of calcareous segments…

A small subclass of the class Magnoliopsida (dicotyledons) in the division Magnoliophyta (Angiospermae), the flowering plants, consisting of 11 orders (Trochodendrales, Hamamelidales, Daphniphyllales, Didymelales, Eucommiales, Urticales,…

A small order of flowering plants [subclass Hamamelidae, class Magnoliopsida (dicotyledons), division Magnoliophyta (Angiospermae)], but whose members are now more typically redistributed across various plant orders. The order Hamamelidales has been…

The genus Tsuga of the pine family, characterized by flattened needles with two white lines beneath the needlelike leaves, which have distinct short stalks. The cones of hemlock are small and pendent (see illustration). Eastern hemlock (Tsuga…

An agave plant, Agave fourcroydes, and the fiber obtained from its leaves. Henequen is produced only in Mexico, Cuba, and El Salvador. It is a hard plant fiber and is used to make rope, twine, and cord. Henequen is sometimes incorrectly called…

A class of lower green plants called liverworts that belong to the division Bryophyta. The class is divided into approximately 225 genera and 8500 species. Although there is a great diversity of external form, most of the gametophytes…

A collection of pressed and dried plant specimens, and a description of when, where, and by whom they were collected, arranged in a systematic manner, and serving as a permanent physical record of the occurrence of an individual plant at a specific…