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A genus of extinct calcareous red algae (Rhodophyta). The extinct algal members of the genus Solenopora (family Solenoporaceae, order Corallinales, division Rhodophyta) are characterized by encrusting, rounded, nodular growth forms ranging in size…

Any of a variety of widely cultivated grasses, especially Sorghum bicolor, grown for grain and herbage. Sorghum (Fig. 1) includes many widely grown grasses having a variety of names. Sorghum is known as guinea corn in West Africa, kafir corn in…

A deciduous tree, Oxydendrum arboreum, of the heath family, indigenous to the southeastern section of the United States, and found from Pennsylvania to Florida and west to Indiana and Louisiana. Sourwood is hardy and is often cultivated in the…

An erect annual legume, Glycine max, known for its high protein and oil contents. Soybean (Glycine max, order Fabales) is one of the most significant commercial legume species. Native to China, soybean is widely cultivated for forage and for its…

An order of liverworts in the subclass Marchantiidae, consisting of two families, the terrestrial Sphaerocarpaceae (Sphaerocarpos and Geothallus) and the aquatic Riellaceae (Riella). The plants are characterized by envelopes surrounding each…

A class of the plant division Bryophyta containing plants commonly called peatmosses. The spongelike plants (Fig. 1) grow as perennials in soft cushions or lawns in wet habitats (rarely they grow submerged). The class consists of a single genus,…

One of the major divisions (formerly known as Equisetophyta) of vascular plants that includes both living and fossil representatives. The three principal orders are Pseudoborniales (Devonian), Sphenophyllales (Devonian-Triassic), and Equisetales…

A cool-season annual, Spinacia oleracea, of Asiatic origin, belonging to the plant order Caryophyllales. Spinach is grown for its foliage (Fig. 1) and is served as a cooked vegetable or as a salad. New Zealand spinach (Tetragonia expansa) and…

An order of the true mosses (subclass Bryidae), whose members are remarkable perennial plants that grow mainly on nitrogenous substrates, such as dung, and show considerable differentiation of neck tissue below the spore-bearing part of the capsule.…

An evergreen tree belonging to the genus Picea of the pine family. Spruce needles are single, usually four-sided, and borne on little peglike projections; the cones are pendulous. Resin ducts in the wood may be seen with a magnifying lens, but they…

The common name for edible fruits of several species of the genus Cucurbita: C. pepo, C. moschata, C. maxima, and C. mixta (also known as C. argyrosperma). The various species of squash originated in the Americas, but they are now grown in most…

The organ of vascular plants that usually develops branches and bears leaves and flowers. The stem of a vascular plant is the ascending structural axis of a plant (Fig. 1) and is the point of attachment for leaves, flowers, and roots. Functionally,…

A low-growing perennial of the genus Fragaria, order Rosales, that spreads by stolons (creeping stems), and the juicy, usually red, edible fruit consisting of a fleshy receptacle with numerous seeds in pits or nearly superficial on the receptacle.…

A biennial beet plant, Beta vulgaris (order Caryophyllales), characterized by a white root and cultivated for the high sugar content of the root. The sugarbeet (often spelled as sugar beet) was developed in modern times to fill the need for a sugar…

Any insectivorous plant of the genus Drosera of the family Droseraceae. Sundews (see illustration), which number more than 190 species, are small, herbaceous, insectivorous plants that grow on all the continents except Antarctica. They are…

An annual plant, Helianthus annuus, which is native to North America and characterized by broad, ovate leaves growing from a single, usually long stem, and large, composite flowers with yellow petals. Helianthus annuus (Fig. 1) is the most widely…

Liquidambar styraciflua, also called redgum, a deciduous tree of the southeastern United States. Sweetgum (Fig. 1) is found northward as far as southwestern Connecticut and also grows in Central America. The tree is commonly 80 to 120 ft (24 to 37…

Platanus occidentalis, a member of the plane tree family. Platanus occidentalis is most often known as American sycamore, but other names include American plane tree, buttonball, and buttonwood. It ranges from southern Maine to Nebraska and south…

A small tree or shrub (Camellia sinensis); a preparation of its leaves that have been dried and cured; and a beverage made from these leaves. The tea plant, Camellia sinensis (alternatively, Thea sinensis), is an evergreen tree of the Theaceae…

An order of ascolichens (class Lecanoromycetes, division Ascomycota) characterized by an unusual apothecium. Members of the order Teloschistales (formerly Caliciales) are ascolichens, that is, lichens [symbiotic associations of fungi (mycobionts)…

One of the two commonly recognized subkingdoms of plants. In contrast to the more closely knit subkingdom Embryobionta, the Thallobionta (also called Thallophyta) are diverse in pigmentation, food reserves, cell-wall structure, and flagellar…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order Theales consists of about 17 families and more than 3500 species. The largest families include…

An aggregation of cells more or less similar morphologically and functionally. A tissue comprises an agglomeration of structurally and functionally similar cells and their intercellular material. Tissues are found in multicellular organisms,…

Any plant of the genus Nicotiana cultivated for its leaves, and the dried leaves of the plant. Most often, tobacco means a leaf product derived from the plant genus Nicotiana (order Solanales) containing 1–3% of the alkaloid nicotine, which produces…

An important vegetable plant belonging to the genus Solanum, especially Solanum lycopersicum (alternatively Lycopersicon esculentum), that is grown for its fleshy edible fruit, which is red, pink, orange, yellow, white, or green, with fleshy…

Stellar explosions known as supernovae may be behind several anomalous rises in radiocarbon captured in tree rings over the past 40,000 years, according to a recent study that adds mounting evidence to the hypothesis that supernovae can impact…

Edible vaccines generated in plants via genetic engineering. To increase the rate and accessibility of vaccination for the rapidly increasing world population, researchers have begun to explore the use of edible plants for the synthesis and delivery…

A perennial woody plant growing to a considerable height at maturity and having an erect stem or trunk and a well-defined crown or leaf canopy. Trees (Fig. 1) constitute some of the most important plant forms on Earth and are the foundational…

Pathological conditions affecting shade and forest trees. Diseases of both shade and forest trees are caused by the same pathogens, but the trees differ in value, aesthetics, and utility. In forests, disease is significant only when large numbers of…

The common name for fern plants primarily belonging to the families Cyatheaceae and Dicksoniaceae, whose members typically develop tall trunks crowned with leaves (fronds). Tree ferns exhibit a treelike (arborescent) habit (Fig. 1), often reaching 6…

An irreversible increase in the size of a tree. Trees grow to a larger size at maturity than other woody perennials (Fig. 1), have a comparatively long period of development to maturity, and live a long time in the mature state. Trees, like other…

The scientific study of how trees grow and develop. Tree physiology is a discipline of the plant sciences that aims to understand how trees live, function, and grow. It encompasses genetics; biochemistry; cellular, tissue, and organ functions; and…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the Eudicotyledon. The order consists of two families, the Trochodendraceae and Tetracentraceae, each with only a single species. The two species are often united into the…

A tree, Liriodendron tulipifera, also known in forestry as yellow poplar, belonging to the magnolia family, Magnoliaceae. The tulip tree is one of the largest and most valuable hardwoods of eastern North America. It is native from southern New…

A tree belonging to the genus Nyssa of the sour gum family, Nyssaceae. The most common species of tupelo is N. sylvatica, variously called pepperidge, black gum, or sour gum; the authorized name is black tupelo. Tupelo grows in the easternmost…

A membrane-bound cavity within a cell that may function in digestion, storage, secretion, or excretion. A vacuole is an intracellular compartment (bounded by a single membrane lipid bilayer) that functions as a primary site of protein and metabolite…

A tropical climbing orchid of the genus Vanilla, and the choice flavoring obtained from the plant. The vanilla plant (Fig. 1), predominantly Vanilla planifolia (formerly V. fragrans), but also including other species (for example, V. pompona and V.…

Dionaea muscipula, a diminutive and increasingly rare carnivorous plant with snap traps. Although placed in the Droseraceae, the Venus' flytrap species (Fig. 1) and Aldrovanda vesiculosa (waterwheel) diverged from the group at least 65 million…

Any of a group of mostly annual legumes, especially of the genus Vicia (order Fabales), with weak viny stems terminating in tendrils and having compound leaves. There are approximately 150 vetch species in the temperate zones of the world.…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order consists of 24 families and more than 5000 species, including most of the families that have been…

A large order of green algae (Chlorophyceae) comprising all forms that normally are flagellate and motile. In zoological classification, it is called Volvocida and placed in the class Phytomastigophora. The cells are solitary or united into colonies…

The edible fruit of Citrullus lanatus, which belongs to the family Cucurbitaceae. The watermelon plant is an annual prostrate vine with multiple stems alternating from short nodes near the base of the main axis, reaching lengths of 10–15 ft (3–4.5…

An order of gymnosperms represented by one species, Welwitschia mirabilis. The plant W. mirabilis (see illustration) is native to the very arid deserts of Namibia and Angola in southwestern Africa. Its appearance is bizarre; It has a very short,…

A deciduous tree and shrub of the genus Salix, order Salicales, which is common along streams and in wet places in the United States, Europe, and China. Willow twigs are often yellow-green and bear alternate leaves, which are characteristically…

Decay of the components of wood. Despite its highly integrated matrix of cellulose, hemicellulose, and lignin, which gives wood superior strength properties and a marked resistance to chemical and microbial attack, a variety of organisms and…

A class of plants, comprising the yellow-green algae, in the chlorophyll a–c phylectic line (Chromophycota). Alternate names are Tribophyceae, derived from Tribonema, a filamentous member of the class, and Heterokontae, referring to the presence of…

The principal water-conducting tissue and the chief supporting system of higher plants. This tissue and the associated phloem constitute the vascular system of vascular plants. Xylem is composed of various kinds of cells, living or nonliving. The…

The science and analysis of yeast classification. Yeasts (Fig. 1) are single-celled eukaryotic fungi that have a vegetative body, or thallus, under normal growth conditions. The polyphasic approach to yeast systematics is a universal consensus…

A genus, Taxus, of evergreen trees and shrubs, with a fruit containing a single seed surrounded by a scarlet, fleshy, cuplike envelope (aril). The leaves of the yew tree are flat, acicular (needle-shaped), and green underneath, with stalks extending…

An extinct class of the division Lycophyta, comprising primitive vascular land plants that evolved from the rhyniophytes and reached a relatively brief peak in the late Early Devonian, when they were an ecologically important and widely distributed…