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A plant, Musa textilis, of the banana family that is valuable for its hard fiber (also known as Manila hemp) and native to Borneo and the Philippines. Abaca is one of the strongest of the hard fibers. Commercially, it is known as Manila hemp. The…

One of the major plant hormones that plays an important role in plant growth and development. Abscisic acid (ABA) is ubiquitous in vascular plants; the highest levels are found in young leaves and in developing fruits and seeds. Abscisic acid is…

The process whereby a plant sheds one of its parts. Leaves, flowers, seeds, and fruits are parts commonly abscised. Almost any plant part, such as very small buds and bracts to branches several inches in diameter, and scales or sheets of bark, may…

A major constituent of the cell walls of certain red algae, especially members of the families Gelidiaceae and Gracilariaceae. Extracted for its gelling properties, it is one of three algal polysaccharides of major economic importance, the others…

Any of the deciduous shrubs and trees of the genus Alnus in the birch family (Betulaceae). There are approximately 30 species of alder, with 10 in the United States. Alders are widespread in cool north temperate regions and are also found southward…

The world's most valuable forage legume, Medicago sativa, also known as lucerne, and less often as purple medic, medica, snail clover, median herb, Burgundy hay or clover, and Chilean clover. Alfalfa is often referred to as the queen of forages. It…

A major constituent (10–47% dry weight) of the cell walls of brown algae. Extracted for its suspending, emulsifying, and gelling properties, it is one of three algal polysaccharides of major economic importance, the others being agar and…

A small order of flowering plants, division Magnoliophyta (Angiospermae), which gives its name to the subclass Alismatidae of the class Liliopsida (monocotyledons). It consists of three families (Alismataceae, Butomaceae, and Limnocharitaceae) and…

A relatively primitive subclass of the class Liliopsida (monocotyledons) of the division Magnoliophyta (Angiospermae), the flowering plants, consisting of 4 orders, 16 families, and less than 500 species. Typically they are aquatic or semiaquatic,…

An annual plant (seldom perennial) of the genus Amaranthus (family Amaranthaceae) that is distributed worldwide in warm and humid regions. Amaranth plants are botanically distinguished by their small chaffy flowers (see illustration), which are…

Collectively, members of the class Amphibia are facing massive reductions in total numbers, and the overall biodiversity of amphibians across the globe is under threat. Scientists have determined that global climate change and habitat destruction…

A class of the plant division Bryophyta, containing plants commonly called granite mosses. The class consists of one order and two families, the Andreaeobryaceae and the Andreaeaceae. The large tapered foot and short, massive seta of the…

A small class of the plant division Bryophyta, made up of plants commonly called hornworts. There is a single order with six genera. Gametophyte structure The gametophytes are flat thalli, often forming rosettes of uniform thickness (see…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order Apiales (also known as the Umbellales) includes two major families: the Apiaceae, with about 3500…

Correlative inhibition of the growth of lateral (axillary) shoots exerted by the growing apical bud of the plant stem. Competition for growth occurs between plant parts. Strongly growing fruits and branches (organs) act as sinks that divert energy…

Permanently embryonic tissue involved in cell division at the apices of roots and stems, and forming dynamic regions of growth. These apical meri­stems, usually consisting of small, densely cytoplasmic cells, become established during embryo…

A deciduous tree, Prunus armeniaca, in the order Rosales that produces a simple fleshy stone fruit. The apricot is thought to be native to China; then it was distributed throughout Asia and Europe, and eventually North America, South America, and…

A class of nonflagellate unicellular algae, commonly called diatoms, with boxlike silicified walls. Diatoms range in maximum dimension from 4 micrometers to more than 1 millimeter. The diatom wall or frustule (Fig. 1) comprises several interlocking,…

A fast-growing tree, Ochroma pyramidale (also known as O. lagopus), which is widely distributed in tropical America, especially in Ecuador. Balsa (Ochroma pyramidale; also, O. lagopus) belongs to the mallow family, Malvaceae, in the order Malvales.…

Fungi that exhibit the natural phenomenon of bioluminescence (the ability of an organism to emit visible light). Bioluminescence is the emission of photons of visible light by living organisms via the chemical reaction of molecular oxygen (O2) with…

A deciduous tree of the genus Betula, which is distributed over much of North America, in Asia (south to the Himalayas), and in Europe. Birch trees are assigned to the genus Betula. They belong to the family Betulaceae (which also contains alders,…

A group of steroidal plant hormones, typified by the compound brassinolide, that produce effects on plant growth and development. Plant hormones are naturally occurring organic molecules that regulate multiple aspects of plant growth and development…

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

Common pigments, typically of yellow, orange, or red hues, that serve in both light absorption and the protection against too much light in photosynthesis as well as in the vision process. Carotenoids comprise a class of labile, easily oxidizable,…

A linear polymer of (1→4)-linked β-d-glucopyranosyl units, and the most abundant of all naturally occurring substances. Cellulose is the main polysaccharide in living plants, forming the skeletal structure of the plant cell wall. Cellulose…

The generic name for any of the intensely green, blue, or purple pigments found in higher plants, algae, and photosynthetic bacteria that are an integral part of photosynthesis. Chlorophyll is the name given to any member of a group of important…

A tropical evergreen shrub or small tree of the genus Coffea (family Rubiaceae), a native of northeast Africa and adjacent southwest Asia, cultivated for the seeds (coffee beans) of its fruit. Members of the genus Coffea (Fig. 1) grow mainly between…

Zea mays, also known as maize, a grain crop grown for its edible seeds (kernels). Corn (Zea mays) [Fig. 1] is an important cereal grass plant belonging to the order Poales (formerly Cyperales). The top corn-producing countries are the United…

Trees provide substantial benefits to the environment. In addition to improving air quality, reducing stormwater runoff, serving as a wildlife habitat, and sequestering carbon by absorbing carbon dioxide, trees also cool the atmosphere through shade…

A warm-season annual cucurbit (Cucumis sativus), originally native to India, which is grown for its edible, immature, fleshy fruit. The cucumber is originally native to India and is grown for its edible, immature, fleshy fruit (Fig. 1). The cucumber…

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…

An alkene, formula CH2=CH2. Ethylene (see illustration) is a colorless gas with a boiling point of −103.8°C and a melting point of −169°C. Ethylene is the most-produced organic chemical in the world and is used to make hundreds of products as well…

A taxonomic domain consisting of the vast array of living and fossil organisms with complex cells in which the genetic material is organized into chromosomes [linear pieces of deoxyribonucleic acid (DNA) bound with histone proteins and visible as…

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…

Pathological conditions resulting from invasion by pathogenic fungi. Fungi are microorganisms that fill many natural niches in nature. They form a diverse group of eukaryotic microorganisms, including an estimated 2.2 to 3.8 million different…

A eukaryotic kingdom of organisms consisting of the principal decomposers of ecosystems. Fungi are nucleated, usually filamentous, spore-bearing organisms devoid of chlorophyll. Although approximately 100,000 species have been described in the…

Photosynthesis is a key natural process utilized by plants and is necessary for proper plant growth. Specifically, photosynthesis uses light to manufacture chemical compounds, including organic compounds—primarily carbohydrates—that are derived from…

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…

Bipartite, intimate, and mutualistic symbioses that are formed by soil-inhabiting fungi and plants. Mycorrhizae (mycorrhizas) can be formed between different groups of fungi and the roots, rhizomes (underground horizontal shoots), or thalli (plant…

A ground tissue chiefly concerned with the manufacture and storage of food. The primary functions of plants, such as photosynthesis, assimilation, respiration, storage, secretion, and excretion—those associated with living protoplasm—proceed mainly…

A chemical of biological origin, other than an enzyme, that plays an important causal role in a plant disease. Most pathotoxins are produced by plant pathogenic fungi or bacteria, but some are produced by higher plants, and one has been reported to…

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 is one of the world's oldest cultivated crops. It is a native of western…

A deciduous fruit tree species, Prunus persica, of the order Rosales that originated and was first cultivated in western China. The peach (see illustration) is adapted to relatively moderate climates in the temperate zone. Although most peach…

A low-branching, self-pollinated, one- to six-seeded annual legume (Arachis hypogaea) cultivated for its edible seed, which forms beneath the soil in a pod. Peanuts are cultivated throughout the tropical and temperate climates of the world. Peanut…

Any of approximately 20 species of deciduous trees, and their fruits, in the genus Pyrus (order Rosales). About half of the species of pear are native to Europe, North Africa, and the Middle East, especially areas around the Mediterranean Sea; the…

As commonly defined, the outer boundary of the stele of plants. Originally it was interpreted as a band of cells between the phloem and the innermost layer (endodermis) of the cortex. Such pericycle is commonly found in roots and, in lower vascular…

A group of tissues which replaces the epidermis in the plant body. Its main function is to protect the underlying tissues from desiccation, freezing, heat injury, mechanical destruction, and disease. Although periderm may develop in leaves and…

The synthesis of chemical compounds using light, especially the manufacture of organic compounds (primarily carbohydrates) from carbon dioxide and a hydrogen source (such as water), most often with simultaneous liberation of oxygen, by chlorophyll-…

The branch of plant science that seeks physiological (mechanistic) explanations for ecological observations. Physiological ecology is the study of biophysical, biochemical, and physiological processes used by organisms to cope with factors of their…

An organism that belongs to the kingdom Plantae in biological classification. A plant (see illustration) is a member of the taxonomic kingdom Plantae and is generally distinguished by the presence of chlorophyll, a rigid cell wall, and abundant,…

The basic unit of structure and function in plants. Although plant cells are variously modified in structure and function, they have many common features (Fig. 1). The most distinctive attribute of the majority of plant cells is the rigid cell wall,…

The regulated growth and differentiation of a multicellular plant. Plant development involves an organized series of physiological processes that are associated with the plant as it progresses through its life cycle. Plant development begins with…

The process of biological and organic change within the plant kingdom by which the characteristics of plants differ from generation to generation. Understanding of the course of plant evolution (Fig. 1) is based on several lines of evidence. The…

An irreversible increase in the size of a plant. Because plants (Fig. 1), like other organisms, are made up of cells, plant growth involves an increase in cell numbers by cell division and an increase in cell size. Cell division itself is not…

Any of a group of naturally occurring, organic substances that influence plant physiological processes at low concentrations. Plant hormones are chemical messengers synthesized within plants, where they help to regulate a variety of physiological…

The complex of physical and chemical processes necessary to synthesize and transform substances into energy that is made available for use by a plant organism. Plant metabolism is driven by the autotrophic nature of plants, meaning that they must…

The various movements that enable whole plants or plant organs to change their orientation in response to environmental stimuli in order to execute specific functions. Plants are constantly in motion, but most plant movements occur slowly and are…

The study of disease in plants. Plant pathology is the branch of botany concerned with plant diseases. It is an integration of many biological disciplines and bridges the basic and applied sciences. Plant pathologists investigate the pathogenic…

The evolutionary chronicle of plant life on Earth. A phylogeny is a description, in words or diagrams, of the evolutionary history of a group of related species. It depicts a sequence of branching events and may also identify the characteristic…

The branch of plant sciences that aims to understand how plants live, function, and grow. Plant physiology is the discipline of botany concerned with the actions and mechanisms that occur in plants (Fig. 1). It seeks to understand all aspects and…

The metabolism in plants of organic molecules using enzymes to generate usable energy in the form of adenosine triphosphate (ATP). Plant respiration is an important biochemical process in plants whereby, in most cases, specific substrates are…

The extent to which a plant, or plant ecosystem, is susceptible to, or unable to cope with, the adverse effects of climate change. Plants are constantly changing their ecophysiology and distributions over different timescales as they respond to…

More apples are consumed worldwide than any other temperate-zone tree fruit. Apples are eaten fresh, processed into jellies and preserves, cooked in pies and pastries, and made into sauces. Therefore, the cultivation of the trees (genus Malus) that…

Saccharum officinarum, a stout, perennial member of the grass family characterized by two-ranked leaves and a many-jointed stalk; the source approximately 70% of the world's annual sugar production. Sugarcane (also spelled sugar cane) [Fig. 1]…

The plant Brassica rapa (alternatively B. campestris var. rapa), a cool-season, hardy crucifer of Asiatic origin belonging to the order Capparales (Brassicales) and grown for its enlarged root and its foliage. The turnip plant (see illustration) is…

A food grain crop of the genus Triticum, in which the inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). Wheat (genus Triticum) [Fig. 1] is the most widely grown food crop in the world and ranks…

A collective name for those fungi that possess, under normal growth conditions, a vegetative body (thallus) consisting, at least in part, of simple, single cells. Yeasts are a phylogenetically diverse group of organisms that occur in two divisions…

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…

The collective techniques for supplying nutrients and water directly to the roots of plants, without soil or other media. Hydroponics is concerned with the cultivation and growing of plants without soil or other media. Hydroponic systems (Fig. 1)…

Symbiotic associations of fungi (mycobionts) and photosynthetic partners (photobionts). Lichens (Fig. 1) consist of fungi and algae or cyanobacteria growing together symbiotically. Lichen associations always result in a distinct morphological body…

The collective processes involved in plant assimilation and metabolism of all chemical elements, with the exception of carbon, hydrogen, and oxygen. Plants obtain most of their mineral nutrients by extracting them from solution in the soil or the…

A substance in a plant that imparts coloration. Plant pigments are important colored substances produced by plants. There are both photosynthetic and nonphotosynthetic pigments in plants. Chiefly, the photosynthetic pigments are involved in light…

Plants that grow well in soils having a high salt content, referred to as halophytic plants. Plants of saline environments (halophytes) constitute approximately 1% of the world's flora and have evolved to flourish in locations where the soil salt…

The transport of pollen grains from the plant parts that produce them to the ovule-bearing organs, or to the ovules (seed precursors) themselves. Pollination is a process that ensures the successful life cycle of plants. Without pollination, there…

By July 6, 2018, beaches on the eastern coast of St. Vincent—an island located in the southeastern Caribbean Sea (Lesser Antilles)—were covered nearly one-meter deep with rotting brown algae (seaweed), known as Sargassum, posing multiple problems…

To better understand the nutritional effects (health benefits), chemical composition, growing conditions, and shelf life of microgreens, a team of researchers reviewed the science behind them in the Journal of Agricultural and Food Chemistry…

The emergence of a new plant from a seed. Seed germination is the beginning or the process of development of a seed (a fertilized ovule containing an embryo, which forms a new plant upon germination). Hydration of a seed, which is called imbibition…