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Equisetum arvense. (a) Sterile shoot. (b) Fertile shoot growing from an underground rootstock. (c) Cone. (d) Two views of shield-shaped sporangiophores. (e) Spores, greatly enlarged. As spore dries, elaters expand. (After E. W. Sinnott and K. S.…

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from article Equisetales

Equisetum gametophyte. (a) Small gametophyte, showing antheridia only. (b) Male gametes. (c) Larger gametophyte; branching lobes have archegonia at bases. (After E. W. Sinnott and K. S. Wilson, Botany: Principles and Problems, 6th ed., McGraw-Hill,…

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from article Equisetales

Sporophytes. (a) Equisetum gametophyte with sporophytes. (b, c, d) The young sporophytes of Equisetum hiemale. (After G. M. Smith, Cryptogamic Botany, vol. 2, 2d ed., McGraw-Hill, 1955)

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from article Pathotoxin

Oat seedling resistant to Victoria blight obtained by screening a susceptible population with the pathotoxin victorin, a product of the pathogen Helminthosporium victoriae.

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from article Pathotoxin

Separation of corn seedlings resistant (N) and susceptible (T) to southern corn leaf blight by treatment with a pathotoxin produced by Helminthosporium maydis race T.

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from article Pathotoxin

Chemical structures of four pathotoxins. (a) Fusicoccin. (b) Tentoxin. (c) AM-toxin. (d) HMT-toxin.

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from article Tree ferns

Cyathea cooperi (Australian tree fern), a common member of the family Cyatheaceae. (Photo by Forest and Kim Starr)

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from article Tree ferns

Arrangement of leaves of Cyathea cooperi (Australian tree fern). (Photo by Bryan Harry, Haleakalā National Park, National Park Service, Maui, Hawaii)

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from article Circadian clock (plants)

Three-module circadian clock system.

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from article Circadian clock (plants)

Model of the Arabidopsis circadian clock, showing light input (bold arrow), the central oscillator (large box) and output/response (tinted arrows). Light signals synchronize the clock via the cryptochromes (cry) and phytochromes (phy). These are…

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from article Gibberellins

Carbon skeleton of ent-gibberellane showing the carbon numbering system and ring designations. (Credit: Peter Hedden)

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from article Gibberellins

The GA-biosynthetic pathway in higher plants via 2-methylerythritol-4-phosphate (MEP). The biologically active end products of the pathway are GA1, GA3, and GA4. The general diterpene precursor trans-geranylgeranyldiphosphate (GGPP) is formed in…

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from article Gibberellins

Mechanisms for GA inactivation. C19-GAs and C20-GAs may be oxidized on C-2 by different classes of GA 2-oxidases (GA2ox). In rice, the enzyme ELONGATED UPPER INTERNODE (EUI) oxidizes the 16,17-double bond of non–13-hydroxylated GAs, such as GA4, to…

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from article Gibberellins

Illustration of a DELLA protein showing conserved domains, and a model for DELLA degradation via the SCF E3 ubiquitin ligase, which consists of a DELLA-specific F-box, Skp1, Cullin1 (CUL), and Rbx1 subunits. Binding of the GID1-GA complex to DELLAs…

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from article Gibberellins

Model for GA-induced production of α-amylase in the aleurone of germinating cereal grains. GAs produced in the scutellum diffuse to the aleurone cells, where they stimulate transcription, processing, and secretion of α-amylase and other hydrolytic…

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from article Chlorophyceae

Chlorococcales. (a) Chlorococcum (Chlorococcaceae), vegetative cell; (b) cell with zoospores; (c) zoospores; (d) Hydrodictyon (Hydrodictyaceae), portion of coenobium; (e) portion enlarged; (f) Dictyosphaerium (Dictyosphaeriaceae), colony in…

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from article Chlorophyceae

Filamentous green algae with chlorophycean ultrastructure. (a) Microspora (Microsporales), showing H-shaped wall segments; (b) Sphaeroplea (Sphaeropleales); (c) Chaetophora (Chaetophorales), heterotrichous thallus (erect and prostrate systems).

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from article Chlorophyceae

Ulothrix (Ulotrichales).

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from article Osage orange

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from article Bryopsidales

Anatomical structures of selected members of Bryopsidales. (a) Dichotomosiphon, filament with oogonia and antheridia. (b) Ostreobium, filaments. (c) Caulerpa, section of filament showing trabeculae. (d) Codium, group of utricles with gametangia and…

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from article Bryopsidales

Representative members of Bryopsidales. (a) Bryopsis; (b) Caulerpa; (c) Penicillus; (d) Halimeda; (e) Codium.

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from article Plant vulnerability to climate change

Subarctic tundra and vegetation of the Denali National Park and Preserve in Alaska. As a result of climate change and the resultant poleward and upward shift of plant ranges, plants and their ecosystems may become particularly vulnerable. (Credit:…

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from article Plant vulnerability to climate change

Blue grama (Bouteloua gracilis) growing in Montana. As a result of warming temperatures, this type of grass could face decreased productivity, allowing forbs to increase and making the ecosystem less tolerant of drought and grazing. (Credit: Matt…

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from article Plant vulnerability to climate change

Modeled distribution of suitable climate space in Europe for stiff sedge (Carex bigelowii), which is an Arctic-Alpine plant: (a) during the period 1961–1990 (green color = suitable climate space during the 1961–1990 period); (b) climate model…

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from article Plant vulnerability to climate change

The endangered western prairie fringed orchid (Platanthera praeclara) is declining across much of its range in North America. (Credit: U.S. Fish and Wildlife Service)

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from article Plant juvenility

The basic miRNA, siRNA, and ta-siRNA pathways in plants. The enzymes that carry out the different steps are written to the right of the downward arrows. The miRNA pathway schematic shows processing of the hairpin into an miRNA:miRNA* duplex by the…

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from article Plant juvenility

The developmental expression patterns of genes that regulate vegetative phase change. This graph is meant to show only the changes in expression for each gene during development rather than actual expression levels or relative levels between genes.

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from article Rosemary

Leaves of rosemary (Rosmarinus officinalis). (Photograph courtesy of Forest and Kim Starr)

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from article Squash

Zucchini (Cucurbita pepo), a type of summer squash, with flowers. (Credit: Howard F. Schwartz, Colorado State University/www.Bugwood.org)

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from article Squash

Crookneck squash (Cucurbita moschata). (Credit: Howard F. Schwartz, Colorado State University/www.Bugwood.org)

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from article Squash

Delicata squash (Cucurbita pepo), a variety of winter squash. (Credit: Shaun Case)

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from article Squash

Leaves of Cucurbita pepo infected by a squash mosaic virus. (Credit: William M. Brown, Jr./www.Bugwood.org)

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from article Dormancy

Viviparous seeds of maize (Zea mays) germinating on the cob because of a mutation (vp14) preventing abscisic acid synthesis. (From S. H. Schwartz and J. A. D. Zeevaart, Abscisic acid biosynthesis and metabolism, pp. 137–155, in P. J. Davies, ed.,…

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from article Phaeophyceae

Embryonic sporophyte of Desmarestia anceps, showing trichothallic growth resulting in an embryonic stipe and several pairs of embryonic branches.

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from article Coriander

Coriander seeds (Coriandrum sativum). (Photograph courtesy of Steve Hurst, USDA–NRCS PLANTS Database)

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from article Strawberry

June-bearing strawberries (Fragaria × ananassa), which are produced in early summer. (Photo courtesy of Kimberly Lewers, Agricultural Research Service, United States Department of Agriculture)

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from article Strawberry

Botrytis cinerea fungal sporulation on a ripe strawberry. (Photo courtesy of Scott Bauer, Agricultural Research Service, United States Department of Agriculture)

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from article Scrophulariales

Flowers of the common snapdragon (Antirrhinum majus), a typical member of the family Scrophulariaceae in the order Scrophulariales (Lamiales). (Photo by Ondřej Zicha, BioLib, Czech Republic)

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from article Venus' flytrap

Dionaea muscipula (the Venus' flytrap) growing in a South Carolina nature preserve. Winged petioles and traps in various stages of the capture cycle are visible. The plant is surrounded by Sphagnum moss, which is a frequent community associate.…

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from article Venus' flytrap

Stages in the capture and digestion of a fly by the Venus' flytrap. A prey item is attracted to the trap margins by nectar (a). When a trigger hair on the inside leaf surface is twice stimulated (b), the trap closes rapidly (c). Complete closure is…

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from article Oats

Oats (genus Avena). (Photo by Jan Samanek, State Phytosanitary Administration, Czech Republic)

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from article Oats

Oat panicles with many branches and spikelets. (Photo by Jan Samanek, State Phytosanitary Administration, Czech Republic)

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from article Oats

Oat florets. Scale bar = 1 cm (0.4 in.). (Photo by Steve Hurst, USDA–Natural Resources Conservation Service PLANTS Database)

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from article Oats

Crown rust on oat leaves. This devastating disease is caused by Puccinia coronata. (Photo courtesy of the USDA Agricultural Research Service)

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from article Oats

Stem rust infection (caused by Puccinia graminis) on oat stems. (Photo by Howard F. Schwartz, Colorado State University)

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from article Cell plastids

Light microscope view of part of Hypochaeris radicata leaf, showing chloroplasts sectioned in a variety of planes and displaying internal grana.

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from article Cell plastids

Three-dimensional model of grana with intergranal connections. (After W. Wehrmeyer, Planta, 63:13–30, 1964)

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from article Cell plastids

Electron microscope view of two oat leaf chloroplasts, one showing successive layers of grana in side view, and the other showing grana in face view (disk shape of constituent thylakoid lobes are seen).

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from article Cell plastids

Part of oat leaf chloroplast at higher magnification. Grana are seen in side view, revealing profiles of membranes. Thylakoids that interconnect grana are shown, with components of stroma, or ground substance, in which thylakoids lie. The dense…

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from article Cell plastids

Proplastid in cell of broad bean root tip. Double membranous envelope is shown and rudimentary nature of internal membrane system is obvious.

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from article Forensic botany

Surface of a green bean pod, showing its spines using (a) light microscope (courtesy of David O. Norris) and (b) scanning electron microscope (courtesy of Meredith Lane).

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from article Anthropology

Fossil skulls of four different species of Homo (clockwise from upper left): Homo neanderthalensis, Homo antecessor, Homo erectus, and Homo sapiens. Each skull shows different anatomical variations. (Credit: creativemarc/Shutterstock)

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from article Anthropology

The indigenous inhabitants of Siberut Island (West Sumatra, Indonesia) are known as the Mentawai people. They live a seminomadic hunter-gatherer life in the coastal and rainforest environments of the island. (Credit: Chanwit Whanset/Shutterstock)

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from article Lichens

The ascolichen Teloschistes chrysophthalmus. (Credit: Jason Hollinger)

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from article Lichens

Cuplike lichens of the genus Cladonia. (Credit: Jacinta Lluch Valero)

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from article Ebony

Persimmon (Diospyros virginiana). (Photograph by Dot Paul, National Resources Conservation Service, USDA)

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from article Wheat

A sheaf of wheat (Triticum) surrounded by some small piles of seed (grain). (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)

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from article Wheat

A combined harvester-thresher is used to harvest wheat. (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)

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from article Wheat

Adaptation regions for wheat in the United States. (Credit: U.S. Department of Agriculture)

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from article Wheat

Wheat (Triticum) growing in a field. The wheat inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). (Credit: Tim McCabe/Natural Resources Conservation Service, U.S. Department of Agriculture)

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from article Wheat

Black stem rust of wheat, which produces urediniospores in reddish-brown pustules. The fungus Puccinia graminis f. sp. tritici is responsible for this plant disease. The inset shows a close-up view of an infected stem. (Credit: Agricultural Research…

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from article Wheat

Loose smut of wheat, caused by Ustilago tritici. (Credit: Erik Stromberg/Virginia Polytechnic Institute and State University)

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from article Apical dominance

Model of strigolactone production. Auxin promotes genes (listed below the arrow) required for strigolactone biosynthesis. This can occur in roots and shoots. Strigolactones move into the bud region and are perceived by the F-box response protein,…

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from article Apical dominance

Simplified view of the interaction of three branching hormones. Auxin promotes production of strigolactones (SL), whereas limiting that of cytokinins (CK) at bud nodes. This blocks bud outgrowth in intact plants (left). After decapitation, supply of…

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from article Plant phylogeny

A phylogeny of the major groups of plants, showing the history of diversification from a common ancestor (left). The origin of plants in an endosymbiotic event is not depicted, nor are later secondary endosymbiotic events. Major groups are enclosed…

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from article Plant phylogeny

Primary and secondary endosymbiotic events in the history of plants. Plants originated in a primary endosymbiotic event, when a prokaryotic photosynthetic cyanobacterial cell was engulfed by a eukaryotic cell and maintained as a plastid. This line…

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from article Plant phylogeny

The life cycle of a fern, involving the alternation of sporophyte and gametophyte generations. Reproduction by sporophytes yields gametophytes, and reproduction by gametophytes yields sporophytes. A complete life cycle begins with either a…

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from article Tupelo

Leaves of black tupelo (Nyssa sylvatica). (Photograph courtesy of Larry Allain, USGS National Wetlands Research Center)

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from article Kentucky coffee tree

Seeds of the Kentucky coffee tree (Gymnocladus dioica). (Photo courtesy of Steve Hurst, ARS Systematic Botany and Mycology Laboratory, USDA–NRCS PLANTS Database)

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from article Kentucky coffee tree

Kentucky coffee tree (Gymnocladus dioica). (a) Parts of branch showing leaf scars and winter buds. (b) Branch.

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from article Lepidodendrales

Reconstructions of tree-sized Carboniferous rhizomorphic tree-lycopsids, illustrating architectural variation. (After R. M. Bateman et al., Experimental cladistic analysis of anatomically preserved arborescent lycopsids from the Carboniferous of…

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from article Lepidodendrales

Primitive bisexual cone of the Flemingites type, borne by Paralycopodites, with apically concentrated microsporangia and basally concentrated megasporangia containing several megaspores. (After C. A. Arnold, An Introduction to Paleobotany,…

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from article Fungi

Porcini mushrooms (Boletus edulis) are members of the Basidiomycota division of Fungi. (Credit: Digoarpi/Shutterstock)

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from article Fungi

Spore types (upper illustrations) and structures of parent mycelia (lower illustrations) in fungi.

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from article Fungi

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from article Fungi

Sexual mechanisms in fungi: (a) gametic copulation; (b) gametangial copulation; (c) gamete-gametangial copulation; and (d) somatic copulation.

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from article Fungi

Colorized scanning electron micrograph of brewer's yeast cells (Saccharomyces cerevisiae). This fungus consists of single vegetative cells, and small daughter cells can be seen budding off from the larger cells. Brewer's yeast is used in the…

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from article Apple

Empire apple (Malus pumila). (Credit: Peggy Greb/Agricultural Research Service, United States Department of Agriculture)

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from article Apple

Apple trees in an orchard in late autumn. (Credit: Sandrine Bouvier/Alamy)

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from article Pericycle

Pericycles. (a) Part of transection of root Actaea alba, including xylem and phloem. Pericycle thin-walled and one cell in radial dimension. (b) Part of transection of root of Smilax herbacea, including phloem. Pericycle thick-walled and four or…

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from article Pericycle

Transection of central part of sugarbeet. (After K. Esau, Hilgardia, 9(8), 1935)

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from article Wood anatomy

Annual tree rings are distinct features of wood anatomy. The combined concentric bands of light and dark areas can help investigators to determine the age of a tree. (Credit: DrimaFilm/Shutterstock)

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from article Wood anatomy

Light micrograph of a section through the stem of a lime tree (genus Tilia). The pith is at the center and is surrounded by a layer of wood (xylem). A thin cambium separates this from the phloem. An outer layer of collenchyma is enclosed by the…

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from article Wood anatomy

Structure of a typical hardwood. (Credit: U.S. Department of Agriculture)

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from article Wood anatomy

Structure of a typical softwood. (Credit: U.S. Department of Agriculture)

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from article Arales

Anthurium andraeanum (flamingo lily). (Photo courtesy of Forest and Kim Starr)

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from article Potato, Irish

Irish potato (Solanum tuberosum). (Photo by Peggy Greb, Agricultural Research Service, U.S. Department of Agriculture)

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from article Potato, Irish

Diagram of a potato plant. [Adapted from R. E. Thornton and J. B. Sieczka (eds.), Commercial Potato Production in North America, Potato Association of America, Orono, ME, 1980]

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from article Potato, Irish

Irish potato tubers infected by late blight (Phytophthora infestans). (Photo by G. D. Franc; Bugwood.org)

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from article Persian melon

Persian melon (Cucumis melo). (Photo by Mehrdad Aref-Adib)

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from article Cellulose

Microscopic view of cotton fibers, which contain 98% cellulose. (Credit: Martin Kreutz/agefotostock)

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from article Cellulose

Positioning of β-d-glucopyranosyl units in cellulose structure.

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from article Cellulose

Cellulose is the principal structural component of plants. In particular, cellulose in the plant cell wall is found mainly in the form of threadlike fibers, composed of smaller fibrils (microfibrils). (Copyright © McGraw-Hill Education)

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from article Cantaloupe

Cantaloupes (Cucumis melo var. reticulatus). (Photo by Scott Bauer, Agricultural Research Service, United States Department of Agriculture)

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from article Epidermis (plant)

Plant epidermis in surface view. (a) Iris leaf showing kidney-shaped guard cells. (b) Zea leaf showing dumbbell-shaped guard cells; two subsidiary cells are associated with each stoma. (c) Sedum leaf; each stoma is associated with three or four…

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from article Epidermis (plant)

Specialized epidermal cells in transections of leaves. (a) Leaf of Ficus elastica, each side having approximately three layers of cells in the multiple epidermis; lithocyst containing cystolith whose calcium deposits were removed during…

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from article Epidermis (plant)

Transection of leaf of Andropogon showing large bulliform cells in the upper epidermis.

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from article Epidermis (plant)

Trichomes. (a) Uniseriate hairs of Gynura. (b) Unicellular anchor hair of Mentzelia. (c) Stellate hair of Solanum. (d) Branched (candelabra) hair of Platanus. (e) Peltate scale of Shepherdia.

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from article Epidermis (plant)

Trichomes. (a) Unicellular and glandular (colleters) hairs of the geranium (Pelargonium). (b) Unicellular-hooked and uniseriate, club-shaped hairs of the bean (Phaseolus). (c) Uniseriate and glandular (colleters) hairs of the tomato (Lycopersicon).

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from article Plants of saline environments

Desert arrowweed (Pluchea sericea) is a halophytic evergreen shrub adapted for growth in the salty basins of Death Valley, California. (Credit: Steven P. Lynch)

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