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Example of a mycorrhizal association. The composite image shows the symbiotic relationship between a fly agaric mushroom (Amanita muscaria) and a birch tree (genus Betula). The mushroom receives sugar (C6H12O6) and oxygen (O2) from the tree and…

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from article Mycorrhizae

There are different types of symbiotic mycorrhizae. Ectomycorrhizae involve fungal hyphae that surround the cell walls of plant roots, but do not penetrate them. Endomycorrhizae involve fungal hyphae that penetrate the outer cells of plant roots.…

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from article Mycorrhizae

Cross section of several types of mycorrhizal fungi. (Credit: Modified from an original drawing by V. Furlan)

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from article Mycorrhizae

Ectomycorrhizae are characterized by a macroscopically visible fungal sheath that surrounds the plant root. (Credit: Robert L. Anderson/U.S. Department of Agriculture Forest Service)

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from article Fig

Panachée fig (Ficus carica). (Photo courtesy of David Karp, Agricultural Research Service, United States Department of Agriculture)

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from article Poison ivy

Three-foliolate leaves of poison ivy (Toxicodendron radicans). (Photo courtesy of Larry Allain, USGS National Wetlands Research Center)

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from article Alder

Red alder (Alnus rubra), Mount Adams, Washington. (Photograph by Susan McDougall, USDA–NRCS PLANTS Database)

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from article Mistletoe

European mistletoe (Viscum album). (Photo by Jan Samanek, State Phytosanitary Administration, Czech Republic)

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from article Oregano

European oregano (Origanum vulgare). (Photo courtesy of Leo Michels)

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from article Grape

Clusters of (left) common black grapes and (right) common red grapes (Vitis vinifera; subgenera Euvitis). (Photo by Patrick Tregenza, Agricultural Research Service, U.S. Department of Agriculture)

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from article Grape

Muscadine grapes (Vitis rotundifolia; subgenera Muscadinia). (Photo by David Nance, Agricultural Research Service, U.S. Department of Agriculture)

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from article Grape

The three main training–pruning systems used in California. (a) Head-trained–spur-pruned. (b) Cordon-trained–spur-pruned. (c) Head-trained–cane-pruned. (After R. J. Weaver, Grape Growing, John Wiley and Sons, New York, 1976)

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from article Grape

Slapper-type mechanical harvester. (After R. J. Weaver, Grape Growing, John Wiley and Sons, New York, 1976)

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from article Grape

Grape anthracnose (caused by Elsinoë ampelina), which is commonly called bird's-eye rot. (Photo courtesy of Clemson University, U.S. Department of Agriculture Cooperative Extension Slide Series; Bugwood.org)

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from article Grape

Downy mildew (caused by Plasmopara viticola) on a grape leaf. (Photo courtesy of the University of Georgia Plant Pathology Archive; Bugwood.org)

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from article Broccoli

Flower buds of broccoli (Brassica oleracea var. italica). (Photo courtesy of Forest and Kim Starr)

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from article Sphagnopsida

Sphagnobrya. (a) Sphagnum capillaceum. (b) Sphagnum palustre. (After E. L. Palmer, Fieldbook of Natural History, McGraw-Hill, 1949)

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from article Sphagnopsida

Cellular structure of a leaf. (After F. W. Emerson, Basic Botany, 2d ed., McGraw-Hill, 1954)

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from article Sphagnopsida

Sporophyte of Sphagnum. (After F. W. Emerson, Basic Botany, 2d ed., McGraw-Hill, 1954)

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from article Sphagnopsida

Stages in the development of a protonema. (a) Germination of spore; (b) division of terminal cell to form an apical cell; (c) formation of multicellular rhizoids (after A. Engler and K. Prantl, Die natürlichen Pflanzenfamilien, Bd. 10, 2 Aufl.,…

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from article Australopith

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from article Australopith

Geochronological distribution of hominin species. The scale at the bottom is in millions of years ago (MYA).

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from article Australopith

Lateral view of the Taung skull of Australopithecus africanus, the type specimen of Australopithecus and the first early hominid specimen to be discovered in Africa. (Courtesy of Frederick E. Grine)

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from article Australopith

Principal sites at which australopith fossils have been discovered in Chad, Ethiopia, Kenya, Tanzania, Malawi, and South Africa.

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from article Oedogoniales

Nannandrous species of Oedogonium, showing sexual reproductive structures.

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from article Maple

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from article Maple

Characteristic maple leaves, twigs, and buds. (a) Sugar maple (A. saccharum). (b) Hedge maple (A. campestre). (c) Box elder (A. negundo). (d) Striped maple (A. pensylvanicum). (e) Sycamore maple (A. pseudoplatanus). (f) Silver maple (A.…

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from article Cypress

Arizona cypress (Cupressus arizonica). (Photo courtesy of Susan McDougall, USDA–NRCS PLANTS Database)

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from article Phytochemicals

Classification of dietary phytochemicals.

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from article Phytochemicals

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from article Phytochemicals

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from article Fungal infections

Ringworm (also called tinea corporis) is a common fungal infection of the skin in humans. It is characterized by ring-shaped, scaly, itching patches on the skin. (Credit: alejandrophotography/Getty Images)

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from article Fungal infections

Photomicrograph of a stained vaginal smear identifying Candida albicans. Candida albicans lives in numerous parts of the body as normal flora. However, when an imbalance occurs, Candida species can multiply, resulting in a mucosal or skin infection…

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from article Fungal infections

Colored scanning electron micrograph of yeast cells (Malassezia species) on the skin of a human foot. Malassezia species can cause the condition known as athlete's foot (tinea pedis). (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock…

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from article Fungal infections

Close-up view of the toenails of a patient with onychomycosis resulting from Trichophyton rubrum. (Credit: Edwin P. Ewing, Jr./Centers for Disease Control and Prevention)

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from article Yew

Arils and leaves of the English yew (Taxus baccata). (Photo by Simon Garbutt)

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from article Yew

Identifying characteristics of yews. (a) Japanese yew (Taxus cuspidata) leaf, (b) male branchlet with staminate flower buds, (c) female branchlet showing ovule-bearing flowers, (d) female branchlet with various stages of development of fleshy aril…

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from article Violales

Downy yellow violet (Viola pubescens). (Photograph by Elsie M. Rodgers, National Audubon Society)

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from article Halimeda

Halimeda kanaloana found in the waters off Hawaii. (Photo courtesy of the Deep Water Macroalgal Meadows 2004 Exploration, Office of Ocean Exploration, National Oceanic and Atmospheric Administration)

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from article Onion

Pungent red onions (Allium cepa). (Photo by Stephen Ausmus, Agricultural Research Service, U.S. Department of Agriculture)

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from article Onion

Collection of yellow onions (Allium cepa) after harvesting. (Photo by Doug Wilson, Agricultural Research Service, U.S. Department of Agriculture)

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from article Onion

Common onions (Allium cepa) infected by Urocystis cepulae, causing onion smut. (Photo by Howard F. Schwartz, Colorado State University)

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from article Neandertal DNA

The geographical range within which Neandertal remains have been found (dashed line). White dots show the sites of the discoveries used to estimate the almost-complete hypervariable segment I (HVS-I) sequence of the Neandertal mtDNA. The approximate…

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from article Neandertal DNA

The mtDNA hypervariable segment I (HVS-I) diversity found in eight Neandertals. The nucleotide substitutions and insertions relative to the Cambridge Reference Sequence (CRS) are shaded. (Credit: Igor Ovchinnikov and William Goodwin)

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from article Neandertal DNA

Phylogenetic analysis of the Neandertal mtDNA hypervariable segment I (HVS-I) sequence. (a) Neighbor-joining tree of the Neandertal mtDNA sequences and 2500 modern human HVS-I sequences from 43 modern populations. (b) Neighbor-joining tree of the…

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from article Redwood

Redwood trees (Sequoia sempervirens). (Photo courtesy of Forest and Kim Starr)

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from article Euglenophyceae

Euglena sp., showing overall morphology and intracellular structures.

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from article Hypodermis

Transection from the outer part of a Smilax root, illustrating a thick-walled hypodermis (exodermis) beneath the epidermis. One hypodermal cell is not thickened. (After K. Esau, Plant Anatomy, 2d ed., John Wiley and Sons, 1965)

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from article Plant cell wall

Stylized model of the plant primary cell wall, showing layers of semicrystalline cellulose microfibrils associating with cross-linking hemicellulose polymers, embedded in a pectin matrix. (Copyright © McGraw-Hill Education)

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from article Plant cell wall

Light microscopy image of the outer cell layers and cuticle of a tomato fruit. The cuticle in this organ, shown here with a red stain, forms an exceptionally thick lipid coating on the outer epidermal cell and also permeates into the underlying cell…

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from article Plant cell wall

Model showing the multiple layers that can be observed in some secondary cell walls, which vary in the direction that the constituent cellulose microfibrils are deposited. (Copyright © McGraw-Hill Education)

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from article Plant cell wall

Cell expansion. (a) Two cells (left) of similar size, but different orientations of microfibril deposition show contrasting directions of cell expansion (right). (b) Model of the deposition of cellulose microfibrils by cellulose synthase complexes,…

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from article Sycamore

Leaves of the American sycamore (Platanus occidentalis). (Photo courtesy of Larry Allain, USGS National Wetlands Research Center)

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from article Bonsai

Major bonsai styles. (a) Formal upright (Chokkan); black pine. (b) Semicascade (Han-Ken-gai); wisteria. (c) Informal upright (Moyogi); juniper. (d) Cascade (Kengai); white pine. (e) Slanting (Shakan); spruce. (f) Rock clinging (Ishezuke); azalea.…

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from article Sclerenchyma

Sclerenchyma. (a) Brachysclereids (stone cells) from fruit of pear. (b) Macrosclereids (rod cells) from macerated seed coat of bean. (c) Branched sclereids from petiole of Camellia. (d) Fiberlike sclereids in cleared leaf of olive. (e) Transection…

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from article Douglas-fir

Douglas-fir (Pseudotsuga menziesii) at Junction Butte, Yellowstone National Park. (Photo courtesy of Jim Peaco, National Park Service)

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from article Douglas-fir

Cone of Douglas-fir (Pseudotsuga menziesii). (Photo courtesy of Christine Duchesne, National Park Service)

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from article Balsa

Leaves and bark of balsa (Ochroma pyramidale). (Credit: Forest and Kim Starr)

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from article Pollen

(a) Fossil pollen (90 million years old) showing the clumping common in the Cretaceous sediments of Minnesota (photo courtesy of Shusheng Hu). (b) Pollen grain of Ipomoea squamosa (a member of the Morning Glory family) showing the large spines that…

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from article Pollen

Tetrad of cattail (Typha latifolia), grains cohering, one-pored, exine reticulate. (Scanning electron micrograph by C. M. Drew, U.S. Naval Weapons Center, China Lake, California)

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from article Pollen

Growth of hellebore (buttercup family) pollen walls: (a,b) matrix of sculpture material forms against callose wall; (c–e) ectexine (tectum, baculum, and foot layer) develops; and (f) endexine and intine appear. (After P. Echlin, Pollen, Sci. Amer.,…

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from article Pollen

Young tetrad of Lavatera (mallow family), with grains free in callose of pollen mother cell. (Photomicrograph by Luc Waterkeyn)

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from article Pollen

Scanning electron micrographs of pollen grains, showing polarity and surface patterns. (a,c) Polar and side (equatorial) views of a reticulate, tricolpate Homalanthus polyandrus (spurge family) grain. (b,d) One-furrowed (monosulcate) grains with…

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from article Pollen

Subfossil Pinnus grain, corroded in soil. (a) Sketch showing cap and two sacs in side view, with right sac broken. (b) View into damaged right sac, which lacks its tough outer wall, to show honeycomb (alveolate) ectexine (sexine) structure in the…

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from article Pollen

Some varied pollen types of (a–d) gymnosperms and (e–g) angiosperms. (a) Inaperturate (Cupressus arizonica). (b) Papillate (Sequoia sempervirens). (c) Monosulcate (Zamia floridiana), a cycad. (d) Young three-saccate grain of kahikatea (Dacrycarpus…

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from article Pollen

Three polyads, each a symmetrical unit of 16 grains, lying free in an open anther lobe of Albizzia julibrissin (mimosa family).

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from article Pollen

Dicot aperture types, (a) Tricolpate (Hebe rapensis). (b) Triporate (Casuarina stricta) (photomicrograph by Isobel C. Cookson). (c) Tricolporate (Griselinia littoralis), side view, unexpanded; (d) polar view, intine present, expanded. (e) Periporate…

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from article Pollen

Some anemophilous dicot types and an entomophilous type of pollen grains. (a) Surface of many-pored Russian thistle (Salsola kali), grain with very small spinules. (b, c) Modern and (d) fossil Nothofagus fusca–type grains notable for endexinal…

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from article Pollen

Polar view of an Aptian Clavatipollenites grain, showing the long furrow and surface pattern (as in living Ascarina). From the Arundel clay of the Atlantic coastal plane, United States. (Scanning electron micrograph by J. V. Ward)

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from article Yeast systematics

Colored scanning electron micrograph of cells of brewer's yeast (Saccharomyces cerevisiae). This fungus consists of single vegetative cells. Small daughter cells can be seen budding off from the larger cells. Once they have reached their full size,…

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from article Yeast systematics

Colored scanning electron micrograph of yeast cells (genus Candida), which multiply by a process called budding. Members of the genus Candida can cause a variety of human diseases, collectively referred to as candidiasis. (Credit: Steve…

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from article Neandertals

Neandertal cranium excavated from Forbes' Quarry, Gibraltar. Note the pronounced brow ridges, large braincase, and receding forehead. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Gorham's Cave, Gibraltar, is the last known site of Neandertal occupation, being dated possibly to 30,000 years ago. (Credit: Clive Finlayson/Gibraltar Museum)

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from article Neandertals

Reconstructed skull of a Neandertal from the cave at La Chapelle-aux-Saints, France. (Credit: Illustration adapted from an original drawing by M. F. Ashley Montagu)

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from article Root (botany)

Kinds of roots. (a) Adventitious, on a cutting or slip (geranium). (b) Prop and other adventitious (corn). (c) Fibrous adventitious (grass). (d) Primary, or taproot (dandelion). (e) Fleshy taproot (carrot). (f) Fleshy, fascicled adventitious…

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from article Root (botany)

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from article Root (botany)

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from article Root (botany)

Distribution of tissues in a typical root apex.

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from article Root (botany)

Transverse sections of roots, showing primary and secondary tissues. (a) Soybean. (b) Barley. (c) Soybean; enlarged part of a, showing early formation of cambium. (d) Soybean with abundant secondary tissue.

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from article Root (botany)

Diagrams of vascular transition in dicotyledonous seedling (beet, Beta vulgaris) from root tip upward to level of cotyledons. (a) Root is diarch; its vascular tissues are continuous with those of (e) the cotyledons through (b–d) the transition…

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from article Hydroponics

Green- and red-leaf lettuce growing in a hydroponic vegetable garden on a bamboo fence. The pipes, which supply nutrients and water, are part of the hydroponic system. (Credit: Piyachok Thawornmat, Shutterstock)

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from article Hydroponics

Hydroponic techniques: (a) aerated standing culture; (b) flowing-solution culture with standing solution; (c) nutrient film technique; (d) aeroponics.

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from article Flower

Flower structure, median longitudinal section.

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from article Flower

Diagrammatic section of an orange blossom. (After J. B. Free, Insect Pollination of Crops, Academic Press, 1970)

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from article Flower

Flower of Penstemon, a member of the foxglove family, in section. (After C. E. Wood, Jr., A Student's Atlas of Flowering Plants: Some Dicotyledons of Eastern North America, Harper and Row, 1974)

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from article Flower

Longitudinal section of a flower bud and one carpel in section of blackberry (Rubus betulifolius). (After K. R. Robertson, The genera of Rosaceae in the southeastern United States, J. Arnold Arbor., 55:344–401, 1974)

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from article Flower

Placentation: (a) parietal, (b) axile, and (c) free central. (After P. H. Raven, R. F. Evert, and H. Curtis, Biology of Plants, Worth Publishers, 1976)

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from article Flower

Nectaries. (a) Cherry flower (after W. H. Brown, The bearing of nectaries on the phylogeny of flowering plants, Proc. Amer. Phil. Soc., 79:549–595, 1938). (b) Flower of nasturtium (after B. J. D. Meeuse, The Story of Pollination, Ronald Press,…

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from article Flower

Sunflower (Helianthus annuus) of the composite family. (a) Inflorescence in section. (b) Side view of ray floret. (c) Side view of tubular floret. (d) Section of tubular floret. (After J. B. Free, Insect Pollination of Crops, Academic Press, 1970)

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from article Flower

Successive stages of flower formation in a wood sorrel. (a) Sepals and petals already initiated; the androecium begins as five bumps on the floral apex; five more will be added. At maturity, five long stamens will alternate with five short ones. (b)…

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from article Physiological ecology (plant)

Mangrove trees have evolved to grow in marshy shallow saltwater bays and swamps. In terms of physiological ecology, mangroves have adapted their physiological mechanisms to cope with the unique characteristics of the ecosystems that they inhabit.…

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from article Physiological ecology (plant)

Plant ecologists often face logistic difficulties in reaching many areas of remote rainforests. In addition, the wet and dense foliage conditions found in rainforests can hamper the efforts of investigators who wish to study the physiological…

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from article Physiological ecology (plant)

Barrel cacti inhabit the arid deserts of southwestern North America. These plants have evolved many water-conservation mechanisms to accommodate life in areas with little water and lots of sunshine. (Credit: George Grall/Getty Images)

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from article Physiological ecology (plant)

Corn (Zea mays) is a common crop plant species that possesses the C4 pathway of photosynthesis. (Credit: Smereka/Shutterstock)

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from article Coca

Leaves of coca (Erythroxylum coca) on a plantation in Peru. (Photo courtesy of Thomas Schöpke, http://www.pharmakobotanik.de/gallery/framgall.htm)

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from article Bryopsida

True moss (Mnium). (a) Location of sex organs (male antheridia and female archegonia). (b) Gametophyte with attached sporophytes. (After W. W. Robbins et al., Botany, 3d ed., 1964)

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from article Bryopsida

Life cycle of a moss. (After E. W. Sinnott and K. S. Wilson, Botany, 6th ed., McGraw-Hill, 1963)

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from article Bryopsida

Complete moss plant showing enlarged views of (a) tip of sporophyte with calyptra removed and (b) capsule (sporangium), with operculum and peristome and, beneath the capsule, the hypophysis. (After F. W. Emerson, Basic Botany, 2d ed., Blakiston,…

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from article Hemlock

Needles and cones of eastern hemlock (Tsuga canadensis). (Photo courtesy of Robert H. Mohlenbrock, USDA–NRCS PLANTS Database)

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from article Pea

Green garden peas (seeds) in pod (fruit) [Pisum sativum].

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