family. The unit of organism classification that falls between order and genus.
far red. The longest wavelengths of the red portion of the spectrum.
fermentation. Anaerobic form of respiration. Produces alcohol or lactic acid as an end product.
fern. A vascular plant possessing roots, stems, and leaves. Reproduces by spores, which produce minute gametophytes upon germination, fiber. In vascular plants, an elongated, tapering, thick-walled sclerenchyma cell, filament. A long, slender object. In botany, the anther-bearing stalk of the stamen.
filamentous. Long, slender, threadlike.
filial. Relating to a son or daughter. In heredity, relating to the offspring of a particular cross.
filterable virus. A viral particle consisting of protein and either DNA or RNA and being so minute that it can pass through the pores of a ceramic filter designed to remove bacteria, finger and toe disease. See clubroot.
fission. A division of single-celled forms. No sexual union is involved, fixation. Here, rendering nitrogen into compounds available to plants, flagellum (plural, flagella). A slender filament projecting from a cell. Longer but having the same internal structure as cilia. Capable of a different kind of movement than are cilia. Used in locomotion and feeding, floridian starch. A reserve carbohydrate characteristic of the red algae, florigen. The flowering hormone. Has not yet been isolated and identified but is presumed to exist and to stimulate flower production, floristics. The branch of ecology that focuses on distribution and numbers of plants.
fluorescence. The emission of light by a substance, as with a chlorophyll extract. Chlorophyll is able to function as a source as well as a receiver of light.
foliose. Having similarity to a leaf. In lichens, a flattened, leaflike structure, follicle. A fruit similar to a pod but dehiscing on only one line, foot. In early sporophyte development, the lower portion of the sporophyte that attaches to gametophytic tissue. In bryophytes, the lower part of the embryo sporophyte. fret membrane. The membrane that covers the frets, or lamellae, that interconnect the grana in plastids at irregular intervals, fruit. In angiosperms, the mature ovary containing the seeds and any adjacent parts that may be adhered to the ovary, frustule. The silicious shell of the diatoms. Composed of two valves that overlap.
fucoxanthin. A brown pigment occurring particularly in the ova of brown algae.
fungus (plural, fungi). Saprophytic or parasitic, plantlike structure that lacks chlorophyll and possesses a body composed of mycelia. Included among the fungi are molds, mildews, rusts, smuts, mushrooms, puffballs, and yeasts.
gametangia. Organs that bear gametes.
gamete. A cell that can fuse with another cell to produce a new individual.
Such cells are regularly haploid. gametophyte. A gamete-producing generation that is haploid. The gametes are produced by mitotic divisions, gel. A colloidal substance that tends to be viscous, more or less jelly-like.
May result from coagulation, gelatinous. Resembling a jelly in appearance and consistency, gemma cup. In liverworts, a minute cupule in which the gemmae reside, gemmae. Small clusters of vegetative cells. On the thallus of the gametophyte generation of liverworts and in certain fungi, outgrowths capable of developing into new plants. No alternation of generations is involved, gene. The unit of heredity. Constructed of DNA molecules, generative nucleus. In a pollen grain, the one of two nuclei that through its division produces two sperm nuclei, genotype. The genetic constitution, whether latent or expressed. The total of all the genes present in an organism. Contrast with phenotype. genus (plural, genera). A group of related species. The taxonomic rank between species and family. The first word of the scientific name, germ plasm. Tissue involved in the production of a new generation.
Reproductive cells. Transmitters of hereditary characteristics, germinate. The resumption of growth after a period of dormancy. Applies to a spore or a seed, gibberellin. Growth hormone involved in elongation of stems in a number of higher plants. First isolated in the fungus Gibberella. girdle. The overlapping edge of a valve in diatoms. Also, a transverse groove on dinoflagellates. glucose. Also called grape sugar. A simple, 6-carbon sugar, glycolysis. An anaerobic step in respiration. A breakdown of sugar to simpler compounds.
graftage. The horticultural practice of grafting to unite a scion and a stock.
Used to increase the number of clonal plants, grana. Those structures within chloroplasts that under a light microscope look like minute granules and under an electron microscope look like stacked thylakoids. Contain the chlorophylls and carotenoids. Sites of the photosynthesis reactions, ground meristem. Meristematic tissue that gives rise to the fundamental tissue system.
guard cells. Specialized, epidermal cells that surround the stomates. Changes in turgor change the shape of the guard cells and serve to open and close the stomates. gullet. A groove present in some dinoflagellates and Euglenids. guttation. The exudation of water and dissolved substances from the leaves of plants.
gymnosperm. Seed plant with seeds not enclosed in an ovary. The conifers are the most familiar, gynoecium. The pistil. The female portion of the flower.
haploid. Having one chromosome complement per cell. A common characteristic of the gametophyte generation, haustorium (plural, haustoria). A cell outgrowth that functions as an adsorbing organ, penetrating a substrate, heartwood. The center of xylem in woody plants. Nonliving, nonfunctional, and commonly dark in color, heliotropism. Positioning in response to sunlight, as in sunflowers turning their heads toward the sun. helix. Spiral in form. Here, describes the form of a DNA or RNA strand, hemoglobin. An iron-containing, protein pigment in red blood cells, herbaceous. Nonwoody and, therefore, persisting only for a single growing season.
herbarium. A collection of dried, pressed plants.
heterocyst. A transparent, thick-walled cell in the filaments of certain blue-green algae.
heterothallic. Refers to organisms that are self-sterile or self-incompatible and, therefore, require two different compatible strains or individuals to bring about sexual reproduction, heterotrophic. Unable to manufacture organic compounds and, therefore, needing to feed on organic materials. Contrast with autotrophic (self-nourishing).
heterozygous. Having two different genes at the same locus on a pair of homologous chromosomes, hexose. A 6-carbon sugar.
holdfast. Structure at the tips of tendrils that allows the organism to attach to a substrate. Also, the basal part of an algal cell that attaches to a solid object.
homologous. Refers to chromosomes that are members of a pair, each member of the pair being derived from different parents.
homothallic. Possessing both male and female reproductive structures in the same organism, homozygous. Having a like pair of genes at a specific locus, hormogonia. Short filaments that result from the breaking apart of longer filaments in certain blue-green algae. They fracture at the site of heterocysts. hormone. A chemical substance that is produced in minute amounts and has a marked effect on some other process, hornwort. With the mosses and liverworts, belong to the division Bryophyta. Distinguished from other bryophytes in that each cell has a single chloroplast, mucilage-filled cavities, and an elongated foot, host. A living organism upon which another organism of a different species dwells and from which that other organism derives its nourishment, hydathode. An epidermal structure functioning in the exudation of water, hydrogenation. The union of hydrogen atoms to a compound, a chemical reaction requiring the enzyme hydrogenase. hydrolysis. The chemical breakdown of molecules accomplished by the insertion of the components of water at the point of the breakage, hydroxyl. A radicle consisting of -OH (i.e., one atom of hydrogen and one atom of oxygen). Characteristic of alcohols, glycols, and hydroxides, hygroscopic. Sensitive to variations in moisture. Changes shape in different conditions of humidity, hymenium. In fungi, a mat of mycelium in the floor of the fruiting structure. Bears basidia or asci. hypertonic. Having a concentration of dissolved substance greater than that of a solution serving as a source of comparison, hypha (plural, hyphae). In fungi, a single, tubular filament. The hyphae collectively compose the mycelium, hypocotyl. That portion of a germinating seedling that lies below the cotyledons.
hypotheca. The younger of the two valves in the wall of a diatom, hypotonic. Having a concentration of dissolved substance less than that of a solution serving as a source of comparison.
IAA. Indole acetic acid. The hormone that is produced at the growing tips of plants and is a cell wall softener, icosahedron. Here, virus having twenty sides.
idioplasm. An old term for that part of the protoplasm that functions in the transmission of hereditary properties. It therefore equates with chromatin, imperfect. Asexual reproduction. In reference to flowers, either the pistil or the stamens are lacking, making the flowers unisexual.
incomplete. Refers to a flower lacking one or more of the four whorls of flower parts.
incomplete dominance. Referring to the phenotype. A blending of traits from each gene of a pair, indehiscent. Not splitting along predeterminable lines, independent assortment. The inheritance of one pair of traits is independent of the distribution of another pair of traits, indusium. On a fern leaf, an epidermal growth that covers the sorus. inferior ovary. An ovary that is attached to the upper part of the calyx. The other whorls of flower parts arise above the ovary, inflorescence. A cluster of flowers, often on a common receptacle, infrared. Lying outside the visible, red end of the spectrum. Wavelengths are longer than those of visible light, initial. A cell of apical meristem that remains meristematic. insectivorous. Said of plants that "capture" insects and "digest" them, integument. A seed coat. An envelope that encloses the nucellus in an ovule.
intercellular. Lying between cells.
internode. That portion of a stem that lies between two nodes or buds, interphase. In mitosis, the so-called "resting" stage between mitotic divisions; in meiosis, the so-called "resting" stage between the first and second meiotic divisions. The term resting is misleading, however, because many changes occur during this stage, intine. An inner layer of the pollen grain wall, intracellular. Within the cell.
inversion. Here, refers to when a chromosome is broken, reverses its end-
to-end arrangement, and is mended again, invertase. The enzyme that acts on sucrose, converting the sucrose into a mixture of glucose and fructose, ion. That part of a molecule in solution that possesses an electrical charge, isodiametric. Having dimensions that are equal in all directions. Said to be true of parenchyma cells, isogamous. When fused gametes are of the same size and shape, isomorphic. Here, when the sporophyte and gametophyte are of the same shape and size.
isotonic. Having the same osmotic concentration as another solution serving as a source of comparison, isotopes. Elements having differing numbers of neutrons in their nuclei, causing them to have differing weights.
Jarovisation. Cold stratification. A cold treatment used to render seeds capable of germination.
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