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Biology II Part I
Exam 1 (Lecture Vocabulary) CHs 28,29,34,35,37,38
| Question | Answer |
|---|---|
| Abscisic acid | a growth-regulating plant hormone, C 15 H 20 O 4 , that promotes dormancy and the aging and abscission of leaves. |
| Abscission | the normal separation of flowers, fruit, and leaves from plants. |
| Abscission zone | the zone at the base of a leaf petiole, fruit stalk, or branch in which the abscission layer develops. |
| Active transport | the movement of ions or molecules across a cellular membrane from a lower to a higher concentration, requiring the consumption of energy. |
| Adhesion | the union of normally separate parts. |
| Aleurone layer | protein granules (aleurone grains) found in a single layer of cells (aleurone layer) in the outermost portion of the endosperm. |
| Alternation of Generations Life Cycle | the alternation in an organism's life cycle of dissimilar reproductive forms, esp. the alternation of sexual with asexual reproduction. |
| Angiosperms | a plant having its seeds enclosed in an ovary; a flowering plant. |
| Annual rings | an annual formation of wood in plants, consisting of two concentric layers, one of springwood and one of summerwood. |
| Annuals | living only one growing season, as beans or corn. |
| Anther | the pollen-bearing part of a stamen. |
| Antheridium | a male reproductive structure producing gametes, occurring in ferns, mosses, fungi, and algae. |
| Anthocerophyta | Small hornworts. They like damp and shady environments. |
| Antipodal cells | A group of cells, situated at the opposite end to the micropyle, in the mature embryo sac of flowering plants. |
| Antitranspirant | any substance that decreases transpiration and, usually, photosynthesis |
| Apomixis | any of several types of asexual reproduction, as apogamy or parthenogenesis. |
| Apoplast | the nonprotoplasmic component of a plant, including the cell walls and intercellular material |
| Arabidopsis | a genus of the mustard family having white or yellow or purplish flowers; closely related to genus Arabis |
| Archegonium | the female reproductive organ in ferns, mosses, etc. |
| Auxin | a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop. |
| Axillary bud | a bud that is borne at the axil of a leaf and is capable of developing into a branch shoot or flower cluster. |
| Bark | the external covering of the woody stems, branches, and roots of plants, as distinct and separable from the wood itself. |
| Biennials | completing its normal term of life in two years, flowering and fruiting the second year, as beets or winter wheat. |
| Blade | the broad part of a leaf, as distinguished from the stalk or petiole. |
| Bolting | to produce flowers or seeds prematurely. |
| Bract | a specialized leaf or leaflike part, usually situated at the base of a flower or inflorescence. |
| Bryophyta | nonflowering plants characterized by rhizoids rather than true roots and having little or no organized vascular tissue and showing alternation of generations between gamete-bearing forms and spore-bearing forms; true mosses, liverworts, and hornworts |
| Bryophytes | any of the Bryophyta, a phylum of nonvascular plants comprising the true mosses and liverworts. |
| Bulb | a usually subterranean and often globular bud having fleshy leaves emergent at the top and a stem reduced to a flat disk, rooting from the underside, as in the onion and lily. A plant growing from such a bud. |
| Bundle sheath | a layer of cells in plant leaves and stems that surrounds a vascular bundle. |
| Calyx | the outermost group of floral parts; the sepals. |
| Capsule | the sporangium of various spore-producing organisms, as ferns, mosses, algae, and fungi. |
| Carpel | a simple pistil, or a single member of a compound pistil. |
| Casparian strip | band of suberized material around the radial walls of endodermal cells: impervious to gases and liquids |
| Cell plate | a plate that develops at the midpoint between the two groups of chromosomes in a dividing cell and that is involved in forming the wall between the two new daughter cells. |
| Charophytes | any green algae of the class Charophyceae (or group Charophyta), comprising the stoneworts. |
| Chlorenchyma | parenchymal tissue containing chlorophyll. |
| Club mosses | any plant of the genus Lycopodium. |
| Cohesion | the congenital union of one part with another. |
| Coleoptile | (in grasses) the first leaf above the ground, forming a sheath around the stem tip. |
| Coleorhiza | the sheath that envelops the radicle in certain plants and that is penetrated by the root in germination. |
| Collenchyma | a layer of modified tissue consisting of cells that are thickened at the angles and usually elongated. |
| Companion cell | any of a number of specialized parenchymal cells adjacent to a sieve tube in the phloem of flowering plants, believed to regulate the flow of nutrients through the tube. |
| Complete flower | A flower having all four floral parts: sepals, petals, stamens, and carpels. |
| Cone | the more or less conical multiple fruit of the pine, fir, etc., consisting of overlapping or valvate scales bearing naked ovules or seeds; a strobile. A similar fruit, as in cycads or club mosses. |
| Coniferophyta | cone-bearing gymnosperms ; most are substantial trees; include Pinopsida, Ginkgopsida, and Taxopsida |
| Conifers | any of numerous, chiefly evergreen trees or shrubs of the class Coniferinae (or group Coniferales), including the pine, fir, spruce, and other cone-bearing trees and shrubs |
| Cork | Also called: phellem a protective layer of dead impermeable cells on the outside of the stems and roots of woody plants, produced by the outer layer of the cork cambium |
| Cork cambium | Also called: phellogen a layer of meristematic cells in the cortex of the stems and roots of woody plants, the outside of which gives rise to cork cells and the inside to secondary cortical cells (phelloderm) |
| Corm | an enlarged, fleshy, bulblike base of a stem, as in the crocus. |
| Corolla | the inner envelope of floral leaves of a flower, usually of delicate texture and of some color other than green; the petals considered collectively. |
| Cortex | the portion of a stem between the epidermis and the vascular tissue; bark. |
| Cotyledon | the primary or rudimentary leaf of the embryo of seed plants. |
| Cuticle | a very thin hyaline film covering the surface of plants, derived from the outer surfaces of the epidermal cells. |
| Cutting | a piece, as a root, stem, or leaf, cut from a plant and used for propagation. |
| Cycadophyta | palmlike gymnosperms: includes the surviving order Cycadales and several extinct orders; possibly not a natural group; in some systems considered a class (Cycadopsida) and in others a subdivision (Cycadophytina or Cycadophyta) |
| Cycads | any gymnospermous plant of the order Cycadales, intermediate in appearance between ferns and the palms, many species having a thick, unbranched, columnar trunk bearing a crown of large, leathery, pinnate leaves. |
| Cytokinins | any of a class of plant hormones, produced by the roots and traveling upward through the xylem, that promote tissue growth and budding and, on application, retard plant senescence. |
| Deciduous | shedding the leaves annually, as certain trees and shrubs |
| Determinate growth | A type of growth characteristic of animals, in which the organism stops growing after it reaches a certain size. |
| Dioecious | (esp. of plants) having the male and female organs in separate and distinct individuals; having separate sexes. |
| Diploid | having two similar complements of chromosomes. |
| Dormancy | alive but in a resting torpid condition with suspended growth and reduced metabolism |
| Double fertilization | the fertilization process characteristic of flowering plants, in which one sperm cell of a pollen grain fertilizes an egg cell while a second fuses with two polar nuclei to produce a triploid body that gives rise to the endosperm. |
| Ecosystem services | the important benefits for human beings that arise from healthily functioning ecosystems, notably production of oxygen, soil genesis, and water detoxification |
| Embryo | the rudimentary plant usually contained in the seed. |
| Embryo sac | the megaspore of a seed-bearing plant, situated within the ovule, giving rise to the endosperm and forming the egg cell or nucleus from which the embryo plant develops after fertilization. |
| Endodermis | a specialized tissue in the roots and stems of vascular plants, composed of a single layer of modified parenchyma cells forming the inner boundary of the cortex. |
| Endosperm | nutritive matter in seed-plant ovules, derived from the embryo sac. |
| Entrainment | to determine or modify the phase or period of rhythms entrain ed by a light cycle |
| Epicotyl | (in the embryo of a plant) that part of the stem above the cotyledons. |
| Epidermis | a thin layer of cells forming the outer integument of seed plants and ferns. |
| Equisetum | any plant of the genus Equisetum, comprising the horsetails. |
| Ethylene | A colorless, flammable gas C 2 H 4 , having a sweet, unpleasant odor and taste, used as an agent to improve the color of citrus fruits |
| Etiolation | to cause (a plant) to whiten or grow pale by excluding light: to etiolate celery. |
| Eudicots | An angiosperm having two cotyledons in the seed, leaves with a network of veins radiating from a central main vein, flower parts in multiples of four or five, and a ring of vascular cambium in the stem. |
| Evaporative cooling | a system or process in which the heat is removed from an object by the evaporation of a liquid coolant; also, the process in which outside air is pre-cooled before passing through a space |
| Evergreen | (of trees, shrubs, etc.) having green leaves throughout the entire year, the leaves of the past season not being shed until after the new foliage has been completely formed. |
| Female gametophyte | Megagametophyte in heterosporous plants |
| Fern | seedless, nonflowering vascular plant. True roots produced from a rhizome, fronds that uncoil upward and have a branching vein system, and reproduction by spores contained in sporangia that appear as brown dots on the underside of the fronds. |
| Fertilization | the union of male and female gametic nuclei. |
| Fiber | a slender, threadlike root of a plant. |
| Fibrous roots | a root, as in most grasses, having numerous, very fine branches of approximately the same length. Aroot system that consists of very fine branches. |
| Fiddleheads | the young, coiled frond of various species of ferns, eaten as a vegetable. |
| Filament | the stalklike portion of a stamen, supporting the anther. |
| Florigen | a hypothetical plant hormone produced in the leaves and transported to the apex to initiate flowering. |
| Flowering plants | a plant that produces flowers, fruit, and seeds; angiosperm. |
| Flowers | the part of a seed plant comprising the reproductive organs and their envelopes if any, esp. when such envelopes are more or less conspicuous in form and color. The analogous reproductive structure in other plants, as the mosses. |
| Frond | an often large, finely divided leaf, esp. as applied to the ferns and certain palms. A leaflike expansion not differentiated into stem and foliage, as in lichens. |
| Fruit | the developed ovary of a seed plant with its contents and accessory parts, as the pea pod, nut, tomato, or pineapple. the edible part of a plant developed from a flower, with any accessory tissues, as the peach, mulberry, or banana. |
| Gametangia | an organ or body bearing gametes, as in mosses and liverworts. |
| Gamete | a mature sexual reproductive cell, as a sperm or egg, that unites with another cell to form a new organism. |
| Gametophyte | the sexual form of a plant in the alternation of generations. |
| Gemmae | a cell or cluster of cells, or a leaflike or budlike body, that separates from the parent plant to form a new organism, as in mosses and liverworts. |
| Generative cell | A cell of the male gametophyte (pollen grain) of seed plants that divides to give rise directly or indirectly to sperm. |
| Germination | to develop into a plant or individual, as a seed, spore, or bulb. to put forth shoots; sprout; pullulate. |
| Gibberellins | any of a class of growth hormones occurring in fungi and plants. |
| Ginkgo | a large shade tree, Ginkgo biloba, with fan-shaped leaves and fleshy seeds with edible kernels: the sole surviving species of the gymnosperm family Ginkgoaceae, which thrived in the Jurassic Period, and existing almost exclusively in cultivation. |
| Girdling | To kill a tree by destroying a band of bark and cambium. The distribution of food down from the leaves and the flow of water and nutrients up from the roots is disrupted. The cambium can no longer regenerate these vascular tissues to repair itself. |
| Gnetales | chiefly tropical or xerophytic woody plants; practically unknown as fossils but considered close to the ancestral line of angiosperms |
| Grafting | a bud, shoot, or scion of a plant inserted in a groove, slit, or the like in a stem or stock of another plant in which it continues to grow. |
| Gravitropism | oriented growth with respect to the force of gravity. |
| Ground meristem | The primary meristem in vascular plants that gives rise to the nonvascular tissues, such as cortex, pericycle, and pith. Within the seeds of angiosperms, it surrounds the procambium. |
| Guard cells | One of the paired cells in the epidermis of a plant that control the opening and closing of a stoma of a leaf. Unlike the other cells in the epidermis, guard cells have chloroplasts and conduct photosynthesis. |
| Guttation | The exudation of water from leaves as a result of root pressure. a process in which water in liquid form is given off by plants. |
| Gymnosperms | a vascular plant having seeds that are not enclosed in an ovary; a conifer or cycad. |
| Haploid | an organism or cell having only one complete set of chromosomes, ordinarily half the normal diploid number. |
| Heartwood | The older, nonliving central wood of a tree or woody plant, usually darker and harder than the younger sapwood. Unlike the sapwood, it no longer conducts water, and its main function is the support of the tree. |
| Herbaceous | (of plants or plant parts) not woody. having the texture, color, etc., of an ordinary foliage leaf. |
| Herbaceous plant | a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests |
| Heterosporous | Producing two types of spores differing in size and sex, the male microspore and the female megaspore. All seed-bearing plants, as well as some ferns and other seedless plants, are heterosporous. |
| Homosporous | Producing spores of one kind only that are not differentiated by sex. The spores of homosporous plants, such as horsetails and most ferns, grow into bisexual gametophytes (producing both male and female gametes). |
| Hormones | Any of various plant compounds, as auxin or gibberellin, that control growth and differentiation of plant tissue. A substance that is synthesized by a plant part and acts to control or regulate the growth and development of the plant. |
| Hornworts | Any of about 100 species of small bryophyte plants belonging to the phylum Anthocerophyta. Unlike liverworts but like mosses, hornwort sporophytes have stomata. The name of the hornworts was suggested by the hornlike appearance of the sporophytes. |
| Horsetails | A member of a genus, Equisetum, of seedless vascular plants having a jointed hollow stem and narrow, sometimes much reduced leaves. The horsetails are the last surviving members of the phylum Sphenophyta. |
| Hypocotyl | The part of a plant embryo or seedling that lies between the radicle and the cotyledons. Upon germination, the hypocotyl pushes the cotyledons above the ground to develop. It eventually becomes part of the plant stem. |
| Imbibition | the action or process of assimilating, taking into solution, or taking in liquid |
| Imperfect flower | A flower that lacks either stamens or carpels. |
| Indoleacetic acid (IAA) | a crystalline, water-insoluble powder, C 10 H 9 NO 2 , a natural plant hormone, used esp. for stimulating growth and root formation in plant cutting. |
| Inflorescence | A group of flowers growing from a common stem, often in a characteristic arrangement. Also called flower cluster |
| Integuments | A natural outer covering of an animal or plant or of one of its parts, such as skin, a shell, or the part of a plant ovule that develops into a seed coat. |
| Internodes | a part or space between two nodes, knots, or joints, as the portion of a plant stem between two nodes. |
| Lateral bud | a bud that is borne at the axil of a leaf and is capable of developing into a branch shoot or flower cluster. |
| Lateral meristem | meristem located along the sides of a part, as a stem or root. |
| Leaf | An appendage growing from the stem of a plant. Most leaves are flat and green. They consist of an outer tissue layer, a spongy inner layer of cells that contain chloroplasts, and veins that supply water and minerals and carry out food. |
| Leaf primordia | a group of cells that will develop into a leaf, seen as small bulges just below the shoot apex. |
| Leaflets | A small leaf or leaflike part, especially one of the blades or divisions of a compound leaf. |
| Lenticel | One of the small areas on the surface of the stems and roots of woody plants that allow the interchange of gases between the metabolically active interior tissue and the surrounding air or pockets of air in the soil. |
| Lepidodendron | A genus of fossil trees of the Devonian and Carboniferous ages, having the exterior marked with scars, mostly in quincunx order, produced by the separation of the leafstalks. |
| Lignin | complex organic compound that binds to cellulose fibers and hardens and strengthens the cell walls of plants. Lignin is a polymer consisting of various aromatic alcohols, and is the chief noncarbohydrate constituent of wood. |
| Liverworts | Any of about 6,000 species of bryophyte plants belonging to the phylum Hepatophyta. The name liverwort comes from the liverlike shape of the thalli of some species |
| Long-day plant | A plant that flowers only after being exposed to light periods longer than a certain critical length, as in summer. Spinach, lettuce, and some varieties of wheat are long-day plants. |
| Lycopods | any erect or creeping, mosslike, evergreen plant of the genus Lycopodium, as the club moss or ground pine. |
| Male gametophyte | Microgametogphyte in heterosporous plants |
| Megagametophyte | The female gametophyte that develops from the megaspores of heterosporous plants. |
| Megaphyll | A leaf with several or many large veins branching apart or running parallel and connected by a network of smaller veins. Megaphylls are thought to have evolved from groups of branched stems that have become fused together. Also called macrophyll . |
| Megasporangia | A plant structure in which megaspores are formed, such as those of the female cones of pines. |
| Megaspore | One of the two types of haploid spores produced by a heterosporous plant. Megaspores develop into female gametophytes and are usually larger than microspores. |
| Membrane potential | the potential difference between the interior of a cell and the interstitial fluid beyond the membrane |
| Meristem | Plant tissue whose cells actively divide to form new tissues that cause the plant to grow. The meristem includes the growing tips of roots and stems (the apical meristems) and the tissue layer known as cambium. |
| Mesophyll | The tissues of a leaf that are located in between the layers of epidermis and carry on photosynthesis, consisting of the palisade layer and the spongy parenchyma . Most mesophyll cells contain chloroplasts. |
| Microgametophyte | The male gametophyte that develops from the microspores of heterosporous plants. The pollen grains of gymnosperms and angiosperms are microgametophytes. |
| Microphylls | A leaf with only one vascular bundle and no complex network of veins. Microphylls on modern plants are generally small but in extinct phyla the same structures could grow quite large. |
| Micropyle | A minute opening in the ovule of a seed plant through which the pollen tube usually enters |
| Microsporangia | A plant structure in which microspores are formed. The pollen-producing male cones of a pine consist of many microsporangia, where the microspores of the pine develop into pollen grains to be dispersed. |
| Microspore | One of the two types of haploid spores produced by a heterosporous plant. Microspores develop into male gametophytes and are usually smaller than megaspores. In angiosperms, the microspore develops into the pollen grain. |
| Middle lamella | the layer of cementing material, composed of pectates and similar substances, between the walls of adjacent cells. |
| Monocots | Angiosperm plants with a single cotyledon, leaves with parallel veins, flower parts in multiples of three, and fibrous root systems. Primary vascular bundles are scattered throughout the stem. Grasses, palms, lilies, irises, and orchids are monocots. |
| Monoecious | (of a plant, species, etc.) having the stamens and the pistils in separate flowers on the same plant. |
| Mosses | Small bryophyte plants belonging to the phylum Bryophyta. The diploid sporophyte grows on the haploid gametophyte generation, which supplies it with nutrients and live in moist, shady areas and grow in clusters. |
| Mycorrhizae | The association of a fungus with the roots of most vascular plants. The fungus assists in the absorption of minerals and water from the soil and defends the roots from other fungi and nematodes, while the plant provides carbohydrates to the fungus. |
| Nodes | A point on a stem where a leaf is or has been attached. A swelling or lump on a tree; a knob or knot. |
| Nucleus | a specialized, usually spherical mass of protoplasm encased in a double membrane, and found in most living eukaryotic cells, directing their growth, metabolism, and reproduction, and functioning in the transmission of genic characters. |
| Nutrients | a substance that provides nourishment for growth or metabolism. Plants absorb nutrients mainly from the soil in the form of minerals and other inorganic compounds, and animals obtain nutrients from ingested foods. |
| Osmosis | the diffusion of fluids through membranes or porous partitions. |
| Ovary | the enlarged lower part of the pistil in angiospermous plants, enclosing the ovules or young seeds. |
| Ovule | The female reproductive structure that develops into a seed in a seed-bearing plant. The ovules of angiosperms are contained in a structure called the ovary within in the flower. |
| Parenchyma | The basic tissue of plants, consisting of cells with thin cellulose walls. The cortex and pith of the stem, the internal layers of leaves, and the soft parts of fruits are made of parenchyma. |
| Parthenocarpy | The production of fruit without fertilization. Many varieties of the common fig produce fruit through parthenocarpy. |
| Passive transport | transport of a substance across a cell membrane by diffusion; expenditure of energy is not required |
| Pectin | Any of a group of carbohydrate substances found in the cell walls of plants and in the tissue between certain plant cells. Pectin is produced by the ripening of fruit and helps the ripe fruit remain firm. |
| Perennials | Herbaceous perennials survive winter and drought as underground roots, rhizomes, bulbs, corms, or tubers. Woody perennials, including vines, shrubs, and trees, usually stop growing during winter and drought. |
| Perfect flower | A flower having both stamens and carpels. Most angiosperms have perfect flowers. |
| Pericarp | The tissue that arises from the ripened ovary wall of a fruit; the fruit wall. In fleshy fruits, the pericarp can often be divided into the exocarp, the mesocarp, and the endocarp. |
| Pericycle | A layer of nonvascular tissue that surrounds the vascular tissues in the roots of plants and is in turn surrounded by the endodermis. New lateral roots begin growth from the pericycle. |
| Periderm | The outer, protective layers of tissue of woody roots and stems, consisting of the cork cambium and the tissues produced by it. See more at cork cambium. |
| Petals | One of the often brightly colored parts of a flower surrounding the reproductive organs. Petals are attached to the receptacle underneath the carpels and stamens and may be separate or joined at their bases. |
| Petiole | the slender stalk by which a leaf is attached to the stem; leafstalk. |
| Phloem | Tissue in vascular plants that conducts food from the leaves and other photosynthetic tissues to other plant parts. Consists of several different kinds of cells: sieve elements, parenchyma cells, sclereids, and fibers. |
| Photoperiodism | The response of an organism to changes in its photoperiod, especially as indicated by vital processes. |
| Photoreceptor | A specialized structure or cell that is sensitive to light. |
| Phototropism | the growth response of plant parts to the stimulus of light, producing a bending towards the light source |
| Phytochromes | Any of a group of cytoplasmic pigments found in green plants and some green algae that absorb red light and regulate dormancy, seed germination, and flowering. |
| Pistil | One of the female reproductive organs of a flower, consisting of a single carpel or of several carpels fused together. A flower may have one pistil or more than one, though some flowers lack pistils and bear only the male reproductive organs, stamens. |
| Pith | the soft, spongy central cylinder of parenchymatous tissue in the stems of dicotyledonous plants. |
| Pits | The hard, inner layer (the endocarp) of certain drupes that are valued for their flesh, such as peaches, cherries, or olives. Not in scientific use |
| Plantlets | a little plant, as one produced on the leaf margins of a kalanchoe or the aerial stems of a spider plant. |
| Plasmodesmata | any of many minute strands of cytoplasm that extend through plant cell walls and connect adjoining cells. |
| Plastids | An organelle found in the cells of plants, green algae, red algae, and certain other protists. Some plastids, such as the chloroplasts in plant leaves, contain pigments. |
| Polar nuclei | either of two female haploid nuclei, in the embryo sac of flowers, that fuse to produce a diploid nucleus, which combines with a male nucleus to form the endosperm. |
| Pollen grain | a single granule of pollen. |
| Pollen tube | the protoplasmic tube that is extruded from a germinating pollen grain and grows toward the ovule. |
| Pollination | the transfer of pollen from the anther to the stigma. |
| Primary growth | growth in vascular plants, esp. an increase in length, that results from cell division and differentiation of an apical meristem. |
| Procambium | the meristem from which vascular bundles are developed. |
| Prothallus | The gametophyte of homosporous ferns and some other plants. Prothalli have chlorophyll for photosynthesis. Prothalli develop from germinated spores, and they bear both archegonia for producing eggs and antheridia for producing sperm. |
| Protoderm | a thin outer layer of the meristem in embryos and growing points of roots and stems, which gives rise to the epidermis. |
| Proton pump | a molecular mechanism that transports hydrogen ions across cell membranes |
| Protonema | The green filamentous or flat, thallus-like structure that grows from the germinated spores of liverworts and mosses and eventually gives rise to a mature gametophyte. |
| Pteridophyta | containing all the vascular plants that do not bear seeds: ferns, horsetails, club mosses, and whisk ferns; in some classifications considered a subdivision of Tracheophyta |
| Radicle | The part of a plant embryo that develops into a root. In most seeds, the radicle is the first structure to emerge on germination. |
| Receptacle | The enlarged upper end of a flower stalk that bears the flower or group of flowers. The fleshy edible part of an apple is actually a modified receptacle. |
| Rhizoids | A slender, rootlike filament by which mosses, liverworts, and the gametophytes of ferns attach themselves to the material in which they grow. |
| Rhizome | A plant stem that grows horizontally under or along the ground and often sends out roots and shoots. New plants develop from the shoots. Ginger, iris, and violets have rhizomes. Also called rootstock . |
| Root | A plant part that usually grows underground, secures the plant in place, absorbs minerals and water, and stores food. Dicots have a larger taproot with many narrower lateral roots branching off. Monocots have a mass of threadlike fibrous roots |
| Root cap | A thimble-shaped mass of cells that covers and protects the root tip of plants. Also called calyptra . |
| Root hairs | A hairlike outgrowth of a plant root that absorbs water and minerals from the soil. Root hairs are tubular extensions of the epidermis that greatly increase the surface area of the root. |
| Root pressure | Pressure produced in the roots of plants, causing exudation of sap from cut stems and guttation of water from leaves. |
| Root system | The configuration of a plant's various roots. |
| Runners | A slender stem that grows horizontally and puts down roots to form new plants. Strawberries spread by runners. Also called stolon . |
| Sapwood | the softer part of the wood between the inner bark and the heartwood |
| Scion | A detached shoot or twig containing buds from a woody plant, used in grafting. |
| Sclereids | A thick-walled lignified plant cell, often branched in shape. Sclereids form many hard structures such as seed coats and nut shells. They are a type of sclerenchyma cell but are usually shorter than fibers. |
| Sclerenchyma | A supportive tissue of vascular plants, consisting of thick-walled, usually lignified cells. Sclerenchyma cells normally die upon reaching maturity but continue to fulfill their structural purpose in the plant. |
| Scutellum | The large, shield-shaped cotyledon of the embryo of a grass plant, specialized for the absorption of food from the endosperm. |
| Seed | A mature fertilized ovule of angiosperms and gymnosperms that contains an embryo and the food it will need to grow into a new plant. The seeds of gymnosperms develop on scales of cones. Angiosperms' are enclosed in an ovary that develops into a fruit. |
| Seed coat | The outer protective covering of a seed. The seed coat develops from the integument of the ovule. Also called testa . |
| Seed plants | The gymnosperms and the angiosperms together form the seed-bearing plants. |
| Seedling | any young plant, esp. one grown in a nursery for transplanting. a plant or tree grown from a seed. a tree not yet 3 ft. (1 m) high. |
| Self-incompatibility | (of a plant) incapable of self-fertilization because its own pollen is prevented from germinating on the stigma or the pollen tube is blocked before it reaches the egg cell |
| Senescence | growing old; aging. |
| Sepals | One of the usually separate, green parts that surround and protect the flower bud and extend from the base of a flower after it has opened. Sepals tend to occur in the same number as the petals and to be centered over the petal divisions. |
| Sieve cells | An elongated, food-conducting cell in phloem characteristic of gymnosperms. Sieve cells have pores through which nutrients flow from cell to cell, but they have no sieve plates like the more specialized sieve-tube elements of angiosperms. |
| Sieve plates | An elongated, food-conducting cell in phloem characteristic of gymnosperms. Sieve cells have pores through which nutrients flow from cell to cell, but they have no sieve plates like the more specialized sieve-tube elements of angiosperms. |
| Sieve tube elements | An elongated, food-conducting cell in phloem in angiosperms. Sieve elements have living protoplasts when mature, but they lack a nucleus and are dependent upon companion cells for certain functions. |
| Simple fruits | A fruit that develops from a single ovary in a single flower. Simple fruits may be fleshy or dry. There are three main kinds of fleshy simple fruit: the berry, the drupe, and the pome. |
| Sink | A part of any physical system, that absorbs some form of matter or energy. For example, a forest acts as a sink for carbon dioxide because it absorbs more of the gas in photosynthesis than it releases in respiration. |
| Sorus | A cluster of sporangia borne on the underside of a fern frond. A sorus is sometimes covered by an indusium |
| Source | any thing or place from which something comes, arises, or is obtained; origin |
| Sperm cells | any male gamete. |
| Spines | A sharp-pointed projection on a plant, especially a hard, narrow modified leaf, as on a cactus, that is adapted to reduce water loss. |
| Sporangia | A cell or structure in which spores are produced. Ferns, fungi, mosses, and algae release spores from sporangia. Also called spore case . |
| Spore | one-celled body in seed-bearing plants; the macrospore or microspore. The macrospore develops into a female gametophyte, which is contained within the ovule and eventually produces the egg cells. The microspore into the male gametophyte or pollen grain. |
| Sporophyll | a modified leaf that bears sporangia. |
| Sporophyte | the form of a plant in the alternation of generations that produces asexual spores. |
| Sporopollenin | An organic polymer that is extremely resistant to degradation. Pollen grains and many kinds of spores have a protective outer coating of sporopollenin, which is so durable that microfossils of sporopollenin are found in rocks over 500 million years old |
| Spring wood | the part of an annual ring of wood, characterized by large, thin-walled cells, formed during the first part of the growing season. |
| Stamen | the pollen-bearing organ of a flower, consisting of the filament and the anther. |
| Stele | The central core of primary vascular tissues in the stem or root of a vascular plant, consisting of xylem and phloem together with pith. |
| Stems | The main, often long or slender part of a plant that usually grows upward above the ground and supports other parts, such as branches and leaves. |
| Stigma | The sticky tip of a flower pistil, on which pollen is deposited at the beginning of pollination. |
| Stock | The trunk or main stem of a tree or another plant. A plant or stem onto which a graft is made. A plant or tree from which cuttings and scions are taken. |
| Stolon | A slender stem that grows horizontally and puts down roots to form new plants. Strawberries spread by runners. |
| Stomata | tiny openings in the epidermis of a plant, through which gases and water vapor pass. occur on all living plant parts that have contact with the air; they are especially abundant on leaves. |
| Stone cells | A thick-walled lignified plant cell, often branched in shape. Sclereids form many hard structures such as seed coats and nut shells. They are a type of sclerenchyma cell but are usually shorter than fibers. |
| Strobilus | A reproductive structure that consists of sporophylls or scales arranged spirally or in an overlapping fashion along a central stem, as in horsetails, some lycophytes, and many kinds of gymnosperms. For example, the cones of pine trees are strobili. |
| Style | The slender part of a flower pistil, extending from the ovary to the stigma. The pollen tube grows through the style delivering the pollen nuclei to the ovary. |
| Suberin | A polyester composed of fatty acids and aromatic compounds that occurs naturally in the cell walls of cork tissue in plants. protect plant surfaces from water loss and microbial attack, and also helps to close tears and breaks |
| Suckers | A shoot growing from the base or root of a tree or shrub and giving rise to a new plant, a clone of the plant from which it comes. The growth of suckers is a form of asexual reproduction. |
| Sucrose | A crystalline sugar found in many plants, especially sugar cane, sugar beets, and sugar maple. |
| Summer wood | the part of an annual ring of wood, characterized by compact, thick-walled cells, formed during the later part of the growing season. |
| Suspensor | a cellular structure, developed along with the embryo in seed-bearing plants, that bears the embryo at its apex and by elongation carries the embryo to its food source. |
| Symplast | the continuous system of protoplasts, linked by plasmodesmata and bounded by the cell wall |
| Synergids | One of two small, short-lived nuclei lying near the egg in the mature embryo sac of a flowering plant. The synergids are part of the egg apparatus and are thought to help the pollen nucleus reach the egg cell for fertilization. |
| Syngamy | union of gametes, as in fertilization or conjugation; sexual reproduction. |
| Taproot | a main root descending downward from the radicle and giving off small lateral roots. |
| Tendrils | A slender, coiling plant part, often a modified leaf or leaf part, that helps support the stem of some climbing angiosperms by clinging to or winding around an object. Peas, squash, and grapes produce tendrils. |
| Tepals | A division of the perianth of a flower in which the sepals and petals are indistinguishable, as in tulips and lilies. |
| Thallus | part found among plants and fungi. is not differentiated into roots, stems, or leaves. found among lichens, mosses, liverworts, and many algae, as well as the gametophyte generations of horsetails and ferns, which have rhizoids but not true roots. |
| Thigmotropism | oriented growth of an organism in response to mechanical contact, as a plant tendril coiling around a string support. |
| Tissue culture | the growth of small pieces of animal or plant tissue in a sterile controlled medium |
| Tonoplast | a membrane separating a vacuole from the surrounding cytoplasm in a plant cell. |
| Totipotency | (of a cell or part) having the potential for developing in various specialized ways in response to external or internal stimuli. |
| Tracheid | An elongated, water-conducting cell in xylem. Tracheids are found in all vascular plants. |
| Tracheophytes | any plant of the former division Tracheophyta, comprising all the vascular plants. |
| Translocation | the conduction of soluble food material from one part of a plant to another. |
| Transpiration | the passage of water through a plant from the roots through the vascular system to the atmosphere. |
| Triploid | a triploid cell or organism. |
| Tube cell | The cell in the pollen grain that develops into the pollen tube (the tube which conveys the male gametes of seed-bearing plants to the ovule). |
| Tuber | The thickened part of an underground stem of a plant, such as the potato, bearing buds from which new plant shoots arise. |
| Turgid | swollen and distended; congested |
| Turgor pressure | Also called: hydrostatic pressure the pressure exerted on a plant cell wall by water passing into the cell by osmosis |
| Vascular bundles | A strand of primary tissues found within the stem of a plant and consisting of xylem and phloem, along with cambium. The vascular bundles develop from the procambium of the growing stem. |
| Vascular cambium | A cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth. The vascular cambium produces vascular tissues, new xylem on its interior side and new phloem on its exterior side. |
| Vascular rays | a radiate band of parenchyma in the secondary xylem extending into the secondary phloem of the stems of certain vascular plants, formed by the cambium and serving for the storage of food and the conduction of nutriments. |
| Vascular tissues | The tissue in vascular plants that circulates fluid and nutrients. There are two kinds of vascular tissue: xylem and phloem. Vascular tissue can be primary or secondary. |
| Vegetative reproduction | Asexual reproduction in plants. Multicellular structures become detached from the parent plant and develop into new individuals that are identical to the parent plant. |
| Veins | One of the narrow, usually branching tubes or supporting parts forming the framework of a leaf. Veins in leaves contain vascular tissue, with the xylem usually occurring on the upper side of the vein and the phloem on the lower side. |
| Vernalization | The subjection of seeds to low temperature in order to hasten plant development and flowering. Commonly used for crop plants such as winter rye and is possible because the seeds and buds of many plants require cold in order to break dormancy. |
| Viviparous | Giving birth to living young that develop within the mother's body rather than hatching from eggs. All mammals except the monotremes are viviparous. |
| Wilt | to become limp and drooping, as a fading flower; wither. |
| Wood | The thick xylem of trees and shrubs, resulting from secondary growth by the vascular cambium, which produces new layers of living xylem. Often each cycle of growth of new wood is evident as a growth ring. |
| Woody plant | a plant having hard lignified tissues or woody parts especially stems |
| Xylem | Tissue in vascular plants that carries water and minerals from the roots and provides support for softer tissues. Consist of several different types of cells: fibers for support, parenchyma for storage, and tracheary elements for the transport of water. |
| Zeaxanthin | a yellow crystalline carotenoid alcohol C 40 H 56 O 2 that is isomeric with lutein and occurs widely with it and that is the chief pigment of yellow Indian corn |
| Zygote | The cell formed by the union of the nuclei of two reproductive cells (gametes), especially a fertilized egg cell. |
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