TERMS AND DEFINITIONS FOR FINAL EXAM

GENERAL BIOLOGY I

SUMMER 2004

Abscisic acid   One of five classes of plant hormone. Inhibits shoot growth. Closes stomata. Induces and maintains seed dormancy.

Angiospermae   A group of plants that produce flowers and whose seeds are borne within a fruit.

Anther   Pollen-producing body at the tip of a stamen.

Antheridia   A sperm-producing structure in algae, bryophytes and seedless vascular plants.

Asexual Reproduction   Any form of reproduction which does not require the fusion of gametes.

Auxin   One of five classes of plant hormone. Stimulates cells in seedlings to elongate.

Axil   The region between a leaf stalk and stem which supports the leaf.

Bryophytes   Collective term for the simplest plants that lack vascular tissue and other parts. They must remain close to water because their sperm

                       must swim.

Calyx  The outermost whorl of a flower. Consists of green, leaflike sepals, which protect the inner floral parts.

Cellulose A polysaccharide that is composed of unbranched chains of glucose; the major structural carbohydrate of plants, insoluble in water, and

                 indigestible in the human intestine.

Collenchyma cells  Cells with thickened walls that support growing regions of leaves and shoots.

Conifers  Plants that are the best example of the gymnosperms.

Corolla   Made up of all the petals of a flower. Encloses the reproductive organs, and is itself protected by the sepal.

Cotyledons    A small leaf of a plant embryo. Used for storing and digesting nutrients and/or for early photosynthesis. Embryos of flowering plants

                       have either one or two cotyledons.

Cuticle   A waxy layer covering the aerial parts of a plant.

Cutin    A fatty material that a plan´s epidermal cells produce that forms a cuticle.

Cytokinin   One of the five classes of plant hormone. Delay leaf senescence and allow lateral bud to grow.

Dermal tissue    Tissue that covers a plant.

Dioecious   In plants, having separate male and female individuals of the same species.

Dormancy   A temporary state of lowered metabolism and arrested growth. Example: many plants and insects experience a period of dormancy

                    during winter.

Double fertilization  In angiosperms and gnetophytes, the fusion of one sperm cell with an egg, and another sperm cell with the polar nuclei to yield a

                                  triploid endosperm.

Epiphyte  A plant that grows on trees or other solid objects, and is not rooted in soil; it is not parasitic.

Essential nutrient   Any chemical element or compound required for normal growth, reproduction and maintenance of a living organism. Includes micronutrients and macronutrients.

Ethylene   One of five classes of plant hormone. Hastens fruit ripening.

Gametophyte   The haploid, gamete-producing stage of the plant life cycle. Male gametophyte in a gymnosperm is a pollen grain.

Gibberellin    One of five classes of plant hormone. Stimulate flowering and seed germination.

Gravitropism   A plant´s growth response towards or away from the pull of gravity.

Green alga   Photosynthetic protist that has pigments, starch, and cell walls most like plants.

Ground tissue  The tissue that makes up most of the primary body of a plant; consists of parenchyma, collenchyma and sclerenchyma cells.

Gymnosperm   A seed-producing plant whose seeds are not enclosed in an ovary. Conifers are example of this.

Heliotropism   Sunflowers turn to face the sun throughout the day. (Solar tracking)

Hermaphrodite  Organism that produces sperm and eggs in the same individual.

Hormone   A chemical synthesized in small quantities in one part of an organism and transported to another, where it affects target cells.

Humus   Small fragments of leaves and stems partially decomposed in topsoil.

Megasporangium   The organ in which megaspores are formed.

Meristem tissue  Undifferentiated plant tissue which gives rise to new cells. The primary growth of a plant shoot tip is due to the apical meristem.

Mesophyll  Thin-walled plant cell that takes part in photosynthesis.

Monoecious   In plants, having male and female reproductive parts on the same individual. A plant containing “perfect” flowers.

Mycorrhizae  An association of a fungus and the roots of a plant.

Node  Area of leaf attachment on a stem.

Nutrients   Elements most vital for maintaining life.

Ovary   One of the paired female gonads that house developing oocytes. In some angiosperms it becomes the fruit.

Ovum  The female gamete, egg.

Parasitism  A long-term relationship between two organisms that is beneficial to one organism (the parasite) but detrimental to the other (the host). A

                    type of symbiosis.

Parenchyma cells   The most abundant plant tissue composed of living, thin-walled cells of variable functions.

Petals  A flower parts often colored to lure pollinators.

Petiole  The stalklike part of a leaf.

Phloem   Plant tissue that transports dissolved sugars throughout the plant.

Photonasty  A nastic response in plants to light and dark, is shown by the prayer closing its leaves.

Phototropism  A plant´s growth towards unidirectional light.

Phytochrome  A pale blue plant pigment involved in timing flowering, seed germination, and other processes. It is called the "clock" pigment molecule

                        in plants.

Plant basic tissues   Ground, vascular and epidermal tissues.

Pollination   Transfer of pollen from an anther to a receptive stigma.

Radicle  The first root to emerge from a seed.

Rhizoid  Rootlike extension on gametophytes of some nonvascular plants that anchors the plant and absorbs water and minerals.

Rhizomes  Fleshy, horizontal underground stem.

Sclerenchyma cells Supportive plant tissue composed of elongated cells with thick, non-stretchable secondary cell walls.

Seed  A plant embryo with nutritive tissue (endosperm) to fuel its early growth, and surrounded by an outer protective layer (seed coat). Formed from

           the fertilizes ovule of a flowers.

Senescence  The cessation of growth and subsequent aging of tissues, to prevent damage during winter.

Sporangium   A structure in which spores are produced.

Sporophyte   Diploid, spore-producing stage of the plant life cycle.

Stamen   Male reproductive structure in flowers; consist of a stalklike filament with a pollen-producing anther at its tip.

Stigma   The tip of a flower´s style that receives pollen grains and on which they germinate.

Stolon   Stem that grows along the soil surface.

Stomata  Pores in a plant´s epidermis through which gases exchange between the plant and the atmosphere.

Style   A stalk that arises from the top of an ovary in a flower.

Thigmonasty   A nastic response to touch.

Thigmotropism   It is plant response to contact with a solid object.

Tracheid    Relatively unspecialized conducting cell in xylem.

Transpiration   The movement of water vapor from plant parts to the atmosphere through open stomata.

Trichome  Extension from the epidermis of the plant that provides shade and protection for the plant.

Turgor pressure  The outward pressure exerted by the fluid contents of a plant cell against its cell wall.

Vascular tissue  Specialized conducting tissue in plants; xylem and phloem.

Xylem  Plant tissue that transports water and dissolved ions from the roots to the leaves.