Glossary

A	abcission zone	n.	A weakened layer of cells at the base of a leaf or fruit that allows the leaf or fruit to separate from the plant without injuring it.
	abscise	v.	A flower, leaf, fruit, or other plant part separating from the plant at the abscission zone.
	abscisic acid	n.	A plant growth regulator involved in the fruit ripening process.
	accessory fruit	n.	A false fruit, whose fleshy parts are not derived from the ovary.
	adhesion	n.	The sticking together of unlike objects or materials.
	adventitious root	n.	Root that forms on shoot tissue.
	adventitious shoot	n.	Shoot that forms on root tissue.
	aggregate fruit	n.	A fruit derived from the separate ovaries of a single flower.
	alkaloids	n.	Bitter-tasting compounds found in many plants, especially in the nightshade family (Solanaceae).
	allelopathy	n.	A form of chemical protection in which a plant produces substances that inhibit the growth of nearby plants.
	alternation of generations	n.	Describes the phenomenon in the plant kingdom in which plants alternate between a sporophyte phase and a gametophyte phase.
	amino acid	n.	Nitrogen-containing organic compounds; the building blocks from which proteins are formed.
	angiosperm	n.	Derived from the words for "vessel" and "seed"; a grouping of plants whose seeds are borne in protective structures.
	annual	adj.	Describes a plant that germinates, grows, flowers, and produces seeds all in one growing season.
	anther	n.	The part of the stamen-the male reproductive structure-that contains the pollen.
	anthocyanin	n.	Red or blue pigment found in the cell sap.
	antitranspirants	n.	A substance sprayed on plant leaves to reduce the rate of transpiration and conserve moisture.
	apical bud	n.	A bud at the uppermost tip of a stem.
	apical dominance	n.	The suppression of growth in lower buds and branches by the uppermost, or apical, bud.
	apical meristem	n.	A region of actively-dividing cells at the tip of a root or stem; growth results in an increase in length.
	aquaponics	n.	The integration of hydroponics (growing plants without soil) and aquaculture (the cultivation of the natural produce of water such as fish or shellfish).
	asexual propagation	n.	Any means of multiplying plants that do not involve the union of gametes, and depend on mitotic, rather then meiotic, cell division.
	asexual reproduction	n.	Propagation by means of plant parts; examples include new plants generated by creeping stems, bulb offsets, and layering.
	atom	n.	The basic unit of matter. The smallest unit into which a chemical element can be broken and still retain its characteristics.
	auxin	n.	A plant growth regulator that controls cell elongation; important in many plant growth responses such as phototropism and geotropism.
	axillary bud	n.	A bud located in the axil of a leaf, at the joint where the leaf meets the stem.
B	biennial	adj.	Describes a plant that grows for two years; it germinates and grows foliage the first season, and produces flowers and seeds the next season.
	bilateral symmetry	n.	Flower type that can be divided into two symmetrical halves only by a single longitudinal plane passing through the axis.
	binomial	adj.	Consisting of two names; for example, a botanical name consists of the genus name followed by the species epithet.
	bio-engineered	adj.	Organisms created using genetic engineering.
	biodiversity	n.	The number of different species-plants or animals-in an area.
	bloom	n.	A powdery, bluish-white coating on some plants’ leaves and fruits. When a plant part’s waxy cuticle occurs in tiny rodlets that protrude from the surface, it results in a visible bloom. (Also, another word for flower.)
	budding	n.	A form of grafting in which a bud is inserted under the bark of another plant.
	bulb	n.	Modified stem consisting of fleshy leaf bases; used for food storage and asexual propagation.
C	carbohydrate	n.	An organic molecule consisting of a chain of glucose molecules; includes sugars, starches, and cellulose.
	carotenoid	n.	Photosynthetic accessory pigment contained within the chloroplast. Carotenes and xanthophylls are carotenoids.
	cellulose	n.	A large molecule made up of a chain of glucose molecules; found primarily in plant cell walls.
	centromere	n.	Location on a chromosome where sister chromatids are held together.
	chilling requirement	n.	The number of hours a plant must be exposed to temperatures between 32ºF and 45ºF before it will break dormancy.
	chlorophyll	n.	A green plant pigment; found in chloroplasts and necessary for photosynthesis.
	chloroplasts	n.	Structures found within some plant cells; they contain chlorophyll and are the sites of photosynthesis.
	chlorotic	adj.	Describes abnormally pale, weak-looking foliage due to reduced chlorophyll content; often caused by a nitrogen or iron deficiency.
	chromatin	n.	The genetic material stored in a cell’s nucleus, made up of DNA and nuclear proteins.
	chromosomes	n.	Genetic material (chromatin) in a cell’s nucleus that has become condensed into strands in preparation for cell division.
	class	n.	A group of orders sharing similar characteristics.
	cloning	n.	The duplication of an organism by asexual means.
	cohesion	n.	The mutual attraction of molecules of the same substance.
	cohesion-tension theory	n.	Theory used to explain the movement of water through the xylem from the bottom to the top of plants. When water evaporates from the surface of a cell, tension is created, pulling water molecules up towards that surface. Due to the cohesiveness of water molecules, this tension is transferred the entire way down the xylem, effectively pulling water to the top of the plant.
	commensalism	n.	Relationship of two or more organisms in which one organism benefits and the other is unaffected.
	complete	*adj.*	This term describes a flower that contains all four whorls-petals, sepals, pistil and stamen.
	compound	n.	A substance composed of one type of molecule.
	compound leaf	n.	A divided leaf whose blade is composed of two or more leaflets.
	consumer	n.	An organism that consumes other organisms to acquire the food that it is unable to synthesize on its own.
	cork cambium	n.	A type of lateral meristem located just under the bark that gives rise to new outer bark.
	corm	n.	Swollen leaf base enclosed in scale-like leaves, used for food storage and asexual propagation.
	cotyledon	n.	A food storage structure within a seed, which provides nourishment for the embryo during germination.
	cultivar	n.	Short for cultivated variety. A unique plant that is the result of breeding efforts by horticulturists. Written in single quotes in plain text after species name.
	cuticle	n.	A protective waxy coating on the epidermis of leaves, herbaceous stems, and fruit.
	cutin	n.	The waxy substance that forms the cuticle layer, providing a protective coating on the epidermis of leaves, herbaceous stems, and fruit.
	cutting	n.	Propagation method that involves inducing adventitious roots or shoots on a plant part.
	cytokinin	n.	A plant growth regulator that stimulates cell division.
	cytoplasm	n.	The liquid component of a plant cell in which various structures are suspended.
D	dark reaction	n.	The second step in the process of photosynthesis, during which simple sugars are manufactured; light is not required.
	day-neutral	adj.	Describes plants for which flower initiation is not dependent upon day length.
	decoction	n.	The liquid produced when bark, stems, and roots (difficult to dissolve because of the presence of lignin) are finely chopped and boiled in water for 10 to 20 minutes after they have been soaked for 12 hours.
	decomposer	n.	Organisms, such as bacteria and fungi, that break down dead organic matter.
	decomposition	n.	The breaking down of organic matter by organisms such as bacteria and fungi.
	deoxyribonucleic acid (DNA)	n.	Nucleic acid-located within a cell's chromosome-that carries the genetic information for an individual.
	dichotomous key	n.	A key used to identify organisms where exactly two mutually exclusive alternatives are offered at each choice.
	dicot	n.	A class of angiosperms in which the seeds’ cotyledons occur in pairs.
	dioecious	adj.	Describes plants in which the male and female flowers occur on separate plants.
	diploid	adj.	Describes cells in which the chromosomes occur in pairs; somatic cells, which make up the bulk of the cells in the plant body, are diploid. Often abbreviated as 2n.
	disaccharide	n.	A sugar made up of two monosaccharide molecules bound together; an example is sucrose, or table sugar.
	disk flowers	n.	The small, tubular flowers in the center of the inflorescence of plants in the Daisy family.
	division	n.	A group of classes sharing similar characteristics.
	dominant trait	n.	A characteristic determined by a gene that hides, or masks, the comparable but recessive gene; this characteristic will be expressed if the dominant gene is present on one or both chromosomes.
	drupe	n.	A simple, fleshy fruit whose inner wall is hard. Examples include peaches and cherries.
E	electron transport chain	n.	The third stage in respiration, during which electrons pass through a chain, releasing energy as they go.
	element	n.	A substance composed of one type of atom.
	embryo	n.	Multi-celled structure resulting from the repeated cell division of the zygote.
	endosperm	n.	A temporary food storage tissue in seeds, created by the fusion of one sperm cell plus the two polar nuclei, and therefore often triploid.
	epidermis	n.	The outermost layer of cells on leaves, roots, and herbaceous stems.
	epiphyte	n.	A plant that grows on the body of another plant, but draws no nutrients from it.
	essential amino acid	n.	One of the eight amino acids the human body cannot synthesize, and therefore a vital nutrient in the human diet.
	ethnobotany	n.	The study of the relationship between plants and people.
	ethylene	n.	A plant growth regulator produced by ripening tissues; stimulates cell walls to soften.
	etiolation	n.	The condition in which a plant has pale, underdeveloped leaves and extended internodes; ususally caused by insufficient light.
	expression	n.	The way a trait shows up in an organism.
F	F₁ or first filial generation	n.	The offspring resulting from a cross between two pure parent lines.
	F₂ or second filial generation	n.	The offspring resulting from cross- or self-pollination of the F₁generation.
	family	n.	A group or genera sharing similar characteristics.
	fertilization	n.	The successful union of egg and sperm.
	fibrous root system	n.	A root system consisting of highly branched, spreading roots.
	filament	n.	The stalk of the stamen-the male reproductive structure-upon which the anther is located.
	nitrogen fixation	n.	A process in which a type of soil-dwelling bacteria, in association with the roots of certain plants (such as legumes), convert nitrogen in the air into a form that plants can use.
	flower	n.	A specialized shoot of a plant bearing its reproductive structures.
	fruit	n.	The matured ovary of a plant; contains the seeds.
G	gametes	n.	Haploid cells (egg and sperm), the fusion of which results in the creation of a new organism. Also called reproductive cells or sex cells.
	gametophyte generation	n.	The phase of growth in which gametes, or sex cells, are produced.
	gene	n.	The basic unit of inheritance; occur along the chromosomes.
	genera	n.	The plural of genus.
	generative cell	n.	One of two cells that make up a pollen grain; upon successful pollination, it divides to form two sperm.
	genetic engineering	n.	The process of taking genetic material from one organism and inserting it into the nucleus of another organism, the result of which is an organism whose cells contain the introduced genes.
	genus	n.	The "generic" name of a plant; in plant classification, refers to a group of related plants.
	geotropism	n.	The bending of a plant organ in response to gravity; also called gravitropism.
	germ	n.	The term used for the embryo within the fruits of the grass family (grains).
	germination	n.	The beginning of growth by a spore, seed, bud, or other structure.
	gibberellin	n.	A plant growth regulator that controls the elongation of internodes.
	glaucous	adj.	Describes a plant part with a visible bloom.
	glycolysis	n.	The breakdown of glucose during respiration resulting in the release of energy (ADP; adenosine diphosophate).
	grafting	n.	Propagation method in which two pieces of live plant tissue are united by placing their meristems in contact.
	gravitropism	n.	The bending of a plant organ in response to gravity; also called geotropism.
	guard cells	n.	Pairs of cells surrounding the stomata, or pores, on a leaf or stem. Swelling or shrinking of the guard cells opens or closes the stomata, depending on the needs of the plant and environmental conditions.
	guttation	n.	Exudation of excess water; appears as droplets on the tips and margins of leaves.
	gymnosperm	n.	Literally, "naked seed", a grouping of plants that produces seed that is borne exposed, rather than in a protective structure.
H	haploid	adj.	Describes cells in which the chromosomes occur singly (as opposed to occurring in pairs); reproductive cells are haploid. Often abbreviated as n.
	hardening off	n.	A process by which a plant is gradually acclimated to a new environment. The term often refers to the adjustment period necessary to allow indoor-grown plants to grow accustomed to the harsher (cooler, windier, sunnier) outdoor environment.
	herbaceous	adj.	Soft and green; describes primary growth tissues containing little or no woody growth.
	homologous	adj.	Describes the two similar chromosomes that form a pair in a diploid cell.
	humus	n.	Organic matter decomposing in the soil.
	hybrid	adj.	Offspring resulting from cross-breeding plants.
	hybrid	n.	Iin botany, offspring resulting from sexual reproduction between two plants; in horticulture, used to describe F1 crosses having mixed ancestry that are the products of plant breeding efforts, and do not grow true from seed.
	hybrid vigor	n.	The increase in vigor, size, fertility, or other positive characteristic of a hybrid compared with its parents.
I	imbibition	n.	The absorption of water into and resultant swelling of a dry seed before germination.
	imperfect	*adj.*	This term describes a flower that is lacking either the male or female reproductive structures.
	incomplete	*adj.*	This term describes a flower that is missing one or more of the four whorls-petals, sepals, pistil, or stamen.
	incomplete dominance	n.	The relationship between two genes, neither of which fully masks the expression of the other.
	indehiscent	*adj.*	Used to describe fruits that do not open to disperse their seeds at maturity.
	intercalary meristem	n.	A meristem located between non-dividing tissues, such as near the base of a blade of grass.
	infusion	n.	The liquid produced when leaves and flowers are stepped in hot water, releasing their active ingredients.
	internode	n.	The part of the stem that is located between to successive nodes.
	invasive plant	n.	A non-native plant that has the ability to outcompete and displace native vegetation.
K	Krebs cycle	n.	The second stage of respiration during which carbon dioxide is produced from the breaking down of pyruvate molecules.
L	lateral meristem	n.	A region of actively-dividing cells located along the length of a root or stem; growth results in an increase in girth.
	layering	n.	Propagation method that induces rooting while daughter plant is still attached to parent plant.
	leaf	n.	A plant structure consisting of an outgrowth arising from a stem or branch. Most leaves are green and contain chlorophyll.The primary function of a leaf is to capture sunlight for photosynthesis.
	leaf blade	n.	The broad, flat part of a leaf whose primary function is to capture sunlight for photosynthesis.
	legume	n.	A member of the Fabaceae, the pea or bean, family.
	lenticel	n.	A pore on the surface of young woody stems; provides a pathway for air to reach inner tissues.
	light duration	n.	A measure of the amount of time a source of light is illuminated; usually represented by the number of hours of light in a 24-hour period.
	light intensity	n.	A measure of the brightness of light reaching a surface. Light intensity decreases as the distance from the source of the light increases.
	light quality	n.	An analysis of the color, or wavelengths, of light from a given source.
	light reaction	n.	The first step in the process of photosynthesis, which begins when the chlorophyll molecule absorbs a photon; light is required.
	lignin	n.	An important constituent of many secondary cell walls that increases the cell wall’s hardness and strength.
	lipid	n.	A category of organic macromolecules including fats and oils.
	long-day	adj.	Describes plants that initiate flowers when day length is longer than their critical day length.
M	macrofibril	n.	A structure made up of several microfibrils wound together into a "cable;" provide the framework for the plant cell wall.
	macromolecules	n.	Relatively large molecules made up of smaller molecules bound together with chemical bonds.
	macronutrients	n.	The mineral nutrients that plants require in relatively large quantities; includes carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
	megaspore	n.	Haploid cells formed by meiosis in plants; divide by mitosis to form several daughter cells, one of which functions as the egg cell.
	meiosis	n.	Cell division that results in four haploid daughter cells.
	meristem	n.	A region of actively-dividing cells.
	mesophyll	n.	The tissue sandwiched between the epidermal layers of a leaf; containing both the palisade cells and the spongy cells.
	metabolic	adj.	The chemical processes occurring within a living cell or organism.
	microbe	n.	A minute organism.
	microfibril	n.	A structure made up of several cellulose molecules united into a thread-like strand.
	micronutrients	n.	The mineral nutrients that plants require in relatively small quantities includes magnesium, iron, copper, zinc, manganese, molybdenum, and boron.
	micropyle	n.	The opening in the ovule where the pollen tube enters.
	microspore		Haploid cells formed by meiosis in plants; divide by mitosis to form pollen—precursor to the sperm cell.
	middle lamella	n.	A pectin-rich layer between adjoining plant cell walls, cementing them together.
	mitochondria	n.	A double-membrane-bounded organelle found in eukaryotic cells.
	mitosis	n.	Cell division that results in two daughter cells that are genetically identical to the parent cell.
	molecule	n.	The smallest unit of a compound; consists of two or more different atoms in a specific ratio and configuration, held together with chemical bonds.
	monocot	n.	A class of angiosperms in which the seeds’ cotyledons occur singly.
	monoecious	adj.	Describes plants with separate male and female flowers.
	monosaccharide	n.	A simple sugar made up of a chain or ring of carbon atoms to which hydrogen and oxygen atoms are attached.
	mordant	n.	A chemical agent that fixes dye to fabric.
	multiple fruit	n.	The fruit that results from the fusion of the ovaries of flowers that are growing very close to one another on a shared flower stalk.
	mutation	n.	A random genetic variation that is passed on to offspring.
	mutualism	n.	Relationship of two or more organisms in which both organisms benefit.
N	nastic movement	n.	Movement of plant parts not associated with a specific stimulus such as light or gravity.
	natural selection	n.	A process by which the healthiest, strongest, and most well-adapted organisms flourish and reproduce.
	nodes	n.	Sites on a stem where the leaves and axillary buds are attached.
	non-native plant	n.	A plant that has been introduced-either intentionally or accidentally-into an area in which it was not found previously.
	nucleus	n.	A structure within a plant cell; controls cell functions, including inheritance.
O	order	n.	A group of families sharing similar characteristics.
	organelle	n.	A membrane-bound part of the cell that has a specialized function.
	organic	adj.	Refers to substances containing carbon; pertaining to living organisms.
	osmosis	n.	The movement of water across a differentially permeable membane, from a place where water concentration is higher to one where the concentration is lower.
	ovary	n.	A female reproductive structure, containing ovules, usually found at the basal portion of the flower. After pollination, the ovary matures into a fruit; the ovules develop into seeds.
	ovule	n.	A female reproductive structure which, upon fertilization, develops into a seed.
	oxidative phosphorylation	n.	The last stage of respiration, during which ATP (adenosine triphosphate) is formed from ADP (adenosine diphosphate).
P	palisade cells	n.	A layer of closely-packed, elongated cells located just beneath the upper epidermis of a leaf. These cells contain chloroplasts, and are the main sites of photosynthesis.
	parasite	n.	An organism that derives some or all its nutrients from another organism.
	pathogen	n.	A disease-causing organism.
	pectin	n.	A gluey substance found in the middle lamella between adjoining cell walls that cements the adjoining cells together.
	perennial	adj.	Describes a plant that lives for more than two years; commonly used to describe herbaceous (non-woody) plants.
	perfect	*adj.*	This term describes a flower that has both male and female reproductive structures.
	petiole	n.	The stalk or support that attaches the blade of a leaf to the stem.
	phloem	n.	The food-conducting tissues of plants; part of the vascular system.
	photoperiodism	n.	The initiation of flowering based on the relative amounts of darkness and light in a 24-hour period.
	photosynthesis	n.	The process by which plants use light energy to manufacture sugars.
	phototropism	n.	The bending of a plant organ in response to light.
	phytochrome	n.	A light-sensitive protein pigment involved inthe photoperiodic response.
	pigment	n.	A substance that absorbs light.
	pistil	n.	The female reproductive structure.
	plant growth regulators	n.	Chemical messengers within the plant body that control growth.
	plastids	n.	Structures found in plant cells; often contain pigments.
	pollen tube	n.	A long, hollow tube formed by the pollen grain's tube cell that penetrates the pistil's tissues to reach the egg cell.
	pollination	n.	The successful transfer of pollen from the anther to a receptive stigma.
	pollinator	n.	Any organism responsible for transferring pollen to stigma of flowers, including bees and other insects, small rodents, and bats. Many plants require a specific pollinator.
	polyploid	*adj.*	Used to describe a nucleus with more than two complete sets of chromosomes.
	polysaccharide	n.	A carbohydrate composed of many monosaccharide units bound together in a long chain; examples include cellulose and starch.
	pome	n.	A simple, fleshy fruit. Examples include pears and apples.
	poultice	n.	Moistened herbs applied directly to the skin and held in place with a bandage.
	primary growth	n.	Growth arising from cell division and elongation in the regions of apical meristems.
	primary wall	n.	The initial layer of a plant cell wall.
	producer	n.	An organism that manufactures complex organic molecules from simple inorganic substances. In most ecosystems, producers are photosynthetic organisms.
	protein	n.	A category of organic macromolecules composed of many amino acids chemically bound together.
R	ray flowers	n.	The flowers that surround the disk flowers in the inflorescence of plants in the Daisy family.
	recessive trait	n.	A characteristic whose expression is masked by the presence of the comparable dominant gene; this characteristic will be expressed only if both genes are recessive.
	replication	n.	The exact duplication of the genetic material within a cell.
	reproductive cells	n.	Haploid cells (egg and sperm), the fusion of which results in the creation of a new organism. Also called gametes or sex cells.
	respiration	n.	The process of breaking chemical bonds in carbohydrates to release the energy necessary to perform metabolic functions.
	rhizobium	n.	Bacteria that form a symbiotic relationship with plants in the legume family, resulting in the ability of the members of this family to fix atmospheric nitrogen.
	rhizome	n.	Horizontal underground stem; may be fleshy or not. Used for food storage and asexual propagation.
	roots	n.	The plant part generally found underground; responsible for anchoring the plant as well as water and nutrient uptake.
	rosette	n.	Aboveground vegetative growth that is present in certain species before flowering in which the leaves are present but the internodes between them are not elongated.
S	saprophyte	n.	An organism that fills its nutritional needs from dead and decaying organic matter.
	scarification	n.	Abrading or softening of the seed coat to encourage germination.
	secondary growth	n.	Growth arising from cell division and elongation in the regions of lateral meristems.
	secondary wall	n.	A second layer of cell wall laid down by the protoplast inside the primary wall.
	seed	n.	The fertilized and matured ovule of a flowering plant, containing an embryonic plant, and which, on being placed under favorable circumstances, develops into an individual similar to the one that produced it.
	seed coat	n.	The hard, protective coating covering a seed.
	seedless plants	n.	A category of evolutionarily primitive plants that do not form seeds. Includes mosses and ferns.
	seta	n.	In mosses, the tall, stem-like structures on which spore capsules are borne.
	sexual reproduction	n.	The creation of offspring from the union of egg and sperm.
	shoot system	n.	The aboveground portion of a plant, consisting of the stem and leaves.
	short-day	adj.	Describes plants that initiate flowers when day length is shorter than their critical day length.
	simple fruit	n.	The fruit that develops from a single pistil on a single flower.
	simple leaf	n.	An undivided leaf that has only a single blade.
	sister chromatids	n.	Genetic material composed of one original chromosome and one exact duplicate produced during replication.
	somatic cells	n.	Diploid cells that make up the bulk of the plant body; all cells in a plant that are not reproductive cells.
	species	n.	The "specific" name of a plant; used to describe a plant within a genus.
	specificity	n.	The degree to which two organisms must be compatible before a relationship will form.
	spongy cells	n.	A layer of loosely-packed cells located beneath the palisade cells of a leaf. The spaces between the cells allow for the exchange of gases necessary for photosynthesis.
	spore	n.	The product of meiosis in plants; germinates to form the gametophyte generation.
	sporophyte generation	n.	The phase of growth in which spores are formed.
	starch	n.	A carbohydrate composed of several hundred glucose units; the chief food storage substance in plants.
	stamen	n.	The male reproductive structure in the flower-composed of the anther and the filament-where pollen produced.
	stem	n.	The leaf- and flower-bearing part of a plant.
	stem nodes	n.	The location on the stem where branches or leaves are attached.
	stigma	n.	The sticky surface of the stigma where pollen is received and on which pollen germinates.
	stipule	n.	Small, leaf-like outgrowth found at the base of a leaf stalk.
	stolon	n.	Horizontal creeping aboveground stem; sprouts new plants at nodes.
	stomata	n.	Tiny pores in the epidermal cells of leaves and stems; most numerous on the undersides of leaves. (Singular: stoma or stomate. Plural: stomata or stomates).
	stratification	n.	Exposure of seeds to cool temperatures to break dormancy and encourage germination.
	stroma	n.	The structure within the chloroplast where the dark reactions of photosynthesis take place.
	style	n.	The column of tissue that stretches from the ovary to the stigma through which the pollen tube grows.
	succession	n.	The sequence of changes in the vegetative composition of a community from initial colonization to climax.
	sucker	n.	Shoot arising from adventitious bud on underground root; sometimes used to describe any shoots arising at the base of a plant.
	symbiosis	n.	Relationship of two or more organisms living in close association.
T	taproot system	n.	A root system consisting of one or more prominent, swollen roots with few side roots; often a food-storage structure.
	taxonomist	n.	A scientist who specializes in the classification of organisms.
	terrarium	n.	An enclosure for raising plants or animals indoors.
	thigmotropism	n.	The reaction of a plant in response to physical contact.
	thylakoid	n.	The structure within the chloroplast where the light reactions of photosynthesis take place.
	tissue culture	n.	Propagation method that produces many plants from one or a few initial cells. Must be done under sterile, controlled conditions.
	trait	n.	An inherited physical or physiological characteristic.
	transgenic	adj.	Organisms created using genetic engineering.
	transpiration	n.	The loss of water vapor from a plant; most of this water escapes from open stomata.
	triploid	adj.	Describes a plant cell in which the chromosomes occur in three’s.
	tube cell	n.	One of two cells that make up a pollen grain; upon successful pollination, it germinates and grows into the pollen tube.
	tuber	n.	Swollen tip of an underground stem, used for food storage and asexual propagation.
	tuberous root	n.	Enlarged secondary root, used for food storage and asexual propagation.
	tuberous stem	n.	Swollen section on underground portion of main stem, used for food storage and asexual propagation.
	turgor pressure	n.	The pressure within a plant cell; maintained by osmosis.
V	variegated	adj.	Describes leaves or petals exhibiting an irregular, inherited pattern of color.
	variety	n.	A population within a species that differs from other members of the species in some significant way. Written in italics after the species name.
	vascular cambium	n.	A type of lateral meristem that gives rise to new xylem (wood) and phloem (inner bark).
	vascular tissues	n.	Food- or water-conducting tissues.
	vermiculture	n.	Worm composting.
	vernalization	n.	The promotion of flowering due to exposure to low temperatures, or chilling.
W	whorl	n.	A circle of flower parts of one kind. Most flowers are composed of four whorls: petals, sepals, stamen, and pistil.
X	xylem	n.	The water-conducting tissues of plants; part of the vascular system.
Z	zygote	n.	The cell created by the union of egg and sperm; divides to become the embryo.