GLOSSARY

ABERRATION (ab-burr-ay-shun) A nontypical form or function. A straying from the normal. Some abnormality of an individual organism or part or of a biological happening.

ABNORMAL Unusual; away from the natural pattern.

ABORT (uh-bort) To fail in the early stages of formation. The development of the young seed may be stopped early in its growth; its cells collapse and largely disappear.

ABSCISSION (ab-sizh-un) Separation of plant parts from the main body of the plant, such as the dropping of leaves, flowers, fruits, or buds. Generally associated with the formation of a special layer of thin-walled cells called the abscission layer or zone.

ACCESSORY ORGANS Attached structures that may or may not contribute to the main function of the organ.

ACHENE (ay-keen) A small, dry, one-seeded fruit with a thin distinct wall that does not split open.

ACORN The nonsplitting, one-seeded fruit of the oak.

ACREABLE In terms of an acre, or per acre.

ADAPTATION (add-ap-tay-shun) The reaction of plants to environmental conditions. One kind may respond to some conditions of soil, site, or climate favorably while another kind does not.

ADVENTITIOUS (add-ven-tish-us) A descriptive term for a structure that arises in an unusual place, such as a bud that develops from areas of a plant other than the base of a leaf or a leaf scar.

ADVENTITIOUS EMBRYONY (add-ven-tish-us em-bree-ah-nee) The embryo origin from a somatic diploid cell of the nucellus or integuments by a series of somatic cell divisions.

AERATION (ay-er-ay-shun) Bringing air into a substance or tissue. Making air, and therefore oxygen, available to a material.

AGAR A gelatinous substance extracted from a seaweed such as certain red algae. It is an ingredient used in making culture media to study the growth characteristics of micro-organisms.

AGGREGATE FRUIT (ag-gre-gate) Fruit developed from several pistils in one flower, as in strawberry or blackberry.

ALBINO (al-by-no) An organism that lacks normal color; plants that are white because of a lack of chlorophyll and other colored substances.

ALKALOID (al-kah-loid) An organic, nitrogenous, basic substance derived from vegetable or animal sources. Some are now synthesized. Morphine, codeine, strychnine, and quinine are alkaloidal compounds important in medicine to relieve pain or to stimulate the central nervous system.

ALLOTETRAPLOID (al-lo-teh-trah-ployd) A plant of hybrid origin with two sets of chromosomes from one parent and two sets from the other parent. Although four sets of chromosomes are present, associations of three or four chromosomes are rarely found at meiosis since the chromosomes contributed by the two parents are dissimilar.

AMINO ACIDS (a-me-no) Organic acids containing one or more amino groups ( NH₂) and at least one carboxyl group ( COOH). In addition. some amino acids (cystine and methionine) contain sulfur. Many amino acids linked together in some definite pattern form a molecule of protein.

AMYLOSE (am-il-los) The straight chain fraction of normal starch. The starch of normal corn is made up of two molecular types; amylose (straight chain) and amylopectin (branched chain). In both starch types the basic units consist of the sugar glucose.

ANAEROBIC (an-air-oh-bick) Living or functioning in the absence of air or free oxygen. The opposite of aerobic.

ANDROGENESIS (an-dro-jen-eh-sis) Development in which the embryo contains only paternal chromosomes.

ANGIOSPERM (an-gee-oh-sperm) A kind of plant the seeds of which are formed within a fruit.

ANNUAL The kind of plant that normally starts from seed, produces its crop of flowers and fruits, or seeds, and then dies within one growing season.

ANTERIOR A position that is forward, before, or toward the front of an object.

ANTHER (an-they) The saclike structure in which the pollen is formed in the flower. Anthers commonly have two lobes or cavities, which open by longitudinal slits or by terminal pores and release the pollen.

ANTHOCYANIN (an-tho-sigh-ah-nin) A water-soluble plant pigment that produces many of the red and blue colors of plants; for example, the red color of apples and the red and blue colors of many flowers.

ANTIPODAL NUCLEI (an-tip-o-dal new-klee-eye) Three of the eight nuclei that result from meiosis or sexual cell division in the female organ of seed-bearing plants. They are usually in the base of the embryo sac, contain one member of each pair of chromosomes, and in most plants have no known function.

APEX Extreme point or distal end.

ARCHESPORIAL (ahr-keh-spa-ree-ul) Refers to the differentiated cell situated in the nucellar tissue of the ovule which is destined to undergo meiosis and give rise to the haploid generation.

ARIL A loose, fleshy bag that encloses the seed, as in the white waterlily and yew.

ASEXUAL (a-sex-shu-al) Nonsexual; denotes reproduction by purely vegetative means, or without the function of the two sexes.

AUTOTETRAPLOID (aw-to-teh-trah-ployd) A plant with double the usual number of chromosomes. Each specific chromosome is present four times and multiple associations are found at meiosis.

AUXINS (awk-sins) Any of several substances found in plants that may stimulate cell growth, root development, and so on.

AWN A slender bristle, such as the "beards" of wheat or rye.

AXILLARY (ax-sill-a-ree) Pertaining to the angle between the leaf and the stem.

BACKCROSS A plant obtained by crossing two plants that have different characters is a hybrid. Pollen of the hybrid used on either parent, or pollen from either parent used on the hybrid, produces a backcross generation.

BACTERIOPHAGE A viral agent that produces a dissolution of specific bacterial cells. Bacteriophage agents will only multiply in actively multiplying cells. Cells parasitized by phage seem to swell, burst, and disintegrate, liberating large numbers of phage particles.

BERRY A simple, fleshy, or pulpy and usually many-seeded fruit, that has two or more compartments and does not burst open to release its seeds when ripe.

BIENNIAL The kind of plant that produces vegetative growth during the first year or growing season. After a period of storage or overwintering out of doors, flowers, fruits, and seeds are produced during the second year, and the plant dies.

BIOCHEMISTRY The chemistry of life; the branch of chemistry that is concerned with biological organisms and processes.

BOLT Formation of an elongated stem or seedstalk. In the case of biennial plants, this generally occurs the second season of growth.

BROADLEAF Used in weed terminology to designate a broad group of nongrasslike plants.

BUD A plant structure that contains an undeveloped shoot or flower.

BUDDING, The process of transferring a live bud from one plant to another, usually by insertion under the bark. Also, the plant process of forming buds.

BULB An enlarged, fleshy, thick, underground part of a stem surrounded by a mass of leafy scales. Scales of a bulb are actually thickened and shortened leaves. Roots develop from the base of a bulb. The lily is an example.

BULBIL A small bulb produced above ground usually in the axil of a leaf. Sometimes spelled "bulbel."

BULBLET Usually refers to a small underground bulb formed on a parent stem.

CALLUS A hard or thickened layer at the base of certain grass seeds (florets).

CALLUS TISSUE A shapeless, noncorky mass of cell growth that develops from a wounded or cut surface of a stem or root.

CALYX (kay-licks) All of the sepals of the flower; forms part of the covering of some seed.

CAMBIAL TISSUE (cam-bee-ul) The layer of cells found between the bark and the wood that gives rise to new growth. It consists of a very thin layer of cells, which normally may give rise later to either bark or wood.

CAMBIUM (cam-bee-um) A layer of cells in a stem between the bark and the wood in which cell division (resulting in lateral growth) occurs.

CARBON DIOXIDE A gaseous compound that is formed when carbon combines with oxygen. It leaves the body chiefly when air is exhaled from the lung.

CARBON-I4 One of several isotopes of the chemical element carbon. (See Isotope.) It is somewhat radioactive; this activity decreases very slowly with time. Carbon-14 occurs in very small, and varying, amounts in all organisms and in all organic material containing carbon. In a complicated chemical and electronic apparatus, the carbon-14 content can be used to date approximately ancient organic materials. The common isotope of carbon, carbon- 12, which accounts for about 99 percent of the carbon in nature, emits no radiation.

CAROTENE A yellow compound of carbon and hydrogen that occurs in plants, a precursor of vitamin A. Alpha, beta, and gamma carotenes may be converted into vitamin A in the body.

CARPEL (car-pelt) The ovule-containing receptacle of a pistil.

CARUNCLE (care-unk-1) An outgrowth or thick appendage of the testa or outer seed-coat, as in the seed of the castor-oil plant.

CARYOPSIS (care-e-op-sis) A one-seeded fruit with the pericarp and seedcoat fused into one covering, as in corn and other grains.

CATABOLISM (ka-tab-o-lism) The breaking down in the body of chemical compounds into simpler ones, usually accompanied by the production of heat.

CATALYZE (kat-ah-lies) To induce or accelerate a chemical reaction by a substance that remains unchanged in the process.