Seed Testing: Principles and Practices

Glossary

339 Glossary Abnormal seedling. A seedling (in a germination test) that does not have the essential structures indicative of the ability to produce a normal plant under favorable conditions. Absorption. The uptake of moisture into the tissues of an organism (e.g., seed). Achene. A small, dry, one-seeded fruit with a thin, dry wall that does not split open at maturity (e.g., sunflower seed). Acorn. The fruit of an oak; see the definition of a nut. Adsorption. The accumulation and adhesion of a thin layer of water (or gases) on the surface of another substance. ADP. Initials for adenosine-diphosphate, a complex sugar-phosphorus compound formed as the result of expenditure of energy and the loss of a phosphate group from the energy-rich ATP (adenosine-triphosphate ) compounds. Agamogony. A type of apomixis in which cells undergo abnormal meiosis during megasporogenesis, resulting in a diploid embryo sac rather than the normal haploid embryo sac. Agamospermy. A type of apomixis in which sporophytic tissue is formed, ultimately leading to seed development. Aggregate fruit. Fruit development from several pistils in one flower, as in strawberry or blackberry. Albuminous seed. A seed having a well-developed endosperm or perisperm (nucellar origin). Aleurone layer. The layer of high-protein cells surrounding the storage cells of the endosperm. Its function is to secrete hydrolytic enzymes for digesting food reserves in the endosperm. Ambient conditions. The outside conditions (e.g., relative humidity and temperature) that exist at any given time and place. Amino acid. Organic acid containing one or more amino groups (-NH2 ), at least one carboxyl group (-COOH), and sometimes, sulfur. Many amino acids are linked together by peptide bonds to form a protein molecule. Proteins are a fundamental constituent of living matter. Amphitropous ovule. A type of ovule arrangement in which the ovule is slightly curved so the micropyle is near the funicular attachment. Amylase. The enzyme responsible for catalyzing the breakdown of starch into sugars. It may be active in one of two forms: α-amylase and ß-amylase. Amylopectin. A type of starch molecule composed of long, branched chains of glucose units (a polysaccharide). Amylose. Atype of starch molecule made up of glucose units in long, unbranched chains (a polysaccharide). Anatropous. A type of ovule arrangement in which the ovule is completely inverted, having a long funiculus with the micropyle adjacent to the base of the funiculus. Androecium. Collectively, the stamens of a flower. Angiosperm. A kind of plant that has seeds formed within an ovary. Annual. The type of plant that normally starts from seed, produces its flowers, fruits, and seeds, then dies within one growing season. Annuoline. The fluorescent protein pigment exuded by the roots of ryegrass seedlings. The fluorescent nature of this material makes it useful in distinguishing annual and perennial ryegrass. Anther. The saclike structure of the male part (stamen) of a flower in which the pollen is formed. Anthers normally have two lobes or cavities that dehisce at anthesis and allow the pollen to disperse. Anthesis. The period of pollination, specifically the time when the stigma is ready to receive the dispersed pollen. 340 Glossary Antipodal nuclei. Three of the eight nuclei that develop from the megaspore by mitotic cell divisions within the developing megagametophyte (embryo sac). They are usually located at the base of the embryo sac and have no apparent function in most species. AOSA. The initials of the Association of Official Seed Analysts, the organization of state and federal seed analysts from the United States and Canada. AOSCA. The initials of the Association of Official Seed Certifying Agencies, the organization composed mostly of certification agencies from the United States and Canada—formerly (prior to 1968) known as the International Crop Improvement Association (ICIA). Apical placentation. A type of free-central placentation in fruit where the seeds are attached near the top of the central ovary axis. Apogamy. Atype of apomixis involving the suppression of gametophyte formation so that seeds are formed directly from somatic (body) cells of the parent tissue. Apomixis. Seed development without the benefit of sexual fusion of the egg and the sperm cells. Archesporial cell. The cell of the nucellus that differentiates and gives rise to cells ultimately destined to undergo meiosis and produce the megaspore mother cell. Aril.Aloose, papery appendage in some seeds (e.g., elm) originating as an extension (or proliferation) from the outer integument. Asexual reproduction. Reproduction by vegetative means without the fusion of two sexual cells. ASTA. The initials of the American Seed Trade Association. Astered...