Glossary - Seed Testing - page 316

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., sun-
lower seed).
Acorn. The fruit of an oak; see the deinition 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-triphos-
phate) 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 lower, 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 (-NH 2 ), 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. A type 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 funicu-
lus with the micropyle adjacent to the base of the funiculus.
Androecium. Collectively , the stamens of a lower.
Angiosperm. A kind of plant that has seeds formed within an ovary.
Annual. The type of plant that normally starts from seed, produces its lowers, fruits, and seeds, then dies
within one growing season.
Annuoline. The luorescent protein pigment exuded by the roots of ryegrass seedlings. The luorescent
nature of this material makes it useful in distinguishing annual and perennial ryegrass.
Anther. The saclike structure of the male part (stamen) of a lower 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, speciically the time when the stigma is ready to receive the dispersed
pollen.
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