Glossary - Seed Testing - page 317

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 Oficial Seed Analysts, the organization of state and federal seed
analysts from the United States and Canada.
AOSCA . The initials of the Association of Oficial Seed Certifying Agencies, the organization composed
mostly of certiication 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. A type 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 beneit 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 . A loose, 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 embryo type. A type of embryo classiication in which the terminal cell of the proembryo divides
by a longitudinal wall and both the basal and terminal cells contribute to embryo development.
ATP . The initials for adenosine-triphosphate, an energy-rich complex sugar phosphorus compound which
provides energy for many metabolic reactions.
Auxins. A group of growth regulators that may stimulate cell growth, root development, and other growth
processes, including seed germination.
Awn . A slender appendage often associated with seeds, such as the “beards” of wheat or barley.
Axile placentation. The type of ovule attachment within a fruit in which the seeds are attached along the
central axis at the junction of the septa.
Bacteriocide. A chemical compound that kills bacteria.
Bacteriophage. A virus that infects speciic bacteria and usually kills them. Speciic phages are used to
identify certain bacterial plant pathogens.
Basal placentation. A type of free-central placentation in which the seeds are attached at the bottom of the
central ovary axis.
Berry. A simple, leshy, or pulpy and usually many-seeded fruit that has two or more compartments and
does not burst open to release its seeds when ripe (e.g., blueberry).
Biennial. A kind of plant that produces only vegetative growth during its irst growing season. After a
period of storage or overwintering out-of-doors, lowers, fruits, and seeds are produced during the
second year and the plant dies (i.e., a plant that requires two years to complete its life cycle).
Bitegmic testa. A testa (seed coat) composed of two integumentary layers.
Brick grit test. A type of seedling emergence (vigor) test utilizing uniformly crushed brick gravel through
which seedlings must emerge to be considered vigorous.
Bulb . An enlarged, leshy, thick, underground part of a stem surrounded by thickened, leafy scales and
shortened leaves. Roots develop at the base of a bulb (e.g., wild onion).
Bulbil. A small bulb or bulblet produced above the ground, as in wild garlic.
Callus. A hard or thickened layer at the base of certain grass lorets.
Calyx. A collective term for all the sepals surrounding a lower; it forms part of the covering of some seeds.
Campylotropous ovule. A type of ovule arrangement in which the ovule is slightly curved and the micro-
pylar end is pointed slightly downward so the funiculus and micropyle are close together on the mature
seed on opposite sides of the hilum, as in legumes.