Glossary - Seed Testing - page 319

Conditioning. The term used to describe the process of cleaning seed and preparing it for market; formerly
called processing.
Conductivity test (of seed leachates). An electrical conductivity test that associates the concentration of
leachates from seeds, after soaking in water, to their quality.
Corymb. An indeterminate inlorescence in which the lower pedicels arising from the peduncle are succes-
sively longer than the upper ones, giving a rounded or lat-topped appearance (e.g., Prunus emarginata ) .
Cotyledon. Seed leaves of the embryo. In most dicotyledon seeds they are thickened and are storage sites
of reserve food for use by the germinating seedling.
Crucifer embryo type. A type of embryo classiication in which the terminal cell of the proembryo divides
by a longitudinal wall and the basal cell plays only a minor part (or none) in subsequent embryo
development.
Cultivar. A variety of a cultivated crop.
Cyme . A type of inlorescence in which the main axis ends in a lower. Further growth is by lateral branches,
which may also terminate in a lower.
Cytoplasm. The contents of a cell between the nucleus and the cell wall.
Dehiscence. The splitting open at maturity by pods or capsules along deinite lines or sutures.
Dicot. An abbreviated name for dicotyledon, which refers to plants having two seed leaves.
Disinfectant. A chemical treatment used to disinfect seed for planting. It is especially useful for surface-
borne pathogens.
Diverticulae. The tendril-like forks projecting from the ends of the haustoria (adsorptive arms) of the
developing embryo or endosperm.
DNA . Deoxyribonucleic acid, a component of the nucleus (chromosomes) and the basic building block of
genes. It carries the hereditary information of a cell.
Dormancy. A physical or physiological condition of a viable seed that prevents germination even in the
presence of otherwise favorable germination conditions.
Drupe. One-seeded, stone fruit (e.g., cherry, peach, plum).
Electrophoresis. A technique used to separate a mixture of proteins or DNA based on their electric charges
and molecule size. It is used to determine genetic purity.
Electrophoresis test. A method for separating and mapping protein bands from homogenized plant (or
seed) preparations. The separations are made within a gel preparation across an electrical ield. The
test is used in varietal identiication and tests for varietal purity.
ELISA . An acronym for Enzyme-Linked Immunosorbent Assay, which is qualitative or quantitative test
using one or more antibodies to detect antigens (e.g., hormone, fungus, virus, microbial antigens) in
seed plant tissue, or other samples.
Embryo. The generative part of a seed that develops from the union of the egg cell and sperm cell and
during germination becomes the young plant.
Embryo sac. The female sexual spore of the ovule; also known as the mature female gametophyte or
megagametophyte.
Embryogeny. Embryo growth and development.
Endocarp. Inner layer of the fruit wall (pericarp).
Endosperm. The tissue of seeds that develops from sexual fusion of the polar nuclei of the ovule and the
second male sperm cell. It provides nutrition for the developing, growing embryo.
Enzyme. A catalyst produced in living matter. Enzymes are specialized proteins capable of promoting
chemical reactions without themselves entering into the reaction; consequently, they are not changed
or destroyed.
Epicotyl. The portion of the embryo or seedling above the cotyledons.
Epidermis. The outer layer of cells in plants that protects them against drying and mechanical injury.
Epigeal germination. A type of germination in which the cotyledons are raised above the ground by elon-
gation of the hypocotyl.