Glossary

Achene. A small, dry, hard, indehiscent, one-seed fruit.

Afterripening. The collective changes that occur in a dormant seed that makes it capable of germination. It is usually considered to denote physiological change.

Air-screen cleaner. The basic piece of equipment for cleaning seed, utilizing airflow and perforated screens. Also called a fanning mill. ~

Anthesis. Strictly, the time of expansion of the flower but also the period during which the flower is open and functional.

AOSA. Association of Official Seed Analysts.

Aril. A portion of the placenta adhering about the hilum of a seed.

Aspirator. An airblast seed separator.

Awn. A terminal, slender bristle on an organ, such as a grass caryopsis.

Beard. Strong, stiff hair. Often used for awn.

Berry. A simple, fleshy or pulpy and, usually, many-seeded fruit.

Bract. A reduced leaf subtending a flower, usually associated with an inflorescence.

Callus. A hard or thickened layer at the base of certain grass florets.

Calyx. The external, usually green, whorl of a flower, contrasted with the inner showy corolla.

Capsule. A dry, dehiscent fruit composed of more than one carpel.

Caryopsis. The grain or fruit of grasses.

Chaff. The seed covering and other debris separated from the seed during threshing.

Corolla. The inner perianth of a flower, composed of colored petals.

Corymb. An indeterminant inflorescence in which the lower pedicels arising from the peduncle are successively longer than the upper ones, giving a rounded or flat-topped appearance.

Cotyledon. Seed leaf of the embryo.

Cu1m. The type of hollow or pithy, slender stem found in grasses and sedges.

Cyme. A type of inflorescence in which the main axis ends in a flower.

Dehiscence. The splitting open at maturity of pods of capsules along definite lines or sutures.

Dormancy. A physical or physiological condition of a viable seed that prevents germination even in the presence of otherwise favorable germination conditions.

Embryo. The beginning of a plant or apparent plantlet in a seed.

Endocarp. Inner layer of the fruit wall or pericarp.

Endosperm. The tissue of seeds that develop from sexual fusion of the polar nuclei of the ovule and the second male sperm cell.

Far-red light. The radiant energy in the long wavelength range of the visible spectrum between 700 and 760 nanometers.

Florets. The individual flowers of the sunflower and grass families.

Fruit. A mature ovary and any associated parts.

Gibberellic acids. A group of growth-promoting substances first discovered in the Gibberella spp. They regulate growth responses and appear to be a universal component of seeds.

G1umes. The pair of bracts that occur at the base of a grass spikelet.

Hard seed. A seed that is dormant because of its seedcoat and is impervious to either water or oxygen.

Hilum. The scar remaining on the seed at the place of its detachment from the seedstalk.

Imbibition. The initial step in seed germination involving the uptake of moisture by absorption of the seed tissue from the germination media.

Indehiscent. Pods or capsules that do not split open at maturity along definite lines or sutures.

Indeterminate flower. A flower that terminates in a bud, which continues to be meristematic throughout the growing season, resulting in flowers of different maturity within the same inflorescence.

Inflorescence. The flowering structure of a plant; far example, the umbel, spike, or panicle.

ISTA. International Seed Testing Association.

Lemma. One of two bracts of the grass floret.

Meristematic. A formative plant tissue made up of cells capable of dividing indefinitely and giving rise to new cells.

Noxious weed. A weed species that is defined by law as being a threat to agriculture, to living beings, or to the general public.

Palea. One of the thin bracts of grass floret enclosing the caryopsis and lo- cated on the side opposite the embryo.

Pappus. The modified calyx-limb in Compositae, consisting of a crown of bristles or scales on the summit of the achene.

Pedicel. The stalk of a single flower in a flower cluster or of a spikelet in grasses.

Peduncle. The general term for the stalk of a flower or a cluster of flowers.

Pericarp. The ripened walls of the ovary, referring to a fruit.

Pheno1ogy. The study of growth stages of plants.

Raceme. A simple, elongated inflorescence with each flower of nearly equal length stalks.

Rachis. The central stem or axis of a spike, raceme, or compound leaf.

Scarification. The process of mechanically or chemically abrading a seedcoat to make it more permeable to water.

Second-year twig. Twig produced during previous growing season in contrast to current annual growth, which is produced in the same season as flowering occurs.

Seedcoat. The protective covering of a seed.

Sepal. A leaf or segment of the calyx.

Sessile. Attached directly by the base, not stalked.

Spike. A basic type of inflorescence in which the flowers arise along the rachis and are essentially sessile.

Spikelet. The unit of the grass flower that includes the two basal glumes and one or more florets. Stratification.--The practice of exposing imbibed seeds to cool (5 degrees to 10 degrees Centigrade) (sometimes warm) temperatures prior to germination in order to break dormancy.

Tetrazo1ium. A class of chemicals that have the ability to accept hydrogen atoms from dehydrogenase enzymes during the respiration process in viable seeds.

Urtic1e. A small, thin-walled, one-seeded fruit in which the seed is only loosely attached to the pericarp.

Viable. Alive. In seeds, viable indicates that a seed contains structures and substances, including enzyme systems, that give it the capacity to germinate under favorable conditions in the absence of dormancy.

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