Glossary - Seed Testing - page 321

Gymnosperm. A kind of plant that produces seeds but no fruits. The seeds are not borne within an ovary
and are said to be naked (hence the name).
Gynoecium. The female part of a lower or pistil formed by one or more carpels and composed of the
stigma, style, and ovary.
Hard seed. A seed that is dormant due to the nature of its seed coat, which is impervious to either water or
oxygen.
Haploid (1N). A term indicating one-half the normal diploid complement of chromosomes.
Haustoria. In seeds, a type of armlike absorptive organ sometimes projecting from the developing endo-
sperm or embryo into other seed parts to gather nutritive support.
Head . An inlorescence in which the loral units on the peduncle are tightly clustered and surrounded by a
group of lowerlike bracts called an involucre (e.g., sunlower).
Helobial endosperm. Intermediate between the nuclear and cellular endosperm types in which develop-
ment is characterized by free nuclear division as well as cell wall formation in some areas.
Hemianatropous ovule. A type of ovule arrangement in which the straight ovule axis orientation is per-
pendicular to that of the funiculus.
Hemicellulose. Complex cell wall constituent that is similar in appearance to cellulose but more easily
broken down to simple sugars. Common forms include xylan, mannans, and galactans.
Hesperidia. Berrylike fruit with papery internal separations (septa) and a leathery, separable rind (e.g.,
citrus fruits).
Hilum. The scar remaining on the seed (ovule) at the place of its detachment from the seedstalk (funiculus).
Hormone. A chemical substance that is produced in one part of a plant and used in minute quantities to
induce a growth response in another part.
Hydrogen peroxide (H 2 O 2 ) test. Quick test to determine seed viability. In response to a H 2 O 2 soak, viable
seeds elongate their roots through a cut in the seed coat; a commonly used quick test for conifer seeds.
Hygroscopic. In seeds, the high tendency to take up moisture, even as water vapor.
Hypocotyl. The part of the embryo axis between the cotyledons and the primary root which gives rise to
the stalk of the young plant.
Hypogeal germination. A type of germination in which the cotyledons remain below the ground while the
epicotyl grows and emerges above the ground.
Imbibition. The initial step in seed germination involving the uptake of moisture by absorption from the
germination media and hydration of the seed tissue.
Immunoassay. A test that uses antibodies prepared in advance to recognize molecules of a speciic antigen
(e.g., protein, fungus, bacteria or virus present in a sample such as seed or plant).
Imperfect lower. Unisexual lowers; lowers lacking either male or female parts.
Incomplete lower. A lower that lacks any of the four basic parts (pistils, stamens, sepals, petals).
Indehiscent. Not splitting open at maturity.
Indeterminate lower. A lower which terminates in a bud which continues to be meristematic throughout
the growing season, resulting in lowers of different maturity within the same inlorescence.
Inert matter. One of the four components of a purity test; it includes both nonseed and seed material that
is classiied as inert according to the Rules for Testing Seeds.
Inlorescence. The lowering structure of a plant (e.g., umbel, spike or panicle).
Inhibitor. A chemical substance that retards or prevents a growth process such as germination.
Inoculum. Any material such as spores, bacteria or fungus bodies that serve as a means of propagating or
spreading a pathogenic disease. In legume seed inoculation, the inoculum is the bacterial inoculant
(see above).
Integuments. The tissues covering or surrounding the ovule, usually consisting of an inner and outer layer
which comprises the seed coat of the mature ovule.
Keel (lower). The two fused anterior petals of a legume lower.