Agriculture Reference
In-Depth Information
Synergid nuclei. Two of the eight cells of the embryo sac—usually remaining nonfunctional.
Syngamy. Sexual fusion of the sperm and egg cells.
Synthetic seeds. Seeds (often a somatic embryo surrounded by a synthetic encapsulation) produced from
vegetative tissue (usually by tissue culture) that are clones possessing identi cal genotypes.
Synthetic variety. A variety composed of an interbreeding population of several cross-polli nated plant
lines.
Tenuinucellate. The nucellar condition in which the embryo sac originates and develops only one cell layer
beneath the nucellar epidermis.
Testa. The outer covering of the seed; the seed coat.
Tetrad. A group (quartet) or tetrad of four spores formed by division of the same mother cell, as in a tetrad
of microspores.
Tetrazolium (TZ) . Indicates a class of chemicals that have the ability to accept hydrogen atoms (and
undergo reduction) from dehydrogenase enzymes during the respiration process in viable seeds. This
is the basis of the tetrazolium test during which the tetrazolium chemical undergoes a color change,
usually from colorless to red.
Tolerance. The amount by which a second test may differ from a irst test without being attrib uted to an
actual difference in seed quality.
Trier. A hand manipulated probe for sampling seeds.
TZ test. Quick test to determine seed viability (and sometimes vigor) using tetrazolium solution.
Unitegmic testa. A testa (seed coat) made up of only one integument.
Vermiculite. A porous form of mica, a mineral, which makes a good rooting medium for seed germination
because of its capacity to retain moisture and permit aeration.
Vernalization. Bringing into a spring condition. In reference to lowering, it is the process by which loral
induction is promoted. It is sometimes (perhaps erroneously) applied to seeds to indicate stratiication
in order to break dormancy, enabling them to germinate.
Viable (viability). Alive. Seed viability 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.
Vigor . The AOSA has deined vigor as “those seed properties which determine the potential for rapid uni-
form emergence and development of normal seedlings under a wide range of ield conditions.
Weed . Any plant in a place where it is a nuisance might be considered a weed. The term is usually used to
denote unwanted, noncultivated plants growing in ields, lawns, gardens, or other areas used by man.
Weed seed (percent). The total percentage (by weight) of a seed lot which is composed of seed of plants
considered to be weeds. One of the four components of a purity test.
Wing . A membrane, or thin, dry expansion or appendage of a seed or fruit.
Xenia . The direct, visible effects of the pollen on endosperm and related tissues in the formation of a seed
(e.g., seed color). It results in hybrid characteristics of form and color.
Zygote. A fertilized egg.
Search WWH ::




Custom Search