Glossary - Seed Testing - page 322

Legume. A member of the pea family characterized by having dry, multiseeded pods that dehisce along two
sutures at maturity.
Lemma. One of two bracts of the grass loret; it is located on the side nearest the embryo and opposite the
rachilla.
Lignin. The extremely complex strengthening or deposition material in plants that tend to make them hard
and woody. Chemically, lignin shows both phenolic and alcoholic characteristics.
Locule. The cavity of an ovary.
Loculicidal capsule. A type of capsule that at maturity splits open through the midrib of the carpel into the
locules (e.g., iris, tulip).
Malpighian layer . A protective layer of cells in the coats of many seeds characteristically comprised of
close-packed, radially positioned, heavy-walled, columnar cells without intercellular spaces. They are
usually heavily cutinized or ligniied and relatively impervious to moisture and gases.
Megagametogenesis . The development of the female gametophyte (megagametophyte) from a functional
megaspore.
Megaspore . One of the four cells (of archesporial cell origin) formed in the ovule of higher plants as a
result of meiosis, or sexual cell reduction division. One of these later undergoes mitosis to give rise to
the female gamete (megagametophyte, or embryo sac).
Megasporogenesis . The development of the megaspore from the archesporial cell.
Meiosis . Cell division during which homologous chromosomes pair; one member of each pair separates and
passes to daughter cells, each having one-half the original chromosome num ber. Also called reduction
division.
Mericarp . One-half of a two-sectioned fruit known as a schizocarp. Characteristic of the carrot family.
Meristem . Undifferentiated tissue located at the tips or growing points of vegetative or reproduc tive organs
capable of undergoing cell division and elongation.
Meristematic cells . Undifferentiated cells in plant meristems which are capable of undergoing cell division.
Mesocarp . Middle layer of the fruit wall (pericarp).
Metabolism . The chemical changes within a living cell.
Microgametogenesis . The development of the microgametophyte (pollen grain) from a micro spore.
Microgametophyte . A mature pollen grain, or male gamete.
Micropyle . The integumentary opening of the ovule through which the pollen tube enters prior to
fertilization.
Microspore . The male spore in the anther from which the male gametes develop.
Microspore mother cell . One of many cells in the microsporangium (anther) which undergoes microspo-
rogenesis to yield four microspores.
Microsporogenesis . The development of microspores from the microspore mother cell.
Mitosis . Normal cell division in which each daughter cell has exactly the same chromosome number as the
mother cell.
Monocot . An abbreviated name for monocotyledon, referring to plants having single seed leaves (cotyle-
dons). Examples are bamboo and corn.
Monogerm seed (sugar beet). A sugar beet “seed” (botanically a fruit) containing only one ovule in con-
trast to a multigerm “seed” which represents aggregate fruit containing several ovule units.
Mother cells. Special cells in the anther and ovule that give rise to pollen or egg cells.
Mucilages. The gummy (sticky when wet) complex carbohydrate substances which cover the seeds, bark
or stems of some plant species (e.g., buckhorn plantain seeds).
Multigerm seed (sugar beet). An aggregate fruit containing several ovules.
Multiple fruit. Developed from a cluster of lowers on a common base (e.g., ig).
Noxious weed. A weed species that is deined by law as being noxious; usually highly objection able when
found in crop seed lots.