germination Sprouting of a seed; the first stages in
the growth of a seed from a seedling to an adult. After
germination the embryonic shoot emerges and grows
upward while the embryonic root grows downward.
Food for germination is located in the endosperm tissue
within the seed and or seed leaves. Sprouting of pollen
grains on a stigma and growth of fungus or algal
spores are examples of germination.
See alsoFERTILIZATION.
gestalt Grasping an overall concept without under-
standing the details; perceiving the whole or patterns
over that of the pieces, e.g., the tune of a song. It is
based on an object or thing, its context in the environ-
ment, and the relationship between it all. Gestalt is
German for configuration or figure.
g-factor SeeELECTRON PARAMAGNETIC RESONANCE
SPECTROSCOPY.
gibberellins A group of about 50 hormones or
growth regulators that primarily stimulate cell division
and elongation in plants. Gibberellic acid (GA), the
first of this class to be discovered, causes extreme elon-
gation (bolting) of stems. Gibberellins are also involved
in flower, fruit, and leaf enhancements, germination,
and vernalization (temperature effects).
giemsa stain Stains developed specifically for the
phosphate groups of DNA in which the staining of
chromosomes produces light and dark bands charac-
teristic for each chromosome, called g-bands. Each
homologous chromosome pair has a unique pattern of
g-bands, enabling easy recognition of particular chro-
mosomes. Also used for looking for Schuffner’s dots,
which are small, red-staining granules in red-blood-
cell cytoplasm infected with either Plasmodium vivax
or P. ovale.
gigantism Animals that evolve on islands are affect-
ed by gigantism or dwarfism, the evolution of body
form as either large (e.g., Komodo dragon weighs up to
365 pounds) or small (e.g., Island fox in Channel
Islands). Island animal populations tend to acquire dif-
ferent sizes from their mainland counterparts. Gigan-
tism is also the condition of too much growth hormone
production in humans where people grow taller than
normal.
See alsoDWARFISM.gill Arespiratory organ in aquatic animals; an out-
fold of epidermal tissue; the gas-exchange surface of
many aquatic animals; a filamentous outgrowth with
blood vessels where gas exchanges (oxygen and carbon
dioxide) between water and blood. A bony structure
supporting the gill filaments is called the gill arch. A
flap of bony plates that cover the gills of bony fish is
called the gill cover, or operculum.
In fish, gill slits are openings or clefts between the
gill arches. Water is taken in by the mouth and then
passes through the gill slits and bathes the gills. Gills
are also rudimentary grooves in the neck region of
embryos of air-breathing vertebrates like humans. A
gill is also the part of fungi that contains the basidia,
the reproductive cell (meiotangium) that typically pro-
duces four spores on the outside.gizzard Part of an animal gut, e.g., in birds, that is
specialized for grinding and mixing food with digestive
enzymes. Also called the gastric mill.glaciation A long period of time characterized by cli-
matic conditions associated with maximum expanse of
ice sheets. The process of glaciers spreading over the
land. In North America, the most recent glacial event is
the Wisconsin glaciation, which began about 80,000
years ago and ended around 10,000 years ago. Most
glacial ice today is found in the polar regions, above
the Arctic and Antarctic Circles.gland A group of cells (organ), or a single cell in ani-
mals or plants, that is specialized to secrete a specific
substance such as a hormone, poison, or other sub-
stance. Two types of animal glands are endocrine and
exocrine. Endocrine glands place their products directly146 germination