Sporopollenin
A secondary product, a polymer synthesized by a side branch of a major metabolic pathway
of plants that is resistant to almost all kinds of environmental damage; especially important
in the evolutionary move of plants onto land.
Stablizing selection
Natural selection that favors intermediate variants by acting against extreme phenotypes.
Stalks
A slender or elongated support or structure, as one that connects or supports an organ.
Stamen
The pollen-producing male reproductive organ of a flower, consisting of an anther and
filament.
Staminode
A sterile stamen, sometimes resembling a petal, as in the canna.
Starch
A storage polysaccharide in plants consisting entirely of glucose.
Statocyst
A type of mechanoreceptor that functions in equilibrium in invertebrates through the use of
statoliths, which stimulate hair cells in relation to gravity.
Statocysts
A small organ of balance in many invertebrates, consisting of a fluid-filled sac containing
statoliths that stimulate sensory cells and help indicate position when the animal moves.
also called otocyst.
Statoliths.
A granule of the statoconia.
Stele
The central vascular cylinder in roots where xylem and phloem are located.
Stem
The aboveground part of the axis of vascular plants, as well as anatomically similar portions
below ground (such as rhizomes).
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