Stoma
In
botany,
stomata (sing.
stoma or
stomate) are tiny pores, mostly on the undersurface of
leavess, used for
gas exchange. Air containing
carbon dioxide and
oxygen enters the
plant through these openings for
photosynthesis and
respiration. Waste
oxygen produced by photosynthesis in the
chlorenchyma cells of the leaf interior exits through these same openings. Also, excess water is released into the atmosphere through these pores in a process called
transpiration. The opening and closing of a stoma is controlled by
guard cells that surround the opening and involves
sodium-
potassium pumps.
Stomata can be seen under a microscope by taking nail varnish impressions of the leaf.
In medicine, a stoma is a surgically created opening into the body. The best known form of a stoma is the opening created by a colostomy to let feces out of the body.