The opening and the of the
stomata dependupon necessity of
the plant lose water and heat
transpiration (exit of water means
elimination of heat). the plant has
excessive the guard cells become
and the ostiole opens. little
water is available guard cells
become flaccid the ostiole closes.
Water and goes out the
by osmosis.

Other factors light intensity and
carbon concentration in the
leaves the opening and the
of the stomata. When
is high the photosynthesis
increases and the stomata to
absorb more carbon from the
environment and heat; when
luminosityis low stomata tend to
close. the carbon dioxide
concentration the photosynthetic
parenchyma is the stomata open to
more of the gas make
photosynthesis possible; when
concentration is high the tend
to close.