#biology11class #biologyfirstyear #F.Sc. #chapter14 #Transport
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OPENING AND CLOSING OF STOMATA
The guard cells function as multisensory hydraulic valves. Environmental
factors, such as light intensity and quality, temperature, relative humidity,
and intracellular CO2 concentration are sensed by guard cells and these signals
are integrated into well-defined stomatal responses.
There are two hypotheses which may explain the opening and closing of
stomata.
i) Starch Sugar Hypothesis:
Proposed by.
The German botanist H. Van Mohl proposed that the guard cells are the only
photosynthesising cells of epidermis of leaf and sugars are produced in them
during day time when light is available.
Opening in Day time
When sugar level rises i.e. solute concentration increases or water potential
decreases - and the guard cells become turgid due to entry of water and they
separate from one another, and stoma or pore opens.