Question

explain the mechanism of closing and opening of the stomata

Answer 1

Mechanism of opening and closing of stomata
Opening of stomata: Solutes from neighbouring epidermal and mesophyll cells enter the guard cells lowering its osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water into guard cells from neighbouring cells. Guard cells become turgid due to water accumulation in them which results in the opening of the guard cells.
Closing of stomata: As the somata open the solute concentration is reduced. This makes the water from the guard cells to move away into neighbouring cells. Now, guard cells becom flaccid with no water. They collapse against each other and result in the closing of stomata.

Answer 2

the basic principle for opening and closing of stomata is based on K+ ion release The stomatal pores are largest when water is freely available and the guard cells turgid, and closed when water availability is critically low and the guard cells become flaccid. Photosynthesis depends on the diffusion of Carbon dioxide (CO2) from the air through the stomata into the mesophyll tissues. oxygen(O2), produced as a byproduct of photosynthesis, exits the plant via the stomata. When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by the roots. Ion uptake into guard cells causes stomatal opening: The opening of gas exchange pores requires the uptake of potassium ions into guard cells. Potassium channels and pumps have been identified and shown to function in the uptake of ions and opening of stomatal apertures.
Ion release from guard cells causes stomatal pore closing: Other ion channels have been identified that mediate release of ions from guard cells, which results in osmotic water efflux from guard cells due to osmosis, shrinking of the guard cells, and closing of stomatal pores.