Question

Describe the process of closing of stomata.

Answer 1

Stomata function as turgor operated valves. When osmotic concentration of guard cells increases, water comes in and guard cells become turgid and stomata get open. Whenever, osmotic concentration of guard cells decreases water moves out, guard cells becomes flaccid and hence get closed. Closing of stomata occurs in the dark. It is explained by Potassium pump theory. As CO2CO2 is not utilized in photosynthesis during light, hence its concentration in the sub stomatal cavity increases. An inhibitor hormone - abscissic acid (ABA) functions in the presence of CO2CO2 ion uptake by changing the diffusion and permeability of the guard cells for positive ions. The K+K+ ions are transported back to the epidermal or subsidiary cells from the guard cells.