Question

Opening and closing of stomata is due to

• A. Pressure of gases inside the leaves.
• B. Changes of turgor pressure in guard cells.
• C. Effect of hormones.
• D. Their genetic constitution.

Answer 1

The correct option is B Changes of turgor pressure in guard cells.

Opening and closing of stomata take place due to turgor changes in guard cells. When the solute enters into the guard cells from the neighbouring epidermal and mesophyll cells both osmotic potential and water potential of the guard cells is lowered. This creates a water potential gradient between the guard cells and the neighbouring cells and make the water move into the guard cells and thus become turgid and swell in size which causes stomatal opening. With a decline in guard cells solutes, water moves out of the guard cells, making them flaccid, so stomata close.