Question

How do guard cells regulate opening and closing of stomata?

Answer 1

The opening and closing of thestomata is controlled by the guard cells. In light, guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost and the inner walls move together closing the pore.

Answer 2

The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Simillarly the pore closes if the guard cells shrink