Question

Explain the mechanism that brings about closure of stomata.

Explain the mechanism that brings about closure of stomata at night.

Answer 1

The closing mechanism of stomata is driven entirely by the loss of turgor pressure within the guard cells, causing them to become flaccid. During the night or under conditions of severe water deficiency, potassium ions (K⁺) actively diffuse out of the guard cells and move into the adjacent epidermal cells. This outward movement reduces the solute concentration inside the guard cells, which lowers their osmotic pressure and triggers the process of exosmosis. As water moves out of the guard cells, their inner thick walls and outer thin walls lose their turgidity and flatten back into their original straight shape, which brings the inner edges together and closes the stomatal pore.