Question

Explain the mechanism of opening and closing of stomata.

Answer 1

Guard cells regulate the opening and closing of stomata. Sunlight is the main agent to induce the opening and closing of stomata.

Complete answer:
Stomata are the pores present in abundance at the lower epidermis of the leaf. They are also present in the stem. The gaseous exchange and transpiration occur through stomata. The stomata are surrounded by two guard cells which regulate its opening and closing. Stomata open during the day time for gaseous exchange and also release water vapour through transpiration. The opening and closing of stomata is due to the change in turgor pressure of the guard cell.
During the day the roots absorb water due to greater transpiration pull and it is transported to different parts of the plant through xylem. The guard cell on receiving this water swells and becomes turgid. As a result of which the stomatal pore is open.
At night, the roots absorb less water, thus the guard cell becomes flaccid and shrinks. As a result of which stomatal pores closes.

Additional information During the day time plant takes carbon dioxide from the atmosphere for photosynthesis and releases oxygen which we breathe. This gaseous exchange occurs through stomatal pore. At night photosynthesis doesn’t take place. Plants take in oxygen for respiration and release carbon dioxide.

Note: The rate of transpiration is regulated by the guard cells. When the guard cells are turgid, stomata open and when it is flaccid, the stomata closes.