Question

Describe how the guard cells regulate the opening and closing of stomata?

Accepted Answer

Leaves comprise tiny pores called stomata that help in the gaseous exchange. Distribution of stomata varies between monocots and dicots, between plant species, and between the underside and top side of the leaves on a plant. Each stoma has two bean-shaped guard cells. The outer wall of guard cells is thin, and the inner wall is thick. The opening and closing of stomata depend upon the bulging or stretching of guard cells.

During the daytime, photosynthesis occurs. So sugar formed is accumulated in the guard cells and concentration of cell-sap inside guard cells increases and water flows from epidermal cells to guard cells and turgor pressure of guard cells is increased. This results in the stretching and bulging out of their thin outer walls and pulling apart from inelastic inner thick walls and opening of stoma takes place.

When respiration takes place, concentration of cell sap is decreased and water flows out. Thin outer walls are expanded, and inner thick walls also expand outside that leads stomata to close.

Describe how the guard cells regulate the opening and closing of stomata?

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