Question

An important factor in the mechanism of opening and closing of stomata is

• A. Chlorophyll content of the guard cells
• B. Shape of guard cells
• C. Hormone content of the cell
• D. Protein content of the cell

Answer 1

The correct option is B Shape of guard cells

In most of the plants stomata are surrounded by kidney bean shaped guard cells. The guard cells have thicker walls on the concave side adjoining the stomatal pore. The outer convex walls of guard cells are thin and elastic. The thick inner walls also show radial arrangement of cellulose microfibrils. The unevenly thickened walls of guard cells result in the bulging of outer wall towards outside, when guard cells become turgid on absorbing water. The bulging of outer wall towards outer side pulls the inner wall with the help of radial cellulose microfibrils.

In members of family Poaceae and some members of Cyperaceae and many palm, the guard cells are dumb-bell shaped with thin end walls and thick middle parts.