Question

Stomatal movement is not affected by
A. $O_2$ concentration
B. Temperature
C. $CO_2$ concentration
D. Light

Answer 1

Hint: The stomatal movement mainly depends on availability of water, light, temperature, and the concentration of carbon dioxide in the atmosphere.

Complete Answer:
- Stomata are the minute pores found in the green parts mainly in the leaves of the plants. We know that plants can respire through the stomata. These pores can pass oxygen and carbon dioxide into the atmosphere.
- The stomata are surrounded by guard cells that are bean-shaped. The closing and opening of stomata is a function of these guard cells. When the guard cells swell the stomatal pore opens and when the guard cells shrink, the stomatal pore closes.
- Increased temperature allows the stomata to open. Temperature has a significant impact on the permeability of the guard cells wall and thus has a significant effect on the osmotic phenomenon responsible for the movement of these cells.
- Increased concentration of carbon dioxide in the atmosphere may contribute to changes in the plant cell that cause the closing of the stomata. Low concentration of carbon dioxide can open the stomatal pore. But the atmospheric concentration of oxygen does not have any effect on stomatal movement.
- Both the blue and red light activate the opening of the stomata. Since chlorophyll also absorbs these wavelengths, red and blue light sensitivity is consistent with the role of guard cells in opening stomata under conditions conducive to photosynthesis.

Thus, the correct answer is option A, i.e., $O_2$ concentration.

Note: The increase in temperature allows the stomata to open because of its effect on the permeability of the guard cells. The increase in the strength of light causes the guard cells to turgid, thereby affecting the stomatal movement.