Question

Stomata opening is influenced by
A. $N_2$ concentration, $C{O}_2$ concentration and light
B. Water content of epidermal cells, temperature and light.
C. $N_2$ concentration, light and temperature.
D. $C{O}_2$ concentration, $N_2$ concentration and temperature.

Answer 1

Hint: Stomata are pores guarded by two kidney shaped cells called guard cells. Stomata are present in the epidermal layer of the leaves. But the number of stomata are more in the lower epidermis as compared to upper epidermis. The guard cells contain chlorophyll and they carry out photosynthesis during day (light).

Complete answer:
Stomata are composed of two guard cells. The thickening of the inner and outer side of the wall of guard cells are different. The inner side of the walls are thicker than the outer side wall. This unequal thickening of the guard cells causes the opening and closing of the stomata. The movement of guard cells is due to turgidity. During day guard cells absorb water from the adjoining epidermal cells and become turgid. It results in opening of the stomata. During night, guard cells lose water due to absence of photosynthesis. Stomata closes as guard cells become flaccid. In many plants that grow in dry regions, the stomata closes with high temperature. By closing stomata at high temperature it conserves water or prevents water loss.

Thus, option B. Water content of epidermal cells, temperature and light is the correct answer.

Additional information:
Let’s look at some more functions of the stomata:
- Allow gaseous exchange (carbon dioxide and oxygen) with the atmosphere.
- Helps in transpiration.
- Stomata remains open during the day and closed at night. The closing of stomata at night prevents water loss.
- Stomata closes when the plant is under stress.

Note: The environmental factors affect the opening and closing of stomata are light, water and carbon dioxide concentrations. Generally stomata open during the day and close at night and they also close when conditions are very dry. Nitrogen does not involve the opening and closing of stomata.