Question

Assertion: Stomata are generally open in light and close in dark.
Reason: Transpiration is enhanced by the heating effect of light.
A) Both assertion and reason are correct and the reason is the correct explanation for assertion
B) Both assertion and reason are correct but the reason is not the correct explanation for assertion
C) Assertion is correct but the reason is incorrect
D) Both assertion and reason are incorrect

Answer 1

Hint:Stomata are the pores that are present on the surface of the leaves. The pores help in the regulation of the exchange of gases from the atmosphere. Carbon dioxide is taken in from the stomata. The opening and closing of the stomatal pore are regulated by the guard cells.

Complete answer:
Transpiration is the process in which the water gets evaporated by the leaves and other parts of the plant. The rate of the transpiration is affected by the temperature, humidity, wind speed and the light intensity received. An increase in the light intensity increases the rate of the transpiration of the plants.

The plants present in high light intensity tend to have a higher rate of transpiration than the plants present in the low sunlight areas. The stomata open in the presence of sunlight because the water gets collected in the stomatal cells which helps in the opening of the stomatal pore.

When the water is removed or gets evaporated it leads to the closing of the stomatal pore. So, in the absence of the sunlight, the stomata usually remain closed and no transpiration occurs. In some plants, the stomatal pores open during the nighttime and close during the daytime to prevent the loss of water during the daytime due to the high amount of rate of transpiration. Such plants are found in the desert areas.

So, the correct answer is option ‘B’ i,e, ‘Both assertion and reason are correct but the reason is not the correct explanation for assertion’.

Note: Transpiration and the opening and closing of the stomatal pore are not regulated due to each other. But they both are the independent events. The carbon dioxide is taken in and oxygen is released out when the stomata are open.