Question

When the relative humidity of atmosphere is 100% in day time, the stomata shall

• A. Continue to remain open
• B. Become closed to stop transpiration
• C. Remain partially opened
• D. Become partially opened

Answer 1

The correct option is B Become closed to stop transpiration

Relative humidity (RH) is defined as the amount of water vapour present in the air compared to the amount of water vapour that air could hold at a given temperature.

Transpiration is the process by which water evaporates from the leaf surface into the atmosphere through stomata.

When there is the reduction in water present in the atmosphere, a gradient is created due to which water moves from leaves into the atmosphere. Thus, lower is the RH, the less moist atmosphere will be and so, the driving force for transpiration will be more.

But when the RH is high, the atmosphere will be saturated with water vapours, so the driving force for transpiration will be less and hence, transpiration rate will decrease because it is difficult for water to evaporate into the saturated air than in dry air. So, in response to the decrease in transpiration rate, stomate tend to close.

So, the correct answer is B.