Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Increase in temperature increases the transpirational rate in plant.
Reason R: Increase in temperature lower the relative humidity and widen the opening of stomata.
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

A higher temperature lowers relative humidity, which increases the vapor pressure deficit (VPD) between the leaf and the atmosphere, driving faster transpiration.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Transpiration is the loss of water vapor from the aerial parts of plants, primarily through stomata.
This process is driven by the vapor pressure deficit (VPD) between the internal leaf space and the surrounding atmosphere.
Environmental factors, such as temperature, relative humidity, wind speed, and light intensity, directly affect transpiration.
Detailed Explanation:
Let us evaluate Assertion A and Reason R:
- Assertion A: An increase in air temperature increases the rate of transpiration. At higher temperatures, water molecules inside the leaf have more kinetic energy, increasing the rate of evaporation. This statement is correct.
- Reason R: An increase in temperature increases the water-holding capacity of the air, which lowers its relative humidity. This increases the vapor pressure gradient between the wet interior of the leaf and the dry external air, driving water vapor out of the leaf more rapidly. Additionally, within moderate physiological limits, warmth promotes metabolic activity and stomatal opening, reducing resistance to diffusion. This statement is correct.
Since the reduction in relative humidity and the opening of stomata directly explain why a rise in temperature increases the rate of transpiration, Reason R is the correct explanation of Assertion A.

Step 2: Final Answer:
Both A and R are correct, and R is the correct explanation of A, corresponding to Option (A).