Given below are two statements, one is labelled as Assertion (A) and other is labelled as Reason (R).
Assertion (A): Transpiration helps in the ascent of sap.
Reason (R): Transpiration increases osmotic pressure in roots.
In light of the below given statements choose the most appropriate answer from the options.

Correct option is D

The correct answer is (d) (A) is true but (R) is false

Explanation:

• Transpiration is the loss of water vapor from the leaves, which creates a negative pressure (suction) known as transpiration pull.
• This pull is the primary driver for the ascent of sap (upward movement of water and minerals) in tall plants.
• Statement (R) is false because transpiration primarily affects the leaves and creates a tension in the xylem; it does not directly increase the osmotic pressure in the roots.
• Root pressure (which involves osmotic pressure) is a separate mechanism that usually works at night or in short plants.

Information Booster:

• The Cohesion-Tension theory explains how water molecules stick together and to the xylem walls to facilitate the ascent of sap.
• Transpiration also helps in cooling the plant surface.

Additional Knowledge:

Both are true (Option a & b)

• Incorrect because the mechanism described in Reason (R) is factually inaccurate regarding the direct result of transpiration.

So the correct answer is (d)