Question

There are two statements marked as Assertion (A) and Reason (R). Choose the CORRECT answer. Assertion (A): Transpiration pull is theprimary force responsible for the ascent of sap in tall trees. Reason (R): It generates negative pressure in leaf xylem, pulling water upward through a continuous column.

• A. Both (A) and (R) are true and (R) correctly explains (A).
• B. Both (A) and (R) are true but (R) does not explain (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Answer 1

Answer:

A. Both (A) and (R) are true and (R) correctly explains (A).

Transpiration pull serves as the main mechanism driving sap ascent in tall trees, overcoming gravity through the cohesive tension in xylem. This process creates negative pressure (tension) in the leaf xylem as water evaporates from mesophyll cells during transpiration, pulling a continuous water column upward from roots.