Question

What is NOT true about cohesion-tension theory of translocation of water in plants?

• A. Transpiration pull is transmitted downward from leaf, stem to root.
• B. Living cells of roots play an active role and ascent of sap occurs actively.
• C. There is a force of attraction between water and lignified walls of xylem cells.
• D. Water molecules have strong mutual attraction so they cannot be easily separated.

Hint:

Water molecules have strong cohesion, but in plants, they are separated through the process of transpiration, creating a pull that helps in water transport.

Answer 1

The Correct Option is D

Step 1: Understanding cohesion-tension theory.
Cohesion-tension theory explains how water moves through plants, relying on transpiration pull and the cohesion between water molecules. The force that pulls water upward is due to the evaporation of water from leaves, creating a negative pressure.
Step 2: Analyzing the options.
(A) Transpiration pull is transmitted downward from leaf, stem to root: Incorrect — Transpiration pull is transmitted upward, not downward.
(B) Living cells of roots play an active role and ascent of sap occurs actively: Correct — Living cells in the roots contribute to the uptake of water, and the ascent of sap is an active process.
(C) There is a force of attraction between water and lignified walls of xylem cells: Correct — Water molecules do interact with xylem walls, helping in capillary action.
(D) Water molecules have strong mutual attraction so they cannot be easily separated: Correct — Water molecules do have strong mutual attraction, but they can be separated during the transpiration process.
Step 3: Conclusion.
The incorrect statement is (D) Water molecules have strong mutual attraction so they cannot be easily separated. This is not true in the context of the cohesion-tension theory.