Question

Cohesion and adhesion theory is otherwise called

• A. Pulsation theory
• B. Relay pump theory
• C. Root pressure theory
• D. Transpiration pull theory

Answer 1

The correct option is D

Transpiration pull theory

The upward movement of water is mainly due to the creation of a negative force or tension attributed to the continuous evaporation of water at the surfaces of leaves in the process of transpiration. As molecule after molecule of water evaporates through the stomata, it creates a pulling action on the next molecule of water in the transpiration stream. This pulling force, otherwise called transpiration pull, is strong enough to overcome the force of gravity which is responsible for the tendency of water to move downward.