Question

Most widely accepted explanation for the ascent of sap in trees is ______?

• A. Root pressure theory
• B. Capillarity theory
• C. Transpiration cohesion theory
• D. Imbibition theory

Hint:

Transpiration pull, combined with cohesion and adhesion, is critical for the ascent of sap in tall plants. Understand these principles for related questions.

Answer 1

The Correct Option is C

The transpiration cohesion theory, proposed by Dixon and Joly, is the most widely accepted explanation for the ascent of sap in trees. Key points of the theory include:
Transpiration pull: Loss of water through transpiration creates a negative pressure (tension) in the leaves, which pulls water upward.
Cohesion: Water molecules stick together due to hydrogen bonding, forming a continuous column in the xylem.
Adhesion: Water molecules adhere to the walls of xylem vessels, helping to counteract gravity.
Continuity: The water column remains unbroken due to cohesion and adhesion, allowing water to move upward to great heights.
Root pressure and capillarity play minor roles, but they are not sufficient to explain the transport of water to tall trees.
Final Answer: \[ \boxed{\text{Transpiration cohesion theory}} \]