Which of the following is the most widely accepted theory for the ascent of sap?
Correct answer: B. Cohesion tension
- A. Water potential
- B. Cohesion tension
- C. Root pressure
- D. Imbibition
Explanation
There are many theories explaining the ascent of sap, including: 1. Cohesion-Tension Theory: The theory states that transpiration pull or tension, the cohesion property of water, and hydration of the cell walls (i.e., adhesion) are collectively responsible for the ascent of sap. 2. Root pressure theory: The theory states that the phenomenon of root pressure is responsible for the ascent of sap. 3. Imbibition: According to this theory, the water rises by imbibition through the thick walls of the xylem cells as well as those of the sclerenchyma of the phloem. The forces of imbibition range from 100 to 1000 atm, and this would seem adequate for carrying water to any required distance. Out of all these, the cohesion-tension theory is the most widely accepted.
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