Question

Choose the correct answers from the alternatives given.
Which of the following is not a part of the transpiration cohesion-adhesion theory of the ascent of xylem sap?

• A. The evaporation of water from the mesophyll cells, which initiates a pull of water molecules from neighbouring cells and eventually from the tracheids
• B. The transfer of this pull from one water molecule to the next due to the cohesion caused by hydrogen bonds
• C. The hydrophilic walls of the narrow tracheids and vessels that help to maintain the column of water against the force of gravity
• D. The use of proton pumps to create membrane potentials that facilitate the accumulation of mineral ions.

Answer 1

The correct option is D The use of proton pumps to create membrane potentials that facilitate the accumulation of mineral ions.

The forces of cohesion (attraction among water molecules) and adhesion (attraction between water molecules and the walls of the xylem vessels), together help to form a thin, unbroken column of water which leads to the mass flow of water in apoplastic pathways. These forces act due to the cohesive and adhesive properties of water. In plants, the capillarity is aided by the small diameter of the tracheary elements like the tracheids and the vessel elements. The proton pump has no role in the facilitation of water and minerals.

Hence,the correct answer is 'The use of proton pumps to create membrane potentials that facilitate the accumulation of mineral ions'.