Question

The rupture and fractionation do not usually occur in the water column in vessel/tracheids during the ascent of sap, because of

• A. Lignified thick walls.
• B. Cohesion and adhesion.
• C. Weak gravitational pull.
• D. Transpiration pull.

Answer 1

The correct option is B Cohesion and adhesion.

The ascent of sap is the mechanism by which water moves from the roots to the top of the trees. Studies on the process of ascent of sap show that the strong cohesive force between the water molecules(cohesion), the attraction between water molecules and the wall of the xylem elements (adhesion) and the transpiration pull creates a tension on the water column, which ensures continuity of water column in plants. Thus, rupture and fractionation of the stressed water columns known as cavitation which tends to block the flow of sap does not take place in the water column, because the continuity of water column is maintained by cohesion and adhesion.

So, the correct answer is option B.