Question

The water moving upward forms a column, which is maintained up to a certain height due to

• A. Osmosis
• B. Transpiration pull
• C. Translocational pool
• D. Diffusion

Answer 1

Answer: (B)

Transpiration pull

The water moving upward forms a column, which is maintained up to a certain height due to transpiration pull. It is the pulling force responsible for lifting the water column. As water is lost in form of water vapor to the atmosphere from the mesophyll cells by transpiration, a negative hydrostatic pressure is created in the mesophyll cells which in turn draw water from veins of the leaves.

The negative tension is then gradually transmitted downwards via xylem tissues of the leaf, stem and finally to the roots. As a result, there is a continuous upward movement of the water column in the plant.

So, the correct answer is option B.