Question

Passive water absorption by root system is due to
(A) Forces created in the cells of the root
(B) Osmotic force in the shoot system.
(C) Increased respiratory activity in the cells of the root.
(D) Tension in the sap as a result of transpiration.

Answer 1

Hint: Root is the important organ of the plant that absorbs water from the soil. This process takes place in two ways as active and passive absorption. The water absorbed by the roots in the soil transports through xylem for the utilization in the process of photosynthesis.

Complete step by step answer:
(1) Active absorption:
In this process, the plant roots actively participate in the absorption of the water. The roots release adenosine triphosphate into the soil for the process of water absorption.

(2) Passive absorption:
Transpiration is the process in which the water is lost through the small minute pores present in the leaves. These pores are called by the name stomata. The water absorbed from the leaves moves to the leaves by the xylem. Thus, the transpiration in the leaves causes some negative pressure in the xylem and this causes the water potential drop in the roots. Thus, the water potential in the soil becomes greater when compared to the water potential of the roots. This causes absorption of water from the soil in order to balance the water potential. This process is called passive water absorption.

So, the correct answer is “Option D”.

Note:
The transpiration occurs when the stomata open. This opening and closing of the stomata is controlled by the action of the guard cell surrounding the stomatal pores. When the guard cell is filled with water, the stomata opens and when it releases water to neighboring cells, the stomata closes.