Question

Which of the following can affect the passive absorption of water from the soil by the root?
(a)Typical tissue organization
(b)Respiratory activity of root
(c)Tension on cell sap due to transpiration
(d)None of the above

Answer 1

Hint: Root takes up water from the soil with the help of suction pressure. This process requires a water pull generated by certain processes that helps the root to take sap from the soil and move it upward to the leaves.

Complete answer:
The passive absorption of water from the soil can be affected by the tension on the cell sap due to transpiration. Transportation is the process in which the excess water absorbed by the root goes to leaves and comes out of the leaf pores called stomata. This water evaporates into the environment. This continuous process produces a tension pull in the whole water current and helps the roots to take up more water from the soil.

Additional Information:
The mechanism explained in the answer section is popularly known as transpiration pull. It controls the upward movement of water sap in trees and other plants which is also known as the Transpiration- cohesion hypothesis.
We know that xylem tissue conducts the transportation of water absorbed by roots to the leaves. The transpiration in the leaves establishes an upward pull in the xylem tissue and helps the water to rise in an upward direction. In this case, the concentration of water gets reduced in mesophyll cells and results in the upward pull of water from the root to these cells. It generates a negative pressure in the xylem to pull the water out of the soil.
Therefore, the correct answer to the question is “tension on cell sap due to transpiration”.

Note: Apart from the suction of water from the soil, the transpiration pull also helps the proper flow of water and the prevention of embolism. Therefore, transpiration is considered a very necessary process for the plants’ physiological systems. It helps in the excretion of water in plants thus maintains the water balance in the plant body. But sometimes over transpiration causes problems like dehydration in plants and loss of energy due to unnecessary absorption and excretion of water.