During passive absorption of water, the low water potential occurs in
Option: 1
Roots
Option: 2
Leaves
Option: 3
Root hair cells
Option: 4
All of these
Answers (1)
Passive absorption of water occurs due to the negative force generated in the shoot system.
Due to the high rate of transpiration, the leaves lose water at a high rate.
The loss of water increases the osmotic pressure of the mesophyll cells of the leaves.
Their water potential is set at low as well.
They start drawing water from the adjacent cells.
This results in the continuous build up of tension.
The cells of the leaves draw water from the xylem elements of the midrib which in turn draw water from the xylem elements of the stem.
The xylem elements of the stem ultimately draws water from the roots, where water potential is high.
Hence, roots only serve as a pathway for water absorption. These are not actively involved in the process.
Since roots are working as passive organs, this and there is no expenditure of energy in the absorption of water, this mechanism of water absorption through roots is called passive absorption.
Roots absorb water due to tension created by transpiration called the transpiration pull.
Leaves have low water potential due to loss of water through transpiration. Hence, the correct answer is option b.