Question

Passive water absorption by root system is due to

• A. Force created in roots
• B. Osmotic force In shoot
• C. High respiratory activity of root
• D. Tension in sap due to transpiration.

Answer 1

Answer: (D)

Tension in sap due to transpiration.

Transpiration causes a negative pressure region in the xylem . The leaves and other apical parts require huge amounts of water as it is lost in Transpiration. So the stomata takes up the water from the intercellular spaces of the neighbouring cells that in turn draw water from the xylem . Hence a tension or negative pressure region is created in the xylem tissue. This process significantly drops the water potential in the xylem as well as the root region and the water potential of the soil is higher than the roots. So the roots start absorbing water passively as water flows from high water potential to low water potential. Hence Transpiration causes passive absorption of water in roots.

So the correct answer is 'Tension in sap due to transpiration'.