Question

Water from soil enters into root hairs owing to

• A. Atmospheric pressure
• B. Capillarity
• C. Root pressure
• D. Osmotic pressure or diffusion
• E. Turgor pressure

Answer 1

The correct option is (D):

Explanation of the correct option:

1. Osmotic pressure of the cell sap of root hairs is usually higher than the osmotic pressure of the soil water.
   
2. Therefore, the diffusion pressure deficit (DPD) and the suction pressure in the root hairs become higher and water form the cell wall enters into then through the plasma membrane by osmotic diffusion.

Explanation of the incorrect options:

Option (A):

1. ​The atmospheric pressure does not act here as the root hair is present deep inside the soil.
   

Option (B):

1. ​Capillarity helps with the movement of water through the soil.
   
2. The capillary water moves into the root hair from the soil.
   

Option (C):

1. Root pressure does not affect intake of water directly. It affects the flow of water towards the upward direction.
   

Option (E):

1. ​Turgor pressure acts on the turgid cells which helps the water move from one cell to another.