Question

Correct sequence in water absorption by root hairs.

• A. Imbibition, diffusion, osmosis.
• B. Osmosis, imbibition, diffusion.
• C. Diffusion, imbibition, osmosis.
• D. Osmosis, diffusion, imbibition.

Hint:

Water absorption in plants begins with imbibition, followed by diffusion into root hair cells, and ends with osmosis into the root cortex.

Answer 1

The Correct Option is A

Step 1: Understanding the process of water absorption. 
Water absorption by root hairs occurs in three distinct stages:

 Imbibition: This is the initial stage where water is absorbed by hydrophilic substances (e.g., cell wall components like cellulose) through capillary action. 

Diffusion: After imbibition, water molecules diffuse from regions of higher concentration (soil solution) to lower concentration (root hair cells). 

Osmosis: Finally, water moves through the semipermeable membranes of root hair cells into the root cortex via osmotic gradients. 

Step 2: Explanation of the correct sequence. 
The correct sequence in water absorption is: \[ \text{Imbibition} \rightarrow \text{Diffusion} \rightarrow \text{Osmosis}. \] Imbibition occurs first as the cell walls absorb water. Diffusion facilitates water movement to the root hair cytoplasm. Osmosis enables water transport across membranes into deeper root cells. 

Step 3: Explanation of other options. 
Option (B): Incorrect. Osmosis does not occur first; imbibition precedes it. 

Option (C): Incorrect. Diffusion does not occur before imbibition. 

Option (D): Incorrect. Osmosis occurs after diffusion, not before. \[ \therefore \text{The correct sequence is: Imbibition, diffusion, osmosis.} \]