Water Potential Gradient in Plant Roots

Steps:

• Water enters root cells from soil via osmosis, moving from higher to lower water potential.
• In roots, water potential decreases progressively from outer cells (epidermis) toward inner cells (xylem) to drive absorption.
• Cell 1, being outermost, has the highest water potential among the marked cells.
• Cell 3, being innermost, has the lowest water potential, creating the gradient.

Why C is correct:

• Water potential (ψ) follows a decreasing gradient inward; ψ2 is intermediate, so lower than ψ1 (outer) but higher than ψ3 (inner), per the osmosis principle where water flows toward lower ψ.

Why the others are wrong:

• A: ψ2 cannot be higher than both, as that would reverse the inward flow.
• B: ψ2 cannot be higher than ψ1, blocking water entry from soil.
• D: ψ2 cannot be lower than ψ3, halting water movement to the xylem.

Final answer: C