Water Potential Gradient Drives Osmosis

Steps:

• Water potential (ψ) is higher (less negative) where solute concentration is lower or turgor pressure is higher.
• In the diagram, cell 1 appears more dehydrated (flaccid), indicating lower ψ due to higher solute pull.
• Cell 2 shows higher turgor, suggesting less negative ψ as water enters from cell 1.
• Thus, water flows from cell 2 (higher ψ) to cell 1 (lower ψ), confirming the gradient.

Why A is correct:

• Water potential decreases (becomes more negative) as water moves into cells with higher solute concentration, per the formula ψ = ψ_s + ψ_p, where ψ_s is more negative in cell 1.

Why the others are wrong:

• B: Cell 3 has the lowest ψ (most negative) in the sequence, not higher than 1 and 2.
• C: Cells differ in turgor and solute levels, so ψ values vary.
• D: Cell 3 ψ is lower (more negative) than cell 2, opposite of the claim.

Final answer: A