Unloading carbohydrates at phloem sink

Steps:

• Carbohydrates move out of phloem sieve tube into sink cells.
• Solute concentration in sieve tube decreases.
• Water potential rises as solute potential becomes less negative.
• Water exits sieve tube by osmosis, reducing liquid volume.

Why C is correct:

• Removing solutes decreases osmotic pressure, raising water potential (ψ = ψ_s + ψ_p) and causing water efflux.

Why the others are wrong:

• A: Water potential rises, not lowers, upon solute removal.
• B: Water potential rises and volume decreases, not the reverse.
• D: Volume decreases due to water loss, not increases.

Final answer: C