Osmosis Driven by Water Potential Gradient

Steps:

• At 0.4 mol dm⁻³ sucrose, the graph shows percentage mass increase, indicating water entry into cells.
• Water moves from higher to lower water potential via osmosis.
• Sucrose solution at 0.4 mol dm⁻³ has lower (more negative) water potential than the initial cell water potential.
• Thus, water enters cells, increasing mass and vacuole volume.

Why A is correct:

• Water potential decreases with solute concentration; initial cell water potential less negative (higher) than 0.4 mol dm⁻³ solution drives water influx per osmosis principle.

Why the others are wrong:

• B: Vacuoles increased, not decreased, due to water entry.
• C: Final cell water potential became less negative (higher) after water gain, not more.
• D: Vacuoles increased in volume from osmosis, but this describes effect, not cause of water potential gradient.

Final answer: A