Determining isotonic point from osmosis graph Steps:

• Identify the concentration where potato tissue shows no net change in mass or length, indicating equal water potential (isotonic point).
• Plot or observe % change vs. NaCl concentration; the zero-change point is isotonic.
• At isotonic concentration, water potential of solution equals potato tissue, so no net water movement.
• Common isotonic for potato in NaCl is around 0.3 mol/dm³ based on typical experiments.

Not enough information: Graph not provided to confirm exact concentrations or trends.

Final answer: Not enough information.