Osmosis Practical Work

1. Measuring the average water potential of cells in a plant tissue

Sections of plant tissue placed in a range of concentrations of a solution. Some of the sections of plant tissue will gain water and some will lose water by osmosis.

• Add water to a series of sucrose solutions of different concentrations, each to separate beakers
• Use a cork borer to cut sections of potato tuber. Use same cork borer to ensure the thickness of each potato cylinder is equal. The cyliners should be cut to same length
• The potato cylinders should be surface dried and weighed
• A potato cylinder should be added to each of the solutions
• After a set period of time (e.g 24 hours) the potato cylinders are surface dried and reweighed
• The percentage change in mass should be calculated for the cylinder in each solution
• The percentage change in mass is plotted against the concentration of the sucrose solution (or solute potential of the sucrose solution)
• Where the line of best fit crosses the x-axis, the solute potential of the immersing solution is equivalent to the water potential of the potato tissue. At this point there is no net osmosis taking place between the tissue…