Water Potential of Potato

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Title:
Osmosis and water potential
Aim of the experiment:
Finding the water potential of potato.
Biological principles:
Independent variable: concentration of the solution.
Dependent variable: percentage changed in weight of the potato strips. Controlled variable: size of the potato strips, it can be controlled by cutting the length of the strips. Procedure: Table 1. Concentration of sucrose solution table Concentration/ M| Sucrose Solution/ ml| Distilled Water/ ml| 0 (Water)| 0| 10|

0.2| 2| 8|
0.4| 4| 6|
0.6| 6| 4|
0.8| 8| 2|
1| 10| 0|
1. Prepared 6 solutions. 0.2M, 0.4M, 0.6M, 0.8M, 1M sucrose solution and water. (Table 1) 2. Filled six boiling tubes with 5 cm3 of the solutions and labeled the boiling tubes. 3. The potato should be cut into 6 strips by cork borer and should be cut with the same length of 5 cm. 4. The potato strips should be dried.

5. The initial reading of the mass should be recorded.(Table 2) 6. Each boiling tube should be immersed one strip.
7. Strips should be taken from the solutions by the forceps after 30mins. 8. The potato strips should be dried.
9. The second reading of the mass should be recorded.(Table 2) 10. Calculate the percentage changed in mass.
Table 2. Initial and final reading of mass and percentage changed in mass | 1 M| 0.8 M| 0.6 M| 0.4 M| 0.2 M| Water(0M)|
Initial mass (g)| 1.01| 1.02| 1.04| 1.01| 0.98| 1.02| Final mass (g)| 0.78| 0.83| 0.89| 1.01| 1.08| 1.21|
Percentage change* (%)| -22.8| -18.6| -14.4| 0| 10.2| 18.6| *percentage changed: [(final – initial)/initial] x100%

Fig 1. Procedure graph P.1

Result:
From the graph, 0M (water) and 0.2M sucrose solution have higher water potential than the cell sap. Water molecules entered the cell by osmosis. Because of it, the cell became heavier, turgid and...
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