Biology Lab - Estimating Osmolarity by Change in Volume of Potato Tuber Tissue

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Graph 1: Final and Initial length and Diameter of Potato Cylinders at Different Osmolarities of Sucrose Solutions.

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Graph 2: The Effects of Different Sucrose Osmolarities on Potato Volume

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Graph 3: Change in Initial and Final Volume of Potato Cylinders at Different Sucrose Osmolarities

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5. Discussion

If diffusion will not occur between the potato and sucrose solution at the same osmolarity then there will be a low percentage change in weight and volume between initial and final volume of the potato cylinder. To reiterate, osmolarity is the total concentration of all the solute particles in a solution and tonicity is the ability of a solution to change the shape or tone of cells by altering their internal water volume (Marieb & Hoehn, 2008). The results of the experiment support my hypothesis and prediction because there was a low percentage in weight change at 0.2M sucrose solution. The potato is isotonic with a 0.2M solution of sucrose because there was only a 4.82 percent change in volume in the potato which was the smallest change in all of the solutions tested (table 1). If you look at graph 3 you can see that from 0.4M sucrose solution and above the potato is hypotonic to the solution from the decrease in weight seen in the potato (Graph 3). The potato is hypertonic when compared to the sucrose solution at 0.0M ,0.1M and 0,3M which is indicated by the gain in final volume and positive change in volume (graph3)(table 1). Scientist use experiments like this to determine optimum water content for physiological processes in plants (Morgan & Carter, 2011). For example, if plan cells have a reduced water content then their vital functions will slow down (Morgan & Carter, 2011).

This experiment was rather straight forward and I think the only major source of error would be human error with measurements. I am sure further familiarity with the calipers would minimize this error but they were rather new to us and measurements of length and diameter could of been more precise. Another source of error that is out of our control is the accuracy of the sucrose solutions used in the experiment. Their potency could of been off or the bottle may have been labeled wrong. Further research should be done on other vegetables or plants to find their ideal water content and isotonicity.

References

Freeman, S., L. Allison, and K. Quillin. Biological Science. United States (2014). Pearson Education Inc.

Marieb, E. N, and K. Hoehn. Anatomy and Physiology. San Francisco (2008). Pearson Education Inc.

Morgan, J. G., and E.B. Carter. Symbiosis: The Pearson Custom Library for the Biological Sciences. United States (2011). Pearson Learning Solutions.

Sperelakis, N. Cell Physiology Source Book: Essentials of Membrane Biophysics. United States (2011). Academic Press