The abstract below was written by Melanie Shadish. It came so close (along with its support documents) to what I wanted that I have added nothing from abstracts by other students. Yes there is some editing that needs to be done, but this one person understood the exercise and communicated that understanding very well.
Osmosis and Water Potential in Potato Tissue
Melanie Shadish, Rob Harris, Patricia Tellekamp
Water appears to cross the differentially permeable membrane of potato cells by a process called osmosis. The measure of the energy involved in osmosis is called water potential. Since water must lose energy as it moves by osmosis, water must move from an area of greater potential to an area of less water potential, until the water potential on either side of the membrane is the same, at which point the cell has reached equilibrium. The two major parameters influencing water potential are solute and pressure potential. In most situations, the addition of these two values equals the water potential of the cell. In this experiment, equilibrium osmotic effects were first examined using potato tissue. Seven cups were set up, one as a control containing water and potato tissue, the other six with differing amounts of 1 M sorbitol stock solution and distilled water, and uniform cylinders of potato, in order to measure the gain or loss of water as an indicator of net osmosis. The cylinders were weighed, placed in their respective solutions, and weighed at 20-minute intervals to test for water loss or gain. Since the weight of the potato in the 0.4 M sorbitol solution did not change, it was determined that this was an approximately isosmotic solution. Finally the osmolarity of our potato sap was measured. To do this, a piece of undamaged potato was ground to a pulp in a mortar, and the sap was squeezed into an Eppendorff centrifuge tube and centrifuged for two minutes. The osmolarity of the sap was measured in a Wescor Vapor Pressure Osmometer. The...
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