An experiment to show the water potential of potato cells

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The aim of this experiment is to determine the water potential of potato tissues when immersed in different concentrations of sucrose solution. The immersion of the tissue in different concentrated solutions will enable an understanding to be developed of which concentrations the water potential is greater in the cell in comparison to the external solution; lower in the cell than in the external solution and ultimately and equal in both solutions.


I predict, as the concentration increases the water potential will decrease. I think this because as the concentration of the sucrose increases there are more solute molecules in the solution. As the solute potential is always negative consequently the water potential is made more positive.

I predict that if the potato cylinders where put in a sucrose concentration where the water potential is higher than the water potential that of the potato itself that would cause the mass and length of the potato to increase and if they had similar water potential there will be no change in mass nor length. Osmosis is the movement of water molecules from a high water potential to a low water potential through a partially permeable membrane. As the concentration of sucrose increases the difference in mass and length of potato will increase since sucrose is a hypertonic solution which means that it has a higher amount of particles dissolved in the solution, while a hypotonic solution such as water where there is fewer particles dissolved.

I predict that for the molarity level of 0 and 0.2 the potato core was going to swell, making the condition the cores were in hypotonic. When the molarity turned into 0.4 I said that the core would stay the same and therefore be isotonic. When the core was placed in the 0.6, 0.7, I predict that the cores were going to shrivel making the conditions hypertonic. The reasoning behind these assumptions is based on the definition of molarity. Molarity is the measure how concentrated something is. The reasoning why I think its starts to swell at first but then shrink is because the less concentrated a solution is causes it to have more water to be available in its surroundings. So the more concentrated the solution is will cause there to be less water in their surrounding so there won’t be as much to take in so it will shrink. At .4 molarity I thought the surroundings would be isotonic just because it was just about in the middle and there wasn't too much or too little concentration.

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The independent variable is the concentration of sucrose solution in which the potato cylinder is placed in (0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 mol ml-3). The dependent variable is the percentage change of mass (grams) of the potato cylinders before and after the experiment and the percentage change of the length of the potato cylinder after being submerged for a day in the sucrose solution.

The factors controlled in this experiment are the ones that are the same from one sucrose solution to another and hence, the variables, other than the concentration of the solution, ...

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