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Determine the Water Potential of Potato tissue.

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Introduction

Determine the Water Potential of Potato tissue The aim of this experiment is to determine the water potential of potato tissue, using different concentrations of sucrose solution. If plant cells are placed in pure water, water will initially move into the cells. After a period of time the cells will become turgid. Turgor pressure is the pressure exerted against the cell wall by contents of the cell. At first most water movement is into the cell. As the turgor pressure increases water will begin to diffuse out of the cell at a greater rate, eventually equilibrium will be reached and water will enter and leave the cell at the same rate. This stage is used to find the water potential of a particular cell. Potato cells contain polysaccharides starch and glycogen they are good for storage. The potato cell is surrounded by plasma membrane it is a fluid mosaic model, which is a mosaic of phospholipids and proteins moving around they are not solid. This is why plant cell can become turgid and flaccid because their walls (plasma membrane) can stretch. The plasma membrane is a selectively permeable barrier between the cell and the extra cellular environment. Water enters in the cell through phospholipids. Water moves into and out of the cell by osmosis. This is a passive process which does not require any energy. ...read more.

Middle

Looking at the results the physical condition of potato after the result the positive number of change in weight represents that the cell is turgid. The negative number of change in weight shows that the cell is flaccid. All solute potential numbers are a negative because water has a solute potential of zero therefore solutions will have a negative solute potential because they contain less water molecules. Graphs 1, 2 and 3 are S-shaped, sigmoid. Even though the concentration of sucrose solution increases in steady increments the graph is not a straight line. This is because as the concentration of sucrose solution increases the water potential does not increase proportionally. This is evident on the graph as the changing gradient of the line. The graphs 1,2 and 3 shows that at 0M (water) the potato cell is turgid and the weight of potato is very high. This is because the potato cell is gaining water molecules, potato has less concentration of water molecules therefore water enters the potato through osmosis from high concentration of water to low concentration. This is a passive process which does not require energy. Graph 1 shows that as you increase the concentration the weight of potato decreases even more because the potato cell is loosing water. Result 1 shows that as you go down concentration from 1 molar to 0.25 molar, change in weight has decreased therefore the potato cell has become flaccid. ...read more.

Conclusion

I think the conclusion reached is quite accurate. Although there was an anomalous result the rest lay on a smooth curve. The exact value of this point may not be exactly accurate as it is calculated from a freehand curve of best fit. I can say that my results were successful at which the conditions I had, I managed to find water potential of potato tissue which is on average -1070 KPa. If I had to do the experiment again I would make sure that all of the accuracy listed about is same each time. This is because there will be less difference in my final results and I will therefore get an accurate and reliable reading. I will use same equipments and weighing machine so I get similar readings. Further investigation I can extend my experiment by further investigation. I could find water potential of different types of potatoes and compare their results and find out which potato has the highest and lowest water potential. I could extend the experiment to a more exact level by looking at the potato cylinders under a microscope, then I would be able to see the cells in greater detail and draw some more observational results. I can also change my variables such as length of potato and see how the water potential changes as the length of potato increases. I can also use some other source of food such as an apple to find its water potential in similar way. ...read more.

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