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Determining the water Potential of Cereliac

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Determining the water Potential of Cereliac The Celeriac Plant produces a beetroot like stem tuber. This stem tuber is called Celeriac. Water leaves or enters cell by osmosis. This depends on the water potential inside and outside the cell. Generally water travels from a region of higher water potential to a region of lower water potential. However other factors like pressure can also have an influence on osmosis. 'Pure water has the highest possible water potential.'1 To determine the water potential of celeriac we must carry out some experiments using a range of solutions with different concentrations and viewing how the cereliac samples change in the solutions by using a microscope to see how many have then plasmolysed. In the class room an experiment was carried out where the incipient point of some onion cells was found in a very similar way as described above. There is a graph present showing the results of the experiment on a separate page. As shown on the graph it takes a sucrose solution of 0.5867 mol/dm� to reach the incipient plasmolysis point of the white onion. The white onion therefore has a water potential of -1.667MPa. ...read more.


The microscope must be focused before the experiment is carried out and use of a medium or high power magnification is recommended 4. Count the number of cells in the field and count the number that has plasmolysed. Calculate the percentage plasmolysis. 5. Plot a graph of the percentage of cells that have plasmolysed against the molarities of the sucrose. 6. From the graph read of the molarity of sucrose that responds to 50% plasmolysis. 7. Make the solution that would create 50% plasmolysis and repeat steps 1 to 4 to ensure that the correct value has been attained. A similar experiment was done before in the classroom but the water potential of some onion cells was found instead. Some of the problems were clearly identifying if cells were plasmolysed or not and also the difficulty of obtaining a one cell thick cell sample to view under a microscope. To obtain small sheets one cell thick of the plant specimen it is advised that one uses an instrument called a microtome. However using this piece of apparatus can be quite tricky. First there has to be enough living tissue at the edge of the instrument to cut. ...read more.


White Tile Provides hard and non reactive surface onto which the celeriac can be cut. A pair of rubber gloves Avoids contact with skin when holding the celeriac. This reduces the possibility that grease from an ones hands can come in contact with the plant specimen. Grease is non-polar, whereas water is polar. The grease could thus hinder osmosis. Scalpel To cut the celeriac peels into suitable sizes. Slides and Cover slip To place the Celeriac on so it can be viewed. Microscope To view cells in detail 18 Small Beakers or Conical flasks These will be used to emerge the plant sections. Their size should be around 100 ml. 2 Pipette Fillers To safely fill the pipettes Calibration table- to find the water potential once the concentration of the sucrose that gives the incipient plasmolysis point is found Concentration/ moldm3 Water Potential /MPa 0.10 -0.26 0.15 -0.41 0.20 -0.54 0.25 -0.68 0.30 -0.82 0.35 -0.97 0.40 -1.12 0.45 -1.28 0.50 -1.45 0.55 -1.62 0.60 -1.80 0.65 -1.98 0.70 -2.12 0.75 -2.37 0.80 -2.58 0.85 -2.79 0.90 -3.01 0.95 -3.25 1.00 -3.51 All water potential values given of thus given molar concentrations of sucrose at 20� Celsius. It is thus important to work in this temperature to ensure accurate results are obtained. 1 Biology One, Page 56 2 Biology One, Page 58 ...read more.

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