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Determination of the water potential of root/tuber cells by the weighing method.

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Introduction

Determination of the water potential of root/tuber cells by the weighing method Introduction When a plant cell is bathed in a solution of the same water potential, its mass and volume remain the same, because water enters ad leaves at the same rate. If samples of tissue are immersed in a range of solutions of different concentrations (molarities), the cells will gain water by a method known as osmosis and therefore, mass, in solutions of higher water potential and lose water and mass in solutions of lower water potential. The water potential of the tissue is equal to that of the solution in which it neither gains nor loses mass. The purpose of this practical is to estimate the water potential of the potato tuber cells by this method. In practice, none of the experimental solutions is likely to have exactly the same water potential as the cells but the solution in which there would have been no gain or loss in mass can be estimated from the graph. Root vegetables and potato tubers are widely available in bulk, but in principle this technique could be applied to any plant tissue. Apparatus * Boiling tubes x6 * Boiling tube rack * Wax pencil * Cork borer * Razor blade or sharp knife * White tile ...read more.

Middle

Where the sucrose solution was stronger than the cell sap of the potato cells, the cells lost water by osmosis. This is clearly shown by the results from the 1.0 Mole concentration; the potato cells are said to be 'plasmolysed'. A.1b The graph gives an adequate set of data, showing that in the distilled water the potato gains in mass by approximately 23% then it gains 18% in the 0.20M solutions. In the 0.60 M solution there is a change, the gradient of the graph decreases steeply and the potato loses mass to 14% then in the 0.80M solutions the gradient decreases as it loses yet more mass to 5.4%. The first observation accounted was after the potato cylinders were placed in their solutions, one could see a difference; the ones in the 0.0M and 0.20M solutions were floating and the potatoes in the 0.40M, 0.60M, 0.80 and 1.0M solutions were at the bottom of the boiling tube, this lead to the compilation of the next conclusion. The graph shows that the potato in the 0.0M solutions and in the 0.20M is hypo-osmotic, as stated in the initial hypothesis; this suggests that there is higher water potential in the distilled water and 0.20M solutions than in the potato, which has a high concentration of solutes. ...read more.

Conclusion

Ways of improving the investigation are as follows; the use of a burette, which is far more accurate than a measuring cylinder and hence it would give more precise readings and therefore the experiment would be more accurate. One final thing that you could do is to conduct the experiment all over again and to make an average of the two averages. This will insure great accuracy, but results obtained from the initial investigation have sufficient evidence to support a firm conclusion regardless of the fact that an anomalous result was obtained. You could also investigate on the other variables, temperature and pH. To enable this experiment to be completed as accurately as possible, one can repeated it three times and then use an average of all the results to best plot a graph with a line of best fit. Also, to extend the experiment to a greater degree, you could place the potato cylinders under a microscope, enabling you to observe the cells in greater detail and draw some more observational results. Given the opportunity to conduct the experiment again, you could test each concentration three times, then record the average reading and plot it against the graph; this helps to enhance both reliability and accuracy of the data collected. E.7a/E. ...read more.

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