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TO FIND THE WATER POTENTIAL OF PLANT TISSUE CELLS.

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Introduction

TO FIND THE WATER POTENTIAL OF PLANT TISSUE CELLS. AIM: To find the water potential of plant tissue cells by using different sucrose concentrations. What is water potential? Water potential is the ability of water to enter or leave a cell that is measured in Kilopascals(Kpa).Water can enter or leave a cell by the process called 'Osmosis', this is the movement of water from a region of high water potential to that of low water potential through a partially permeable membrane e.g. plasma membrane. Pure water is said to have a water potential of zero and it follows that the addition of solutes to pure water lowers its water potential, therefore the more solute added to pure water, the more negative its water potential. STRUCTURE OF A PLANT CELL. PREDICTION. When a cell is put in a highly concentrated sucrose solution, the water will move by osmosis from the cell to the solution because the water potential in the cell is higher than it is in the solution. As a result the cell decreases in mass and size; this is known as 'plasmolysis'.On the other hand when put in a less concentrated sucrose solution, the cell will gain water from the solution because this time the water potential of the solution is higher than that of the ...read more.

Middle

3. Use distilled water, molar sucrose solution and a syringe to make 20cubic cm (you are advised to make more than 20cubic cm) of each dilution in a beaker. Record in a table how sucrose and water you've used in every solution. 4. Mix the solution fully by using a stirring rod or just by shaking. 5. Pour the solutions into the appropriate test tube, arrange the test tubes in a systematic order and put them on the rack. 6. Carefully use the scalpel to remove the outer skin of the potato as it acts as a barrier. 7. Use a cork borer to cut 6 pieces of potato and a ruler to measure about 3cm in length of each potato piece. 8. Gently blot any excess fluid from each the potato before weighing each potato individually, if weighed with excess water the mass of the potato will be affected. Record this as initial mass. 9. To obtain accurate and reliable results, immerse the 6 potatoes in their respective sucrose solutions for 24hours. 10. After 24hrs remove the potatoes from the test tubes, blot any excess fluid from the out side and reweigh them. Notice the changes and record the new mass as final mass. ...read more.

Conclusion

In the 0.75M sucrose concentration, the water potential is lower than in the tissue and as a result the tissue losses water to the solution leading to decrease of mass referred to as plasmolysis. EVALUATION Some results are not on the straight line and these are called anonymous results, they may come up as a result of inaccurate measurements of dilution due to inaccurate apparatus e.g. using a measuring cylinder instead of a syringe, insufficient blotting, the regions of the potato used and how long the potato tissue was left in the solution. To improve the results, the potato tissues should be carefully dried before and after immersing them in the solutions, this is to avoid affecting the mass .The mass could also be affected if the whole of the potato cell is not immersed in water as part of the cell will not be in the solution. The potato should be left in the solution for long enough to the whole osmosis process to take place. However the results do not support the prediction made earlier as to what would happen to the cell when put in an equally concentrated sucrose solution i.e. 0. 5M and this could possibly be because different specie of potato was used due to limited number of the original specie. This could be improved by preparing enough potatoes of the same test. ...read more.

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