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Osmosis - Examining the Effect of Different Molar Sucrose Solution On Plant Tuber or Roots.

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Introduction

EFFECT OF DIFFERENT MOLAR SUCROSE SOLUTION ON PLANT TUBER OR ROOTS. Background Information: Osmosis is the movement of water molecules from a region of high water potential to a region of low water potential across a partially permeable membrane, where the high water potential means less solute molecules and low means high solute molecules. Osmosis occurs in both plant and animal cells, however the effects are different. On the one hand, its different because in a plant cell when the water potential in the cell is greater than the outside, the net movement of water molecules will be out of the cell, but when this happens 'Plasmolysis' occurs. Plasmolysis occurs when there's more water potential inside than outside the cell which causes water to move out, and as they do, the protoplast which is a living part in the cell wall shrinks away from the cell wall. During the process, the solution passes the cell wall but still remains in contact with the protoplast until it completely shrinks away from the cell wall, at this stage the cell is said to be fully plasmolysed. The below diagram shows a diagrammatic representation of plasmolysis: However, if it was the vice versa, where there was a lower water potential inside the cell than outside the net movement of the water molecules would diffuse into the cell down the concentration gradient. When this happens the protoplast pushes on the cell wall thereby increasing the pressure potential, which also increases the water potential until, there's equilibrium between the water potential inside and water potential outside. The presence of the cell wall prevents the cell from bursting; at this point it's fully inflated and regarded as full turgor. On the other hand, in an animal cell when there's a high water potential inside than outside, the cell will shrink as theres loss of water down the gradient to the outside. ...read more.

Middle

the turgidity should happen in the 0.2 molar solution, this is because there's a higher osmotic concentration in the 0.2 molar solution than the cell, it thus causes the drawing in of water via the living cells of the potato which act as the semi permeable membrane, as the solution diffuses into the potato it enters the vacuole of the potato cell, which increases the volume of cell sap, which in turn causes an increase in pressure as the contents of the cell pushes against the cell wall, which prevents it from bursting unlike that of the animal cell. The pressure exerted is turgor pressure and is counteracted by a pressure equal in magnitude but in the opposite direction of turgor to a point where its equalled to the resistance of the cell, thus 0.2 molar gains mass due to the factors of turgor pressure. More also, I predict that for a solution of 0.8 0r 1.0 molar, the mass is likely to decrease because of the term plasmolysis, which happens due to the fact there's a lower osmotic concentration in theses molar solutions than inside the cell, hence movement of water out of the cell down the gradient. The reason for this prediction is that, as the cell loses it's water the cytoplasm shrinks and the plasmodesmata gets detached from the cell wall. From the secondary source/ research and based on my hypothesis, the result should backup the hypothesis as well as highlight the noticeable effect of osmosis on the different molar solutions. For example which molar solution would be Hypotonic i.e. where the cells of the plant tuber/ root takes in water because there's more solute in the cell than the outside solution which then causes water molecules to pass into the cell by osmosis and swell up. Another prediction, which I hope will reflect in the result is the molar solution that appears to be Hpertonic i.e. ...read more.

Conclusion

the hardness (parsnips), stringiness (sweet potato) or softness (Swede). More also, the freshness might affect the result in that the longer the tuber/ root has been on the shelf the less water present in its cells, in addition the errors might have happened due to % errors that happened in the length measurement when using the ruler. The % error can be worked out, and expressed as; 0.5 / 3 * 100% = where 0.5cm is the error of ruler, 3cm is the length of the cut pieces. In terms of the apparatus with the exception of the ruler, had no major errors because for example the burette has an insignificant error due to its 0.05cubic cm degree of accuracy Having looked at the results critically, there could have been improvements to help give more reliable and more accurate results. One of the improvements could have been allowing more than enough time difference between the sets of experiment so as to create more time to move the pieces from test tube to balance if weighing, although I mentioned I would allow enough time in the planning, this became rather impossible due to lack of time. Another improvement could be to use more types of molar strength solutions that would allow the specific strength at which the effects of osmosis occur, also experimenting for longer and repeating the sets about 10 times will surely increase reliability, produce sufficient accurate result, eliminate any chance of errors in the mass 9gained or lost) and help identify the saturation point (where the cut tubers/ roots cannot take in water any more) and dehydration point (where the cut tubers/ roots cannot lose water anymore) as well as test similar types of plant tuber/ root.. Furthermore, I could have used a microscope to look at the cut pieces which would show in great detail the full extent the molar strength had on the process of osmosis, but having said I'll need to devise a method to get the cells. ...read more.

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