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water potential of potato tuber cells

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DAVOR ZIBAR WATER POTENTIAL OF POTATO TUBER CELLS INTRODUCTION: AIM: To find the water potential of potato tuber cells. HYPOTHESIS: When cells are put in a solution with a different water potential than inside of them, cells will gain or loose water. If concentration of solution is the same, there will be no change in mass. THEORETICAL BACKGROUND: If a sample of tissues immersed in solution of varying water potential (concentration of water molecules), the cells will loose or gain water by osmosis. If the cell is put into solution of higher water potential (hypotonic solution), water will go inside the cell. As the pressure potential rises inside the cell it becomes turgid. In the plant cells turgidity is rising up the moment when cell can't take more water because of cell wall. Animal cells don't have cell wall so water is constantly going inside the cell until it lyses. If the cell is put into solution of lower water potential (hypertonic solution) the water will go out of cell and cell will be plasmolysed. In both ways cell will gain or loose mass. APPARATUS AND MATERIALS: * Cork borer * Scalpel * Syringe * Digital balance * Filter paper * Forceps * Blue ink EXPERIMENT 1: METHOD: 1. ...read more.


Digital balance has smaller uncertainty than analog ones so it is better to use. LIST OF VARIABLES AND THEIR CONTROL: * Time: all times are used accurately and measured with stop watch * Potato size: accurate measurements * Volume of solutions: accurate measurements * Ph: use distilled water * Same potato: different potato may have different water potentials RELIABILITY OF VARIABLES: Same potato has to be used because different potato may have different water potential so results wouldn't be reliable. Tap water is ionised so water potential can't be 0 so distilled water is used because it doesn't have any ions in it. Also Ph of distilled water is neutral so there is no change in permeability of membrane. SAFETY: * Carefully use cork borer and scalpel to prevent injuries by cutting * Watch out that you don't break any glass apparatus to prevent cutting RESULTS: EXPERIMENT 2 SUCROSE SOLUTION AFTER POTATO WAS TAKEN OUT mol dm3 CHANGE IN HIGHT OF COLOURED SOLUTION 0.1 SINKING 0.15 RISING 0.2 SINKING 0.25 RISING 0.3 RISING 0.5 RISING 1 RISING ANALYSIS: When potato was immersed in solution it gained or lost water. Sinking in this table means that potato gained water so coloured solution had bigger density and it fell on the bottom of test tube when it was immersed in the solution no1. ...read more.


Experiment 1 is more reliable because electronic gear was used which has less uncertainty than human eye and skill in experiment 2. Errors appeared because of human errors. * There was problem to cut same cylinders of potato because any difference in length can affect the result. * Making appropriate solutions was easy but there is also some kind of uncertainty in them because we are never sure that exactly correct solution is made. * There is potential error in weighting the potato after it stayed in solutions for 24 hours. If the potato hasn't been dried when it was weighted, mass of water also affects the result because masses are small and measured in grams with numbers smaller than 0. * The trickiest part of experiment 2 was to put the drop of coloured solution in other without dispersing it. In my attempts to put it in the solution I had little success. I squeezed the syringe too hard and drop just popped out of it causing the current in the solution so I couldn't see if colour was sinking or rising. That's why experiment 2 hasn't been successful. The best reliability for experiment would be to repeat it and to take average of solutions. For experiment 2, repetition is also needed so I would improve my skill of immersing a drop into other solution without dispersing it. ...read more.

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