The Effect on Potato Tissue of the Sugar Concentration of the Surrounding Liquid

The effect on potato tissue of the sugar concentration of the surrounding liquid

Introduction

Plant cell walls are freely permeable to water and dissolved substances, but the cell membrane is only partially permeable. Small molecules like water can pass through freely but larger molecules like dissolved sugars cannot.

By putting potato tissue into solution of different concentrations, it is possible to change the amounts of water inside the vacuoles of the cells. If the water leaves the cell, this should reduce the mass of the tissue. If water enters the cell, the mass of the tissue will increase. The potato tissue can be weighed and its length measured before and after the experiment to see how much water has been lost or gained in each solution.

Planned Procedure

Fifteen tubes are labelled : 3-- distilled water, 3--10% Sucrose, 3--20% Sucrose 3--30% Sucrose 3--40% Sucrose ( 3 of each are used to obtain a more accurate average result) Next 20-30ml of distilled water or correct concentration of sucrose is put into the tubes. To make the test fair place the same amount of liquid in each tube. The liquid should be high enough to allow for expansion of the tissue with out it becoming uncovered.

A cork borers will be pushed into a potato using a cutting tile to cut onto. Then push the potato tissue out using smaller borer or mounted needle. Using a ruler+ scalpel cut 15 piece ( cylinders of potato) accurately into the same length (70mm or as long as possible) and record.

Measure the mass of each piece using scales provided, then place in boiling tube, record weight on the label.

Leave for 24 hours. All tubes in the same conditions to ensure the test is fair. The only varied factor is the solution sugar concentrations

Mean while make a chart to record original weight, final weight and change in weight of each sample. 3 samples at each of the five concentrations. Do the same for length.

After 24 hours weigh and measure the length of each piece. Recording its original weight, final weight and length in the chart. ( Before weighing dry each piece with a paper towel.)

Calculate the mean (average) change at each concentration. Then plot two graphs. One the different concentration of the surrounding fluid. Against the change in mass The other different concentration of the surrounding fluid against the change in length.