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Investigating water relations in two different plant tissues

Extracts from this document...

Introduction

A-Level Biology Coursework: Investigating Water Relations In Two Different Plant Tissues Ying-Jun Ng Equipment used in practical * 0.1mol dm-3 Hydrochloric acid * 2 plant tissues (swede & potato) * 4 test tubes * 5x100ml beakers containing 6 different sucrose solutions * 6" ruler * 6 toothpicks * 12 boiling tubes & boiling tube covers * 50cm3 measuring cylinder * 80oC Water bath * Benedict's solution * Blotting paper/paper tile * Chinagraph pencil * Distilled water * Dropping pipette * Filter paper * Iodine solution * Litmus paper * Pestle and mortar * pH indicator chart * Sand * Scalpel * Scissors * Sharp knife * Sodium hydrogen carbonate * Spatula * Stop clock * Top balance (2dp) * White tiles Table I: Results table to show the appearance of potato and swede chips after being submerged in six different sucrose solution concentrations for 24 hours Sucrose solution concentration (Mol dm-3) Potato chip Appearance of potato chips after immersion Swede chip Appearance of Swede chips after immersion 0.0 (distilled water) 1 & 2 Very turgid 1 & 2 Very turgid 0.2 1 & 2 Turgid 1 & 2 Turgid 0.4 1 & 2 Semi turgid, similar to the original potato chip. 1 & 2 Semi turgid, similar to the original swede chip. 0.6 1 & 2 Slightly flaccid. 1 & 2 Slightly flaccid. 0.8 1 & 2 Flaccid 1 & 2 Flaccid 1.0 1 & 2 Very flaccid and fragile. 1 & 2 Very flaccid. Table II: Food test Potato shows Swede shows Testing for starch- iodine test Brown --> Black Brown --> black Presence of starch Yes, the entire tissue turned black Yes, only certain parts of the tissue turned black Testing for reducing sugars- Benedict's Blue-->Yellow Blue-->Yellow/orange Presence of reducing sugar Yes Yes, and as the benedict's turned orange, more reducing sugars are present. Testing for non-reducing sugars- Benedict's Blue -->Green/Yellow Blue-->Yellow/orange Presence of non-reducing sugar Yes Yes, and as the benedict's turned orange, more non-reducing sugars are present A table ...read more.

Middle

The sugar test showed that reducing and non-reducing sugars are present in the potato and swede, the only difference being that the swede contains more of the sugars. This is because the swede sample turned into a yellow/orange colour when the Benedict's was added, whereas the potato sample only turned into a yellow colour. The Benedict's turning into a deeper shade indicates that the swede has more reducing and non-reducing sugars present. This is the reason why the potato has a higher water potential than the swede which is why the swede's line of best fit on graph I is higher than the potato's line of best fit. For this experiment care was taken throughout the methods. A labcoat and goggles were worn all times of the experiment for safety, as different substances were being dealt with that might be harmful. Extra care was taken especially when dealing with glass and sharp objects to avoid being cut or breaking of equipment. As well as this, precaution was taken when dealing with the reagents e.g. hydrochloric acid as it is an irritant to the skin. Water was heated to 80oC, so caution was definitely taken when placing and removing test tubes from the water as one can be burned easily. Unneeded materials such as the potato remainders and solutions were discarded properly. Reagents were put away correctly, and the used equipment was washed. By doing so, the experiment was carried out safely and efficiently producing fair results. Evaluation I carried out this investigation accurately and fairly. To minimise errors from occurring, I made sure I used the correct equipment and followed the protocols exactly. The safety procedures there also followed so there were no accidents during the experiments. The results I obtained are fairly reliable having very little variation between samples I and II and their changes in mass. However, there were also several anomalies in my data sets caused by large differences between samples I and II and their changes in mass. ...read more.

Conclusion

With only two sets of results to compare and use it is difficult to identify any anomalies. It might even be the case that there were anomalies in both sets of results, which is why there should be more repeats of the experiment. There should be a minimum of three repeats of the test. With three repeats of the test, fairer, reliable, and more accurate results can be produced and it would be easier to identify anomalies. Altogether there are five anomalies which are circled on Graph I. In relation to the line of best fit the five anomalies are fairly close, indicating that the anomalies were perhaps produced because of the errors mentioned above. The anomalies are all above the line of best fit meaning that the percentage change in mass is less than expected. Using the samples from 0.8 mol dm-3 as an example as they are both anomalies and are above the line of best fit. It could have been the case that these chips were stuck together or onto the side on the boiling tube, which reduces the chips surface area and the rate of osmosis. With the rate osmosis being reduced, it would have produced these anomalous results which are above the line of best fit. Table V: Table to show the difference between the changes in mass of samples I and II of potato and swede tissue Potato Sucrose solution concentration (Mol dm-3) Potato sample Difference in change in mass (g) Difference in change in mass (%) 0.0 (distilled water) 1&2 (0.55-0.32) 0.23 9.8 0.2 1&2 0.09 4.12 0.4 1&2 0.04 1.67 0.6 1&2 0.07 2.0 0.8 1&2 0.28 10.6 1.0 1&2 0.05 2.0 Swede Sucrose solution concentration (Mol dm-3) Swede sample Difference in change in mass (g) Difference in change in mass (%) 0.0 (distilled water) 1&2 (0.47-0.28)= 0.19 11.8 0.2 1&2 0.19 11.04 0.4 1&2 0.01 0.37 0.6 1&2 0.01 0.09 0.8 1&2 0.05 2.7 1.0 1&2 0.01 1.7 ?? ?? ?? ?? Biology Coursework: Ying-Jun Ng ...read more.

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