Hypothesis
The water potential of apple tissue will by far surpass the water potantial of potato.
Explanation of the hypothesis
Since it is known that fruits generally contain no starch, only fructose and glucose which together form a disaccharide called sucrose (2.07g of sucrose per 100g of tissue) and vegetables contain both starch and sucrose, though inequally distributed (13.49g of starch per 100g of tissue as opposed to 0.28g sucrose per 100g of tissue), we can presume that, if subjected to different sucrose concentration solutions, the potato would require a smaller concentration of sucrose to achieve an isotonic state, i.e. equal water potentials. Finally, we know that the concentration of solute and water potential are directly proportioned, hence we can deduce the greater potential among the samples.
Experiment 1
Materials and methods
*The instructions are given on the hand-out, attached to the report.
Table 1 – Table of variables
Data collection and processing
Table 2 – Change in apple samples’ masses after being submerged into sucrose solutions of different concentrations
Table 3 - Change in potato samples’ masses after being submerged into sucrose solutions of different concentrations
By processing the aquired data above, we came up with average percentage changes in masses of samples and presented them in Graph 1.
Graph 1 – Percentage of changed mass in samples
Experiment 2
Materials and methods
Samples of apple and potato, sized 1 x 1 x 4 cm, two of each; filter – paper; two eprouvettes; Benedict solution (reacting when in contact with reducing sugars, in this case, sucrose) and iodine solutions (sensitive to starch), 2ml of each.
Primarily, the two samples were samshed to form a jelly – like mass, which was then added a small amount of water, enough to rise the mass of the specimen to 2 ml. The samples were then mixed with benedict and iodine solutions, separately, in the two eprouvettes. The test tube containing the sample with the Benedict solution was additionally heated.
Data collection and processing
The results obtained are presented in Table 4.
Table 4 – Proving the existence of starch and/or sucrose in apple and potato tissue
Conclusion
According to the results gained by this research, our hypothesis was proven to be correct, to a great extent. First of all, the first experiment showed that the isotonic solution for potato was achieved at a smaller concentration of sucrose (approximately 0,4 mol/dmֿ³) than for apple (not shown, but projected to be around 1,1 mol/dmֿ³), thereby proving that the water potential is higher for apple tissue than it is of potato. Furthermore, the second experiment was conducted in order to justify the explanation of hypothesis, as well as the first experiment, and it supported the results of the research.
Evaluation and possible improvements
First, the method for cutting the samples was not completely precise, i.e. using the knife for altering the lenght of the samples caused deviations in sample sizes, thus influencing diffusion. This could have been avoided by using more precise techniques and improved equipment.
Secondly, the method for extracting remaining water in samples was not fully efficient (drying samples with paper towels), which made a standard deviation of +/- 0,01g. The best method for obtaining optimal mass would have been drying the samples using the laboratory dryer, with all the samples dryed at the same temperature, for the same time, though not completely extracting water from samples.
Refferences
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,,Zanimljiva biologija’’, I. I. Akimuškin, 1975, Nolit, Beograd
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- http://www.cookitsimply.com/nutritional/apples-raw-with-skin-0090-0p9003.html
Suggestion on methods for the experiment
As a method of comparing water potentials in two different plant tissues, I suggest one of the following, with samples of apple and potato tissues, sized 1cm3 being used as speciments analyzed in each method.
- We should use Benedict solution, which will, after submerging the samples into the solution, react with sucrose, subjected to a certain temperature, thus testing the existence of sucrose in tissue.
- Since iodine reacts with starch, submerging the samples into the solution would prove/dissaprove the existance of starch in tissue.
- Finally, I suggest drying the samples in a „lab – oven“, at approximatelly 150° , for around 2h, with measuring the speciment mass before and after, when we get completely dry mass. After calculating the change in percentage of mass, we would be able to deduce the tissue with higher water potential.
