Results:
Fresh bean extract: The curve indicates a stable increase in light intensity penetrating the solution as the time lengthens.
Boiled bean extract: The curve indicates a stable light intensity penetrating the solution as the time lengthens.
Interpretations:
Since our observation is that during the germination of a Vigna cylindrical bean, the dry weight of the plant drops before it starts to increase, our hypothesis is that food stored inside the beans are used up during germination for energy for growth by the cells inside the beans. This explains why our aim for this experiment is to prove that there is the presence of amylase in germinating seeds, as glucose is the main energy releasing source and can be found in beans when starch inside beans are being digested by amylase.
Since for Hydrolysis,
Water + Starch amylase Maltose
The activity of the enzyme extract in the fresh condition and the boiled condition was studied in this experiment. The method used to indirectly show this was the change in light intensity, which was observed through the sensormeter in each set-up.
Because the fresh enzyme extract was being put into starch solution, which had been added with several drops of iodine solution and had turned blue-black, as the enzyme extract continuously digest the starch molecules inside the solution, the light intensity penetrating the solution will rise because the colour of the solution slowing fade and turns yellowish brown. This was what had happened in the experimental set-up.
Because in the control set-up, the bean extract had been boiled, all enzymes inside had been denatured, and thus there would be no digestion. Therefore, there would no change in the light intensity penetrating through the solution.
Possible errors:
- The sensormeter is not sensitive enough to detect a small change in light intensity penetrating through the solution.
- The black cardboard paper does not cover the plastic vial properly and so the light intensity fluctuates a little bit because of the influence the surrounding.
- The plastic vial was being shaken so that the light passing through the mixture is not evenly distributed.
- The position of the table lamp was changing throughout the experiment and so the light intensity could not be kept constant.
Improvements:
- The temperature should be kept at 37℃
- The two sets of experiments should be carried out at the same time to ensure all the control variables (e.g. temperature) are the same for both experiments
- Thicker black cardboard can be used so as to increase the difficulties for the light from the surroundings to penetrate through the paper and affect the results.
- The black cardboard should also cover the table lamp and the battery powered light sensormeter to exclude any light from the surroundings.
Conclusion:
The hypothesis, which is “food stored in the beans are used up during germination for respiration for energy for growth by cells in the beans”, should be accepted.
To prove the second hypothesis, we can use the following set-ups. For the experimental set-up, we can use fresh beans, whereas for the control set-up, we can use sterilized beans. For the experimental set-up, we fill up half of a test tube and then connect the test tube to a closed container alkaline pyrogallol solution, and test for the changes in gas pressure using a pressure sensormeter. The same applies to the control set-up. If the second hypothesis is true, then there should be a greater increase in the pressure in the experimental set-up.
