How two varieties of Lycopersicon esculentum differ based on Carbohydrate, photosynthesis, and enzyme tests

By: Nilam Patel, Jackie Vandervest, Dianna Anderson

Abstract
By, Dianna Anderson, and Nilam Patel
Revised by, Jackie Vandervest
There are several varieties of tomatoes growing throughout the world (University of Minnesota). But is one variety of tomato different than another? We took two examples of extremely different sized tomatoes, the Grape tomato and a Common Garden tomato. We found that the small Grape tomato differed from the much larger Common Garden tomato on the molecular level. First we tested for sugar concentration by performing Benedict's, Barfoed's, Selvinoff's, Bial's, and iodine tests. These tests showed us that the concentration of sugars was consistent between the two varieties of tomato. Second, we examined the concentration of pigments in the leaves of each type of tomato. We did so by using paper chromatography, and calculating the absorption spectrum of the tomato leaves. In this lab, we found that the Common Garden tomatoes contained chlorophyll with more soluble pigments. We also observed the absorbance spectrum of both varieties of tomato and found them to have a similar absorbance spectrum. Last, we tested the presence of enzymes in each variety of tomato. We found that our tomatoes lacked the PPO enzyme, and we suspect that this may be due to genetic engineering during the growth of the tomato.
Despite their differences in size and taste, our two tomatoes appear to have similar composition as revealed by our tests. However, our photosynthesis testing did show a difference in the concentration of pigments between the two varieties of tomatoes, which supports our hypothesis and suggests that the two tomatoes do vary at the molecular level.

Discussion
By: Dianna Anderson, Jackie Vandervest, Nilam Patel
Revised By: Dianna Anderson, Jackie Vandervest, Nilam Patel

In order to perform any experiments using the Grape tomato, and the Common Garden tomato, we had to make a solution which would give us adequate results for all the carbohydrates experiments. In order to check whether or not the solution was going to work we performed the Benedicts Test, using two controls-Maltose (+), Sucrose (-)--and the solutions. First we performed the test with a 25% solution (figure 4c), this test failed to provide us with adequate results. So then we performed the test with a 12.5% solution (figure 4b). This one failed as well. Next, we performed the test using a 2.5% solution (figure 4a), which also failed. All of these solutions may have failed due to too much tomato puree or too less of it in the solution. So we decided to try using a 6% solution (figure 5), which provided adequate results.
Using the 6% solution we performed all the carbohydrate tests. The results obtained in each of the tests, showed that both of the varieties were made up of the same sugars (Table 1a-1e). This was very unexpected because the difference in taste of the two tomatoes-grape tomato was sweeter than the common garden tomato (Dunne, 2001). Which led to the inaccurate prediction that the grape and common garden tomato have a different molecular composition.
In the pigment Identification lab, we were able to observe the pigments present in the chloroplasts of each variety of tomato. The Common Garden tomato showed a slightly higher concentration of soluble pigments than did the Grape tomatoes based on the solvent front, and the separation of each color on our chromatography paper (figure 11). This suggests that the Common Garden tomatoes have slightly more locations on which photosynthetic reactions can occur. Since both of the tomato plants from which these leaves were acquired were exposed to virtually the same circumstances, we feel that it is accurate to say that the Grape tomatoes differ from the Common Garden tomatoes in their rates of photosynthesis. When we tested the absorption spectrum of the two tomatoes, the Common Garden Tomatoes demonstrated a similar absorption spectrum to the Grape Tomatoes (figure 2). Both showed peak absorption around 400nm. This suggests that the Common Garden Tomato and the Grape Tomato can make use of light from a similar range of the spectrum. This does not support our hypothesis because it suggests that the two varieties of tomato are similar in this respect
In our last series of tests we evaluated the presence of the enzyme PPO in our two varieties of tomatoes. We first took the pH of our tomatoes using pH paper and slices of our tomatoes, which turned out to be a pH of 5 (Tbale 2) as did the tomato slices containing catechol. (Figure 12) Our data suggests that both tomatoes lack the enzyme PPO. However, through research we found that PPO does in fact exist in tomatoes (Kuldiloke, 2002). Through further testing we found that our tomato solution acts as a PPO inhibitor. (Figure 14) Our negative results may be explained by the possibility of our tomatoes being genetically modified (Table 4). Tomatoes are altered to contain such inhibitors in order to reduce browning after the tomato has ripened. This prolongs its shelf life. (Gonzalez, 1999) This may have lead to our presumably inaccurate results. To make sure that the PPO was not simply being inhibited by the low pH found in tomatoes, we also used the 7.0pH (figure 15) buffer to bring our tomato solutions to an optimum enzymatic pH of 7. This test also yielded no positive results (Table 3).
After all of our testing, we have come to the conclusion that our hypothesis was not strongly supported. The two varieties of tomatoes did not test to be different at the molecular level. They appeared to have the same concentration of sugars, and, by default, the same enzyme activity. However, in support of our hypothesis was the pigment test in the photosynthesis lab. Here we found the Common Garden tomatoes to have more soluble pigments than the Grape tomatoes. This supports our hypothesis by demonstrating a chemical difference between the two varieties of tomato.
Many mistakes can be made while performing experiments. Multiple variables exist, making science never fact. During our pigment identification test, factors such as concentration of the solute, temperature, and pH may have affected our results. Therefore, altering our data and producing weaknesses, which may also skew our statistical analysis.
Throughout our laboratory procedure problems arose such as determining a proper concentration of solution for our carbohydrate tests and searching for PPO in our enzyme tests. Our research helped us to make an educated guess as to why we could not detect enzymes in our tomatoes, and helped us to overcome simple challenges as they arose in the lab.

Figure 11: This figure represents the results of the paper chromatography test. On the right are the results from the Grape tomato leaf and on the left are the results from the Common Garden tomato. On both strips there are a total of four bands of color. The dark green band represents chlorophyll b, the lighter green band represents cholorphyll a, the pale-yellow represents xanthophyll, and the top most orange-yellow band represents carotene. As you can see, leafs from the common garden tomato has a wider range of pigments than the Grape tomato. This may be the case due to the larger surface area of the Common Garden tomato.