On day 1, the seeds have just begun germinating and therefore the set of results are lower than day 4. However, the 0% tomato juice concentration remains the concentration which induced the most germination of lettuce seeds, having the mean total of 7.81, compared to the mean value of 0 for 100% tomato concentration. These data from the mean values of the group results suggests that the 100% tomato juice did have an effect on the lettuce seeds, and that the dormancy was prolonged, inhibiting germination. The standard deviation data suggests a measure of the dispersion, therefore I can evaluate 100% tomato concentration induces the least amount of germination. The tomato juice concentration at 100%, which is 1.93, indicates a low standard deviation and the data are tightly clustered. The standard deviation of the tomato concentration at 0% is 182.18, so a high standard deviation means that the values are widely scattered. On the graph, the 95% confidence limits of the readings at 0% and 100% overlap, indicating that there is no significant difference between these means. There is no real difference. I have found some anomalies in the group data, where there are vast differences of germinating seeds at the same concentration, for example, 0% tomato juice concentration in day 3 produced 1 seed and 20 seeds germinating. When averaged out, this gives an inaccurate value. Additionally, on day 3, at 100% tomato juice concentration, there was only one set of seeds (13) that had germinated, whereas the rest of the seeds had not germinated. This also gives the wrong average. My results are statistically significant, as they reject the null hypothesis; I have found out that tomato juice does have an effect on the germination of lettuce seeds.
I reject the null hypothesis, because the group results clearly proves that the more concentrated the tomato juice is, the more of the inhibition effect it has upon the germination of the lettuce seeds.
My results show that the more diluted the tomato juice, the germination of the lettuce seeds take place at the normal rate, where the dormancy stage is broken. Less germination will take place in the presence of more concentrated tomato juice. The general trend is, as the concentration of the tomato juice increase, the rate of germination decreases.
Biological Knowledge:
The tomato juice contains an enzyme which inhibits the germination of lettuce seeds. Enzymes are protein molecules, having a three-dimensional globular tertiary structure. 20 different amino acids that occur naturally and make proteins have the same general structure. There is a central carbon atom, to which four groups of atoms are attached. These are an amino group (-COOH), a hydrogen atom (-H) and another group referred as an R group.
Amino acids are joined together by a condensation reaction, where a hydrogen atom is removed from the amino group of one amino acid and this combines with an (-OH) group removed from the carboxylic acid of the other; this forms a water molecule. The bond formed between the two amino acid is called peptide bonds. Long chains are called polypeptide. In the case of the tomato inhibitor enzyme, the long polypeptide chains are folded into alpha helix or beta plated sheets, and then further folded into a three-dimensional globular shape. In these complex shapes, the tertiary structure of a protein is held by chemical bonds between the amino bonds. One type of bond is the disulphide bond, which is formed between amino acids that contain sulphur. When these bonds and the hydrogen bonding are broken, the enzyme has lost its tertiary structure and the active site no longer works. The enzyme is denatured. Additionally, heating a protein causes the bonds that maintain the tertiary structure of an enzyme to collapse, denaturing the enzyme. As a result, the molecule lose their shape and can no longer carry out the function, for example, if the tomato inhibitor enzyme is heated, the enzyme can no longer prevent germination from taking place.
The Germination inhibitor is an enzyme, which is a globular protein and has a complex tertiary structure. Only the substrate specific for the enzyme cause the changes in shape necessary for the enzyme to function, in which the germination process take place. The 100% concentration of tomato juice had the most number of enzymes, therefore, the most number of active sites, in which the reaction can take place, forming an enzyme substrate complex. On the other had, the 0% concentration of the tomato juice had no germination-inhibitor enzymes, so no active sites.
Molecules with a similar shape to the usual substrate can attach itself to the active site, called an inhibitor. This prevents the normal substrate from attaching to the active site, and then forming a reaction. Molecules of the competitive inhibitors block the active site, where fewer molecules of the enzyme are available for the normal reaction, and therefore, the reaction rate is reduced. Some substances inhibit enzyme reactions by attaching itself to a different part of the enzyme. This distorts the active site enzyme so that the substrate can no longer bind with the enzyme. These substances are called non-competitive inhibitors. The shape of the non-competitive inhibitors can be completely different from the usual substrate and the inhibitor may remain permanently attached to the enzyme. The enzyme is therefore useless. In this way, the germination inhibitor achieves maintaining dormancy, and the seed is not allowed to germinate. When the inhibitor is removed, the germination process can occur.
To classify the tomato, species are organised into biological categories, which the tomato comes under the biological kingdom “plantae”. Species are grouped into biological categories of decreasing similarity. The largest category is the biological kingdom, of which there are five.
