Effects pf tomato juice as a germination inhibitor
...n. I will make each tomato juice solution up to 10cm3 to ensure the seeds receive the same volume of liquid, and water the seeds daily to make sure they have sufficient water. The same variety of tomato will be used throughout to make up the solution, and the seeds will be allowed 14 days to germinate. I shall also use organic tomatoes, to ensure that the inhibition effect is due to chemicals within the tomato and not from pesticides and chemical fertilisers etc used on non-organic tomatoes. Equipment · Petri dishes · Lettuce seeds · Morrisons organic tomatoes · Buchner tunnel and flask · Muslim · Incubator · Filter paper, cut to fit petri dishes Diagram Hypothesis – I predict that greater the concentration of tomato juice, the greater the inhibitory effect that will be seen on the germination of lettuce seeds. Null Hypothesis – There will be no inhibitory effect on the germination of lettuce seeds with any concentration of tomato juice. Adjustments made to initial method From initial testing, I found that 10cm3 of tomato solution was to great a volume of liquid for the petri dishes, and that this much water made the seeds float. In these conditions, the seeds would not have been able to germinate, and so I reduced the total volume of liquid per petri dish to 5cm3, and also used thicker filter paper. I have also decided to increase the number of repeats for each concentration from two to five to give a clearer representation of the proportions germinating at each concentration. Results Percentage tomato juice Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Mean seeds germinated 0 20 19 19 20 18 19.2 20 13 11 10 10 12 11.2 40 6 7 8 5 6 6.4 60 2 3 4 3 5 3.4 80 2 3 1 3 1 2.0 100 0 2 1 0 2 1.0 Accuracy calculations Standard Deviation The standard deviation of results shows how far the results fluctuate from the mean. This is useful to show how close together the results are for each concentration of tomato juice. Standard deviation is calculated from the formula shown below:- SD = x2 - x 2 n n Where x2 is the sum of the values squared and n is the number of values included. When the concentration of tomato juice is 0%, the standard deviation is SD = (202+192+192+202+182) – 19.22 5 SD = (1846/5) – 368.64 SD=0.75 Using the same calculations, I have worked out the other standard deviations to be:- 0% = 0.75 20% = 1.17 40% = 1.02 60% = 1.02 80% = 0.89 100% = 0.89 This shows that the highest variance in the results lies in the middle concentrations, where some seeds are able to germinate and others are inhibited, but at the extreme ends of the concentration range, there is a small standard deviation, as the overwhelming majority of the sample germinate for 0% or die for 100%. Standard error The standard error is useful for results with several sets of data such as with this experiment. It tells us if the differences between the sets are due to chance, or if sampling error is involved. I shall calculate the standard errors for each of the concentrations against the 0% control group, as it is not expected for 100% of the seeds to germinate even in perfect conditions. The standard error can be calculated from the formula:- SE = SD12 + SD22 n1 n2 So for 20% concentration, the standard error is:- 1.172 + 0.752 5 5 therefore SE = 0.27+0.11 = 0.62 Using the same calculations, I can work out the other SE values to be:- 20% = 0.62 40% = 0.56 60% = 0.56 80% = 0.52 100% = 0.52 If these results are significant, it must be ruled out that the decreased germination rate as the concentration of tomato juice rises is due to chance. This can be said to be true if the difference between the mean of the two sets of results is more than twice the standard error, which means there is a less than 5% probability that the results are down to chance. Using these figures, the significance of the 20% tomato juice results can be seen to be:- Difference between means = 19.2-11.2 = 8 2*standard error = 1.24 Therefore the result is significant – the tomato juice has had an inhibitory effect on the germination of the lettuce seeds, even at this low concentration. Percentage concentration of tomato juice Difference between means 2 * standard error Significance 20 8 1.24 Yes 40 12.8 1.12 Yes 60 15.8 1.12 Yes 80 17.2 1.04 Yes 100 18.2 1.04 Yes This shows that in each of my results, the germination has been inhibited by the presence of tomato juice to over 95% certainty, and disproves the null hypothesis. Conclusion The clear negative correlation of the graph and significance proved by standard error tests confirms that tomato juice does in fact have a clear inhibitory effect on the germination of lettuce seeds. This inhibitory effect could be caused by a variety of different things; the tomato juice could contain a directly inhibitory substance in it, used to prevent premature germination of the seeds while still in the fruit. Another possible cause could be that as the tomato breaks down in the petri dish, its seems likely that this decomposition gives acidic product. The enzymes within the seed can only work within a small range of PH values, generally around PH 7. This shift towards more acidic conditions could prevent the enzymes from working and so the seed germinating. The juice of the tomato itself is also acidic, so the greater concentration of it within the seeds growing environment, it seem logical the worse the conditions for the growth of the seed. The rotting tomato matter could also have been host to parasitic growth and bacteria, and the warm damp conditions would also have encouraged fungus growth. All of these things could have fed on not only the decomposing tomato, but the nutrients within the seeds food store, destroying the seed, and also would have been competition for the water etc without which no germination can occur. As well as the prevention of the enzymes working, the hormone gibberellins could be suppressed by either a possible inhibitor in the tomato juice, or a lack of available water due to competition from a fungus. Gibber...