For both graphs however, its shows that the depreciation rate between each concentration decreases. For example, using the “Average Length of Roots” graph it can be seen that the gradient between each concentration becomes steadier and steadier as the concentration increases. This shows that inhibition of growth is affected most directly after the 0% concentration.
When looking at the average mass of roots, we can see that it falls from 0.98g to 0g from 10% copper sulphate solution to 0% concentration. There is a substantial drop between 0% Copper Sulphate and 10% showing that on average the best rate of growth for a seed is without the presence of Copper Sulphate.
Conclusion
In my hypothesis, I stated that as the concentration of copper sulphate solution increased, the level of seed germination would decrease. I feel that my results clearly show this and prove my hypothesis correct. The reason for this is because the enzymes used for germination (amylase, maltase, lipases, proteases etc) are indirectly affected by the heavy metal ions, which change the shape of the active site so that the enzyme cannot properly interact with the substrate. This is known as the allosteric affect. Therefore, the more heavy metal ions (higher concentration) the more enzyme ions are affected resulting in less successful enzyme-substrate collisions.
Evaluation
Within this investigation there were many limitations which may have hindered results and caused anomalies.
Firstly, when we measured out the concentrations of coppers sulphate solution, there is already a degree of error of +/- 0.5mm. This may have caused my results to be misleading and encourage false results. However, my results seem to be pretty reliable and when comparing with other members of my class, we have similar results in context to the experiment. Using a burette or another more accurate measuring device for future investigations could prevent or reduce the margin of error.
One factor to consider is that none of the seeds were the same; they may have had different concentrations of enzymes in them etc. This means that some seeds would have had more successful collisions than others causing inaccurate results. Yet, it would not have been possible to do the experiments on just on seed, so natural variation had to become a limiting factor. We therefore had to use quite a few seeds to get a fairly useful set of data.
The seeds we used were kept out of sunlight so that photosynthesis didn’t affect the germination of the seeds. However, we know that sunlight got to them because the door kept opening to see if any germination was taking place. Yet, all the seeds were subject to the same amount of sunlight as the others, so results should not have been affected significantly. If the investigation was carried out again, I would make sure that the experiments were kept sealed away for a certain amount of time before collecting data. So, time could be another controlled variable on the investigation.
Another factor is human error, such as measuring the length of the shoots and roots etc, which has a margin of error of 0.5mm for length and 0.5g for mass. Although these would only be small inaccuracies, the data would still be affected and allow for inaccurate conclusions to be drawn. Doing this investigation again, I would use much more accurate measuring equipment such as scales which are more accurate or maybe just a ruler with smaller scales.
Finally, when we actually sealed the test tubes into the bag, we blew air into it. So we actually blew in CO2, which may have helped germination to occur as plants take in CO2. This may have caused varied results among the seeds because some seeds may have been subjected to more CO2 than others, causing anomalous, inaccurate data. Doing the investigation again, we could use a more suitable method of maintaining the air concentration within the sealed bag.
These factors may have contributed to the varied result for each repeat.
