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Investigating the Effects of Increasing Copper Sulphate Solution Concentrations on the Germination of Cress Seeds

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Introduction

Investigating the Effects of Increasing Copper Sulphate Solution Concentrations on the Germination of Cress Seeds Hypothesis: I think that as the copper concentrations in the solution rise above natural levels (0.06mg/l), then the seeds will suffer from copper toxic levels, and germination will be stopped. Factors affecting the investigation: * Light availability * Micronutrients availability: copper, zinc, boron, chlorine * Macronutrients availability: nitrogen, sulphur, phosphorus, potassium, calcium, iron, magnesium * Water availability * Temperature * Oxygen availability * Enough time for germination to occur * Enough space for the seeds to germinate Method: Equipment needed (for doing experiment once): * 500ml of copper sulphate stock solution of 60mg/dm-3 * 500ml of pure distilled water * Micropipette * 7 Large Beakers * Stirring rod * 168 clean plant pots, diameter 20cm (7x24) * Cling Film * Filter paper, diameter 20cm * 2520 cress seeds (168x15) * Ruler with millimetre measurements * Glass screen * Needle * Gloves * Digital Thermometer * Magnifying glass Method For Changing Independent Variable: I will change the independent variable, copper concentration, by using a stock solution of 60mg/l. With this stock solution I will use ten fold serial dilutions to make 5 new concentrations of copper sulphate and then I will make a solution of pure water. Each of these will be a solution of 240ml. The final concentrations will be: * 60 mg/l * 6 mg/l * 0.6 mg/l * 0.06 mg/l * 0.006 mg/l * 0.0006 mg/l * 0 mg/l I am going to do this because it will give me differing concentrations which will allow me to run the investigation at the different concentrations which show the effects of the copper on germination. The serial dilution will allow me to create the solutions accurately and easily so there will be no errors in measurements. I am making one at concentration 0.06 so that it is at the natural level that plants will germinate at, to compare them with. ...read more.

Middle

60 6 0.6 0.06 0.006 0.0006 0 60 6 0.6 0.06 0.006 0.0006 0 Having done the 95% confidence standard error test I would reject my null hypothesis. This is because there were significant differences between the means of the number of seeds germinated per concentration at the 5% level of probability. From the standard error test, it shows that there was a 95% chance that the means were significantly different between the concentrations marked above in the table. But because the standard error test is usually suitable for sizes of samples which are at least 30, and unfortunately, due to limitations we could only do 8 repeat samples, this may not be entirely reliable. So I will also do the t-test, which is another test for finding out if there is a significant difference between two means in normally distributed data, but for samples smaller than 25. I will now use the values and the quantities worked out for my manipulated data to work out if the means of the samples are significantly different. As I have worked out the standard errors and the means, I will first use the 95% confidence standard error test. I am using this because it is used to work out if means of different samples are significantly different in normal distribution values. T-Test For the t-test I will compare closely the results from the 60mg/l, 0.06mg/l and 0mg/l tests. This is because the 0.06mg/l is the natural level for cress seeds to germinate in when in their natural environment in the soil. The 60mg/l is the strongest solution of copper sulphate I used, and the 0mg/l is the pure water solution, which shows germination with no excess copper sulphate. Mass of Copper Sulphate Solution (mg/l) Average number of seeds germinated (per batch) Standard Deviation Standard Error 60 1 1 0.4 0.06 13.3 1.8 0.7 0 11.6 3.3 1.2 Table of t distribution Decreasing value of p Degrees of freedom (df) ...read more.

Conclusion

I would also make the seed numbers 20, as this would keep the test statistically viable as the 30 did for the 8 samples, but counting out 30 seeds for 168 different pots is unreasonable for the experiment to be done in time. I would also use an incubator for my tests instead of using glass screens as I planned, or cling film as I had to. This would mean I could keep the temperature constant for the whole experiment and no fluctuations would occur. Therefore, the seeds could be kept at a temperature optimal for the germination of cress seeds. As I had planned I would pierce the cling film with a needle not a stirring rod so that the wholes were small and all the same size. This would be enough for air to get in and out, and for evaporation to be largely prevented form the solution. I would also use a micropipette to take the measurements because this would make them more accurate and so no miss-calculations would be made. These two precautions in procedure, should prevent any pots drying out like they did in the sample number 5 of the 0mg/l of copper sulphate solution in the investigation. As none of the other pots dried out, I would not have to put more solution on each pot to stop it drying out. This would also mean that I could make a lot less of each solution than I would if I was topping up each pot with more solution. I would only need one quarter of what I needed to plan for. I would use different pots (20cm in diameter as planned) for my investigation, so that they were big enough to stop the seeds floating in too much solution and to keep them far enough apart, and small enough to stop the solution being to spread out and shallow in places. If this were not possible I would make less solution (6ml for each pot) and still use the pots which were 15cm in diameter. ?? ?? ?? ?? Owen Laverty 14B ...read more.

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