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Photosynthesis Investigation

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Biology Aim of the Experiment The aim if this experiment is to see if changing one of the variables of photosynthesis will affect the pondweeds rate of photosynthesis. Variables that can affect the rate of photosynthesis: Light duration Photosynthesis is only affected by light duration in that it only occurs during periods of light. Light intensity Very high light intensities may bleach chlorophyll and so make photosynthesis impossible. Carbon dioxide concentration CO2 diffuses into the leaf through the stomata from the atmosphere. This is one of the main things used in photosynthesis and without it photosynthesis can't take place. Temperature Many reactions within photosynthesis are controlled by enzymes and therefore temperature sensitive. Enzymes work best at 37.5? and stop working at about 47? because they start dying. Chlorophyll concentration Chlorophyll is one of the main chemicals used in photosynthesis. Chlorophyll is not normally a limiting factor but it can become one if the levels are abnormally low. Iron, magnesium, nitrogen and sunlight are necessary for chlorophyll production, so if the plant is in an area where there is a little of one of these things then the plant could have a lack of chlorophyll and ?naturally have a lower rate of photosynthesis. ...read more.


The enzymes work best at human body temperature but if they get too hot they start to die and the reaction stops, and if they are too cold they do not have enough energy to take part in the reaction and lie dormant. This is why I think the reaction will cut out at 47?and start at around 15? Method I tried to keep the experiment as simple as possible so that the results would be simple to analyse and see if my prediction is correct. During the experiment the pondweed will be kept underwater. I'm going to add crystals to the water so that there is CO2 for the reaction. I'm going to change the temperature by changing the temperature around the boiling tube that the pondweed is in. To record the rate of photosynthesis I am going to count the number of bubbles of oxygen gas given off by the pondweed. 1. Cut off a piece of pondweed and then place it in a boiling tube of room temperature water. ...read more.


They work best at human body temperature and do not work well in extreme temperatures. Evaluation During this experiment I think that I worked well. While taking the results I think that I could of done a lot better. We only took one set of results. I think that this was a mistake. I had wanted to take 3 different results but I had not done the experiment as efficiently as I could have and only had enough time for one set. If I had done it with three sets like I had wanted I could of averaged out the results and had a better look at how the plant behaves, with only taking one set of results I cannot prove that there are no anomalous results. I think that I put enough effort into my plan but I did want to write up more about my method but because I had kept it simple there was not much else to write. I think that my overall effort in this piece of work is higher than my usual. I have tried to make this a good piece of work but I don't feel that it is long enough or fully shows my understanding of the work. ...read more.

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