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Investigate how light intensity affects the rate of photosynthesis using elodea (pondweed).

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Introduction

Aim: To investigate how light intensity affect rate of photosynthesis using elodea (pondweed). Planning: For this investigation when a pierce of elodea is illuminated 9light) by a lamp (electric) it produces small bubbles of oxygen gas as a result of photosynthesis. The number of bubbles produced per minute can be used as evidence or the measure of the rate of photosynthesis. Background information: Green plants need sunlight. They use the light energy to make a sugar called glucose. Glucose can be converted into another type of sugar called sucrose and carried to other parts of the plant in phloem vessels. Glucose can also be converted into starch and stored. Both starch and sucrose can be turned back into glucose and used in respiration. Photosynthesis happens in the mesophyll cells of leaves. There are two kinds of mesophyll cells - palisade mesophyll and spongy mesophyll. The mesophyll cells contain tiny bodies called chloroplasts, which contain a green chemical called chlorophyll. This chemical is used to catch the light energy needed in photosynthesis. This is the symbol and word equation photosynthesis: 6CO2+12H2O+energy=C6H12O6+6O2+6H2O. Factors affecting rate of photosynthesis: � Temperature � Carbon dioxide � Light intensity Effect of Temperature. ...read more.

Middle

I predict is that the closer the lamp to the pondweed the more bubbles there will be and the further away the lamp is from the pondweed the bubbles will increase. 2) I predict is that the rate of photosynthesis will increase when the lamp is closer and the rate of photosynthesis will decrease when the lamp is far away. 3) I predicted that at 10cm, I will count more bubbles than when it is at 30cm where I will count less bubbles. My predictions are based on previous year 10 elodea photosynthesis results. Fair Test To make this investigation fair I will make sure that I use the same pondweed. I will use same lamp. I will use the same number of watts. I will use the same amount of water and that I will use the same apparatus. If I do not keep these the same then investigation will not be fair and will not give me the right results. Safety: The safety I will use is I will wear gloves to protect my eyes, gloves to keep my hands clean and I will do my experiment standing up to secure my safety of dropping a chair. ...read more.

Conclusion

This meant that the rate of photosynthesis decreased as the light moved further away from the pondweed. This is because photosynthesis is a reaction, which needs energy from light to work, so as the amount of energy available from light increased with the rise in light intensity, so did the amount of oxygen produced as a product of photosynthesis. My graph shows that relationship between the light and the rate of the photosynthesis was a non-linear, as all the graphs produced had a curve. However as I expected in my hypothesis, it does not appear that the curve part on the graphs, the increase in rate is in fact proportional to the light. Evaluation and conclusion Overall my experiment went really well. There was nothing in this experiment, which I could not do. I kept it a fair test as I did not make any changes while I was doing it. I kept everything the same apart from doing the experiment on two different days I think if I had done It all in one day I would have got better result as where was a change over weather over the two days which I done the experiment this may be why I got some anomalous result. ...read more.

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