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# Factors affecting the rate of photosynthesis

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Introduction

Factors affecting the rate of photosynthesis Aims I plan to investigate how different factors affect the rate of photosynthesis. Background Information The rate of photosynthesis is affected by a number of factors including light levels, temperature, availability of water, and availability of nutrients. If the conditions that the plant needs are improved the rate of photosynthesis should increase. The maximum rate of photosynthesis will be constrained by a limiting factor. This factor will prevent the rate of photosynthesis from rising above a certain level even if other conditions needed for photosynthesis are improved. This limiting factor will control the maximum possible rate of the photosynthetic reaction. For instance, increasing the temperature from 10�C to 20�C could double the rate of photosynthesis as the plant's enzymes will be closer to their optimum working temperature. As the temperature is increased, molecules in the cells will be moving at a faster rate due to kinetic theory. If the temperature is raised above a certain level, the rate of photosynthesis will drop as the plant's enzymes are denatured. They will therefore be more likely to join onto the enzymes and react. The amount of water available to the plant will affect the rate of photosynthesis. If the plant does not have enough water, the plant's stomata will shut and the plant will be deprived of CO2. It is difficult in normal lab conditions to prove that water directly affects photosynthesis unless a heavy isotope is used to trace the path of water. ...read more.

Middle

A graph of the rate of reaction against light intensity was drawn. It shows how the amount of CO2 and light affect the rate of photosynthesis. Lines of best fit were drawn for each CO2 concentration to make up for any inaccuracy in any individual result. The line of best fit gives a good picture of how the overall rate of reaction is affected by the light and CO2. Interpretation I will analyse the results for how the amount of light and CO2 affects the rate of photosynthesis. My prediction that the rate of photosynthesis would go up if the light intensity and NaHCO3 levels were increased proved correct. As the elodea absorbed the light and CO2 it produced oxygen gas which increased the pressure in the syringe. This pushed the air bubble in the capillary tube down. The chloroplasts produce ATP and reduce NADP to NADPH2 when exposed to light. It is at this stage of the reaction that oxygen is produced as a waste product. As predicted when the light intensity increases so does the rate of photosynthesis. I predicted that a level would be reached where increasing the light intensity would have no more effect on the rate of reaction as there would be some other limiting factor which limits the rate of the reaction. The rate increases at a steady rate as the light intensity increases until near the end of each line where the rate of increase decreases. ...read more.

Conclusion

The lights are also a source of heat which will affect the experiments with only a small distance between the light and the syringe. this heating could affect the results. Using the same piece of elodea for each experiment was impractical as the elodea's photosynthesis rate decreased over time. By using a different piece of elodea for each experiment did create the problem of it being impossible for each piece to have the same surface area. As the tests took place over a two day period there will be some inaccuracy caused by factors such as temperature. There was no practical way for the long tests to be kept at a totally constant temperature for the two day period and they will probably have cooled down at night and then warmed up in the day leading to a slight inaccuracy. Extension Work This experiment could be improved in a number of ways. It could be repeated more times to help get rid of any anomalies. A better overall result would be obtained by repeating the experiment more times because any errors in one experiment should be compensated for by the other experiments. Each person should have done their experiments in a different room to cut out all background light. All the experiments should be done sequentially. A perspex screen could have been placed between the light and the syringe to reduce any heating effect that the light may have. The experiment could have been carried out with higher NaHCO3 to see if increasing the concentration would increase the rate of photosynthesis, or if a concentration of 0.1M NaHCO3 produces the maximum rate of photosynthetic reaction. ...read more.

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