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The Rate of Photosynthesis From a Plant In Water.

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Introduction

Photosynthesis AT1 AIM: My aim is to investigate the rate of photosynthesis from a plant in water. There are many factors that would affect this. I am going to use light. BACKGROUND KNOWLEDGE: Photosynthesis is a process in which green plants use the energy of light to convert carbon dioxide and water into glucose. This is the basic energy source for virtually all organisms. A by-product of this process is oxygen on which all organisms depend. In the leaves and the green stems of plants is where photosynthesis takes place, within specialised cell structures called chloroplasts. The chloroplast is divided by membranes into disk like compartments called thylakoids and embedded in the membranes of these is chlorophyll, a light trapping pigment needed for photosynthesis. The chloroplast traps light energy and converts it to chemical energy then hydrogen atoms help form the glucose and then it is synthesised. EQUATION: Glucose + oxygen -> carbon dioxide + water + energy CO H12O6 +6 O2 -> 6 CO2 + H2O + ENERGY LIMITING FACTORS: If a plant is given plenty of sunlight, carbon dioxide and water, the rate at which it can photosynthesise is its own ability to absorb these materials and make them react. However quite often plants do no have unlimited supplies of these materials, and so their rate of photosynthesis is not as high as it might be. ...read more.

Middle

Then we decided on the distances that we were going to place the lamp from the plant. We used the clamp to hold the test tube and then set the lamp 5cms away from it and switched it on. As soon as we switched it on we started the stopwatch and we counted the number of bubbles that appeared for one minute, then we stopped the stopwatch and recorded the results in our results table. We did this three times to make sure it was fair. When we finished that length we moved the lamp ten cms away from the test tube and did the experiment again. SAFETY: There are a few safety rules that we needed to follow very carefully, to prevent serious injury. The lamp, when switched on, could become hot, which could be dangerous. Also the water may heat up from the intense heat from the lamp, so we must be careful not to spill it as serious injury could occur. Water and electricity do not mix so we had to be careful that our hands weren't wet when switching the lamp on. RESULTS: 5 cm 15cm 25 cm 35 cm 45 cm 1st 60 41 20 15 13 (plant 1) 2nd 52 43 32 25 19 3rd 67 39 26 5 1 1st 35 39 24 17 16 (plant 2) ...read more.

Conclusion

If we wanted to use the same method but improve it we could involve more people so that we would be able to check we had counted the bubbles correctly. Also we would need to control the background light as it would interfere with the experiment, but we didn't have the means for it this time. Because of all these problems the strange results we got are very likely to be accuracy problems when counting the bubbles. It isn't a fair test to have one person counting them all because they might not count properly, but a way of solving this is to have a few people counting so that the results would be more exact. The background lighting interferes because it adds to the rate of photosynthesis when we want to be testing from a certain light intensity. We managed to keep the temperature pretty much the same for the whole experiment, it dipped between 23c and 25c, so even though we did as best as we could, if there was a way of keeping a constant level temperature it would make the test a lot more fair. An even better way of improving this experiment would be under properly controlled conditions where we wouldn't need to rely on someone having to count the bubbles, and we could use more reliable tools. Michelle Ravenor 10S/X1 ...read more.

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