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The aim of this experiment is to determine how the presence of light and the intensity of it contribute to the rate of photosynthesis.

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Introduction

The Rate of Photosynthesis Aim The aim of this experiment is to determine how the presence of light and the intensity of it contribute to the rate of photosynthesis. To accomplish my aim, I will be measuring the rate of photosynthesis of Elodea, a Canadian water plant, under different levels of light intensity and observing the amount of oxygen given off. Introduction Photosynthesis is an organic reaction which plants use to make glucose from Carbon Dioxide, water and light. The equation to this process is: Carbon Dioxide + Water = Glucose + Oxygen 6CO2 + 6H2O = C6H12O6 + 6O2 Photosynthesis is a very important process in nature. It is the production of energy, in the form of glucose, using water from the soil, carbon dioxide from the air and light energy. Oxygen is released during this reaction as the waste product. Photosynthesis takes place in all green plants, which use the green chlorophyll, held in chloroplasts in the leaves, to trap light. The main site of photosynthesis is the Palisade Mesophyll cells in the leaf of a plant. It is these cells that contain the green chloroplasts and are very well adapted to their task. They are near the upper side of the leaf where they can obtain the maximum amount of light. They are packed very closely together and as already mentioned contain green chloroplasts clustered towards the upper side too. Plants photosynthesise to produce food chemicals that are needed to allow them to grow. ...read more.

Middle

Limiting factors: Light, carbon dioxide, temperature, and chlorophyll are all limiting factors, meaning that even when there is surplus of every other variable, the rate of photosynthesis will be limited by the limiting factor until there is an optimal amount of the limiting factor to increase the rate of photosynthesis further. Otherwise, the rate of photosynthesis can no longer increase. Method We need to find out how the of presence light and the intensity of it contributes to the rate of photosynthesis. To be able to measure the rate we need some type of visible sign that photosynthesis is actually taking place. We will use a type of plant that grows in water and produces bubbles when photosynthesising, in our case, Elodea. By counting these bubbles we can tell how fast oxygen is being given off and therefore produced from photosynthesis. We will place the pondweed in a beaker containing water and also a bit of sodium hydrogen carbonate - NaHCO3 (0.5%). This is put in to provide a steady supply of carbon dioxide. If it wasn't there, the pond weed wouldn't get enough carbon dioxide from the tap water to photosynthesise appropriately. By placing the beaker next to a lamp we can alter the light intensity. We will move the lamp further away every time and then count the number of bubbles that are produced within five minutes. To start with, the lamp will be placed 800mm away from the glass sheet. ...read more.

Conclusion

Another way of fixing this problem would be to place a Perspex block between the lamp and the plant, which would absorb most of the heat, while allowing the light energy to pass through. Some of the good points of this experiment were the fact that we repeated each reading, to make the results more accurate, which we then found an average to. We didn't need to repeat it a third time, since, most pairs of the readings were very similar to each other. We could have also made a few recordings of the different measurements of the equipment we used and many other things e.g. the power of the bulb in watts. We could have recorded the amount of the Sodium Hydrogen Carbonate poured into the beaker. And we could have also recorded the room temperature. Although, I believe that this whole experiment should be done over again to solve some of the errors of this experiment, I still believe that it was accurate enough to support and justify my hypotheses. Improvements could have been made as I have stated. To extend my enquiries into the rate of photosynthesis, I could perhaps try to link in some of the other limiting factors to the same experiment, as well as investigating them in their own right. It could also be interesting to explore the effects of coloured lights on the rate of photosynthesis, which could lead to the question of whether or not other types of light, such as fluorescent lights or halogen lights, would have a different effect on the rate of photosynthesis. Created By Syed Aminul Islam, 11Q ...read more.

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