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What factors affect the rate of photosynthesis?

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Introduction

What factors affect the rate of photosynthesis? Photosynthesis is the reaction that is used in plants to produce simple sugars. The equation is: Carbon dioxide + Water Glucose + Oxygen Or 6CO + 6H 0 C H 0 + 6O Photosynthesis takes place in the leaves of the plants. It needs sunlight and chlorophyll to produce food. Without sunlight and chlorophyll plants will not be able to photosynthesise as the energy from the sunlight is needed and to extract it chlorophyll in the chloroplasts is used. The raw materials needed for photosynthesis are carbon dioxide and water which together in the presence of sunlight and chlorophyll produces glucose and oxygen. The sunlight needed for photosynthesis is trapped by the chlorophyll in the chloroplasts of a leaf. To allow maximum surface area of chlorophyll exposed to light the chloroplasts inside the palisade cells are in tight 'pancake' shaped stacks so that there will be more chlorophyll available to absorb light. A chloroplast consists of a double membrane, stroma (dense fluid) and thylakoids (disc like sacs). The chlorophyll is situated on the thylakoids in the chloroplasts so that it is exposed to more sunlight. Leaves of a plant are green as the chlorophyll absorbs all wavelengths of light except green and so reflect it. There are many types of chlorophyll found in different plants but A and B are the most commonly found which strongly absorb blue and red light. Photosynthesis is a complex reaction, having many reactions before the final products are produced. The two main parts to photosynthesis are the light dependant stage and the dark (or light independent) stage. The light dependant stage involves the splitting of water using solar energy. The sunlight is trapped by chlorophyll and converted to electrical energy and then chemical energy. When sunlight comes in contact with chlorophyll an electron becomes energized and uses that energy to split water. ...read more.

Middle

As the bubble is drawn up it is possible to use the graduations to measure the volume of gas produced by the tip of the plant. Here is a picture of the microburette: For this experiment I am going to use the following apparatus: * Microburette * 3% concentration sodium hydrogen carbonate * Aquatic plant - elodea * Water * Light bulb * Stand + clamp * Meter ruler * Scales * 1 large jar * 1 beaker * Light intensity meter * Scales * Jug * Scissors * Stirring rod * Stopwatch I will use the microburette so that my experiment will be accurate when measuring the volume of the oxygen produced. To ensure that carbon dioxide does not become a limiting factor in my experiment I will use a 3% concentration of sodium hydrogen carbonate to water. I am going to use an aquatic plant so that I can see the oxygen being produced as bubbles being released from the tip. As I am using an aquatic plant I will need to place it in water to be able to photosynthesise. To change the light intensities I am going to use a light bulb so that I can move it away from the plant. To keep the microburette in the same position throughout the experiment I will use a stand + clamp. I will need a ruler in this experiment to measure the exact distances for the light bulb to be from the jar which will hold the elodea, the water and sodium hydrogen carbonate inside and keep the experiment as at steady temperature. To measure the amount of sodium hydrogen carbonate I need I will first use a measuring jug to measure the water and then find 3% of that and, using scales and a small beaker, I will measure 3% to be exact. For the experiment I am going to use a light intensity meter to measure the intensity of light reaching the elodea. ...read more.

Conclusion

However, as my results are very similar I do not believe that this caused a problem. In the experiment I found no anomalous results which suggest accurate and reliable results. All of the results for each lux reading were the same except for the first readings but they evened out when I averaged them. I feel that my experiment was very accurate and as a result there is very little I could do to carry out my experiment in a better way. If it had been possible it may have been better to complete the experiment in darkness. This would have meant that the only light reaching the elodea would have been from the light bulb. This is likely to have improved the reliability of the experiment as no extra light could have changed the rate of photosynthesis. However, as the other light was constant it should not have made any effect on my results. The results I received from my experiment are very good and show the reliability of my experiment. I do not know of any way to improve the reliability of my experiment as I had no anomalous results. Also, my results from each experiment were the same except for at 10cm which means that another set of results would not be needed. From this experiment I believe that I have found enough evidence to support a firm conclusion. The experiment shows that as light intensity increases the rate of photosynthesis also increases. Therefore, the light stage of photosynthesis is a quick reaction, quickly splitting water to produce hydrogen and oxygen. My experiment also proves that the oxygen produced is a by product and so released from the plant. To extend my investigation on the rate of photosynthesis I think it may be useful to experiment other factors to see how they affect the rate of photosynthesis. This would ensure that all factors affect photosynthesis in a similar way to light intensity. Sarah Riva 10D 1 ...read more.

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