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How light intensity affects the rate of photosynthesis

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Introduction

How light intensity affects the rate of photosynthesis The aim of my experiment was to determine whether intensity of light would affect the rate of photosynthesis in a plant. To do this, I placed a piece of elodea in varying light intensities, and observed the amount of oxygen being given off. I used elodea because it gives off bubbles from a cut end of a stem. Plan Photosynthesis occurs only in the presence of light, and takes place in the chloroplasts of green plant cells. Photosynthesis is the production of sugar from carbon dioxide and water causing the release of sugar and oxygen. It is a chemical reaction and the chemical equation for it can be written as: Carbon Dioxide + Water ==> Glucose + Oxygen 6CO2 + 6H2O ==> C6H12O6 + 6O2 The chloroplasts in the cells take in the Carbon Dioxide and water and by using sunlight, convert it into glucose and oxygen. The oxygen is released through tiny holes in the bottom of the leaf called stomatas. There are three factors that limit the rate of photosynthesis. These three factors are: * Carbon Dioxide - The more carbon dioxide there is for the plant, the higher the rate of photosynthesis. There can be an unlimited amount of carbon dioxide and the plant will only use what it needs. ...read more.

Middle

Variable I shall keep the same Variables I will change Variables I will measure Throughout the whole experiment, I will use the same piece of elodea, water and Potassium Hydrogen Carbonate and the temperature. Should the water have to be changed due to temperature rise, then the exact same amount of KHCO3 will be used to make sure that extra CO2 is not let off. The distance between the elodea and the lamp will change throughout the experiment to give us the results. I will measure the number of bubbles that appear from the stem of the elodea. This will not be very exact but most of the bubbles are the same size so it will not change the results much. To make this a fair test I will make all the above precautions and make sure that all measurements are recorded with accuracy and care. The amount of CO2 would be hard to measure because we do not know how much is actually being released per bubble. It may be a big bubble and still be counted as "1" bubble. It will be difficult to control how much light the elodea is getting. In the room in which we did these tests, the main lights were on and so that may change our results to a higher rate of photosynthesis. ...read more.

Conclusion

My results matched my prediction and secondary data source. I am happy with the results that we gathered for this investigation. Evaluation My results were accurate enough to make a firm conclusion. This was because I had completed 3 tests for each measurement and taken an average. There are slight things which may have changed the results but these are only minor problems: * The size of the bubbles - these could vary between big and small and no matter what size they were, they were still counted as "one bubble!". To get over this problem, you would have to use a syringe to take in all the CO2 and measure the volume in cm�. * The light in the room - could have sped up the rate of photosynthesis and made our results slightly faulty. To overcome this problem, the experiment should have no background light, just a desk lamp. * Miscounting bubbles - due to human error. This could be overcome by using a syringe to take in all the bubbles, or use a computer to count the bubbles. These could all be changed and improved to make the perfect environment to complete this test in. The results we gathered were that of a fair test. All our recorded measurements came from a single piece of elodea. This test all ran smoothly and there were no unexpected results and no mistakes were made during the test. ...read more.

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