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An experiment to show the relation between light intensity (voltage) and photosynthesis

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An experiment to show the relation between light intensity (voltage) and photosynthesis Introduction Photosynthesis takes places in the leaves of plants, mostly in the palisade layer of the leaf. Photosynthesis is the plants way of creating energy for itself(sugar), for growth, repair, storage and energy production. The test will be to find out the relationship between light intensity (voltage) and the rate of photosynthesis. Photosynthesis is: Carbon dioxide + water + sunlight ---> oxygen + carbohydrate + water Or 6CO2 + 12H2O + sunlight ---> 6O 2 + C6 H12O 6 + 6H2 O Oxygen is a product of photosynthesis; therefore we will be measuring the amount or rate of this product being produced. Plan and Pulmonary test Prior to the official test I conducted a pulmonary test. This was so that I could identify any initial problems and work out how to resolve them. Some problems I encountered where; that the plant clearly took a few minutes to adjust to its optimum rate of photosynthesis at the specific light intensity. In order to combat this problem in the official test I would leave the plant subjected to the required light intensity for 3 minutes prior to measuring and recording the volume of oxygen produced. To allow it to photosynthesise at its optimum rate. ...read more.


2 X h. Prediction I predict that the light intensity (controllable by volts) will be directly in proportion to the rate of photosynthesis. Until the light intensity is no longer a limiting factor and there is another limiting factor(s) i.e. Carbon dioxide. I predict that the rate of photosynthesis will increase in proportion to the light intensity as long as there are no other limiting factors. This is because the plant seeks to perform photosynthesis in order to stay alive; the plant will photosynthesise at the optimum rate in the conditions provided. I believe that above a certain light intensity the plant will no longer be able to increase its rate of photosynthesis as there is another limiting factor. i.e. light intensity will no longer be a limiting factor and there will be another factor limiting the rate of photosynthesis e.g. temperature or There will also be a point at where the temperature of the water becomes so hot that the chloroplast cells would de-nature. I predict that if I where to make a graph of my results with voltage along the x axis and amount of oxygen produced per minute along the y axis, I predict that the graph would look like this: The Equipment I will use * 1 retort stand * 1 12 watt bulb (with variable intensity) * 1 lux meter (light intensity meter) ...read more.


2 2.35 3.14 2.35 2.6 0 0 0 0 0 Evaluation If there was any way I could have made the test any fairer it would have been to prevent temperature from becoming a variable, I would have done this probably by placing the entire experiment in a huge test tube this test tube would have a flow of water running through it to remove heat and prevent temperature from changing. This test tube would also be acting as the beaker. I could make this experiment more accurate by questioning weather all of the oxygen is contributing to the down force pushing bubbles down. Some of the oxygen may be dissolved in the water and I could find a more accurate way of measuring the distance travelled by the bubbles. Also I could have positioned a volt meter in between the transformer and the lamp to get an exact measurement of the voltage used. Also temperature was a variable so using the above method of a large water bath test tube could prevent this. I did not encounter any anomalous results but my graphs do not show the plateau, or flatting out that I described. This is because the light was still a limiting factor and the higher voltages where not capable and therefore could not be tested. ?? ?? ?? ?? William Biggs Tuesday, 01 May 2007 ...read more.

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