Light Intensity On Photosynthesis Essay

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Aim: To investigate the effects of different light intensities on photosynthesis in plants BACKGROUND INFORMATION: Aquatic plants can be used to demonstrate oxygen evolution in the process of photosynthesis. In theory, when an aquatic plant is placed in a solution containing a source of carbon dioxide (CO2), in the presence of light of appropriate intensity, the plant will photosynthesise and produce bubbles of oxygen-containing gas. These bubbles can be counted and the rate of bubbling can serve as an indication of the rate of photosynthesis. When the light intensity is increased, the rate of bubble production should increase. Decrease the light intensity and the rate of bubbling should decrease. Remove the light source altogether, or…show more content…
At low light intensity, water will not undergo photolysis and therefore will not produce O2 as a by product. As the light intensity increases, more electrons are energised in the reaction centre of the photosystem, and so more photolysis occurs to replace the high energy electron, thus releasing more oxygen which can be detected as more bubbles.2 At the highest light intensities it is possible that the number of bubbles will plateau, as photosynthesis can be limited by several factors: light intensity, temperature, and carbon dioxide concentration. The rate of photosynthesis is unlikely to continue increasing even with high light intensities because e.g. carbon dioxide concentrations may not be optimal. Photosynthesis also requires CO2 to be present as a solution of dissolved CO2. Light is absorbed by chlorophyll during photosynthesis, in the blue/green spectrum. White light provides these wavelengths, so using a normal light bulb (white light) without filters is sufficient. Simplistic graph to show relation of light intensity and CO2 concentration on photosynthesis

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