The Effect of Light Intensity on the Rate of Photosynthesis
Aim
I aim to investigate the effect of light intensity on the rate of photosynthesis in pondweed.
Development of Research Question
Primary production is the production of organic compounds from atmospheric or aquatic carbon dioxide, principally through the process of photosynthesis.
Photosynthesis is the process by which green plants use the energy from sunlight to produce food compounds from carbon dioxide and water. It is how plants feed themselves. The conversion of unusable sunlight energy into usable chemical energy is associated with the actions of chlorophyll.
The chemical expression of photosynthesis is:
H2O + CO2 -----> C6H12O6+ O2
When green plants photosynthesize, they take in CO2 and give out O2. This only happens in daylight when light is available as an energy supply. In darkness O2 is taken in and CO2 is given out, which means there is no photosynthesis; in bright light, CO2 is taken in to use for photosynthesis and the CO2 made from the plant’s respiration is also used to make O2. Therefore, as the light intensity increases, the rate of photosynthesis increases, until the plant reaches the light saturation point (LSP) and cannot photosynthesize any faster, even when the light gets brighter. According to Blackman’s Law, “the factor in least supply will be the limiting factor”, so this means CO2, H2O or temperature will be the limiting factor.
Similarly, as the amount of CO2 available increases, the rate of photosynthesis increases, until the plant reaches the CO2 saturation point (CSP). If both CO2 and light supply are increased together, the rate of photosynthesis will level out. Therefore either H2O or temperature is limited.
At a lower temperature, the rate of photosynthesis is increasing with increasing light intensity or the availability of carbon dioxide, but the LSP or CSP is quickly reached. At a higher temperature, the rate of photosynthesis increases...