RE: Explain the limiting factors with reference to light intensity, carbo dioxide affect the rate of photosynthesis?
A limiting factor is a factor that controls a process. Light intensity, temperature and carbon dioxide concentration are all factors which can control the rate of photosynthesis. Usually, only one of these factors will be the limiting factor in a plant at a certain time.
This is the factor which is the furthest from its optimum level at a particular point in time.
If we change the limiting factor the rate of photosynthesis will change but changes to the other factors will have no effect on the rate.
If the levels of the limiting factor increase so that this factor is no longer the furthest from its optimum level, the limiting factor will change to the factor which is at that point in time, the furthest from its optimum level.
For example, at night the limiting factor is likely to be the light intensity as this will be the furthest from its optimum level. During the day, the limiting factor is likely to switch to the temperature or the carbon dioxide concentration as the light intensity increases.
So how the light intensity factor have an effect on the rate of photosynthesis? When the light intensity is poor, there is a shortage of ATP and NADPH, as these are products from the light dependent reactions.
Without these products the light independent reactions can’t occur as glycerate 3-phosphate cannot be reduced. Therefore a shortage of these products will limit the rate of photosynthesis.
When the carbon dioxide concentration is low, the amount of glycerate 3-phosphate produced is limited as carbon dioxide is needed for its production and therefore the rate of photosynthesis is affected.
Finally, many enzymes are involved during the process of photosynthesis. At low temperatures these enzymes work slower. At high temperatures the enzymes no longer work effectively. This affects the rate of the reactions in the Calvin cycle and therefore the rate of photosynthesis will be affected.