Answer:
Although the light dependent reactions of photosynthesis are not affected by changes in temperature, the light independent reactions of photosynthesis are dependent on temperature. They are reactions catalysed by enzymes. As the enzymes approach their optimum temperatures the overall rate increases. It approximately doubles for every 10°C increase in temperature. Above the optimum temperature the rate begins to decrease, as enzymes are denatured, until it stops.
Explanation:
At low light intensities, as light intensity increases,the rate of the light-dependent reaction,and therefore photosynthesis generally, increases proportionately (straight line relationship). The more photons of light that fall on a leaf, the greater the number of chlorophyll molecules that are ionised and the more ATP and NADPH are generated. Lightdependent reactions use light energy and so are not affected by changes in temperature.As light intensity is increased further, however, the rate of photosynthesis is eventually limited by some other factor. So the rate plateaus. At very high light intensity, chlorophyll may be damaged and the rate drops steeply (not shown in the graph).Chlorophyll ais used in both photosystems. The wavelength of light is also important. PSI absorbs energy most efficiently at 700 nm and PSII at 680 nm. Light with a higher proportion of energy concentrated in these wavelengths will produce a higher rate of photosynthesis.An increase in the carbon dioxide concentrationincreases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor.As it is normally present in the atmosphere at very low concentrations (about 0.04%), increasing carbon dioxide concentration causes a rapid rise in the rate of photosynthesis, which eventually plateaus when the maximum rate of fixation is reached.
