Effect of varying light intensity:

The rate of photosynthesis varies with light intensity. It decreases as the light intensity decreases and increases as the intensity increases. However, at a much higher light intensity, the rate of photosynthesis becomes constant.

Effect of varying temperature:

The rate of photosynthesis decreases with a decrease in temperature. It increases as the temperature is increased over a limited range. But if the light intensity is low, increasing the temperature has little influence on the rate of photosynthesis.

Effect of varying carbon dioxide concentration:

As carbon dioxide concentration rises, the rate of photosynthesis goes on increasing until limited by other factors. The initial enzyme of dark reactions, which combines carbon dioxide with a 5-carbon compound, has a binding affinity for both carbon dioxide and oxygen. When the concentration of carbon dioxide is high, the enzyme will capture carbon dioxide. However, if the oxygen concentration is high, it will bind oxygen instead of carbon dioxide and there would be no photosynthesis. An increase in carbon dioxide concentration beyond a threshold level causes the closure of stomata and decreases the rate of photosynthesis.