Affect of CO2 on photosynthesis : Carbon dioxide acts as a major limitin factor for photosynhesis. The CO2 is 0.03 % in atmosphere and increase in amount of CO2 upto 0.05% in atmosphere increases the rate of photosynthesis. Beyond it the rate declines. It is due to the increase in the temperature.
The C3 and C4 plants responds differently o the CO2 concentration. The C3 plants respond to a higher concentration of CO2 by showing increased rates of photosynthesis while the C4 plants saturate at low level of CO2 and do not show increase in the rate of photosynthesis.