A limiting factor is defined as a factor which is deficient to such an extent that increase in its magnitude directly increases the rate of the process. The effect of limiting factors was studied by Blackman in 1905. Blackman (1905) studied the effect of CO2concentration, light intensity and temperature on rate of photosynthesis. He formulated the principle of limiting factors which states that when a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the slowest factor.