Law of Limiting Factors: When several factors affect any biochemical process, Law of Limiting Factors comes into effect. It was given by Blackman in 1905. This states the following:
If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value: it is the factor which directly affects the process if its quantity is changed.

Light:

There is a linear relationship between incident light and CO2 fixation rates at low light intensities.
At higher light intensities, gradually the rate does not show further increase as other factors become limiting.
The light saturation occurs at 10 percent of the full sunlight.
Hence, except for plants in shade or in dense forests, light is rarely a limiting factor in nature.
Increase in incident light beyond a point causes the breakdown of chlorophyll and a decrease in photosynthesis.

Carbon dioxide:

Carbon dioxide is the major limiting factor for photosynthesis.
The concentration of CO2 is very low in the atmosphere (between 0.03 and 0.04 percent).
An increase in concentration up to 0.05 percent can cause an increase in CO2 fixation rates; beyond this, the levels can become damaging over longer periods.
At high light intensities, both C3 and C4 plants show an increase in the rates of photosynthesis.
What is important to note is that the C4 plants show saturation at about 360 µlL-1 while C3 responds to increased CO2 concentration and saturation is seen only beyond 450 µlL-1.
Thus, the current availability of CO2 levels is limiting to the C3 plants

Temperature:

The dark reactions being enzymatic are temperature controlled.
Though the light reactions are also temperature sensitive they are affected to a much lesser extent.
The C4 plants respond to higher temperatures and show a higher rate of photosynthesis while C3 plants have a much lower temperature optimum.
The temperature optimum for photosynthesis of different plants also depends on the habitat that they are adapted to.
Tropical plants have a higher temperature optimum than the plants adapted to temperate climates.

Water:

Even though water is one of the reactants in the light reaction, the effect of water as a factor is more through its effect on the plant, rather than directly on photosynthesis.
Water stress causes the stomata to close hence reducing the CO2 availability.
Besides, water stress also makes leaves wilt, thus, reducing the surface area of the leaves and their metabolic activity as well.