The Limiting Factors of Photosynthesis

Limiting factor can be any environment factor e.g., absence of some metabolic reaction or deficiency of light or in avail ability of suitable temperature, CO2, water etc.

Effect of Absence/ Deficiency of Light

The rate of photosynthesis is proportional to light intensity up to a certain limit. As the light intensity increases the rate of reaction also increases but at very high light intensity the rate of reaction doesn’t change.

Effect of Suitable temperature Availability

The process of photosynthesis goes well certain range of temperature. If temperature exceeds this range the reaction retards / stops. Decrease in temperature decreases the rate of reaction.

Effect of CO2 Amount Provided

CO2 is the major reactant of photosynthesis. So, its high amount will induce rate of photosynthesis to increase only when factors are ideally present / available.

Rubiso

Rubiso is an enzyme, which catalyzes the first step of photosynthesis. It has affinity both for Co2 & O2. So in the presence of large amount of CO2, it binds O2 when large concentration of CO2 is available (to bring about respiration). That mean in presence of large amount of oxygen, Rubisco will not be available to catalyze fixation of CO2.

In contrast, if concentration of available CO2 exceeds the threshold level, the stomata get closed & thus rate of photosynthesis declines.