Photorespiration is a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP instead of getting carboxylated. This process reduces the efficiency of photosynthesis by 25% in ${\mathrm{C}}_3$ plants. In it, plants use oxygen and release carbon dioxide as by product that making use of it. Photorespiration is generally found to occur in peroxisome.

It more in common in ${\mathrm{C}}_3$ plants as they have higher ${\mathrm{C}\mathrm{O}}_2$ compensation point due no net evolution of carbon dioxide gas because the rate of photosynthesis (which consumes carbon dioxide) is equal to the rate of respiration (which evolves carbon dioxide).

In a normal photosynthesis process, there is light reaction and dark reaction. In the light reaction, photophosphorylation occurs to generate ATP which will be utilised in making of glucose. The photophosphorylation process occurs in both cyclic and non-cyclic steps with the involved of the photosystem I and II. Dark reaction or light independent reaction process reduces carbondioxide to glucose using the enzyme RuBisCO.