The respiration that occurs in green plants(cells) by the oxygenation process of Rubisco in the presence of light results in the evolution of the excess of co2 is called photorespiration.
Photorespiration was first observed by Decker in 1995. He and his coworker were the first to use the word photorespiration.
It has been reported in the green cells of different plants like Glycine, Chlorella etc. Photorespiration always requires light and its rate maximum between 25-35 degree Celsius. The process also depend on the concentration of oxygen in the mesophyll cell.
Site of photorespiration: The process occur in chloroplast, peroxisomes and mitochondria. The association of these three cell organelles form the site of photorespiration.
Process of Photorespiration: When carbon dioxide conc. is less in the mesophyll cell. The glycolic acid produced as a result of oxidation of ribulose bisphosphate results in the form of 3-phosphoglyceric acid and 2-phosphoglycolic acid in the presence of enzyme Rubisco it catalyze the oxygenation instead of carboxylation.
Rubisco is the most abundant enzyme in the world, its active site can bind both carbon dioxide as well as oxygen. Rubisco has greater affinity towards carbon dioxide than for oxygen this binding is competitive. The relative concentration of oxygen and carbon dioxide determine which of the two will bind to the enzyme.
In photorespiration pathway, there is neither synthesis of sugars, nor of ATP. Rather it results in the release of carbon dioxide with the utilization of ATP. The biological function of photorespiration is not known yet.