why do green plants evolving carbon dioxide instead of oxygen on a hot sunny day
Answers
On a hot sunny day, the enzyme RuBisCo carries out the oxygenation of RuBP instead of carboxylation. The compound formed is 2- phosphoglycolate which is finally converted into 3-phosphoglyceric acid with the release of oxygen. This process is known as photorespiration. The site for photorespiration is chloroplast, peroxisome and mitochondrion. Photorespiration occurs because the active site of RuBisCo for carboxylation and oxygenation is the same. At high temperature, concentration of dissolved carbon dioxide in equilibrium with air decreases more than cocentration of oxygen which favors oxygenation. Thus, at high temperature RuBisCo functions as a oxygenase and instead of fixing carbon dioxide, oxidises ribulose 1,5-bisphosphate to produce a 3-carbon phosphoglyceric acid and a 2-carbon phosphoglycolate. Phosphoglyceric acid is used up in Calvin cycle.