(c) : Photorespiration is the light dependent process of oxygenation of ribulose biphosphate (RuBP) and release of carbon dioxide by the photosynthetic organs of a plant. It leads to oxidation of considerable amount of photosynthetic products to CO2 and H2O without the production of useful energy. Photorespiration occurs only in C3 plants because at high temperature and high oxygen concentration RuBP carboxylase changes to RuBP oxygenise. Photorespiration is absent in C4 plants. Peroxisome and mitochondria are required for completing the process.