Question

Photorespiration is favoured by

• A. high $O_2$ and low $CO_2$
• B. low light and high $O_2$
• C. low temperature and high $O_2$
• D. low $O_2$ and high $CO_2$

Answer 1

Answer: (A)

high $O_2$ and low $CO_2$

Answer 2

Photorespiratory loss of $CO_2$ occurs when RuBisCo starts functioning as an oxygenase instead of carboxylase under conditions of high $O_2$ and low $CO_2$. It involves three organelles chloroplast, mitochondria and peroxisomes. Half of the photosynthetically fixed carbon (in the form of RuBP) may be lost into the atmosphere through this process and no ATP formation occurs.