Question

Decreased rate of photosynthesis at high concentration of $O_2$ is referred to a

• A. Pasteur effect
• B. Emerson effect
• C. Warburg effect
• D. Richmond Lang effect

Answer 1

Answer: (C)

Warburg effect

The concentration of oxygen in the atmosphere is about 21 percent by volume and it seldom fluctuates. An increase in oxygen concentration decreases photosynthesis and the phenomenon is called Warburg effect. The explanation to Warburg effect lies in the phenomenon of photorespiration. In $C_3$ plants the rate of light respiration is faster than the dark respiration. This enhanced rate of respiration is called as photorespiration. It operates in high light intensity, high oxygen concentration and high temperature. Here oxygen competes with carbon dioxide for the oxidation of RUBP to phosphoglycolic acid, thus reducing the net fixation of carbon dioxide.