Question

What is called Warburg's effect on photosynthesis?
A. Low rate of process due to $O_2$ supply
B. Low rate of process due to $CO_2$ supply
C. Both A and B
D. None of the above

Answer 1

The Warburg effect is a decrease in photosynthetic rate caused by high oxygen concentrations in plants. Oxygen is a competitive inhibitor of RuBisCO’s carbon dioxide fixation, which is required for photosynthesis to begin. Additionally, oxygen promotes photorespiration, which lowers photosynthetic production. The Warburg effect is caused by these two mechanisms functioning together.

Complete answer:
Low rate of process due to $O_2$ supply: The Warburg effect is the photosynthesis-inhibiting effect of high oxygen concentrations. The German scientist Warburg discovered that high levels of chlorella alga hinder photosynthesis, and this inhibition of photosynthesis by increasing concentration is known as Warburg’s effect. Hence option A is the correct answer.
In isolated spinach chloroplasts, increasing levels have been found to increase photosynthesis rate, abolish oxygen inhibition of photosynthesis, and decrease glycolate production.
Low rate of process due to supply: Warburg effect is caused by oxygen supply and not carbon dioxide supply. Hence option B is not correct.
Both A and B: Since only option A is correct, option C is wrong.
None of the above: Since option A is correct, option D is wrong.

Hence, option A. Low rate of process due $O_2$ to supply is the correct answer.

Note:
The Warburg effect is a decrease in photosynthetic rate caused by elevated oxygen levels. In the process of photosynthesis, oxygen is released as a by-product. When the concentration of oxygen rises, photosynthesis is suppressed and photorespiration is stimulated. This can be avoided by boosting carbon dioxide levels in the atmosphere, which stimulates photosynthesis.