Question

During photorespiration oxidation of RUBP by O2 takes place when ..................

• A. temperature is high, light intensity is high and CO2 concentration is low
• B. temperature is low, light intensity is low and CO2 concentration is low
• C. temperature is low, light intensity is high and CO2 concentration is low
• D. temperature is high, light intensity is high and CO2 concentration is high

Hint:

Photorespiration occurs when the concentration of CO2 is low, and O2 is taken up by Rubisco instead of CO2, especially under high temperature and light conditions.

Answer 1

The Correct Option is A

Step 1: Understanding photorespiration.
Photorespiration occurs when oxygen (O2) competes with carbon dioxide (CO2) for binding to Rubisco in plants. This typically happens when temperatures are high, light intensity is high, and CO2 levels are low.
Step 2: Analyzing the options.
(A) temperature is high, light intensity is high and CO2 concentration is low: Correct — This is the condition that promotes photorespiration, leading to the oxidation of RUBP by O2.
(B) temperature is low, light intensity is low and CO2 concentration is low: Incorrect — This combination does not favor photorespiration.
(C) temperature is low, light intensity is high and CO2 concentration is low: Incorrect — Though light intensity is high, low temperature and low CO2 concentration are not conducive to photorespiration.
(D) temperature is high, light intensity is high and CO2 concentration is high: Incorrect — High CO2 concentration prevents photorespiration by allowing Rubisco to fix CO2, not O2.
Step 3: Conclusion.
The correct answer is (A) temperature is high, light intensity is high and CO2 concentration is low, as this condition leads to photorespiration.