Question

Assertion :Nitrogenase enzyme gets inactivated in presence of oxygen yet $N_2$ fixation occurs In aerobic cells of legume nodules. Reason: Leghaemoglobin allows presence of oxygen just sufficient for cellular respiration only.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false

Answer 1

The correct option is A If both assertion and reason are true and reason is the correct explanation of assertion.

Leghaemoglobin is an oxygen carrier haem protein found in the nitrogen-fixing root nodules of leguminous plants, produced by legumes in response to rhizobia. The presence of oxygen in root nodules reduces the activity of oxygen-sensitive nitrogenase which is responsible for nitrogen fixation. Therefore, leghaemoglobin binds to oxygen and allows the nitrogenase to function but the leghaemoglobin has a high affinity to oxygen which gets provided to bacteria for cellular respiration.

So, the correct option is 'Option A' .