Given below are two statements, one is labelled as Assertion (A) and other is labelled as Reason (R):
Assertion (A): Leg-haemoglobin in nodules of legumes plays an important role in biological nitrogen fixation.
Reason (R): It protects the nitrogen (N₂) fixing enzyme, nitrogenase, from oxygen.
Select the correct answer using the options given below:

Correct option is B

The correct answer is: (b) Both (A) and (R) are true and (R) is the correct explanation of (A)
Explanation
Assertion (A): Leg-haemoglobin is important in nitrogen fixation - TRUE Leg-haemoglobin is a red pigment found in the root nodules of leguminous plants. It helps create the ideal low-oxygen environment required for nitrogen fixation.
Reason (R): It protects nitrogenase enzyme from oxygen - TRUE The enzyme nitrogenase, which fixes atmospheric nitrogen (N₂), is extremely oxygen-sensitive. Even small amounts of oxygen can inactivate it. Leg-haemoglobin binds oxygen and maintains very low oxygen concentration in nodules → enabling nitrogen fixation.
Is (R) the correct explanation of (A) YES Leg-haemoglobin's key role is to protect nitrogenase from oxygen, which allows nitrogen fixation to occur.
Thus, both statements are true, and R explains A.
Additional Information
· Leg-haemoglobin gives nodules their pink/red colour.
· Nitrogenase reduces atmospheric nitrogen into ammonia (NH₃).
· Rhizobium bacteria form symbiosis with legumes for nitrogen fixation.