87. Which one among the following is the correct function of leghaemoglobin?
A. It sequesters oxygen to facilitate nitrogen fixation
B. It protects nitrogenase from 𝐶𝑂2
C. It facilitates the supply of 𝐶𝑂2 to nitrogen fixing bacteria
D. It binds to nitrogen and moves it out of the nodule

Detailed Explanation:

Leghaemoglobin is a plant hemoprotein found in the root nodules of leguminous plants. It plays a critical role in the biological nitrogen fixation process, which is facilitated by symbiotic Rhizobium bacteria.

What Is Nitrogen Fixation?

Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into ammonia (NH₃), which plants can use for growth. This process is catalyzed by the enzyme nitrogenase, which is highly sensitive to oxygen.

Role of Leghaemoglobin:

• Leghaemoglobin binds to oxygen molecules in the root nodules with high affinity.

• By sequestering free oxygen, it maintains a low-oxygen environment, which is essential because:

  • Nitrogenase is inactivated by oxygen.

  • At the same time, bacteria need oxygen for their own respiration and energy needs.

Leghaemoglobin acts as a buffer—it allows controlled oxygen supply for respiration while shielding nitrogenase from oxygen toxicity.

Correct Answer:

A. It sequesters oxygen to facilitate nitrogen fixation