Question

What is the function of leghemoglobin present in root nodulus of leguminous plants?

• A. Inhibition of nitrogenase activity
• B. Removal of oxygen
• C. Nodule differentiation.
• D. Expression of nif gene

Hint:

Think of leghemoglobin as the nodule's "security guard" for the nitrogenase enzyme. Its job is to keep the enemy (free oxygen) away from the enzyme so it can do its work, while still letting the bacteria breathe.

Answer 1

The Correct Option is B

Step 1: Concept Overview:
The question concerns the role of leghemoglobin, a protein in root nodules of nitrogen-fixing legumes.
Step 2: In-Depth Explanation:
Nitrogen fixation by symbiotic bacteria (Rhizobium) requires a high ATP production via aerobic respiration, which necessitates oxygen. However, the nitrogenase enzyme, crucial for nitrogen fixation, is highly oxygen-sensitive and irreversibly deactivated by it.
Leghemoglobin addresses this issue. Functioning like hemoglobin, it binds oxygen, imparting a pink/red hue to active nodules. It acts as an "oxygen buffer" by binding free oxygen, maintaining a low O\(_2\) concentration. This protects nitrogenase while ensuring oxygen supply to the bacteria for respiration.
Consequently, leghemoglobin's role is to effectively remove free oxygen from the vicinity of the nitrogenase enzyme.
Step 3: Concise Answer:
Leghemoglobin removes free oxygen to safeguard the nitrogenase enzyme.