In root nodules of leguminous plants, the pigment leghamoglobin that gives pink colour to the nodules, is present in the

Options

A. (a) intercellular spaces
B. (b) cytosol of bacteroids
C. (c) inside the bacterial wall
D. (d) outside the peribacterial space in the cytosol of nodule cells.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the location of the pigment leghemoglobin in the root nodules of leguminous plants, which gives them their pink color.

2. **Identifying the Context**: Leguminous plants form root nodules in association with nitrogen-fixing bacteria, such as Rhizobium. These nodules are crucial for nitrogen fixation.

3. **Role of Leghemoglobin**: Leghemoglobin serves two primary functions:
- It provides oxygen to the bacteria for respiration.
- It protects the nitrogenase enzyme from being inactivated by oxygen, as nitrogenase is sensitive to oxygen.

4. **Locating Leghemoglobin**:
- Leghemoglobin is synthesized within the nodule cells of the leguminous plant roots.
- It is not produced by the bacteria themselves, which helps in eliminating options that suggest it is located within the bacteria or their walls.

5. **Evaluating Options**:
- Option A (Intercellular spaces): Incorrect, as leghemoglobin is not located here.
- Option B (Cytosol of bacterioids): Incorrect, as leghemoglobin is not synthesized in the bacteria.
- Option C (Inside the bacterial wall): Incorrect, as leghemoglobin is not found here.
- Option D (Outside of peribacterial space in the cytosol of nodule cells): Correct, as this accurately describes the location of leghemoglobin.

6. **Conclusion**: The correct answer is Option D, which states that leghemoglobin is present outside of the peribacterial space in the cytosol of the nodule cells.

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