The nodules present in the leguminous plants appear pink in colour due to the presence of

Options

A. RBCs
B. leghaemoglobin
C. nitrogenase enzyme
D. bacterial secretion.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why the nodules in leguminous plants appear pink in color.

2. **Identifying the Key Components**: The nodules are specialized structures formed in the roots of leguminous plants, which are associated with nitrogen-fixing bacteria known as Rhizobia.

3. **Recognizing the Role of Leghemoglobin**: The pink color of these nodules is primarily due to the presence of a pigment called leghemoglobin.

4. **Function of Leghemoglobin**: Leghemoglobin serves a critical function in these nodules. It is an oxygen-carrying protein that helps maintain an oxygen-free environment, which is essential for the nitrogen-fixing enzyme nitrogenase to function effectively.

5. **Comparing with Hemoglobin**: Leghemoglobin has structural and chemical properties similar to hemoglobin, the oxygen-carrying protein found in red blood cells.

6. **Eliminating Incorrect Options**: The other options provided (RBCs, nitrogenase enzyme, and bacterial secretion) do not account for the pink color of the nodules. Therefore, they can be ruled out.

7. **Conclusion**: The correct answer to the question is that the nodules in leguminous plants appear pink due to the presence of leghemoglobin.

**Final Answer**: The nodules present in leguminous plants appear pink in color due to the presence of leghemoglobin.

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