Infection thread during nodule formation in legumer is made up of:

Options

A. cell wall of root hair
B. plasma membrane
C. cell wall and plasma membrane both
D. cell wall of Rhizobium

Answer

**Step-by-Step Solution:**

1. **Understanding Nodule Formation**: Nodule formation in legumes occurs when certain bacteria, primarily nitrogen-fixing bacteria like Rhizobium, infect the root hairs of leguminous plants.

2. **Role of Infection Thread**: The infection thread is a structure that forms from the root hair and serves as a pathway for the bacteria to enter the plant cells. It is crucial for the establishment of symbiosis between the plant and the bacteria.

3. **Composition of the Infection Thread**: The question specifically asks what the infection thread is made up of. The infection thread is not made of the root hair itself, but rather it is formed by the extension of the plasma membrane of the root hair cells.

4. **Clarifying Common Misconceptions**: Many students mistakenly think that the infection thread is made of the cell wall of the root hair. However, while the root hair provides the initial structure, the infection thread itself is derived from the plasma membrane that extends into the thread.

5. **Identifying the Correct Answer**: Given the options, the correct answer to the question is that the infection thread is made up of the plasma membrane. The other options, such as the cell wall of the root hair or the cell wall of Rhizobium, are incorrect.

**Final Answer**: The infection thread during nodule formation in legumes is made up of the plasma membrane.

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