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 involves a symbiotic relationship between legume plants and specific bacteria known as rhizobia.

2. **Role of Root Hairs**: The root hairs of legume plants secrete certain proteins (like lectins) that attract rhizobium bacteria.

3. **Hook Formation**: Under the influence of hormones and Nod factors secreted by rhizobium, the root hairs become hook-like in shape.

4. **Entry of Bacteria**: The cell wall of the root hair breaks at the tip, allowing the rhizobium bacteria to enter the root hair.

5. **Formation of Infection Thread**: Once inside, the plasma membrane of the root hair folds inwards, creating a structure known as the infection thread.

6. **Conclusion**: The infection thread is primarily formed by the folding of the plasma membrane of the root hair, not the cell wall.

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

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