Plasmodesmata are cytoplasmic bridges between adjacent plant cells, lined by___and often have desmotubules.

Options

A. Apoplasm
B. Plasma membrane
C. Desmosomes
D. ER tubule

Answer

To solve the question regarding what plasmodesmata are lined by, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Plasmodesmata**: Plasmodesmata are microscopic channels that connect adjacent plant cells. They allow for the transport of materials and communication between cells.

2. **Structure of Plasmodesmata**: These channels are formed by the fusion of the cell membranes of adjacent plant cells, creating a bridge of cytoplasm between them.

3. **Components of Plasmodesmata**: Inside the plasmodesmata, there are structures known as desmotubules, which are extensions of the endoplasmic reticulum.

4. **Identifying the Lining**: The question asks what plasmodesmata are lined by. Since plasmodesmata are formed by the fusion of the plasma membranes of adjacent cells, they are lined by the plasma membrane.

5. **Evaluating Options**:
- **Apoplasm**: This refers to the non-living component outside the plasma membrane, so it is incorrect.
- **Plasma Membrane**: This is the correct answer as it lines the plasmodesmata.
- **Desmosomes**: These are structures that anchor cells together, not relevant here.
- **Endoplasmic Reticulum**: While desmotubules are extensions of the ER, they do not line the plasmodesmata.

6. **Conclusion**: Therefore, the correct answer is that plasmodesmata are lined by the plasma membrane.

### Final Answer:
Plasmodesmata are cytoplasmic bridges between adjacent plant cells, lined by the **plasma membrane**.

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