The reverse flow of water in to the lower tracheid is checked by

Options

A. closing membrane
B. pit chamber
C. margo
D. torus

Answer

To solve the question regarding what checks the reverse flow of water in the lower tracheid, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Tracheids**:
- Tracheids are elongated cells found in the xylem of vascular plants. They are responsible for the conduction of water and minerals from the roots to the rest of the plant.

2. **Identifying the Problem**:
- The question asks what prevents the reverse flow of water in the lower tracheid. This is important for maintaining the upward movement of water.

3. **Analyzing the Options**:
- The options provided are:
- A) Closing membrane
- B) Pit chamber
- C) Margo
- D) Torus

4. **Understanding Each Option**:
- **Closing Membrane**: A thin membrane that can cover the pit but does not primarily prevent reverse flow.
- **Pit Chamber**: The area where the pits are located; it does not actively prevent reverse flow.
- **Margo**: A structure made of microfibrils that supports the torus but does not prevent reverse flow on its own.
- **Torus**: A convex structure that can move in response to pressure changes. It acts as a valve to prevent backflow of water.

5. **Conclusion**:
- The torus is the structure that checks the reverse flow of water in the lower tracheid. It can move in response to pressure differences, effectively sealing the pit and preventing backflow.

6. **Final Answer**:
- The answer is D) Torus.