Which xylem element have highly thickened walls and obliterated central lumen?

Answer

To answer the question "Which xylem element have highly thickened walls and obliterated central lumen?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- The term "obliterated central lumen" refers to a condition where the central cavity of the cell is either reduced or completely filled, leading to the absence of a functional lumen.
- "Highly thickened walls" indicates that the cell walls of the xylem element are significantly reinforced, often due to the deposition of lignin.

2. **Identify Xylem Elements**:
- The primary xylem elements include tracheids, vessel elements, and xylem fibers.
- Each of these elements has distinct characteristics related to their structure and function.

3. **Analyze the Characteristics**:
- **Tracheids**: These are elongated cells with thick walls and are involved in water conduction. They have a central lumen, but it is not obliterated.
- **Vessel Elements**: These are also involved in water conduction and have a larger lumen compared to tracheids. They do not have obliterated lumens.
- **Xylem Fibers**: These are supportive cells with very thick walls. They are known for their lignification and can have obliterated lumens due to the thickness of their walls.

4. **Conclusion**:
- Based on the analysis, the xylem element that has highly thickened walls and an obliterated central lumen is the **xylem fiber**.

### Final Answer:
The xylem element with highly thickened walls and obliterated central lumen is **xylem fiber**.

---