Unlike tracheids, vessel elements -

Options

A. Function when dead
B. Are spindle shaped
C. Are found primarily in gymnosperms
D. Lose part or all of the end walls

Answer

**Step-by-Step Solution:**

1. **Understanding the Structures**: Begin by recognizing the two types of water-conducting cells in vascular plants: tracheids and vessel elements. Both are involved in the transport of water and minerals.

2. **Functionality When Dead**: Both tracheids and vessel elements function when they are dead. This means that the first option stating that vessel elements function when dead is incorrect as it applies to both types.

3. **Shape of the Cells**: Tracheids are generally elongated and tapered at the ends, while vessel elements are typically shorter and wider. The second option claiming vessel elements are spindle-shaped is also incorrect.

4. **Distribution in Plant Groups**: Tracheids are found in both gymnosperms and angiosperms, whereas vessel elements are primarily found in angiosperms. The third option stating that vessel elements are found primarily in gymnosperms is incorrect.

5. **End Walls of the Cells**: The key difference lies in the structure of the end walls. Tracheids have solid end walls that are not perforated, while vessel elements have either perforated end walls or completely lack them. This allows for more efficient water transport in vessels. Therefore, the fourth option, which states that vessel elements have lost part or all of the end walls, is correct.

6. **Conclusion**: Based on the analysis, the correct answer is option 4, as it accurately describes a significant difference between vessel elements and tracheids.