Xylem is generally considered dead at maturity, although some living cells are also present within the xylem tissue.
Here's a more detailed explanation:
Xylem is a complex vascular tissue in plants responsible for transporting water and minerals from the roots to the rest of the plant. It's composed of several cell types, including:
- Tracheids: These are elongated, dead cells with tapered ends. They have pits that allow water to move from one tracheid to another.
- Vessel elements: These are also dead at maturity and are wider and shorter than tracheids. They connect end-to-end to form long tubes called vessels. Perforations in their end walls allow for more efficient water transport.
- Xylem parenchyma: These are living cells that store food and help in lateral water transport.
- Xylem fibers: These provide structural support to the xylem tissue, and are typically dead at maturity.
While tracheids, vessel elements, and xylem fibers are dead when they are fully functional, contributing to the water transport and structural support functions, xylem parenchyma cells remain alive. The presence of these living parenchyma cells is crucial for the overall function of xylem, as they help in processes such as repair, storage, and sometimes even lateral water transport.
Therefore, even though xylem contains living parenchyma cells, the primary water-conducting elements (tracheids and vessel elements) are dead. Since water transport is the primary function of xylem, it is often described as a dead tissue.
In summary:
| Cell Type | Living/Dead at Maturity | Primary Function |
|---|---|---|
| Tracheids | Dead | Water transport, structural support |
| Vessel elements | Dead | Water transport, structural support |
| Xylem parenchyma | Alive | Storage, repair, lateral water transport |
| Xylem fibers | Dead (typically) | Structural support |
