Transport through xylem
Xylem tissue transports water and dissolved mineral ions from the roots towards the stems and leaves. Together with phloem, it forms part of the vascular tissue of a plant.
The water carried in xylem is needed for photosynthesis and maintaining cell structure, while transported mineral ions are used to produce important biological molecules such as proteins and chlorophyll.
Adaptations of xylem vessels
| Feature | Importance |
|---|---|
| Long vessels formed from dead tissue with no cell contents | Leaves a hollow space through which water can move. |
| Open ends with no end-wall barriers | Creates a continuous pathway for water along the vessel. |
| Lignin in the walls | Strengthens the xylem and provides waterproofing. |
| Spiral lignin thickening | Strengthens the vessel wall while retaining flexibility. |
| Pits in the walls | Allow water to move sideways between neighbouring xylem vessels. |
The strengthened xylem vessels also contribute to the structural support of the plant.
Exam Tip: Build a structure–function answer using precise links: open ends → continuous route for water; lignin → strong, waterproof walls; pits → sideways movement between vessels.