Answer:
The walls of xylem cells are lignified (strengthened with a substance called lignin). This allows the xylem to withstand pressure changes as water moves through the plant.
Explanation:
The xylem transports water and minerals from the roots up the plant stem and into the leaves.
In a mature flowering plant or tree, most of the cells that make up the xylem are specialised cells called vessels.
Vessels:
- Lose their end walls so the xylem forms a continuous, hollow tube.
- Become strengthened by a chemical called lignin. The cells are no longer alive. Lignin gives strength and support to the plant. We call lignified cells wood.
- Transport in the xylem is a physical process. It does not require energy.
