Xylem is a type of vascular tissue that transports water and dissolved minerals from the roots of a plant to its leaves. It is one of the two types of vascular tissue, the other being phloem. Xylem consists of dead cells that have thick, lignified cell walls. The lignification of xylem cells makes them strong and resistant to collapse, allowing them to withstand the high pressure that is generated when water is transported up the stem of the plant.

The xylem tissue is made up of three main types of cells:

- Tracheids are elongated, spindle-shaped cells that are arranged end-to-end to form long tubes. Tracheids have thick, lignified cell walls and they are the main water-conducting cells in xylem.

- Vessel elements are similar to tracheids, but they are wider and have thinner cell walls. Vessel elements are also arranged end-to-end to form long tubes, but they are more efficient at transporting water than tracheids because they have larger diameters and fewer cell walls.

- Xylem parenchyma cells are living cells that are found in the xylem tissue. They are responsible for storing water and nutrients, and they can also help to transport water and minerals.

Xylem is a vital tissue for vascular plants, as it allows them to transport water and minerals from the roots to the leaves. This is essential for photosynthesis, which is the process by which plants convert sunlight into chemical energy. Without xylem, plants would not be able to survive.

In addition to its role in transporting water and minerals, xylem also provides structural support for plants. The thick, lignified cell walls of xylem cells make it a strong and rigid tissue, which helps to keep plants upright. Xylem also helps to protect plants from damage by pests and diseases.

The role of xylem in vascular plants can be summarized as follows:

- Transports water and dissolved minerals from the roots to the leaves.

- Provides structural support for plants.

- Helps to protect plants from damage by pests and diseases.