What are the main functions of xylem in plants?

Xylem in plants primarily functions to transport water and nutrients from the roots to the rest of the plant.

Xylem is a type of tissue in vascular plants that plays a crucial role in maintaining the plant's water balance. It is essentially the plant's plumbing system, responsible for the upward movement of water and dissolved minerals. This transportation process is known as transpiration pull, which is facilitated by the cohesion-tension theory.

The xylem is composed of several types of cells, including tracheids, vessel elements, xylem parenchyma, and xylem fibres. Tracheids and vessel elements are the water-conducting cells, characterised by their long, tube-like structure. These cells are dead at maturity, allowing for the unimpeded passage of water. Xylem parenchyma aids in the storage and transport of nutrients, while xylem fibres provide structural support.

The xylem's structure is uniquely adapted to its function. The walls of the xylem cells are thickened with lignin, a complex organic polymer that provides mechanical strength and prevents the cells from collapsing under the tension created by the transpiration pull. The end walls of the cells are either partially or completely dissolved, creating a continuous, unobstructed pathway for water movement.

In addition to water transport, the xylem also plays a role in the plant's structural support due to its rigid, woody texture. It forms the bulk of the plant's 'wood' and contributes to the plant's ability to grow tall and withstand various environmental pressures.

In summary, the xylem's main functions are to transport water and nutrients from the roots to the rest of the plant, and to provide structural support. Its unique structure and composition enable it to effectively carry out these functions.