Xylem is a complex tissue. The cells are thick-walled and many of them are dead cells. Xylem is mainly concerned with the conduction of water and minerals. It also provides mechanical support to the plant. As a conducting strand, xylem forms a continuous channel through the roots, stem, leaves and other aerial parts. Xylem consists of four types of cells—xylem vessels, tracheids, xylem fibres and xylem parenchyma.