Why are xylem and phloem called complex tissues?

Explanation

The xylem and phloem are called complex tissue because they are made up of different kinds of cells which work together as a unit. Xylem consists of four types of elememts i.e., tracheids, vessels, xylem fibres and xylem parenchyma. Phloem also consists of four types of elements sieve tube elements, companion cells, phloem parenchyma and phloem fibres.