Why are xylem and phleom called complex tissue?

Explanation

Xylem tissue and phloem tissue both are made up of more than one type of cells and they perform one common function. So they are called complex tissues. Xylem transports water and soluble salts. Phloem tissue mainly transports food.
Xylem and phleom both collect living and dead cells and possess primary or secondery origin.
Xylem is made up of four types of cells. Tracheids, vessels, xylem fibre and xylem parenchyma.
Phleom is made up of (i) sieve tube, (ii) sieve cells (iii) phloem parenchyma and (iv) phloem fibre.