Why are xylem and phloem called complex permanent tissue ? What are their chief constituents ? Also, mention their role.

Explanation

These are a group of more than one type of cells having a common origin and working together as a unit to perform a common function. Both xylem and phloem are together called vascular tissues.
Xylem is composed of (i) Tracheids (ii) Vessels (iii) Xylem parenchyma , and (iv) Xylem fibres.
It is the major conducting tissue. It serves in the upward movement of water and mineral salt fromo root to different aerial parts of the plant.
Phloem is composed of (i) Sieve tubes (ii) Companion cells (iii) Phloem parenchyma , and (iv) Phloem fibres. Phloem is the chief food conducting tissue of vascular plants. It is responsible for translocation of organic solutes from leaves to all other plant body parts.