Question

Why is xylem and phloem known as complex tissue ??

Answer 1

as the xylem and phloem are made up of more than one type of cells as shown below,,

xylem : trachieds
vessels
xylem parenchyma
xylem sclerenchyma

phloem : sieve tubes / sieve cells
companion cells
phloem parenchyma
phloem sclerenchyma

Answer 2

Xylem and phloem are known as complex tissues as they are made up of more than one type of cells. These cells work in a coordinated manner, as a unit, to perform the various functions of the xylem and phloem. ... Sieve tube elements are tube-like elongated structures associated with companion cells.