Question

Why is the xylem considered as one way road and phloem double way road?

Answer 1

xylem is considered as one way road since it carries water from roots to leaves and in one direction only that is down to up
and phloem is considered as double way because it transport food from leaves to other parts of plants that is down to up and up to down.

hope it helps :)

Answer 2

because xylem helps in transport of materials only vertically upward but phloem transport materials in both vertically upward downward as well as horizontal.