Question

the term to describe vascular bundles in which phloem lies at the centre surrounded by xylem

Answer 1

xylem transfer water whereas phloem transfer food materials.

Answer 2

The term used to describe vascular bundles in which phloem lies at the center surrounded by xylem tissues is called amphivasal or leptocentric.

Although seed plants mainly have collateral bundles but some have amphivasal or amphicribral pattern of vascular bundles.

Amphivribral is a pattern in which phloem tissues surround xylem tissues.