Question

A concentric amphivasal vascular bundle is that in which

• A. Centrally located xylem is surrounded by phloem
• B. Centrally located phloem is surrounded by xylem
• C. Phloem is flanked by xylem on interior sides only
• D. Xylem is flanked by phloem on exterior sides only

Answer 1

Answer: (B)

Centrally located phloem is surrounded by xylem

Concentric vascular bundles are those in which one vascular element surrounds other on all sides. It is of two types - amphivasal and amphicribal.

When xylem surrounds the phloem tissue from all sides the vascular bundle is called as an amphivasal vascular bundle or leptocentric type. Such bundles are seen in monocot plant, like Dracaena after secondary growth.

When phloem surrounds the xylem tissue entirely, the vascular bundle is called as 'amphicribal vascular bundle' or hadrocentric type. Such vascular bundles are seen in pteridophytes, like Lycopodium, Selaginella.

So, the correct answer is option B.