Q. Radical vascular bundles are those in which

Explanation by: Bhakti Bliss

In plants, vascular bundles are the arrangements of xylem and phloem tissues that transport water, nutrients, and food throughout the plant. The arrangement of these vascular bundles can vary depending on the type of plant and the organ (stem, root, leaf, etc.).
In the case of radical vascular bundles, which are commonly found in roots, the xylem and phloem are positioned in such a way that they occur on different radii. This means that:
The xylem is typically positioned towards the center of the vascular bundle (closer to the core of the root).
The phloem is located on the outer side of the xylem, usually towards the periphery or outer part of the root.
This type of arrangement is characteristic of the root because the root structure is designed to absorb water and nutrients from the soil and transport them upward. The arrangement of the vascular bundles in the root helps in the efficient movement of these substances.
Here’s a breakdown of the other options:
(A) Xylem is surrounded by phloem: This is not true for radical vascular bundles, as it suggests a different type of vascular bundle arrangement found in some stems or leaves, but not typically in roots.
(B) Phloem is surrounded by xylem: This arrangement is often seen in collateral vascular bundles found in some stems, where the phloem is positioned outside the xylem.
(C) Xylem and phloem occur on the same radius: This arrangement is typical in conjoint vascular bundles (like in the stems of dicots), where the xylem and phloem are on the same radius but typically alternate. This is not the case in radical vascular bundles.
Thus, the correct answer is (D), where xylem and phloem are on separate radii, a common characteristic in the root vascular bundles.