Radial vascular bundle: When xylem and Phloem is a vascular bundle lie on different radii alternately from one another, it is called the radial vascular bundle. So, a vascular bundle, in which the primary xylem and primary phloem strands are divided from each other by nonvascular tissues and they are located on alternate radii of an axis, is known as a radial vascular bundle. In radial vascular bundles, the components are arranged separately. Here the xylem and phloem are arranged separately in different Radii. Radial vascular bundles are typically found in the roots of monocots and dicots. Here the xylem lies towards the periphery. This arrangement is seen in the root.
Radial vascular bundles are found in monocotyledonous roots. These bundles are the characteristic of roots. Radial vascular bundles are typically found in the roots of monocots and dicots. There is no primary cambium in this bundle and the secondary thickening occurs by the secondary cambium that originates at the time of secondary growth in dicotyledonous root only. Here the xylem and phloem are arranged separately in different radii.
The dicot roots generally have four to six numbers of protoxylem poles in contrast to monocot root where many poles of xylem (more than six) are present. The number of protoxylem poles in a root maybe 1, 2, 3, 4, 5, 6 or more. Therefore they are called monarch, diarch, triarch, tetrarch and so on.