Radial Bundle

in botany, a group of vascular root tissues. In the radial bundle, alternating groups of primary xylem and phloem that originated from individual bundles of procam-bium are arranged along the radii. Around the periphery, the radial bundle is surrounded by a layer of pericyclic cells that are adjacent to the inner layer of primary cortex, the endoderm. In the center of the root arises either a metaxylem vessel or parenchymal or mechanical tissue. In monocotyledons, the primary structure is retained throughout the life of the root; in dicotyledons, with the appearance of the cambium, the root acquires a secondary structure.