Woody Dicot Root: Quercus
cross section: Older Quercus root
The vascular cylinder consists of an outer narrow ring of phloem,and deep to this, the vascular cambium. The vascular cambium remains active, producing annual growth of secondary phloem towards the outside of the root and secondary xylem towards center of the root. Because of greater production of xylem, the bulk of the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Annual growth rings of spring and summer wood is difficult to distinguish in roots
Both the pericycle and endodermis, which wrap vascular cylinder in younger roots, are lost due to seasonal growth of the vascular cylinder,
The center of the root is made up of parenchyma and primary xylem.