Secondary Growth in the dicot root, the vascular cambium is completely secondary in origin. It originates from the tissue located just below the phloem bundles, a portion of pericycle tissue, above the protoxylem forming a complete and continuous wavy ring, which later becomes circular (Figure). Further events are similar to those already described above for a dicotyledon stem.
Figure: Different stages of the secondary growth in a typical dicot root
Secondary growth also occurs in sterns and roots of gymnosperms. However, secondary growth does not occur in monocotyledons.