Botany - Anatomy of Flowering Plants Question with Solution | TestHub

When secondary growth in thickness is initiated in a dicot root, parenchyma between xylem and phloem becomes meristematic.

Vascular bundles in dicot root are radial, exarch and mostly triarch Vascular cambium is formed from conjunctive parenchyma cells lying just below each phloem strand. Thus the number of cambium strips formed equals the number of phloem strands. The cells of pericycle lying outside the protoxylem also become meristematic to form part of strips of cambium. These-cambial strips join the first formed cambium strips to form complete but wavy ring of vascular cambium. This cambium ring produces secondary xylem on inner-side and secondary phloem on outer side. In roots, the growth rings are not distinct, because there is no seasonal variation under the soil. From the outer layers of pericycle arises the phellogen which cuts phellem (cork) or the outer side and secondary cortex or phelloderm toward the inner side.