Secondary wall is always located closer to the plasma membrane of a plant cell than the primary wall. Root hairs are the smallest type of roots complete with a functional stele. The boundary between the cortex and the stele is called endodermis. Branching in roots originates from meristem activity of surface buds much like branching in stems. Procambium gives rise to vascular tissue.
Collenchyma cells are still alive at functional maturity - thus they can grow as the plant grows.
Sclerenchyma and vessels are the only types of cells that are dead at functional maturity. Vascular cambium gives rise to xylem toward the center of the stem and phloem toward the periphery of the stem. In young trees, lenticels prevent gas exchange through the bark, thus giving leaves control of this activity for the plant. The zones of cell division, is found further from the root tip than the zone of elongation. Wood consists mostly of primary xylem.