secondary growth in root and stem

In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate, and gives rise to primary tissue. Secondary growth occurs in many roots and usually results in the thickening of the root diameter by the addition of vascular tissue. Initiation of secondary growth occurs when cells in the residual procambium and parts of the pericyle begin to make periclinal divisions. Primary growth produces growth in length and development of lateral appendages. Secondary growth is the formation of secondary tissues from lateral meristems. ... Secondary growth occurs in perennial gymnosperms and dicots such as trees and shrubs. It is also found in the woody stems of some herbs.