Explanation

Primary Growth results due to (i) Elongation of plant along the axis is called the primary growth (ii) Primary growth happens due to the presence of root apical meristem and shoot apical meristem. Root Apical Meristem (RAM), Shoot Apical Meristem (SAM) and intercalary meristem are responsible for the primary growth to the plants and they principally contributes to the elongation of the plants along their axis. In the dicotyledons and gymnosperms, the lateral meristems, vascular cambium and cork cambium appear later in life. These are the meristems that causes increase in the girth of the organ in which they are active. This is known as the secondary growth of the plant