The secondary cell wall is a structure found in many plant cells, located between the primary cell wall and the plasma membrane. The cell starts producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding.
Based on its location in a plant, meristematic tissues are of two categories: primary and secondary.
Meristematic cells have very thin cell walls, small vacuoles, a well-centralized nucleus and they are constantly undergoing mitosis. Meristematic cells need a high mitotic rate because they are responsible for plant growth.
Secondary meristematic tissue helps the plant increase the girth or lateral growth of its stems, branches, and roots. Secondary meristematic growth is also responsible for producing the bark on woody trees.