Meristematic cells are plant cells that divide and create new cells. They are physically responsible for the growth of the plant. There are two main types of meristematic cells: primary or apical meristems, which are responsible for increases in length, and secondary or lateral meristems, which cause an increase in width.
Apical meristematic cells are found at the tips of stems and roots and are responsible for the elongation of these structures. These cells have thin cell walls, which makes the cell division process simpler. They are also notably smaller than mature cells, have large nuclei and do not have vacuoles because they do not need to store materials for long periods of time. Apical meristematic cells put all of their resources into dividing to create permanent tissues. The plant protects these delicate meristematic cells by growing leaves at the tips of stems.
Lateral meristematic cells are responsible for an increase in width of a plant's trunk, stems and roots. Trees have an abundance of lateral meristematic cells. Found between the xylem and phloem in the cambrian layer of the trunk, they divide to create more xylem and phloem tissue, pushing the xylem tissue towards the inside and the phloem towards the outside of the trunk.