Meristem is a type of tissue in plants consisting of unspecialized, youthful cells called meristematic cells and found in areas of the plant where growth is or will take place. Differentiated plant cells have shapes and structures that would make it problematic for them to produce cells of a different type; thus, cellular divisions of the basic cells of the meristem provide new cells for expansion of tissues. Meristematic cells are analogous in function to stem cells in animals, are incompletely or not at all differentiated, and are capable of continued cellular division (youthful).
The most general form of meristem is the apical meristem, found in buds at the tips of shootss and roots. Apical meristem is completely undifferentiated. It differentiates into three different kinds of primary meristem:
- Protoderm lies around the outside of the stem, and develops into the epidermis.
- Procambium lies just inside the protoderm. It develops into the primary xylem, primary phloem. It also produces the vascular cambium, which may continue to produce secondary xylem and phloem throughout the life of the plant.
- Ground meristem develops into the pith and the cork cambium.