The growth tissues of the plants are the meristems. Meristems are the tissues that produce the plant growth giving birth to all other tissues; they are formed of undifferentiated cells having intense cell division rate. Meristems classify as primary meristems and as secondary meristems.
Primary meristems are found in the apex of the stem, in the lateral buds of the stem, in the basis and tips of the shoots and within the root cap. Primary meristems are responsible for the primary growth (lengthening) of the plant.
Secondary meristems are those that make the plant grow in thickness (secondary growth) and they are formed by tissues that thicken the stem: cambium and phellogen .