meristematic

Meristematic tissue refers to plant tissue composed of actively dividing, undifferentiated cells that retain the capacity to differentiate into various specialized cell types. These cells are essential for growth and the generation of all subsequent tissues.

There are several main classes of meristem. Apical meristems occur at the tips of roots and shoots and drive primary growth, lengthening the plant. Lateral meristems, such as the vascular cambium and cork cambium, contribute to secondary growth by increasing girth and producing wood and bark. Intercalary meristems are found at certain positions in grasses, typically at the base of leaves or at internodes, and enable rapid elongation and regrowth after damage.

Meristematic cells are usually small with dense cytoplasm, a large nucleus, thinly pitted cell walls, and often several small vacuoles. They divide by mitosis with little cytoplasmic expansion between divisions. A key feature is their ability to maintain a pool of initials that generate derivatives which subsequently differentiate into the three primary tissue systems: dermal, ground, and vascular.

In development, primary meristems arise from the apical meristems and give rise to the epidermis (protoderm), ground tissues (ground meristem), and vascular tissues (procambium). Secondary meristems form later to produce secondary xylem and phloem, as well as periderm. Meristematic cells are often considered totipotent, retaining the potential to differentiate into many cell types under appropriate conditions.