Lateraalimeristeemien

Lateraalimeristeemien, known in English as lateral meristems, are plant tissues responsible for secondary growth, leading to an increase in the girth of stems and roots. Unlike apical meristems, which are found at the tips of shoots and roots and cause primary growth (lengthening), lateral meristems are arranged in cylinders along the plant axis. There are two main types of lateral meristems: the vascular cambium and the cork cambium.

The vascular cambium is a cylindrical meristematic layer that develops between the xylem and phloem in dicotyledonous plants and gymnosperms. It produces secondary xylem (wood) towards the inside and secondary phloem towards the outside. This continuous production of new vascular tissue is what causes the stem or root to thicken. In woody plants, the accumulation of secondary xylem forms the bulk of the wood.

The cork cambium, also known as the phellogen, is another lateral meristem that arises in the outer parts of stems and roots, typically replacing the epidermis. It produces cork cells (phellem) to the outside and sometimes a layer of phelloderm to the inside. The cork cells are dead at maturity and their thick, waxy walls provide protection against desiccation, mechanical injury, and pathogens. The combined activity of the cork cambium and the tissues it produces is referred to as the periderm, which forms the outer bark of trees. These lateral meristems are crucial for the long-term survival and structural support of perennial plants.