Lateraalimeristeemeissä

Lateraalimeristeemeissä, known in English as lateral meristems, are plant tissues responsible for secondary growth. This type of growth increases the diameter of roots and stems, distinguishing it from primary growth which increases length and originates from apical meristems. There are two main types of lateral meristems: vascular cambium and cork cambium.

Vascular cambium is a cylindrical layer of actively dividing cells located between the xylem and phloem in dicotyledonous plants and gymnosperms. Its activity produces secondary xylem (wood) towards the inside and secondary phloem towards the outside. This continuous production of wood is what causes trees to grow wider over time.

Cork cambium, also known as the phellogen, is another cylindrical meristematic tissue that forms later in the development of stems and roots. It produces phellem (cork) cells to the exterior and a layer of phelloderm cells to the interior. Together, these tissues form the periderm, which replaces the epidermis in woody plants, providing protection and insulation.

The activity of lateral meristems is crucial for the structural support and water transport capabilities of mature woody plants. It allows them to grow to significant sizes and withstand environmental stresses. Monocotyledonous plants generally lack true lateral meristems and therefore do not exhibit secondary growth in the same manner as dicots and gymnosperms.