Lateral Meristems

Secondary or lateral growth increases the girth of plant organs in dicots and gymnosperms. It is achieved by the coordinated activities of lateral meristems, namely the vascular cambium and cork cambium (phellogen). The vascular cambium produces the conductive tissues secondary xylem (wood) and secondary phloem (bark), while the cork cambium generates the protective phellem (cork) against stresses from the surrounding environment. These meristematic tissues contain the stem cells to generate new tissues continuously and represent the hallmarks of perennial growth habit. Key Concepts Lateral meristems are responsible for the girth growth of plant organs. Lateral meristems consist of the vascular cambium and cork cambium (phellogen), which produces the conductive tissues and protective tissues for the growing plant body, respectively. The vascular cambium is uniseriate, and a single, bifacial stem cell produces both phloem and xylem cells in a cell file. Development and activity of the vascular cambium are complex and governed by the genetic factors and plant hormones. Phellogen initiation requires the activation of the vascular cambium formation. Recent advances and tools developed for sequencing, imaging and segmentation will improve our understanding and modelling of plant lateral growth.