Growth coordination and the shoot epidermis.

Cell-cell communication is essential for growth and development of multicellular organisms. In higher plants, the shoot organs are derived from three clonally distinct cell layers present in the meristem. The role of the outermost L1 cell layer and its derived epidermis in coordinating growth of the inner-cell layers has long been debated. This question has been revisited recently using molecular tools to manipulate cell cycle progression or cell expansion, specifically in the epidermis. These studies conclude that cells in the epidermis both promote and restrict growth of the entire shoot by sending growth signals - either physical or chemical - to the inner layers.