The Stem Cell Niche in Leaf Axils Is Established by Auxin and Cytokinin in

This analysis provides a further example of how the coordinated regulation of two classic plant hormones contributes to the maintenance of cells in a pluripotent state. In previous studies, the development of complementary tools to describe both relative levels and the polar movement of auxin has helped to define key elements that contribute to the maintenance of cells in an undetermined state versus differentiation in the primary shoot apical meristem. Convergent flows of auxin in the superficial layer of the shoot apex create auxin maxima, which promote the formation of leaf primordia. By contrast, lower levels of auxin, combined with elevated levels of cytokinin signalling, are a prerequisite for the establishment and maintenance of undetermined cells that enable the indeterminate growth of the primary shoot apical meristem.