Hormonal regulation of primary root development

Plant post-embryonic development is characterized by the unceasing generation of new tissues and organs that allow plants to adapt their growth and architecture to environmental conditions. Primary root indeterminate growth is sustained by the activity of the root apical meristem (RAM), an organized structure containing stem cells that continuously divide to generate new tissues. RAM, thanks to its simple and symmetric structure, is an excellent system for studying how hormone distributions and interactions regulate growth. Plant hormones are pivotal actors in establishing and maintaining RAM patterning, and their developmental outputs are dependent on their integrated activities. In this review, we discuss recent findings on hormonal crosstalk that shapes the root meristem, focusing our attention on both the root radial and longitudinal axes.