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. Author manuscript; available in PMC: 2019 Jun 9.
Published in final edited form as: Annu Rev Cell Dev Biol. 2018 Aug 22;34:289–310. doi: 10.1146/annurev-cellbio-100617-062459

Figure 1.

Figure 1

An Arabidopsis seedling depicting the developmental organization of (moving counterclockwise from top left) the shoot apical meristem (SAM), root apical meristem (RAM), root developmental zones, and hormone domains of the RAM and SAM. (Top left) The SAM is positioned by the central organizing center (OC), which maintains the stem cells in the overlying central zone (CZ). Cells differentiate into either leaf or shoot cells as they are displaced into the peripheral zone (PZ) or the rib meristem (RM). (Bottom left) The quiescent center (QC) maintains the surrounding stem cells (gray) that give rise to all the tissues in the root. (Bottom center) Actively dividing cells are found in the meristematic zone. The transition to differentiation starts in the elongation zone when cells exit the mitotic cycle and enter a period of endoreduplication. Cells acquire their specialized features, such as root hairs, in the differentiation zone. (Right) The hormones auxin and cytokinin establish juxtaposed signaling domains that regulate division and differentiation in the SAM and RAM.