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. Author manuscript; available in PMC: 2014 Sep 1.
Published in final edited form as: Nat Rev Genet. 2013 Sep;14(9):10.1038/nrg3541. doi: 10.1038/nrg3541

Figure 1. Schematic representation of Arabidopsis thaliana meristems and types of signalling.

Figure 1

Arabidopsis thaliana is a dicotyledonous plant that is used as a model organism for developmental studies. Two classes of signalling are used in A. thaliana: long-range signalling encompassing travel over a considerable distance (for example, shoot to root) (part A); and short-range signalling involving local intercellular movement (parts Ba,Bb). A. thaliana organs originate from two meristem populations, one in the shoot and the other in the root. Both meristems contain niche cells and stem cells or initial cells. However, each meristem has a distinct organization and cell types that arise from it. The shoot apical meristem (SAM) contains three layers (L1, L2 and L3) and three developmental zones (peripheral zone, central zone and rib zone) (part Ba). The niche cells, or organizing centre, of the SAM are specified at the junction of the three developmental zones and function to maintain stem cells in the shoot. The root apical meristem (RAM) (part Bb) is radially symmetric and consists of central niche cells (the quiescent centre) surrounded by stem cells. In the root, each stem cell population gives rise to one or two cell types.