Figure 1.

Organization of the Arabidopsis root. (Left): Longitudinal section through the root showing apical-basal polarity. Different cell types (each differently coloured) are arranged in cell files, forming concentric single-celled layers surrounding the central vascular tissue. Distinct developmental zones are formed along the growing root. Cell division occurs in the meristematic zone, especially the apical meristem. Cell division rate slows down in the basal meristem and cells start to elongate in the elongation zone. The boundary between meristematic and elongation zone is indicated as the transition zone. Cell differentiation occurs in the differentiation zone; (Right): Radial polarity in on a cross section of the differentiated root zone showing the formation of root hairs and Casparian strips (Based on Petricka et al., 2012 [1] and Péret et al., 2009 [2]).