Fig. 4. Defects in the cellular organisation of scz meristem. (A) Schematic representation of meristem organisation of the Arabidopsis root. The colour code identifies the different cell types. The initials of the epidermis/lateral root cap and cortex/endodermis are shown in white. (B,C) Median longitudinal section through 3-day-old wild-type (B) and scz (C) roots. (B) In wild type, the asterisk indicates a cell that has divided asymmetrically to generate epidermal (inner) and lateral root cap (outer) daughter cells and the arrowhead indicates a cell that has divided asymmetrically to produce the endodermis (inner) and cortex (outer) daughter cells. (C) In scz, the epidermis/lateral root cap daughter cells are not clearly defined (asterisk). Division pattern of the cortex/endodermis daughter cell is abnormal. Often an anticlinal division occurs instead of a periclinal one (arrowhead). More than one periclinal division can occur (arrows) resulting in supernumerary layers (C). Bar, 25 µm.

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