Cell division pattern of the lateral root cap, columella (a), and epidermal endodermal initial cells (b). a Columella initials are regenerated through a first anticlinal division (black arrows), whereas peripheral root cap cells are formed following a first periclinal division followed by several anticlinal divisions. Cell types are color-coded according to Figs. 3 and 6. b Divisions of the epidermis–endodermis initials. The dotted double arrow describes the first anticlinal division near the QC that regenerates the initial and produces the epidermis–endodermis-derived initial. Eight successive asymmetrical periclinal cell divisions (yellow arrows) follow the first anticlinal division and generate, successively, the epidermis–endodermis, sclerenchyma layer, exodermis, and five layers of the cortex.