Estimation of the critical size of dividing and elongating cells by the sMSC approach. (A) Cortex cell length profile of the growing part of a representative root of wt Col-0, 9 DAS. (B) Sorted cell length profile in ascending order of the growing part of the root shown in (A). Vertical dashed lines represent positions of breakpoints, estimated by the MSC approach, that correspond to the PD/TD and the RAM/EZ boundaries of sorted cell lengths. (C) Sorted RAM cell length profile of the RAM of the root shown in (A) and (B). Vertical dashed line represents the breakpoint that delimitates the PD and TD cell length sets. (D) Linear models for PD and TD cell length sets. The black dot represents the estimated critical size of dividing cells (L_critD) and the white triangle represents the critical size for the initiation of rapid elongation (L_critE) for the file of the cortex shown in (A).