Figure 2A. Cartoon of each cell terminal differentiation mechanism (Ruler in gray, Timer in pink and Sizer in red) and (right) juxtaposed confocal images of an 8-day-old WT seedling with the zones being indicated. Colors of zones as in Fig.1. Note the differences in subindex nomenclature compared with Fig. 1. B. Pseudocode of the algorithm used in each model. C-E. Relationships between pairs of phenotypic traits. C. Length of the elongation zone LEZ versus its number of cells, NEZ. Panels from left to right: the Ruler, Timer and Sizer models, and epidermal Col-0 data. Symbols in the three left-most panels represent simulated data of individual simulated root files (gray triangles for Ruler, pink squares for Timer and red diamonds for Sizer, n=122 each). Data from individual epidermal files in Col-0 is in green circles (n=122 from day 6, 8 and 10 post germination (Tables EV1, EV2)). Dashed lines are minimum square linear fits. Pearson correlation coefficient (r) for each pair of data are indicated. p stands for the p-value using standard Pearson correlation test. The epidermis exhibits of the number of cells in the EZ with its length, and also with 1/ln(rEZ). The epidermal mature cell length does not have correlation with the inverse of the elongation factor. These features are only reproduced in the Sizer model. For each model, the simulated roots and cells differ in the threshold value for cell elongation termination, the cell elongation rate, the meristematic activity and the initial cell length, according to a variability inferred from the epidermal Col-0 data (Appendix Fig. S4B-F). The parameter values are the same for the three models except for the threshold for cell elongation termination, which is specific of each model and has relative variability of 35% (Ruler), 7% (Timer) and 26% (Sizer) (Table EV3). Parameter values selected such that no statistical significance is found between model (for each model) and epidermal data in any of five phenotypic traits (Wilcoxon-rank sum test, p-value >0.01, Table EV4, Appendix Fig. S4B-F). Continuous lines are theoretical predictions for each model (Appendix Text S1E). All models have the same dependence on the threshold value for differentiation (blue line) but each model has its own dependence on the the spatial profile of cells along the EZ (rEZ) (lines in gray for Ruler, black and red for Timer and red for Sizer). The Timer model depends on the cell elongation dynamics and, in contrast with the Ruler and Sizer models, its relationships are not univocally defined by the spatial profile of cells along the EZ (rEZ). For the Timer model, the continuous lines represent the theoretical prediction obtained when either relong (black line) or Rprod (red line) changes. For all the boxplots, boxes represent the interquartile range (25th-75th percentiles, with the median indicated by the black horizontal line) of the distribution, whiskers extend to the minimum and maximal values excluding outliers. Outliers are those values more (less) than 3/2 of upper (lower) quartile. C-E. Relationships between pairs of phenotypic traits. D. Length of mature cell (EZ cell closest to DZ) lmax versus 1/rEZ. Panels from left to right: the Ruler, Timer and Sizer models, and epidermal Col-0 data. Symbols in the three left-most panels represent simulated data of individual simulated root files (gray triangles for Ruler, pink squares for Timer and red diamonds for Sizer, n=122 each). Data from individual epidermal files in Col-0 is in green circles (n=122 from day 6, 8 and 10 post germination (Tables EV1, EV2)). Dashed lines are minimum square linear fits. Pearson correlation coefficient (r) for each pair of data are indicated. p stands for the p-value using standard Pearson correlation test. The epidermis exhibits of the number of cells in the EZ with its length, and also with 1/ln(rEZ). The epidermal mature cell length does not have correlation with the inverse of the elongation factor. These features are only reproduced in the Sizer model. For each model, the simulated roots and cells differ in the threshold value for cell elongation termination, the cell elongation rate, the meristematic activity and the initial cell length, according to a variability inferred from the epidermal Col-0 data (Appendix Fig. S4B-F). The parameter values are the same for the three models except for the threshold for cell elongation termination, which is specific of each model and has relative variability of 35% (Ruler), 7% (Timer) and 26% (Sizer) (Table EV3). Parameter values selected such that no statistical significance is found between model (for each model) and epidermal data in any of five phenotypic traits (Wilcoxon-rank sum test, p-value >0.01, Table EV4, Appendix Fig. S4B-F). Continuous lines are theoretical predictions for each model (Appendix Text S1E). All models have the same dependence on the threshold value for differentiation (blue line) but each model has its own dependence on the the spatial profile of cells along the EZ (rEZ) (lines in gray for Ruler, black and red for Timer and red for Sizer). The Timer model depends on the cell elongation dynamics and, in contrast with the Ruler and Sizer models, its relationships are not univocally defined by the spatial profile of cells along the EZ (rEZ). For the Timer model, the continuous lines represent the theoretical prediction obtained when either relong (black line) or Rprod (red line) changes. For all the boxplots, boxes represent the interquartile range (25th-75th percentiles, with the median indicated by the black horizontal line) of the distribution, whiskers extend to the minimum and maximal values excluding outliers. Outliers are those values more (less) than 3/2 of upper (lower) quartile. C-E. Relationships between pairs of phenotypic traits. E. NEZ versus 1/ln(rEZ), which can be interpreted as the ratio between the meristematic activity (Rprod) and the elongation rate (relong). Panels from left to right: the Ruler, Timer and Sizer models, and epidermal Col-0 data. Symbols in the three left-most panels represent simulated data of individual simulated root files (gray triangles for Ruler, pink squares for Timer and red diamonds for Sizer, n=122 each). Data from individual epidermal files in Col-0 is in green circles (n=122 from day 6, 8 and 10 post germination (Tables EV1, EV2)). Dashed lines are minimum square linear fits. Pearson correlation coefficient (r) for each pair of data are indicated. p stands for the p-value using standard Pearson correlation test. The epidermis exhibits of the number of cells in the EZ with its length, and also with 1/ln(rEZ). The epidermal mature cell length does not have correlation with the inverse of the elongation factor. These features are only reproduced in the Sizer model. For each model, the simulated roots and cells differ in the threshold value for cell elongation termination, the cell elongation rate, the meristematic activity and the initial cell length, according to a variability inferred from the epidermal Col-0 data (Appendix Fig. S4B-F). The parameter values are the same for the three models except for the threshold for cell elongation termination, which is specific of each model and has relative variability of 35% (Ruler), 7% (Timer) and 26% (Sizer) (Table EV3). Parameter values selected such that no statistical significance is found between model (for each model) and epidermal data in any of five phenotypic traits (Wilcoxon-rank sum test, p-value >0.01, Table EV4, Appendix Fig. S4B-F). Continuous lines are theoretical predictions for each model (Appendix Text S1E). All models have the same dependence on the threshold value for differentiation (blue line) but each model has its own dependence on the the spatial profile of cells along the EZ (rEZ) (lines in gray for Ruler, black and red for Timer and red for Sizer). The Timer model depends on the cell elongation dynamics and, in contrast with the Ruler and Sizer models, its relationships are not univocally defined by the spatial profile of cells along the EZ (rEZ). For the Timer model, the continuous lines represent the theoretical prediction obtained when either relong (black line) or Rprod (red line) changes. For all the boxplots, boxes represent the interquartile range (25th-75th percentiles, with the median indicated by the black horizontal line) of the distribution, whiskers extend to the minimum and maximal values excluding outliers. Outliers are those values more (less) than 3/2 of upper (lower) quartile.