Table 1. Compact model overview.
| Model | Fig. | Exit DZ -Start EZ | Exit EZ – Start MZ | Division rule | Growth rate |
| 1 | 1C | Counter | Timer | Timer | Constant |
| 2 | 3A–D | Timer | Timer | Timer | Linear |
| 3 | S1A | Counter | Timer | Timer | Linear |
| 4 | 4A | Timer | Timer | Timer+noise | Linear |
| 5 | 4B | Counter | Timer | Timer (variant) | Linear |
| 6 | 4C | Counter | Timer | Sizer (uniform) | Linear |
| 7 | S3B | Counter | Timer | Sizer | Linear |
| 8 | 5A–D | Ruler | Ruler | Sizer | Linear |
| 9* | 6A–D | Ruler | Ruler | Sizer | Linear |
| 10 | 7A,B | Auxin threshold | Auxin threshold | Sizer | Linear |
| 11 | 8 | Layer-specific auxin threshold | Layer-specific auxin threshold | Sizer | Linear |
| 12 | 9 | SHY2 threshold | GA threshold | Sizer | Linear |
*Model 9 differs from Model 8 in that auxin was added as a model variable to study its dynamics in a realistic, expanding cellular grid.
Overview of the models used in this study. Various categories w.r.t. developmental decisions are presented. Column (3) specifies the transition between division and elongation zone (DZ and EZ, respectively); column (4) specifies the transition to mature (differentiated) cells (mature zone or MZ) based on timing since the release from the QC or a spatial signal at a fixed distance from the root apex; column (5) specifies whether division rate is determined via a timer or sizer mechanism; and column (6) how cellular growth rates are defined. Developmental events can be determined to happen after a fixed duration (‘Timer’), a fixed number of divisions (‘Counter’), a fixed cell size (‘Sizer’), and a fixed distance from the root apex (‘Ruler’). For Models 10–12 more complicated regulatory mechanisms are specified. In Model 4 extra random noise was added to the timer (‘+ noise’). For Model 5 cell division is dependent on a timer mechanism, with a different cell cycle time for inner and outer layers (‘Timer (variant)’). Model 6 uses a uniform size (area) criterion for cell division, irrespectively of cell geometry (‘Sizer (uniform)’). For Model 7 the size criterion is adapted to the difference in the width between inner and outer layers, thereby acting effectively as a length criterion. In the other (non-cell autonomous) cases the cell division sizer differs between layers. It is usually assumed that DZ and EZ have a characteristic elongation rate. More details of the models can be found in Table S1, Text S1 and in the corresponding figures.