| Coefficient | Unit | Definition |
| P1 | ˚C day | Thermal time from seedling emergence to the end of the juvenile phase |
| P2 | Days | Extent to which development is delayed for each hour increase in photoperiod above the longest photoperiod at which development proceeds at a maximum rate (which is considered to be 12.5 h). |
| P5 | ˚C day | Thermal time from silking to physiological maturity |
| G2 | Number | Maximum possible number of kernels per plant. |
| G3 | mg day−1 | Kernel filling rate during the linear grain filling stage under optimum conditions |
| PHINT | ˚C day | Phyllochron interval, the interval in thermal time between successive leaf tip appearances |