| Variables | Statistics | BACK |
| Group | Variable | Units | Description |
|---|---|---|---|
| Root morphology | SRL | mg-1 | Specific root length; root length per root dry weight |
| SRT | mg-1 | Specific root tips; root tip number per root dry weight | |
| SRSA | cm2 mg-1 | Specific root surface area; root surface area per root dry weight |