Cluster heat map of phenotypic traits. Hierarchical clustering of a few phenotypes was generated using Spearman correlation of max-min scaled phene values of maize phenotypes at 40 days (a). The color scale indicates the magnitude of the trait values (blue, low value; red, high value). The numbers indicated on the heat map refer to a phenotype in the specific row of the heat map. The corresponding phenotypes are visualized in (b). Primary roots are in black; seminal roots are in red; nodal roots are in green. #: number of axial roots; Axial.Diam: axial root diameter; LRBD: lateral root branching density; Lat.Length: lateral root length; Lat.Diam: lateral root diameter; NR1: nodal roots at position 1; NR2: nodal roots at position 2; NR3: nodal roots at position 3; NR4: nodal roots at position 4; SR: seminal roots; PR: primary root.