Sorghum germination process; embryo and seedling development and sampling time points. A, Timeline of imbibition, germination, and collection of samples. Sorghum grain were imbibed in water for 12 h and germinated for 72 h. Samples were collected every 12 h at the desired time points, as indicated with arrows. All eight time points were subjected to metabolite profiling. From the eight time points, four developmental stages (S) were selected for analysis by MSI and named: S0, dry seed; Si, after 12 h of imbibition; S1, emerged radicle and coleoptile; and S2, developed shoot and primary root. B, Graphical representation of the stages collected for MSI analyses. For the cvBTx623 line these stages matched the indicated time points (for tcd1 see Fig. 3). C, Schematic of longitudinal sections of the four developmental stages selected for MSI analysis, showing detailed morphological features and main compartments.