Supplementary Figure 2: Stereoscope and scanning electron micrograph (SEM) imaging showing enlarged meristems of the fab and fin mutants at different stages.

(a–c) Stereoscope images from the primary-shoot apex comparing the SAM at the early vegetative meristem (EVM, fifth leaf initiated) stage from WT (a), fab (b) and fin (c). Dashed lines mark the height and width dimensions used for meristem size measurements. (d) Quantification and statistical comparisons of EVM size from WT, fab and fin. Data are means ± s.d., n = 8–21. A two-tailed, two-sample t test was performed, and significant differences are represented by black asterisks: *P < 0.01. (e–h) SEM images showing the enlarged transition meristem (TM) stage of WT (e) compared to fab (f) and fin (g,h). (i,j) Two stages of sympodial inflorescence development in WT plants. Multi-flowered unbranched inflorescences arise from sympodial inflorescence meristems (SIM), each of which initiates one SIM before terminating (i)¹⁴. A sympodial shoot meristem (SYM) from the last PSM leaf produces a sympodial shoot with three leaves and the next inflorescence, and initiation of a new SYM from each prior sympodial shoot perpetuates growth (j)¹⁴. (k,l) The enlarged SAM of fin at the TM stage allowed additional leaf primordia to develop at its periphery, resulting in multiple SYMs (k). Likewise, multiple SIMs developed as the SAM terminated in a large fasciated flower (l). Orange arrowheads indicate extra SYMs and SIMs. L, leaf. Scale bars, 100 μm.