Fig. 3.

Morphometric traits of panicle meristems in O. barthii (Ob) and O. glaberrima (Og). Measurements were taken at different stages of panicle development via virtual sectioning of 3D micro-computed tomography (micro-CT) images: rachis meristem (RM), early primary branch elongation (PB initiation), primary branch elongation before spikelet differentiation (PB elongation) and just after spikelet differentiation at the top of the panicle (early spikelet differentiation). Upper panel: box-plots of meristem width measured from X-ray or histological images (Additional files 2 and 3). Black lines within box-plots show the median value; box limits indicate the 25th and 75th percentiles. Lower panel: illustration of the considered morphological areas (i.e., width of the meristem at 40 μm from the apical part of the meristem). For the RM stage, meristem widths were quantified from X-ray tomography images (left) and classical histological section (right) of rachis meristem images (n = 9 for each genotype). Black lines represent the area of measurement. For the other developmental stages, meristem width was measured for all apical PB meristems of each panicle (n = 9 meristems at least for each genotypes). Scale bars = 100 μm. T test p values: stage RM, p = 0.06; stage PB initiation, p = 0.22; stage PB elongation, p = 0.35; stage Sp, p = 0.24