BPS1 is required for postembryonic shoot apical meristem maintenance. A, Confocal images of the SAM of the wild type (Col-0) and bps1-2 mutants. White arrowheads indicate the center of the SAM, the CZ. For mature embryos and 5 dpi seedlings, the images show frontal longitudinal sections, while for 3 dpi seedlings, the images show sagittal longitudinal sections. Bars = 50 µm. B, Quantitative analysis of SAM sizes in 3 and 5 dpi seedlings. Between 16 and 24 SAMs were analyzed for each developmental stage and for each genotype. A diagram depicting the measurements is provided in Supplemental Figure S1B. Data are shown as the mean ± sd. C, Quantitative analysis of SAM size in mature embryos from the wild type and from the progeny of a self-pollinated bps1-2 heterozygote. The box and whisker plots depict the SAM width, with the box showing the sizes ranging from the 25th to the 75th quartile, and the whiskers showing the data extremes. L1 cell numbers show the mean ± sd.