Extended Data Fig. 10: Emergence of endothecium reduces tension in the epidermis.

(a) Representative digital cross-sections of the anther lobe region in WT, bam1bam2, and spl-1 from around 3 to 13 days*. Asterisk indicates estimated days after initiation. (b) Quantification of cell area per lobe region in WT anthers (n = 35, 36, 35, 53, 31, 70, 18, 20 cells in epidermis; 10, 18, 34, 22, 50, 15, 15 cells in endothecium; 59, 41, 19, 24, 13, 26, 19, 14 cells in inner tissue at consecutive time points; 5 independent inflorescences). (c) Example of transmission electron microscopy micrograph of an anther lobe after ‘butterfly’ shape acquisition. Brackets indicate the layers considered for measurements. (d) Quantification of cell wall thickness in different layers of the lobe (n = 24 walls in epidermis, 24 walls in endothecium, and 38 walls in inner tissue; 3 independent anthers). (e) Quantification of volume increase per region in 12 h interval (n = 88, 78 cells in epidermis, 36 cells in endothecium, and 42, 54 cells in inner tissue at consecutive time points; 4 independent time lapse series). In box plots, the lines represent the median and dots represent the mean values, the edges of the boxes define interquartile ranges, the whiskers represent 90% confidence intervals. For each time-point different letters indicate statistical significance determined by two-sided Mann Whitney U test (p < 0.01). Scale bar, 40 μm (a) 2.5 μm (b).