Dichotomous root branching in S. moellendorffii. A, A young hairless rhizophore. B, Root emergence from the rhizophore. The transition from the rhizophore to the root is marked by the appearance of a collar of root hairs. Scale bars: 0.1 mm. C and D, Formation of first- (C) and second-order (D) bifurcated roots. Scale bars: 1 mm The insets are magnifications of the squares (Scale bars: 0.1 mm). The arrows indicate newly formed root apices. E, Percentage of root tips that underwent the first bifurcation during 17 d after transfer on 1/2 MS. The bifurcation percentage was calculated as the number of first-order bifurcated roots divided by the total number of roots. Values are averages of three repeats ± SD. F, Percentage of root tips that underwent the second bifurcation during 15 d after the first bifurcation. The bifurcation percentage was calculated as the number of second-order bifurcated root apices divided by the total number of the apices from roots that underwent a first bifurcation. Values are averages of two repeats ± SD. G, Confocal image showing a bifurcated apical meristem: root tip with two new clearly recognizable young meristems (arrowheads). Scale bar: 50 μm. H, Percentage of bifurcated meristems in the root branching time course, i.e. days after the first branching. The percentage was calculated as the number of root apices showing clear apical meristem bifurcation (see Figure 1G) divided by the total number of sampled root tips. n (daily sample number) ≥ 10.