Fig. 6. Apical initial number varies during shoot growth and branching. (A-F) Frontal longitudinal sections through recently bifurcated meristems (A,E,F), the meristems of major branches that have initiated at least two (B) or three (C) leaf pairs, and an apex that has visibly begun to split into two (D). Arrowheads point to large epidermal cells that are deduced from sector analysis and KNOX and ARP in situ hybridisation patterns (Harrison et al., 2005) to be apical initials (red) or merophytes (black). Scale bars: A, 32 µm; B, 20 µm; C, 27 µm; D, 24 µm; E, 32 µm; F, 27.5 µm. (G-J) Schematic representation of sectors that span branch points. (K-N) Deduced cell division patterns giving rise to the sectors in G-J. The boxes represent the presumed number of initials and merophytes present in the surface layer. Light grey represents au/+ tissue and dark grey represents +/-tissue. M, merophyte; I, initial. The ventral branch-point leaf is represented at the six-cell stage.