Fig. 2. Phyllotaxy defect in blr mutants. (A,C,E,G) Wild-type inflorescence apex; (B,D,F,H) blr mutant inflorescence apex. (A,B) Longitudinal sections of 23-day-old plants showing comparable size and shape of wild-type (A) and blr (B) inflorescence meristems. The width of the stem is also similar in wild type and blr. (C-F) 18-day-old plants. In wild type (C,E) organs are initiated on average 137.5° apart forming a continuous spiral. In wild type (C) the divergence angle between primordia 2 and 3 is 130.6°. In blr mutants (D,F) flowers can initiate in aberrant positions as in primordia 3 in D and 5 in F. In D the divergence angle between primordia 2 and 3 is 79.3°. (G,H) Inflorescence apex from 23-day-old plants. Clockwise (red) and counterclockwise (yellow) contact parastichies connecting floral primordia in a 3+5 phyllotactic pattern. Additional organs in blr mutants result in contact parastichies forming a tighter curve than in wild type. Numbering of each inflorescence starts at the youngest visible primordium. Scale bars: 0.5 mm (A,B), 50 µm (C,D), 200 µm (E,F) and 500 µm (G,H).