Fig. 7. bif2 is required for branch meristem maintenance: double mutant analysis with ra1. (A) In ra1 mutant tassels, spikelet pairs are converted to branches resulting in a highly branched tassel (Gernart, 1912). Scale bar, 3.33 cm. (B) bif2;ra1 double mutant tassels have a similar phenotype to bif2 mutants, except that when branches form they have more spikelets than bif2 mutants. (C) bif2 mutant tassel. In this genetic background, the bif2 mutant phenotype is weak and single spikelets form on the main spike. D to G are branches dissected from midway along the main spike of a family segregating normal (D), bif2 (E), bif2;ra1 (F) and ra1 (G) mutant plants. Scale bar, 600 µm. (D) Normal spikelet pair with pedicellate and sessile spikelet. (E) bif2 mutant spikelet. Note that bif2 mutants produce spikelets singly instead of in pairs and that the pedicel is elongated. (F) bif2;ra1 double mutant branch with several spikelets. G) ra1 mutant branch with many spikelets.