Figure 1.

The ra2 Mutant Phenotype.

(A) Wild-type tassel; inset, a spikelet pair.

(B) ra2-mum4 tassel.

(C) The transition of branch lengths in a ra2 mutant. Mixed branches are formed after main branches (data not shown) and bear single spikelets and spikelet pairs. Spikelet multimers are formed after the mixed branches and consist of more than two single spikelets. mb, mixed branch; sm, spikelet multimer; sp, spikelet pair; ss, single spikelet.

(D) Wild-type ear with well-defined rows of kernels.

(E) ra2-mum4 ear with disorganized rows.

(F) Open-pollinated ra2-dm ear with numerous branches.

(G) to (J) Scanning electron microscopy of developing ears.

(G) Wild-type ear. im, inflorescence meristem; sm, spikelet meristem; spm, spikelet pair meristem.

(H) Scanning electron micrograph of a ra2-R ear showing meristems initiating branches (arrows) and some well-developed branches at the base.

(I) Detail of a wild-type ear row consisting of a pair of spikelet meristems.

(J) Detail of the formation of three spikelet meristems in a ra2-R ear.

Bars = 0.5 mm in (G) and (H) and 50 μm in (I) and (J).