Fig. 2. Zmm16 RNA in situ hybridization of maize developing male spikelets. (A) Two young male spikelets with Zmm16 expression throughout the upper floral meristem (Uf) and absent from the emerging lower floral meristem (Lf). (B) Developing spikelet surrounded by inner (Gi) and outer (Go) glumes. In this section, Zmm16 expression appears throughout the upper floral meristem, but is absent from emerging lemma (Le) and palea (Pa) primordia. (C) Subsequent section of the same spikelet shown in B, showing absence of Zmm16 in the center of the floral meristem. (D) Zmm16 expression in the developing stamen (St), lodicule (Lo) and lower floral meristem. (E) Later stage spikelet with lower floret, reiterating the pattern of expression seen in the upper floret, shown in C. (F) Transverse section showing expression in stamens, but not in the aborting carpel (Ca).