Fig. 4. SEM of normal and ifa1-r spikelets and florets. (A-D) Normal floret. (F-I) ifa1-r floret. (A,F) The upper FMs have initiated three stamens, one of which is hidden. Part of the glume is removed from the spikelet in F to reveal more of the lower FM. (B,G) The carpel ridge forms on the adaxial side of the FM. (C,H) The carpel ridge begins to envelope the ovule primordium in normal (C) but not in ifa1 mutants (H). (D) The carpels have almost completely enveloped the ovule. (I) The ovule primordium in ifa1 mutants is forming organs in a distichous pattern. The lower FM is also abnormal. (E) Spikelets develop in pairs in normal plants with the outer glumes forming at the abaxial side. The upper floret, which develops ahead of the lower floret, forms at the adaxial side of the spikelet. Both the inner glume and lower floret are obscured. (F) In ifa1 mutants, an extra spikelet forms between the spikelet pair. This extra spikelet develops in a reverse orientation such that the outer glume (see small arrow) is adaxial and the inner glume and the carpel ridge of the upper floret (see large arrow) are abaxial. lf, lower floret; st, stamen; op, ovule primordium; og, outer glume; ig, inner glume.
