Fig. 2. Effects of ett-7 seu-3 on floral meristem patterning. Numbers refer to stages of flower development (Smyth et al., 1990). (A) Wild-type inflorescence shows four evenly spaced sepal primordia arising from stage 3 and 4 floral meristems (arrows and arrowheads), and sepals completely enveloping the floral buds by stage 6. (B) Like wild type, seu-3 has four uniformly positioned sepal primordia (arrows and arrowheads), but sepals are smaller and often do not tightly enclose the inner organs (compare the amount of exposed floral meristem at the asterisks in A and B). (C) ett-7 flowers characteristically have five sepals, with an extra abaxial sepal (top arrowhead) (D,E) A greater number of developing meristems are present in ett-7 seu-3 than in either single mutant. ett-7 seu-3 floral meristems are distinctive by stages 3-4, when an uneven ring of sepal primordia tissue becomes evident (r). As the flower develops, sepals grow out erratically, causing some to be fused and some to be filamentous. Tiny petal primordia in stage 5 and 6 meristems are indicated by arrowheads. Genotypes described are in Col. Scale bars are 0.1 mm.