ABSTRACT
Floral symmetry describes whether, and how, a flower, and in particular its perianth, can be divided into two or more identical or mirror-image parts. Enantiostyly is the asymmetrical deflection of the style, either to the left (left styled) or to the right (right styled) side of the floral axis and has evolved in at least ten angiospermous families. Zygomorphic flowers are considered as evolved from actinomorphic flowers. From phylogenetic studies it can be inferred that during flowering plant diversification transitions from radial to bilateral flower symmetry (and back to radial symmetry) have occurred. A single Mendelian locus with two alleles, with the right-styled allele (R) dominant to the left-styled allele (r), governs stylar deflection. In the snapdragon, unequal corolla and stamen development along the dorsoventral axis depends on the activity of four genes: CYCLOIDEA (CYC), DICHOTOMA (DICH), RADIALIS (RAD), and DIVARICATA (DIV).
