Evolution of floral symmetry.

Floral monosymmetry, which is conspicuous and prominent in many angiosperms, has attracted much attention from both developmental geneticists and pollination biologists. A combined evolutionary biological approach to studying floral monosymmetry in the Lamiales, the order that contains the model plant Antirrhinum, is just beginning to take shape. In contrast, floral left-right asymmetry has largely been neglected, although it is much in discussion in animal biology, probably because in flowers (unlike in animals) left-right asymmetry is not predominant. Nevertheless, there are patterns in the evolution of floral left-right asymmetry that are interesting enough to be addressed by developmental genetics. These are the direction of contortion in flowers with contort petal aestivation, and the direction of deflection of pollination organs in groups with enantiostylous flowers or in some groups with enclosed pollination organs, such as beans (Phaseolinae, Fabaceae) or louseworts (Pedicularis, Orobanchaceae).