Floral development in Daviesia cordata (Leguminosae: Papilionoideae: Mirbelieae) and its systematic implications

Abstract

The floral development of Daviesia cordata Smith is studied by the use of scanning electron microscopy. This is the first study of a member of Mirbelieae. Although organ initiation in Papilionoideae is said to be almost uniformly unidirectional from the abaxial to the adaxial side, the presented floral development shows striking differences from this mode. Sepals, petals and the antepetalous stamens are initiated in simultaneous whorls, which is seen as a consequence of harmonisation of the plastochrons within the whorls. The antesepalous stamens are initiated unidirectional from the adaxial to the abaxial side, which is the reversed direction of the common mode of Papilionoideae. This is the first record of reversed unidirectionality in Papilionoideae, which can be linked with isolated findings in Caesalpinioideae and Mimosoideae. Concerning developmental aspects, the results seem to link the papilionoid flower closer to those of Caesalpinioideae and Mimosoideae. Further developmental studies are necessary to broaden the data matrix for a detailed phylogenetic analysis.