Floral ontogeny of Aeschynomene falcata and A. sensitiva (Leguminosae: Papilionoideae) supports molecular phylogenetic data

Abstract

Floral ontogeny and morphology of the Leguminosae are of interest because of their potential to provide characteristics useful for phylogeny. To determine if these features corroborate the phylogenetic segregation of the section Ochopodium from Aeschynomene, this study used comparative analysis between Aeschynomene falcata and A. sensitiva, which are within the sections Ochopodium and Aeschynomene, respectively. Flower buds were analysed by use of scanning electron microscopy. Aeschynomene falcata has a unidirectional initiation of sepals from the abaxial side, and a tendency toward whorled initiation for petals and stamens. At maturity, it has a calyx tube with five lobes, a pubescent standard petal, keel petals with coherent (but not fused) margins above and below the stamens, and a carpel with a long hairy stipe. Aeschynomene sensitiva has a distinct initiation pattern of petals (1st abaxial, 2nd adaxial, and 3rd lateral) and a tendency toward whorled initiation of sepals and stamens. Overlap between sepals, petals, and antesepalous stamens initiation was observed. At maturity, A. sensitiva has a glabrous bilobed calyx and a glabrous standard petal, keel petals postgenitally fused above the stamens, and a carpel with a short and glabrous stipe. Floral ontogeny and morphology of A. falcata are very similar to those of Machaerium and Dalbergia species so far studied, corroborating the phylogenetic proximity of section Ochopodium to these genera. Important features of the floral ontogeny of A. sensitiva seem to be related to the origin of the bilobed calyx, which is shared with the rest of Aeschynomeninae except section Ochopodium, suggesting they are synapomorphies for those species.