Floral ontogeny in tribe Dalbergieae (Leguminosae: Papilionoideae):: Dalbergia brasiliensis, Machaerium villosum s. l. Platymiscium floribundum, and Pterocarpus rotundifolius

Floral organogenesis and development of the tropical legume trees Dalbergia brasiliensis, Machaerium villosum, Platymiscium floribundum, and Pterocarpus rotundifolius were studied using scanning electron microscopy. The aims were to compare ontogenies and to elucidate if floral ontogenetic data will provide new character states diagnostic of the tribe Dalbergieae, which is considered a basal papilionoid tribe and primarily defined on fruit characters. Organ inception is principally acropetal in all taxa studied. Carpel inception is, however, consistently precocious. In D. brasiliensis sepals are initiated in an order not previously reported in Papilionoideae. It may be considered modified helical. In P. rotundifolius the inner whorl of stamens initiate in an unusual way, this is lateral two stamens first, then the two abaxial ones, and last the adaxial one, opposed to the unidirectional order usually seen in Papilionoideae. Generally the differences in flower development among the studied genera appear at initiation and late stage in ontogenesis, rather than at mid-stage.