Pollen morphology of Butea, Kunstleria, Meizotropis and Spatholobus (Leguminosae, Papilionoideae), with notes on their position in the tribes Millettieae and Phaseoleae

Abstract

Pollen descriptions are given of Butea (two species), Kunstleria (eight), Meizotropis (two) and Spatholobus (29) based on LM, SEM and TEM data. The pollen of Spatholobus is more diverse than that of the other genera. Most species of these four genera have tricolporate pollen; (para)syncolporate pollen occurs in several Spatholobus species. The ornamentation is rugulate in Kunstleria, perforate to microreticulate in Butea, fossulate to verrucate in Meizotropis, and psilate-perforate to fossulate or microreticulate in Spatholobus. The infratectal layer is mostly columellate in Kunstleria and Butea, more or less granular in Meizotropis, and either columellate or coarsely granular in Spatholobus. The foot layer is well developed in most species except for Butea, Meizotropis and S. parviflorus, where it is very thin compared to the endexine. In Spatholobus, three types and three subtypes can be recognised. The pollen of Kunstleria closely resembles that of the tribe Millettieae. Pollen of Spatholobus shows features of both Millettieae and Phaseoleae pollen. Pollen of Butea and especially that of Meizotropis is similar to Phaseoleae pollen. The results of a cladistic analysis of the four genera agree with trends in ornamentation, aperture system, and infratectal structure reported for Phaseoleae pollen in the literature.