Pollen morphological and morphometric analysis in species of the Aeschynomeneae and Adesmieae tribes (Faboideae: Fabaceae)

The aim of this study was to analyse the pollen morphological diversity among 19 species of the Adesmieae and Aeschynomeneae tribes with the purpose of evaluating their importance for the taxonomical delimitation of the Argentinean species and their systematic significance. Observations and measurements were performed on acetolysed pollen grains. The samples were examined under light and scanning electron microscopes. Principal component analysis (PCA) and conglomerate analysis were performed for quantitative morphological variables. The tribe Adesmieae is stenopalynous while the tribe Aeschynomeneae is eurypalynous; their pollen grains are 3-colporate, and they have lolongate, circular or lalongate endoapertures, semitectate-reticulate or tectate-perforate, fossulate, supra-rugulate exine, small to large size, and suboblate to prolate shapes. A key was made to identify and distinguish species of Adesmia, Aeschynomene, Chaetocalyx, Discolobium, and Poiretia. Exine sculpture and structure, presene of operculum, exine thickness, pollen shape, endoaperture shape, and pollen size all had taxonomic importance to distinguish the species inhabiting Argentina. The groupings recognised in recent classifications are hard to delimit on the basis of the palynological knowledge at this time since there are different pollen types but various of them occur among the three subclades. A framework for future evolutionary analyses within the dalbergioid clade is thus provided.