Comparative anatomy of leaflets of Mimosa L. (Fabaceae, Mimoseae): contributions to taxonomy

Abstract In the genus Mimosa, which is recognized as monophyletic, four of the five sections are traditionally described as unnatural groups in phylogenetic analyses. Although the infrageneric relationships in the phylogenies are well documented, in-depth studies are still needed to provide morphological and molecular characters that corroborate the new classifications proposed for Mimosa. Therefore, the present study aims to characterize the morphoanatomy of Mimosa leaflets and to select characters that could be useful for infrageneric taxonomy. Ten Mimosa taxa occurring in the Pantanal region were analysed using traditional methods of plant anatomy. The results obtained enabled the identification of diagnostic characters for all species and varieties evaluated. The characters found, alone or in combination, coincide with the current proposals of the clades in which the species are arranged. Parallelodromous venation and the presence of mucron are exclusive characters for distinct series. In addition to these characters, we evaluated mucilage idioblasts in the epidermis and glandular and non-glandular trichomes and performed histochemistry for lipids and phenolic compounds. Our findings enhance the resolution of diagnostic characters across Mimosa series. This is the first morphoanatomical study of leaflets in these species.