Comparative leaf anatomy and morphology of some Brazilian species of Crotalaria L. (Leguminosae: Papilionoideae: Crotalarieae)

Anatomical characters often provide strong taxonomic evidence and many times help define species whose morphological limits are in question. This study aimed to survey characters of the leaf anatomy of 16 species of Crotalaria L. occurring mostly in the cerrado (savanna) of central Brazil and in areas of restinga (coastal woodland, or sandy forest) along the coast of the country, in order to improve the current taxonomic circumscription of sections and species. Leaf samples were collected in the field and obtained from herbarium specimens. Standard techniques in plant anatomy were employed, including analyses under light and scanning electron microscopy. Many of the characters analyzed are relatively uniform, but some are diagnostic for species. At the section level, only trichomes with a base composed of radially distributed cells proved useful in the diagnosis of C. sect. Calycinae. The other characters analyzed showed interspecific variation, but no diagnostic value for recognition of the sections. At the species level, unlike the results found for sections, various characters have diagnostic value. Among the characters with diagnostic value at the species level, those related to texture, the venation pattern (such as the formation of areolas and insertion of the ribs secondary to midrib), and, in particular, the epidermis, showed potential for aiding the circumscription of some species.