Leaf structure of species from three closely related genera from tribe Crotoneae Dumort. (Euphorbiaceae s.s., Malpighiales)

Euphorbiaceae s.s. is one of the largest angiosperm families, comprising nine major lineages. Molecular analysis indicated a polyphyletic condition in the subfamily Crotonoideae s.l., with four lineages identified, including one termed inaperturate crotonoids, which encompasses the tribe Crotoneae. Anatomical data were obtained from 15 species of Croton sect. Cyclostigma (Griseb.) Müll. Arg., Brasiliocroton P. Berry & I. Cordeiro and Astraea Klotzsch, which belongs to this lineage. The presence and protodermal origin of the idioblasts with lipophilic content and the interruption of the palisade by collenchyma layers on the adaxial side of the mid vein are common to the Croton L. species analysed and Brasiliocroton. The presence of dorsiventrality, paracytic stomata, collateral vascular bundles, branched non-articulated laticifers and crystal idioblasts in the species studied indicates morphological similarities among the three genera. The interpretation of the stipite of the complex trichomes as emergences is a structural novelty for the group. Leaf anatomy provided an excellent source of characters for future studies of the tribe Crotoneae (Euphorbiaceae s.s., Malpighiales).