Anatomia e micromorfologia comparada do limbo de Lepidaploinae S.C.Keeley & H.Rob. (Vernonieae: Asteraceae)

Abstract

Anatomical and morphological data are valuable tools for inferring homologies and character states, contributing significantly to the resolution of taxonomic problems. These approaches are frequently employed to clarify the taxonomy of Angiosperm families. The subtribe Lepidaploinae (Vernonieae) is taxonomically complex, with poorly defined genera and overlapping characters identified in previous studies. This work analysed leaf morphological and anatomical characters to distinguish eight genera within the subtribe. Cross-sections of herborized leaf blades from Chrysolaena (6 spp.), Echinocoryne (2 spp.), Harleya (1 sp.), Lepidaploa (10 spp.), Lessingianthus (19 spp.), Stenocephalum (2 spp.), Stilpnopappus (1 sp.) and Strophopappus (2 spp.) were examined using standard sectioning and staining techniques. Most species have amphistomatic leaves with both glandular and non-glandular trichomes, although their distribution varies among taxa. The epidermis is predominantly uniseriate, with a thin, inconspicuous cuticle. Hydathodes were observed in species of Lessingianthus. The mesophyll is mainly dorsiventral, and sheath extensions occur in Echinocoryne, Lepidaploa, Lessingianthus and Strophopappus. The midrib is typically convex on the adaxial surface, although some species show flattened or grooved configurations. Collenchyma is present on both surfaces in most species. Vascular bundles are collateral and often associated with adaxial and/or abaxial fibers. Crystals were found in the mesophyll and/or midrib of Chrysolaena, Harleya, Lepidaploa, Lessingianthus, and Strophopappus. Although no single leaf pattern reliably segregates the genera, certain traits support the distinction of individual species. As observed in previous palynological, micromorphological, anatomical, and phylogenetic studies, our results reinforce the structural complexity of Lepidaploinae and the challenges in delimiting its genera. Nonetheless, several anatomical features offer useful markers for species-level differentiation.