Comparative anatomical and micromorphological studies on foliage leaf blades of South American species of Guadua (Poaceae, Bambusoideae, Bambuseae)

Abstract

Guadua is the most diverse genus within the Neotropical subtribe Guaduinae, with 37 species, characterized by thorny culms with bands of hairs in the infra and supranodal regions. Like other Neotropical woody bamboos, Guadua is monocarpic, with long flowering cycles ranging from 19 to 38 years. Consequently, vegetative traits may aid in species delimitation when reproductive material is absent. Anatomical and micromorphological studies of foliage leaves were performed based on herbarium specimens for 11 species of Guadua from southern South America—including first-time descriptions for G. chaparensis, G. sarcocarpa, G. superba, and G. weberbaueri. Anatomical features were analyzed in cross section and surface view, emphasizing their potential as additional information for taxonomic identification. Traits traditionally associated with Guaduinae, such as a midrib with an arrangement of different number and orders of vascular bundles and papillae on epidermal long cells, were compared for their diagnostic value. The cross-sectional analysis revealed that the complex vascularization was not more frequent than the simple vascularization in the southern species. Regarding surface features, papillae on long cells were found to be highly inconsistent. As in previously studied Guadua species, silica cells with a saddleshape and smooth walls were identified as the most frequent type. These findings underscore the challenges of using foliar anatomical traits to delimit Guadua species. The low variability observed may reflect a combination of historical and ecological factors, such as the location of these taxa at the southern limit of the genus distribution.This study provides descriptive evidence for future assessments of character homology in a phylogenetic context. Also supports the importance of integrative approaches that use anatomical and molecular data to improve the taxonomic and phylogenetic resolution of Guadua.