Anatomy and ontogeny of inflorescence and flower of Bactris simplicifrons Mart. (Arecaceae, Arecoideae, Bactridinae)

Abstract

Bactris simplicifrons Mart. is considered a complex of species, due to its extensive distribution and considerable variability. Therefore, we investigated the ontogeny and morphoanatomy of its inflorescences and flowers to provide valuable biological information and identify features of interest for the taxonomy and systematics of the species and genus. To achieve this, we collected inflorescences from individuals growing in Manaus, Brazil. Based on the observed morphological characteristics, we established different developmental stages. The sampled material underwent standard protocols for light and scanning electron microscopy. This study reports for the first time, the development of connate bracts in Bactris and Arecaceae. Noteworthy is the centripetal development of the androecium, as opposed to the centrifugal pattern observed in other Bactris species. We identified traits that may be included in a phylogenetic study, such as epipetaly and the papillose style canal. The synascidiate proximal portion and symplicate distal portion of the gynoecium, becoming assimplicate in the most distal zone, is a relevant characteristic compared to other Arecaceae. Additionally, we characterized the histological arrangement of the inflorescence and each floral organ, and described the observed trichomes. Features with potential diagnostic value compared to other species in the genus include the length of stigmatic lobes, trichome morphology, absence of rigid emergence, staminal filament morphology, among others.