Ontogeny, histochemistry, and the influence of rocky outcrops on secretory ducts in leaves of Kielmeyera rubriflora Cambess (Calophyllaceae)

Abstract Calophyllaceae in Brazil is represented by seven genera and 96 species, including trees, subshrubs, shrubs, and some lianas, characterized by the presence of canals and cavities responsible to produce bioactive compounds. Although investigations on these structures have been conducted in adult leaves of Kielmeyera rubriflora Cambess, gaps in knowledge remain. Therefore, this study aims to investigate the ontogeny of the ducts, their distribution pattern, the main metabolites present in the secretion, and the influence of rocky outcrops in the Amazonian Savanna on duct density and lumen area. Samples of shoot apices with leaf primordia and leaves at different developmental stages were collected from three distinct substrates in the Amazonian Savanna in Nova Canaã do Norte. The samples were processed using standard plant anatomy methodologies. The ducts of K. rubriflora Cambess develop from the ground meristem through schizogenous formation and are located beneath the epidermis, in the cortical parenchyma, near the phloem, and in the central parenchyma. The anatomical characteristics described for K. rubriflora Cambess are consistent with previous studies. Based on histochemical analyses, we observed that the secretion is of a lipophilic and hydrophilic nature. Regarding the influence of rocky outcrops, variations in duct density and lumen size were observed. We conclude that anatomical studies of K. rubriflora Cambess eaves are essential for understanding its adaptive strategies and for the taxonomic delimitation of Kielmeyera . The metabolites identified play crucial roles in plant protection and resistance, and the differences observed in duct density and lumen area among substrates suggest a possible environmental influence, which should be tested using broader sampling.