Tolerance of Hancornia speciosa Gomes (Apocynaceae) to potassium fluoride: physiological and anatomical traits

Fluoride (F) is considered one of the most phytotoxic pollutants, even when present in low concentrations. When dispersed in the air, F can be transported to about 100 km from the polluting source, reaching plants, animals and humans and causing serious damage. Nevertheless, studies are still scarce on the effect of fluoride in Cerrado species integrating morphological, anatomical and physiological responses. Therefore, this study aimed to investigate the effect of simulated rainfall containing potassium fluoride (KF) on Hancornia speciosa leaves and roots, to determine its bioaccumulator potential. Young plants at approximately 45 days of emergence were treated daily with simulated KF rain at four concentrations (0, 4, 8 and 12 mg L −1 ), and four replicates. The experiment was carried out for 40 days, in completely randomized design. After KF exposure, visual, morphological and chlorophyll a fluorescence analyses were performed, alongside fluoride accumulation assessments in roots and shoots. Hancornia speciosa did not present any visual, anatomical and physiological symptoms in response to fluoride; however, it showed an accumulation of phenolic compounds in mesophyll root and leaf cells in all treatments. Physiological characteristic preservation and fluoride accumulation in roots and leaves allow us to suggest that Hancornia speciosa displays tolerance potential at the investigated doses.