Rudgea viburnoides (Rubiaceae) overcomes the low soil fertility of the Brazilian Cerrado and hyperaccumulates aluminum in cell walls and chloroplasts

Abstract

Rudgea viburnoides (Cham.) Benth. is an aluminum (Al) hyperaccumulator species native to the Brazilian Cerrado and can be found on soils with different fertilities and Al availabilities. We studied the relationship between the chemical composition of different soils and the Al and nutrient concentrations in the species. Histolocalization of Al and its probable complexation with phenols were investigated. Aluminum in R. viburnoides roots, stems and leaves was detected through histochemical tests, confocal microscopy, and X-ray microanalysis. Phenol localization and concentration were determined, as was the plant nutritional status. Despite the low soil fertilities, nutrient concentrations in vegetative organs were high. Even with the differences in Al availability in the soils, R. viburnoides accumulated more than 10 g Al kg−1 DW on leaves. Pectocellulosic cell walls were preferential sites for Al deposition, but the metal also accumulated in suberized cell walls and chloroplasts. Aluminum localization coincided with Si distribution in cell walls and phenol distribution in the cytosol. Rudgea viburnoides has a great ability to absorb nutrients from poor soils and the hyperaccumulation of Al is independent of the metal availability in the soil. Aluminum accumulation on the phellem and chloroplasts was described for the first time in this species.