Aluminum in native plants from the Campo Rupestre: Investigating accumulation sites and detoxification mechanisms in...

The presence of aluminum (Al) in the soil as a factor promoting adaptations in the flora of Campos Rupestres (CR)/(Quartzite Rupestrian Grasslands) has been neglected. Our aim was to highlight the accumulation of Al in CR species and to understand the metal resistance strategies of twenty Melastomataceae species collected together with soil samples. The following analyses were carried out: Al and nutrient levels; tests for histolocalization of Al, phenolic compounds and mucilage; mapping of Al, Ca, Fe, Mn and Si in leaves and stems using SEM/EDS; and chemical analysis of the soils. All analyzed species are Al accumulators, with leaf Al concentrations ranging from 1.46 to 27.74 g kg⁻¹ of dry mass. The primary cell walls of different tissues are the main accumulation sites. The presence of Al in meristematic tissues, nuclei, and chloroplasts corroborates the metal's non-toxicity in CR plants. Compartmentalization of Al inside sclereids and mucilaginous idioblasts, complexation with silicon in cell walls and mineralized structures, and exudation of the metal together with secretion from glandular trichomes are possible mechanisms of Al internal detoxification. This study is the first to demonstrate Al accumulation by plants from Campo rupestre quartzitic, a megadiverse Brazilian OCBIL.