Ecophysiological, anatomical and ultrastructural characteristics of Vitex polygama Cham. (Verbenaceae) submitted to different concentrations of fluoride

Resumo

Fluorides released during the manufacture of aluminum, fertilizers, glass and ceramics are considered to be highly toxic to plants, causing damages in relatively small concentrations. This study aimed to evaluate fluoride (F) accumulation and its effects on Vitex polygama Cham. (Verbenaceae) exposed to simulated rain containing potassium fluoride in concentrations of 5, 10, 15 and 20 mg L^-1. Vitex polygama presented no visual symptoms of foliar injury and accumulated a relatively small amount of F-, significant only for the treatments with higher concentrations of the pollutant.  F- promoted an increase in non-photochemical quenching (qN) and in the coefficient due to non-photochemical extinction (NPQ), which indicates higher dissipation of radiant energy in the heat form. Damages in the chloroplast structure, in cellular membranes and in epicuticular waxes, besides cytoplasm granulation and irregularities in the epidermal cell walls were also detected in plants exposed to the pollutant. The results show a considerable resistance of Vitex polygama to F and reinforce the prognostic value of physiological, anatomical and ultrastructural analysis in the detection of damages caused by the pollutant in the leaf structure of this species.