Effects of Emissions from an Aluminium Smelter in a Tree Tropical Species Sensitive to Fluoride

Abstract

Fluoride is among the most phytotoxic atmo- spheric pollutants, commonly linked to the appearance of lesions in susceptible plants around emitting sources. In order to assess the effects of fluoride on leaves of Spondias dulcisParkinson (Anacardiaceae), plants were examined 78 km (non-polluted area) and 0.78 km (pol- luted area) from an aluminium smelter. The level of fluoride increased with the exposure time of the plants in the polluted area. On the third day of exposure in the polluted area, necroses with typical colouration were observed. Micromorphological damage began at the abaxial epidermis, mainly associated with the stomata. Starch grain accumulation was more pronounced in the midrib. The cell membranes and chloroplasts were greatly affected by the pollutant. We observed accumu- lation of phenolic compounds and electron-dense mate- rial at the boundaries of the ending veinlets. The micro- scopic events described precede the appearance of symptoms and are therefore of prognostic value in predicting injury by fluoride and will be useful as biomarkers. The high sensitivity of S. dulcis to fluoride and the specificity of the symptoms confirm, for the first time, in an experiment of active biomonitoring, the potential of this species as a bioindicator.