P. maximum and C. gayana were treated with potassium fluoride artificial rain (15 mg ml-1) to identify injury caused by fluoride (F-), as an atmospheric pollutent, on the leaf structure of these two species, providing diagnostics characteristics for plant selection to be used as bioindicators. The observed symptons were clorosis and necrosis in the leaf blade. Four types of cell alterations were observed in transversal sections: reductions of number, size and chloroplasts disposition; necrosis of tissues in the leaf; leaf surface erosions and cells hypertrophy. In C. gayana chloroplast alterations were not observed and the other symptoms were less evident. Phenolic compounds were registered in the regions where lesions occurred. In the scanning electron microscopy external cell wall flattening was observed. This experiment assures the greatest P. maximum sensitivity to fluoride and reveals anatomic characteristics of C. gayana that can contribute for great resistance of this species to fluoride.
Anatomy; Poaceae; bioindicators; fluoride; pollution
