The emission of fluorides to the atmosphere arising from the production of superphosphate and ceramics has caused concern because of toxic effects on plants. However, few studies have been developed about fluoride (F) pollution with agricultural crops. A study evaluated the effect of atmospheric F in guinea grass and maize plants, using reference bioindicator plants of the type sensitive and tolerant. The plants were exposed to atmospheric contamination by F for short periods during 32 days in a misting system delivering 0.16 mol L-1 of hydrofluoric acid inside a chamber (~ 0.20 mmol m-3 of F). Unexposed plants (control) were also evaluated, with four replications. Exposure of plants to F caused an increase in leaf fluoride concentration up to 60 mg kg-1 for guinea grass and 100 mg kg-1 in the new leaves and 170 mg kg-1 in the old leaves for four varieties of maize, which demonstrated the cumulative effect of the element in the environment. Visual symptoms of toxicity were observed in plants and characterized by occurrence of chlorosis and necrosis on leaf blades. The guinea grass proved to be a species very sensitive to air pollution. The maize varieties DKB 390 and Omega 8315 were more sensitive to F when compared to the AG7088 and 2B707 ones. Chlorophyll a in plants was more affected by the F in relation to the contents of chlorophyll b.
Panicum maximum Jacq.; Zea mays L.; bioindicators; fitotoxicity; chlorophyll content
