Tibouchina pulchra (Cham.) Cogn., a native Atlantic Forest species, as a bio-indicator of ozone: Visible injury

Tibouchina pulchra saplings were exposed to carbon filtered air (CF), ambient non-filtered air (NF) and ambient non-filtered air + 40 ppb ozone (NF + O3) 8 h per day during two months. The AOT40 values at the end of the experiment were 48, 910 and 12,895 ppb h−1, respectively, for the three treatments. After 25 days of exposure (AOT40 = 3871 ppb h−1), interveinal red stippling appeared in plants in the NF + O3 chamber. In the NF chamber, symptoms were observed only after 60 days of exposure (AOT40 = 910 ppb h−1). After 60 days, injured leaves per plant corresponded to 19% in NF + O3 and 1% in the NF treatment; and the average leaf area injured was 7% within the NF + O3 and 0.2% within the NF treatment. The extent of leaf area injured (leaf injury index) was mostly explained by the accumulated exposure of ozone (r2 = 0.89; p < 0.05).