GENOTOXIC ACTIVITY OF OZONE IN TRADESCANTIA

Ozone is a strong oxidizing agent commonly present at concentrations o f more than twice the background levels found in most of the continent al United States. Studies on tile mutagenic effects of ozone have freq uently yielded positive results, but die concentrations used were gene rally unrealistically high. In tile present research, the bioindicator plant Tradescantia (clone 4430) was exposed to low levels of ozone in controlled-environment fumigation chambers. Genotoxicity was evaluate d in two standardized genetic endpoints: the formation of micronuclei in the meiotic pollen mother cells (Trad-MCN assay), and the color con version resulting from a point mutation in the mitotic cells of the st amen hairs (Trad-STH assay). No statistically significant (P=0.71) mut agenic effects were observed in the Trad-STH assay, but an increase in genotoxicity (P=0.011) was detected in the Trad-MCN assay. A tendency for genotoxicity to increase with duration of exposure to ozone was a scribed to the generation of free radicals especially in the form of t he hydroxyl (OH.) radicals which indiscriminately attack most cell mac romolecules, including nucleic acids, leading to possible DNA lesions.