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In this study, impacts of O on four cultivars ('Rose', 'Pink', 'Blush' and 'White') of the polka dot plant with variegated leaves were investigated for the first time. Ozone fumigation [(120 ± 20 ppb) for 14 days (8 h day, from 8:30 to 16:30)] resulted in visible foliar injuries, decreased contents of pigments (chlorophyll a and b, and carotenoid), the inhibition of photosynthesis, the increase of quantum yield of non-regulated heat dissipation and fluorescence emission (Y(NO)), and the damage of cell membrane. Elevated O increased the content of anthocyanin (Ant). 'White' showed the highest, and 'Rose' the lowest amount of injured leaf area, indicating that the former was the most sensitive, and the latter the most tolerant to O stress. After O exposure, the highest Ant content was found in 'Rose', followed by 'Pink', 'Blush', and 'White'. Levels of Ant were likely responsible for the different sensitivities to O due to their roles in photoprotection.

Ozone (O) is one of the major pollutants in near-surface air. In order to protect sensitive plants from O pollution, many kinds of protectants including synthetic ones, were assessed in previous studies. Although they have certain protective effects, some of them are not environment-friendly. In the present study, leaf water extracts of aromatic plants [Plectranthus hadiensis var. tomentosus (PHT), Pelargonium hortorum (PHB), Tagetes patula (TP)] were compared for mitigating the damages caused by O (150 ppb for 3 days, 8 h day) on snap bean (Phaseolus vulgaris 'Jiangjunyoudou'). Our results showed that O fumigation impaired plasma membrane, decreased chlorophyll content, increased contents of malondialdehyde and superoxide anion, inhibited photosynthesis, and caused visible injury. Leaf water extracts of PHT, PHB or TP ameliorated the negative effects of O. Among them, extract of PHT showed the greatest potential to alleviate the O-caused injury, followed by PHB and TP.