Ameliorating Effects of Leaf Water Extract of Three Aromatic Plant Species on Ozone-Polluted Snap Bean (Phaseolus vulgaris L. 'Jiangjunyoudou')

Ozone (O₃) is one of the major pollutants in near-surface air. In order to protect sensitive plants from O₃ 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 O₃ (150 ppb for 3 days, 8 h day^-1) on snap bean (Phaseolus vulgaris 'Jiangjunyoudou'). Our results showed that O₃ 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 O₃. Among them, extract of PHT showed the greatest potential to alleviate the O₃-caused injury, followed by PHB and TP.

Effects of Elevated Ozone on Polka Dot Plant (Hypoestes phyllostachya) with Variegated Leaves

In this study, impacts of O₃ 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^-1, 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 O₃ 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 O₃ stress. After O₃ 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 O₃ due to their roles in photoprotection.