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

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.