Changes in the trade-offs between photosynthesis and detoxification capacity among different tree species under ozone...

The persistent elevation of ozone (O₃) levels threatens urban air quality, further exacerbating human diseases and harming vegetation. Urban tree species can take up gaseous pollutants including O₃, through the stomata, to improve air quality and other services for urban ecosystems. In this study, we exposed five urban tree species to five O₃ gradients during one growing season. Our purpose was to comprehensively elucidate the variance in O₃ sensitivity among species and the trade-offs between photosynthesis and detoxification capacity as a function of O₃ pollution. The study revealed variance in O₃ sensitivity among the five species, which were determined by the leaf mass per area and area-based total antioxidant capacity. Fraxinus chinensis and Platanus orientalis were better suited to defend against urban O₃ pollution. The factors limiting photosynthesis reduction under O₃ pollution differed among five species. Additionally, we developed a composite detoxification indicator to assess different trade-offs between photosynthesis and detoxification capacity among species. The trade-offs depended on accumulated O₃ dose and O₃ sensitivity within trees, and disruption of this relationship might further exacerbate biomass suppression under a high accumulated O₃ dose. Thus, for a comprehensive assessment of O₃-induced damage in woody plants, it is needed to focus not only on photosynthetic carbon assimilation but also on plant assimilation-metabolism-accumulation strategy. Incorporation of changes in photosynthesis-detoxification trade-offs would facilitate the selection of species that are more appropriate to local or regional urban O₃ pollution conditions as well as improve measures for the protection of vegetation against O₃ pollution.