Effect of ambient-level gas-phase peroxides on foliar injury, growth, and net photosynthesis in Japanese radish (Raphanus sativus).

Abstract To investigate the effects of ambient-level gas-phase peroxides concurrent with O 3 on foliar injury, photosynthesis, and biomass in herbaceous plants, we exposed Japanese radish ( Raphanus sativus ) to clean air, 50 ppb O 3 , 100 ppb O 3 , and 2–3 ppb peroxides + 50 ppb O 3 in outdoor chambers. Compared with exposure to 100 ppb O 3 , exposure to 2–3 ppb peroxides + 50 ppb O 3 induced greater damage in foliar injury, net photosynthetic rates and biomass; the pattern of foliar injury and the cause of net photosynthetic rate reduction also differed from those occurring with O 3 exposure alone. These results indicate for the first time that sub-ppb peroxides + 50 ppb O 3 can cause more severe damage to plants than 100 ppb O 3 , and that not only O 3 , but also peroxides, could be contributing to the herbaceous plant damage and forest decline observed in Japan's air-polluted urban and remote mountains areas.