Effects of the interaction between ozone and carbon dioxide on gas exchange,photosystem II and antioxidants in rice leaves |
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Authors: | H. Kobayakawa K. Imai |
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Affiliation: | (1) State Key Laboratory of Plant Breeding and Genetics, Sichuan Agricultural University, 625014 Ya’an, Sichuan, China;(2) School of Life Science and Technology, University of Electronic Science and Technology of China, 610054 Chengdu, Sichuan, China;(3) College of Life and Science, Sichuan Agricultural University, 625014 Ya’an, Sichuan, China; |
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Abstract: | To understand the interactive effects of O3 and CO2 on rice leaves; gas exchange, chlorophyll (Chl) fluorescence, ascorbic acid and glutathione were examined under acute (5 h), combined exposures of O3 (0, 0.1, or 0.3 cm3 m−3, expressed as O0, O0.1, or O0.3, respectively), and CO2 (400 or 800 cm3 m−3, expressed as C400 or C800, respectively) in natural-light gas-exposure chambers. The net photosynthetic rate (P N), maximum (Fv/Fm) and operating (Fq′/Fm′) quantum efficiencies of photosystem II (PSII) in young (8th) leaves decreased during O3 exposure. However, these were ameliorated by C800 and fully recovered within 3 d in clean air (O0 + C400) except for the O0.3 + C400 plants. The maximum PSII efficiency at 1,500 μmol m−2 s−1 PPFD (Fv′/Fm′) for the O0.3 + C400 plants decreased for all measurement times, likely because leaves with severely inhibited P N also had a severely damaged PSII. The P N of the flag (16th) leaves at heading decreased under O3 exposure, but the decline was smaller and the recovery was faster than that of the 8th leaves. The Fq′/Fm′ of the flag leaves in the O0.3 + C400 and O0.3 + C800 plants decreased just after gas exposure, but the Fv/Fm was not affected. These effects indicate that elevated CO2 interactively ameliorated the inhibition of photosynthesis induced by O3 exposure. However, changes in antioxidant levels did not explain the above interaction. |
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