Abstract: By using open top chambers (OTCs), soybean plants were grown in pots, and exposed to charcoal-filtered air (［O₃］<10 μg·kg^-1) and elevated O₃(80 μg·kg^-1) after anthesis, aimed to investigate the responses of soybean’s agronomic characters, leaf area, chlorophyll content, antioxidant system, and grain yield to elevated O₃. Under elevated O₃, the leaf area and chlorophyll content decreased significantly (P<0.05), and the leaf catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activities had a significant increase(P<0.01) first but a gradual decrease then, compared with those under charcoal-filtered air. Elevated O₃ decreased the leaf soluble protein and ascorbate content (AsA) contents while increased the leaf malonaldehyde (MDA) content (P<0.05), suggesting that the leaf membrane lipid peroxidation was accelerated. The dry mass per plant, effective pod number, grain number, 100-grains weight, and grain yield under elevated O₃ had somewhat decreased, among which, grain yield decreased significantly, with the decrement reached to 47% (P<0.01).

Key words: ozone, soybean, chlorophyll, antioxidant enzyme, yield, natural wetland ecosystem, CH₄, climate change, TRIPLEX-GHG.