Abstract: With opentop chamber (OTC), the effects of elevated CO₂ (550 μmol·mol^-1) and O₃ (80 nmol·mol^-1) and their combination on the biomass, total phenols, and flavone at different growth stages of spring wheat, as well as the yield components at maturity stage, were studied. The results showed that under elevated CO₂, the biomass and yield components were significantly higher than those under ambient CO₂ (342 μmol·mol^-1), while under elevated O₃, these parameters were significantly lower than those under ambient O₃ (30 nmol·mol^-1). The combination of elevated CO₂ and O₃ was at the ntermediate place, indicating that CO₂ could mitigate the negative effects of O₃, while O₃ could weaken the positive effects of CO₂. Elevated CO₂ and O₃ increased the content of total phenols in wheat leaves, and the combination of elevated CO₂ and O₃ had the greatest effect. However, at late growth stage, the increment of total phenols was decreased. At early growth stage, the total content of leaf flavone under elevated CO₂ and O₃ and their combination was lower than the control, but at maturing stage, it was in adverse.

Key words: elevated O₃ concentration, elevated UV-B radiation, soybean, active oxygen, chlorophyll.