<p style="text-align:left"><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Effects of O3, Doubled CO2 Concentration and drought stress on wheat (<em>Triticum aestivum</em> L.) plants were studied in open-top chambers (OTC). Under doubled CO2 concentration, grain yield and biomass increased, the SOD activity, and carotenoid (Car) content also increased while relative conductivity yield parameters significantly decreased. But under Elevated O3 concentration, the SOD activity, Carotenooids decresaed. The final result was decreased grain yield and plant biomass. Interactive effects of doubled CO2 and O3 concentrations on soybean were mostly counteractive. However, the beneficial effects of concentration-doubled CO2 is more than compensate the negative effects imposed by doubled O3 and the latter in its turn partly counteracted the positive effects of the former.</span></span></p>