Influence of elevated CO2 on the sensitivity of two soybean cultivars to sulphur dioxide

Two cultivars of soybean (Glycine mat cv. Bragg and PK 472) were subjected to elevated concentrations of CO2 (600 mul l(-1)) and/or SO2 (0.06 mul l(-1 )), for 8 h from germination to grain maturity in open top chambers under f ield conditions to assess the modification in response to SO2 exposure resu lting form CO2 enrichment. Exposure to SO2 alone resulted in reductions in plant growth, biomass and yield, as well as declines in foliar starch and p rotein content in both the cultivars of soybean. Elevated CO2 stimulated pl ant growth, yield and enhanced foliar starch content, photosynthesis and WU E in both the cultivars. In plants exposed to the combination of elevated C O2 + SO2, the adverse influence of SO2 was mitigated by CO2 enrichment. Thi s effect was considered to result from the provision of extra carbon source s required for repair and detoxification processes and a reduction in SO2 u ptake through reduction in stomatal conductance. PK 472 exhibited greater s ensitivity to SO2 than Bragg. PK 472 also showed greater stimulation of yie ld under CO2 + SO2 treatment than Bragg. (C) 2001 Elsevier Science B.V. All rights reserved.