Responses of field-grown soybean (cv. Essex) to elevated SO 2 under two atmospheric CO 2 concentrations

Abstract

The objective of this research was to determine the effects of elevated concentrations of carbon dioxide (CO 2) and sulfur dioxide (SO 2) on field-grown soybean. Soybeans ( Glycine max L. Merr. cv. ‘Essex’) were grown a full-season in open-top field chambers exposed to either ambient (350 μl L −1) or elevated CO 2 (500 μl L −1) levels under two levels of SO 2 (0.00 and 0.12 μl L −1). Enriched CO 2, with or without SO 2 treatments, significantly increased net photosynthesis rates, leaf area index (LAI; in R4 growth stage) and leaf dry weight, but did not significantly affect stomatal resistance, transpiration rates, leaf area, plant height, total biomass or grain yield. Elevated SO 2 treatments significantly decreased photosynthesis and LAI during pod fill stages, but did not significantly affect stomatal resistance, transpiration, total biomass, plant height or grain yield. Sulfur dioxide inhibited growth and development (i.e., LAI) during canopy coverage before any effects on photosynthesis were detected. The interactive effects of CO 2 and SO 2 treatments on the gas exchange parameters were significant during pod fill, where high SO 2 reduced photosynthesis at ambient CO 2 but not under elevated CO 2. Leaf area index values were likewise reduced by SO 2 exposure under ambient CO 2 during late flowering and pod fill stages. Thus, enriched CO 2 under high SO 2 exposure partially compensated for the negative impact of SO 2 stress on PS and LAI during the pod fill stages.