[Responses of soybean cultivar Dongsheng-1 to different O3 concentrations in northeast China].

Soybean cultivar Dongsheng No. 1 [Glycine max (L.) Mer.] was exposed to charcoal-filtered air (CFA), non-filtered air (NFA) and non-filtered air with ozone addition (NFA + O3) in nine open-top chambers. Individual yield and yield components at maturity, C, N concentration in leaf and seed, gas exchange, chlorophyll a fluorescence and pigments content at the full bloom stage were measured with an AOT40 value of 10.6 microL x L(-1) x h during the growing season. Compared to CFA, NFA reduced individual yield and 100-seed weight by 4.5% and 4% respectivley, while NFA + O3 treatment significantly reduced each of them by 34% and 18%. However, plant height, node numbers of main stem, pods per plant and number of seeds per pod remained unchanged by O3 addition. Leaf C, N concentrations at the seed filling stage under NFA + O3 also significantly increased by 3% and 26%, respectively, while the CN ratio significantly decreased by 18%. Moreover, compared to CFA and NFA, NFA + O3 caused significant reductions in the photosynthetic parameters at the full bloom stage, e.g. significant declines in net photosynthetic rates, stomatal conductance, water use efficiency, fluorescence parameters of F'(v)/F'(m) and phi(PS II). It is proposed that lower photosynthetic rates, reduced photochemical efficiency in PS II and the decline in 100-seed weight might be the main reasons contributing to the lower individual yield of soybean plant by elevated O3.