Investigations across the world have elucidated common chemical and physiological responses of plants to the influence of elevated atmospheric CO 2 concentration ([CO 2]). Focus is now turning to the influence of elevated [CO 2] on yield quality among a number of globally important crops including soybean ( Glycine max (L.) Merr). Soybean cv. Zhonghuang 35 was grown in a free-air CO 2 enrichment (FACE) field experiment at Changping-Beijing (China) under ambient (41516 mol mol -1) and elevated (55019 mol mol -1) CO 2 concentrations. Results showed that elevated [CO 2] increased the yields of soybean seeds (g m -2) by 26% and 31% respectively, in 2009 and 2011. Total protein concentration in seeds was significantly reduced by 3.3% under CO 2 enrichment, but oil concentration increased by 2.8%. Accordingly, most proteinogenic amino acid concentrations were significantly reduced under elevated [CO 2], whilst two fatty acids (linoleic acid and palmitic acid) increased in concentration. The protein and oil yield per unit ground area increased by 24.5% and 32.0%, respectively. Results indicate that whilst future elevated atmospheric [CO 2] may improve the oil quantity of soybean, corresponding reductions in the nutritive value are likely to occur.
