Effects of open-air elevated atmospheric CO2 concentration on yield quality of soybean (Glycine max (L.) Merr)

Investigations across the world have elucidated common chemical and physiological responses of plants to the influence of elevated atmospheric CO2 concentration ([CO2]). Focus is now turning to the influence of elevated [CO2] 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 CO2 enrichment (FACE) field experiment at Changping-Beijing (China) under ambient (415 ± 16 μmol mol−1) and elevated (550 ± 19 μmol mol−1) CO2 concentrations. Results showed that elevated [CO2] 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 CO2 enrichment, but oil concentration increased by 2.8%. Accordingly, most proteinogenic amino acid concentrations were significantly reduced under elevated [CO2], 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 [CO2] may improve the oil quantity of soybean, corresponding reductions in the nutritive value are likely to occur.