Elevated CO(2) alters distribution of nodal leaf area and enhances nitrogen uptake contributing to yield increase of soybean cultivars grown in Mollisols

Understanding how elevated CO(2) affects dynamics of nodal leaf growth and N assimilation is crucial for the construction of high-yielding canopy via breeding and N management to cope with the future climate change. Two soybean cultivars were grown in two Mollisols differing in soil organic carbon (SOC), and exposed to ambient CO(2) (380 ppm) or elevated CO(2) (580 ppm) throughout the growth stages. Elevated CO(2) induced 4–5 more nodes, and nearly doubled the number of branches. Leaf area duration at the upper nodes from R5 to R6 was 4.3-fold greater and that on branches 2.4-fold higher under elevated CO(2) than ambient CO(2), irrespective of cultivar and soil type. As a result, elevated CO(2) markedly increased the number of pods and seeds at these corresponding positions. The yield response to elevated CO(2) varied between the cultivars but not soils. The cultivar-specific response was likely attributed to N content per unit leaf area, the capacity of C sink in seeds and N assimilation. Elevated CO(2) did not change protein concentration in seeds of either cultivar. These results indicate that elevated CO(2) increases leaf area towards the upper nodes and branches which in turn contributes yield increase.