Atmospheric CO2 increase benefits symbiotic N2 fixation by legumes under drought

Leguminous plants are considered to have a competitive advantage under global climate change because of increased rates of symbiotic nitrogen (N2) fixation in response to increased atmospheric CO2. However, this hypothetical advantage may not be realized under actual climate change due to the associated increase in frequency and duration of drought, as N2 fixation in legume species such as soybean is sensitive to soil drying. Yet, it has been discovered that N2 fixation in soybean becomes drought-tolerant under increased CO2 concentration. The reduced susceptibility of N2 fixation to drought was associated with an increase in total nonstructural carbohydrates and a decrease in ureides in leaves. These results empirically indicate that legumes will have substantial comparative advantage over cereals under climate change