Investigating the Impact of Elevated CO ₂ on Biomass Accumulation and Mineral Concentration in Foliar and Edible Tissues in Soybeans

Rising atmospheric carbon dioxide (CO₂) levels are expected to enhance biomass and yield in C₃ crops. However, these benefits are accompanied by significant reductions in the concentrations of essential nutrients in both foliar and edible tissues, posing potential global nutritional challenges. In this study, we grew three soybean cultivars (Clark, Flyer, and Loda) in ambient ( ~ 438 ppm) and elevated CO₂ ( ~ 650 ppm) conditions using open top chambers and measured changes in leaf-level physiological responses, biomass accumulation, and nutrient concentrations across developmental stages. Elevated CO₂ increased carbon assimilation and decreased stomatal conductance, which led to an increase in seed yield, while root biomass remained unchanged. Seed nutrient concentrations, particularly iron (Fe), zinc (Zn), manganese (Mn), boron (B), phosphorus (P), potassium (K), and magnesium (Mg), decreased at maturity. We hypothesize that reductions in seed mineral concentration resulted from enhanced carbon assimilation and biomass accumulation without a concomitant response in root biomass and nutrient uptake. This constrained the plant's ability to maintain nutrient status with increased yield at elevated CO₂, and this response was conserved across the cultivars included in this study. Future work is needed to further understand the molecular mechanisms associated with these physiological responses at elevated CO₂ in soybean.