Elevated CO(2) has concurrent effects on leaf and grain metabolism but minimal effects on yield in wheat

While the general effect of CO(2) enrichment on photosynthesis, stomatal conductance, N content, and yield has been documented, there is still some uncertainty as to whether there are interactive effects between CO(2) enrichment and other factors, such as temperature, geographical location, water availability, and cultivar. In addition, the metabolic coordination between leaves and grains, which is crucial for crop responsiveness to elevated CO(2), has never been examined closely. Here, we address these two aspects by multi-level analyses of data from several free-air CO(2) enrichment experiments conducted in five different countries. There was little effect of elevated CO(2) on yield (except in the USA), likely due to photosynthetic capacity acclimation, as reflected by protein profiles. In addition, there was a significant decrease in leaf amino acids (threonine) and macroelements (e.g. K) at elevated CO(2), while other elements, such as Mg or S, increased. Despite the non-significant effect of CO(2) enrichment on yield, grains appeared to be significantly depleted in N (as expected), but also in threonine, the S-containing amino acid methionine, and Mg. Overall, our results suggest a strong detrimental effect of CO(2) enrichment on nutrient availability and remobilization from leaves to grains.