Changes in grain protein and amino acids composition of wheat and rice under short‐term increased CO2 and temperature of canopy air in a paddy from East China

Summary Projected global climate change is a potential threat for food security. Both rising atmospheric CO 2 concentrations (CO 2 ) and temperatures have significant impacts on crop productivity, but the combined effects on grain quality are not well understood. We conducted an open‐air field experiment to determine the impacts of elevated CO 2 (E‐CO 2 , up to 500 μmol mol −1 ) and warming (+2°C) on grain yield, protein and amino acid (AAs, acid digests) in a rice–winter wheat rotation system for 2 yr. E‐CO 2 increased grain yield by 11.3% for wheat and 5.9% for rice, but decreased grain protein concentration by 14.9% for wheat and by 7.0% for rice, although E‐CO 2 slightly increased the ratio of essential to nonessential AAs. With a consistent decline in grain yield, warming decreased protein yield, notably in wheat, despite a smaller increase in protein concentration. These results indicate that warming could partially negate the negative impact by E‐CO 2 on grain protein concentration at the expense of grain yield; this tradeoff could not fully offset the negative effects of climate change on crop production.