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

: Projected global climate change is a potential threat for food security. Both rising atmospheric CO2 concentrations ([CO2 ]) 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 [CO2 ] (E-[CO2 ], 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-[CO2 ] 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-[CO2 ] 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-[CO2 ] 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.