Physiological and Proteomic Evidence for the Interactive Effects of Post-Anthesis Heat Stress and Elevated CO₂ on...

Elevated CO₂ promotes leaf photosynthesis and improves crop grain yield. However, as a major anthropogenic greenhouse gas, CO₂ contributes to more frequent and severe heat stress, which threatens crop productivity. The combined effects of elevated CO₂ and heat stress are complex, and the underlying mechanisms are poorly understood. In the present study, the effects of elevated CO₂ and high-temperature on foliar physiological traits and the proteome of spring wheat grown under two CO₂ concentrations (380 and 550 µmol mol^-1 ) and two temperature conditions (ambient and post-anthesis heat stress) are examined. Elevated CO₂ increases leaf photosynthetic traits, biomass, and grain yield, while heat stress depresses photosynthesis and yield. Temperature-induced impacts on chlorophyll content and grain yield are not significantly different under the two CO₂ concentrations. Analysis of the leaf proteome reveals that proteins involved in photosynthesis as well as antioxidant and protein synthesis pathways are significantly downregulated due to the combination of elevated CO₂ and heat stress. Correspondingly, plants treated with elevated CO₂ and heat stress exhibit decreased green leaf area, photosynthetic rate, antioxidant enzyme activities, and 1000-kernel weight. The present study demonstrates that future post-anthesis heat episodes will diminish the positive effects of elevated CO₂ and negatively impact wheat production.