Safeguarding crop photosynthesis in a rapidly warming world

Continued greenhouse gas emissions will accelerate global warming and intensity of heat waves, which already harm crop productivity. From the stability of key enzymes to canopy processes, photosynthesis is affected by temperature. All crops suffer declines in photosynthetic rate when temperatures cross critical thresholds, with irreversible losses typically occurring above 40° to 45°C. Protective measures within plants can be induced by growth at elevated temperatures but not from the sudden temperature elevation of heat waves. Strategies to improve the heat resilience of photosynthesis include modifying surface energy balance, optimizing canopy architecture, improving enzymatic heat tolerance, and (re)engineering key metabolic pathways for greater efficiency or to remove bottlenecks. This Review summarizes present knowledge on the major mechanisms that underlie high-temperature inhibition of photosynthesis and explores opportunities for breeding and biotechnological interventions to overcome them.