Plant photosynthesis under heat stress: Effects and management

Climate change and global warming have increased the frequency of extreme heat stress events that severely affect plant production. Photosynthesis is an intricate heat-sensitive physiological process. Heat stress affects CO₂ assimilation, photochemical reactions, D1 and D2 protein turnover, and chlorophyll biosynthesis. Heat stress-induced damage to chloroplast downregulates important chloroplast components and inactivates heat-sensitive proteins, including RuBisCo activase, causing redox imbalance, reducing photosynthetic efficiency, and possibly causing cell death. As all photochemical processes in the Calvin cycle in the stroma and thylakoid lamellae of the chloroplast are prone to heat stress injury, these organelles are the primary activators of cellular heat stress responses and signaling. This review describes approaches to protect crop plants against heat-induced photochemical damage and discusses chloroplast responses, sensitivity, and retrograde signaling that contribute to the sensitivity and tolerance of photosynthetic apparatus.