Photosynthesis is a significant source of reactive oxygen species (ROS) in plants, and the photosynthetic electron transport chain (PET) operates in an aerobic environment, necessitating regulatory systems to minimize ROS production. An efficient antioxidant network is essential for processing ROS effectively and maintaining low intracellular ROS levels. Studies using molecular genetics approaches to disable or boost antioxidant enzymes or alter the abundance of antioxidants like ascorbate (AsA) and reduced glutathione (GSH) have demonstrated the importance of the antioxidant network in maintaining high rates of photosynthesis. However, these studies often overlook the context of cellular redox homeostasis and redox signaling within the photosynthetic production of reductants and oxidants. The authors discuss the role of ROS in signaling and their potential to function as useful signaling molecules, particularly under conditions favoring cellular oxidation. They argue that ROS-scavenging systems may have evolved to be "leaky" to allow ROS to serve as signaling molecules. The regulation of photosynthesis is crucial, with efficient regulation of PET minimizing ROS production and preventing photoinhibition. The linear and cyclic electron flow pathways play important roles in balancing energy metabolism and redox status. The antioxidant network in chloroplasts includes AsA-GSH and TRX/GPX cycles, which metabolize H₂O₂ and dissipate excess excitation energy. These cycles are essential for maintaining photosynthetic function, and their coordination is critical. Genetic manipulation of antioxidant defenses, such as overexpression of SOD, GR, and DHAR, has shown effectiveness in enhancing plant tolerance to abiotic stress. The authors also explore the involvement of antioxidants in redox signaling pathways, including chloroplast-to-nucleus retrograde signaling, which regulates gene expression in response to environmental changes. They conclude that enhancing antioxidant capacity can desensitize photosynthesis to environmental changes and improve stress tolerance by allowing ROS signals to persist within the cellular environment.Photosynthesis is a significant source of reactive oxygen species (ROS) in plants, and the photosynthetic electron transport chain (PET) operates in an aerobic environment, necessitating regulatory systems to minimize ROS production. An efficient antioxidant network is essential for processing ROS effectively and maintaining low intracellular ROS levels. Studies using molecular genetics approaches to disable or boost antioxidant enzymes or alter the abundance of antioxidants like ascorbate (AsA) and reduced glutathione (GSH) have demonstrated the importance of the antioxidant network in maintaining high rates of photosynthesis. However, these studies often overlook the context of cellular redox homeostasis and redox signaling within the photosynthetic production of reductants and oxidants. The authors discuss the role of ROS in signaling and their potential to function as useful signaling molecules, particularly under conditions favoring cellular oxidation. They argue that ROS-scavenging systems may have evolved to be "leaky" to allow ROS to serve as signaling molecules. The regulation of photosynthesis is crucial, with efficient regulation of PET minimizing ROS production and preventing photoinhibition. The linear and cyclic electron flow pathways play important roles in balancing energy metabolism and redox status. The antioxidant network in chloroplasts includes AsA-GSH and TRX/GPX cycles, which metabolize H₂O₂ and dissipate excess excitation energy. These cycles are essential for maintaining photosynthetic function, and their coordination is critical. Genetic manipulation of antioxidant defenses, such as overexpression of SOD, GR, and DHAR, has shown effectiveness in enhancing plant tolerance to abiotic stress. The authors also explore the involvement of antioxidants in redox signaling pathways, including chloroplast-to-nucleus retrograde signaling, which regulates gene expression in response to environmental changes. They conclude that enhancing antioxidant capacity can desensitize photosynthesis to environmental changes and improve stress tolerance by allowing ROS signals to persist within the cellular environment.