Reactive oxygen species in plants: spatiotemporal organization, redox signaling, and stress adaptation

Reactive oxygen species act as source-specific signals whose timing, buffering, and network interactions regulate plant development, defense, stress acclimation, and crop resilience. Reactive oxygen species (ROS) serve as key regulators of plant biology, functioning not only as harmful oxidants produced during aerobic metabolism but also as precisely controlled signaling molecules that coordinate growth, development, defense, and environmental adaptation. Recent advances in plant redox biology reveal that the biological effects of ROS depend more on their chemical nature, subcellular source, spatiotemporal dynamics, and integration with broader signaling networks than on their overall accumulation. In plants, chloroplasts, mitochondria, peroxisomes, the apoplast, and plasma membrane-associated oxidases form interconnected ROS-producing hubs, whose outputs are continually modulated by enzymatic and non-enzymatic antioxidant systems. Such dynamic buffering does not simply eliminate ROS, but preserves redox homeostasis while maintaining signaling competence. Additionally, ROS signals are interpreted through extensive cross-talk with calcium, phytohormones, nitric oxide (NO), mitogen-activated protein kinase cascades, and transcriptional regulators, enabling identical or similar ROS species to induce diverse developmental or stress responses depending on the context. Current understanding of compartment-specific ROS generation, scavenging, sensing, and signal propagation in plants is synthesized here, with particular emphasis on signaling specificity, redox thresholds, and intercompartmental communication. Attention is also directed toward the operation of ROS-regulatory networks during development and under abiotic and biotic stress, including increasingly complex multifactorial stress scenarios. In addition, recent advances in ROS imaging, biosensing, and quantitative analysis are evaluated for their contribution to resolving persistent questions in plant redox biology. By emphasizing spatial and temporal regulation rather than oxidative stress alone, the review provides an integrated framework for understanding how plants decode ROS signals and how such knowledge may be harnessed to improve crop resilience, productivity, and sustainability.