Reactive oxygen species (ROS): Chemistry and role in plant physiology

During the life cycle of plants, including the postharvest period of fruit and vegetable products, reactive oxygen species (ROS) are produced in the electron transfer processes of basal metabolism and they can accumulate in intra- and extracellular compartments under certain conditions. ROS are key players in physiological processes of development and response to environmental conditions, participating in growth, defense, acclimation, and genetically programmed cell death. ROS homeostasis and actions depend on the balance between ROS generation, and their counterpart ROS processing systems, playing a central role in short- and long-term local and systemic signaling processes involving hormones, enzymes, calcium, among others. This chapter analyzes the characteristics of ROS production in plants under basal and stress conditions, and the signaling pathways in which they play a fundamental role, such as development and response to environmental modifications.