Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) in plants– maintenance of structural individuality and functional blend

•ROS/RNS in connection with redox biology constitute a fundamental approach to aerobic life.•Characterization of ROS and RNS based on the aspect of their mode of action in plant cells.•ROS and RNS acquire a pivotal role as regulatory mediators in signaling processes.•Genesis of reactive species in terms of localization of their source and their targets.•Interplay between ROS and RNS during their biosynthesis, protein modification, in signaling pathways and degradation.•Understanding the interventions of ROS and RNS with respect to plant metabolic activity.•Free radicals (ROS and RNS) and their basis in diversification of biomolecules by far ensuing molecular evolution.