The book deals with dual role of reactive oxygen species (ROS) which is beneficial and harmful at below and above threshold limits, respectively. To date, the emphasis has been laid only on ROS aspects damaging/ disrupting cellular machinery and inflicting crop productivity loss. The ROS is believed to be a hallmark of both abiotic and biotic stress. However, the recent researches have unambiguously established that the ROS at below threshold confers protection against both abiotic and biotic stress, augmenting crop productivity. This emphasizes for a proper understanding of ROS based physio-molecular mechanisms and their upgradation in crops to adapt them to stress conditions. As a result, the cultivation area of various economically important crops and their productivity and quality can be enhanced, arresting degradation of sites, improving environment quality and mitigating ill impact of climate change. The book encompasses recent information on positive and negative impact of ROS on stress tolerance mechanisms and their management in augmenting crop performance. The information has been well illustrated and categorized in several chapters crafted lucidly, maintaining connectivity and synergy with each other. The book provides up-to-date comprehensive scientific information dual role of ROS, hitherto neglected, in crop abiotic and biotic stress management that would immensely benefit and educate graduate/ post graduate students, entrepreneurs, researchers, scientists and faculty members alike.