ABSTRACT
Climate change and global warming have exacerbated the intensity as well as the duration of abiotic stresses such as extreme temperature events, excess or deficient precipitation in different zones of the globe, etc. Plants during development often encounter a particular stress or combination of stresses that not only damages their growth and productivity but also incurs economic losses and challenges food security. To feed the world’s population, enhancing plant development and yield under the increasingly challenging changing climate is a herculean task. Plants normally produce a small number of reactive oxygen species (ROS) as part of aerobic metabolism. ROS generated during routine plant metabolic activities are generally regulated by plant intrinsic defense mechanisms comprising enzymatic and non-enzymatic antioxidants. However, the onset of abiotic stress triggers over-production of ROS, primarily including superoxide radical (O2⸱⁻), singlet oxygen (1O2), hydroxyl radical (⸱OH), and hydrogen peroxide (H2O2) in different plant cell organelles. Production of ROS above the antioxidants’ quenching threshold level results in an oxidative burst. As some of the ROS are extremely toxic and reactive, the excess accumulation leads to oxidative stress. ROS molecules affect plant performance by disrupting the structure and function of cellular biomolecules, particularly DNA, RNA, proteins, and lipids, and lead to plant cell death. Though ROS negatively stimulate plant growth under stress, however, they also participate in molecular signaling leading to enhanced plant tolerance against abiotic stress(es). Thus, due to their dual properties, ROS are regarded as a double-edged sword. In this chapter we have summarized the metabolism of ROS and the mechanism of stimulating plant defense systems under abiotic stress(es).
