ABSTRACT
Biological systems show the operation of metabolic phenomena in a coordinated manner. Such coordination occurring among various cellular organelles is involved in the generation of reactive oxygen species (ROS). Of the various ROS, superoxide anions ( ),O2-singlet or activated oxygen (1O2), hydrogen peroxide (H2O2), hydroxyl ions (OH−), and activated oxygen (O2) (also referred to as prooxidants) are biologically the most important. Since aerobic life originated 2.7 billion years ago, these partially reduced forms of oxygen have been uninvited companions of molecular oxygen. Although initially thought as toxic by-products of the metabolism, ROS are now known to play important roles in modulating plant growth by acting as signaling molecules (Bailey-Serres and Mittler 2006). Reactive oxygen species are involved in the regulation of growth, development, and defensive pathways (Dat et al. 2003) and the unfavorable induction of lipid peroxidation of biomembranes (Liu and Huang 2000; Farooq et al. 2009). These properties make ROS versatile actors in plant biology.
