Reactive oxygen species (ROS) are generated in the plants during cellular metabolism. But extreme environmental conditions like drought, salinity or floods etc. lead to an enhanced level of these ROS in plants, which cause deterioration of lipids, proteins and nucleic acids and ultimately death of a plant. Growing evidence has suggested that ROS play a critical role as the signaling molecules throughout the entire cell death pathway. Though ROS act as a signalling molecule, but they can cause oxidative burst if there is an imbalance between ROS generation and their scavenging. Apart from these ROS, nitrogen species (RNS) also play a significant role in causing oxidative damage and tissue dysfunction and act as molecular signals. Consequently, cells develop a balanced system to counteract the effect of ROS, such as antioxidative defense system comprises enzymatic antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidases etc. and non-enzymatic antioxidants which cooperatively reduce oxidative state. Herein, we review the novel findings of cellular processes induced by ROS and RNS and recapitulate the functions of cellular endogenous antioxidant systems as well as natural anti-oxidative compounds in plants to facilitate the illustration of the imperative role of antioxidants in prevention against oxidative stress.
