A REVIEW OF REACTIVE OXYGEN SPECIES (ROS) IN PLANTS

Reactive oxygen species (ROS) are highly reactive intermediates of oxygen formed during successive reduction ofoxygen. Most common ROS include singlet oxygen 1O2, Superoxide (O2•−), Hydrogen Peroxide (H2O2), and Hydroxylradical (•OH). ROS are produced as by-products of normal aerobic metabolism in plants. However, during biotic orabiotic stress conditions ROS greatly increase in number causing oxidative stress. The highly reactive nature of thesespecies poses a problem for cellular metabolism. Oxidative damage caused by ROS can even lead to cell death. As theproduction of ROS is inevitable, plants have evolved means to eliminate ROS and maintain a reducing environment inthe cell. These strategies involve antioxidant enzymes as well as non-enzymatic antioxidant compounds. Two systemswork together to neutralise reactive species and protect the cell from oxidative injury. A useful aspect of ROS has alsobeen observed in that they act as second messengers in signalling. Ultimately, it is important to maintain equilibriumbetween the production and removal of ROS for a healthy cellular environment. This review deals with mechanisms ofproduction of ROS and strategies of a plant cell to scavenge them.