A REVIEW OF REACTIVE OXYGEN SPECIES (ROS) IN PLANTS

Abstract

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