Reactive oxygen species and environmental stresses

Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. They are generally very small molecules and are highly reactive due to the presence of unpaired valence shell electrons. ROSs form as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling. While ROS have the potential to cause oxidative damage to cells during environmental stress, recent studies have shown that ROS play a key role in plants as signal transduction molecules involved in mediating responses to pathogen infection, environmental stresses, programmed cell death and developmental stimuli. The rapid increase in ROS production, referred to as 'the oxidative burst', was shown to be essential for many of these processes, and genetic studies have shown that respiratory burst oxidase homolog (Rboh) genes, encoding NADPH oxidases, are the main producers of signal transduction-associated ROS in cells during these processes.