ABSTRACT
This chapter discusses some factors that are specific for reactive oxygen species (ROS) formation in plants. The term ROS is used to incorporate the molecule of hydrogen peroxide, which is not a radical by definition, but its chemical properties are similar to those of superoxide, and it can easily form the highly reactive hydroxyl radicals. The generation of oxygen free radicals during photosynthesis is, therefore, practically unavoidable. Besides providing the energy for photosynthesis, solar radiation can directly energize molecules, leading to the formation of radicals. It has long been suspected that ROS participate in tissue damage observed during plant infection by pathogens. The chapter concluded with that how so many different environmental stresses generate a secondary oxidative stress and proposed an intriguing speculation that the secondary oxidative stress may function as a genetic rheostat regulating the plant's mutation rate. Plants adapted to given conditions do not experience the stress; therefore, they do not produce ROS.
