The book is about complex antioxidant system development in Plants under heavy metal stress by which they scavenge ROS thereby protecting cell from oxidative attack. A common feature of different stress factors is there potential to increase the production of reactive oxygen species in plant tissues. Reactive oxygen species are also generated in plant cells during normal metabolic functions especially in chloroplast during photosynthesis. ROS are produced as intermediate products in a number of metabolic reactions in various cellular organelles, generated by oxidative stress in plants. Heavy metals are known to generate these toxic ROS such as H2O2,O2-, OH- etc which degrade important cellular components by including oxidative stress. In order to control the level of ROS and protect cell from oxidative injury, plant and developed a complex antioxidant defense system to scavenge the ROS and result in the degradation of sulphate reducing enzymes leading to toxic effects. Cr at both toxic and mild concentrations can inhibit uncoupled electron transport indicating electron transport chain to be a common site of chromium binding in plants.