This volume provides basic information on reactive oxygen species (ROS) and describes the new developments in the action of ROS and the role of antioxidants and the mechanisms that have been developed to scavenge free radical associated cellular damage. It illustrates the chemistry of ROS, ROS signaling, antioxidative defense systems, transgene approach in scavenging ROS and the role of oxidative stress in plant recalcitrance and hyperhydricity, and how plants orchestrate their response to morphogenesis. It also includes a brief account on the use of medicinal plants for natural antioxidants, focusing biochemical details.