ROS Generation in the Light Reactions of Photosynthesis Triggers Acclimation Signaling to Environmental Stress

In the light reactions of photosynthesis, reactive oxygen species (ROS), such as superoxide anion radical (O2•−), hydrogen peroxide (H2O2), singlet oxygen (1O2*), and hydroxyl radical (OH•), are continuously generated at basal levels and are kept in homeostasis by the antioxidative enzymatic and non-enzymatic systems. Nevertheless, under abiotic or biotic stress conditions, this balance between the creation and elimination of ROS is disrupted, and the increased ROS production leads to oxidative stress, which is involved in the growth retardation of plants. However, ROS are also beneficial, since they trigger the plant’s defense mechanisms for handling oxidative stress and are fundamental signaling molecules for the regulation of a range of physiological functions under optimum growth conditions or environmental stress circumstances, activating a plethora of acclimation responses. Gaining insight into the relationship between ROS generation, ROS scavenging, and the protective role of ROS will contribute to improving agricultural sustainability in the face of global climate change.