Antioxidant Defense Mechanism and High-Temperature Stress Tolerance in Plants

Plants are continuously exposed to various abiotic stresses that limit plant growth, metabolism, and productivity worldwide. Various temperature-sensitive biochemical processes are involved in plants’ growth and development. Oxidative stress is generated by producing several reactive oxygen species (ROS) as by-products during metabolic activities such as respiration and photosynthesis. Rapid cell damage is caused by ROS quick reaction to biological elements such as mitochondrial and nuclear DNA, membrane lipids, cellular proteins, and RNA. To deal with the toxic levels of ROS, plants have a defense mechanism against oxidative damage to overcome stress-induced biochemical and physiological changes. These mechanisms employ the use of proteins, osmoprotectants, antioxidants, ion transporters, and other crucial factors in signaling cascades and transcriptional control. These plant enzymes primarily function as components of the antioxidant defense system and include superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferases (GST), ascorbate peroxidase (APX), and monodehydroascorbate reductase (MDHAR). Together, these enzymes create a sophisticated system of processes that effectively reduce and scavenge reactive oxygen species (ROS). This article summarizes the contemporary significance of the enzymatic and nonenzymatic antioxidative defense mechanisms and cross-talks and strategies being used to improve plant thermotolerance.