Antioxidative Response Mechanisms in Halophytes: Their Role in Stress Defence

Soil salinisation has become a severe environmental issue that threatens future food security and sustainable agriculture, which is the result of inappropriate anthropogenic activity and climate change. The generation of reactive oxygen species (ROS) within diverse cellular bodies of a cell is a common factor in all these unfavourable situations. These are the byproducts of regular plant metabolism and environmental stress like salinity; severe heat and drought increase their production. Cellular homeostasis is disturbed by the overproduction of ROS under salinity that is the major reason for cell death. Halophytes have evolved adaptation mechanisms at various metabolic levels and maintain ROS-antioxidant equilibrium in the cell, which allows them to live and reproduce in soils with high salt concentrations. These adaptation mechanisms include ROS-scavenging systems (enzymatic and nonenzymatic antioxidants, certain osmoprotectants) and stress-avoidance mechanisms (e.g. alteration in proteins engaged in electron transport chains, changes in lipid composition, harmless dissipation of surplus energy). In general, all plants at various growth stages, including in embryonic growth phases, have many antioxidant defence systems. The proficient antioxidant systems in halophytes can prepare plants to deal with subsequent stress factors by triggering a signal to activate the stress response and decrease oxidative damage. The antioxidant enzyme responses during salt stress in halophytes, particularly mangroves, are discussed here. We conclude that antioxidants protect the halophytes by scavenging the accumulating reactive species during oxidative stress.