Antioxidant Defense Mechanism in Plants Under Salt Stress: Physiological, Biochemical and Molecular Insights
Recent researches focus on intensive high-input agricultural practices for maximizing crop yield, involve heavy use of fertilizers, pesticides, and irrigation. These methods increase food production but often lead to environmental degradation, including soil erosion, and increased soil salinity. On the cellular level, salinity elevates the formation of reactive oxygen species (ROS), which cause oxidative damage to lipids, proteins, and nucleic acids, and also serve as signalling molecules and trigger stress responses in plants. Plants counteract these challenges by integrating cellular, biochemical, and molecular adaptations that help to sustain cellular homeostasis. The major component of this whole mechanism is the antioxidant defense system, which consists of various enzymatic components (superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and non-enzymatic antioxidants (ascorbate, glutathione, tocopherols, carotenoids, phenolics, compatible osmolytes). These systems synergize to control the ROS levels and maintain redox balance in a saline environment. Moreover, salinity stress triggers intricate networks of molecular signalling, which comprise ROS, calcium signalling, and kinase-mediated pathways. Other pathways that maintain ion homeostasis include the SOS signalling system. A combination of these mechanisms helps plants maintain metabolic stability and adapt to saline conditions. The present review aims to provide in-depth critical insights into these interdependent responses in plants to understand how they contribute to enhancing stress tolerance and improving crop productivity. Such understanding will be highly valuable for developing strategies to optimize plant responses under rising salinity levels and, consequently, improve crop yield.