Physiological and Biochemical Mechanisms of Waterlogging Tolerance in Plants

Waterlogging is a growing environmental challenge that significantly affects plant health and agricultural productivity by lowering soil oxygen levels, which creates hypoxic and anoxic conditions. This review consolidates the current knowledge of the physiological and biochemical mechanisms behind waterlogging tolerance in plants. Key physiological adaptations include alterations in energy metabolism, where anaerobic respiration pathways, such as glycolysis and fermentation, are activated to sustain ATP production in low-oxygen environments. Increased glycolytic and fermentation activities facilitate NAD⁺ regeneration, crucial for continuous energy production. Furthermore, antioxidant defense mechanisms are activated to mitigate oxidative stress from elevated reactive oxygen species (ROS) during waterlogging, emphasizing the role of enzyme-based antioxidants in protecting cellular integrity. The review also explores the significance of osmoprotective compounds, such as proline and soluble sugars, which contribute to osmotic balance and protein stabilization under stress. Moreover, the roles of phytohormones, particularly ethylene and abscisic acid (ABA), serve as signaling molecules that regulate adaptive physiological changes. These hormones influence critical processes such as stomatal closure to conserve water, leaf senescence to allocate resources efficiently, and the induction of root adaptations to improve gas exchange. By elucidating these complex adaptive mechanisms, this review provides a comprehensive overview of the multifaceted strategies that contribute to plant resilience under waterlogged conditions, ultimately enhancing the understanding of plant survival in fluctuating environmental conditions.