ABSTRACT
Waterlogging is considered as one of the major abiotic stresses that adversely affects crop growth, development, and productivity. It impedes diffusion of gases and gaseous exchange leading to conditions of hypoxic followed by anoxic which in turn affects the plant metabolic processes including photosynthesis, respiration, induces production of reactive species oxygen, synthesis and release of ethylene, etc. Redox potential and pH of waterlogged soils are altered resulting in derangement in nutrient availability to plants causing either their deficiency or toxicity. Plants tolerant to waterlogging exhibit adaptations at morphological, anatomical, biochemical, and molecular levels. Morphological adaptations like formation of adventitious root and rapid elongation of above-ground parts of plants help in tolerating submergence stress. Anatomical adaptations include development of aerenchyma to facilitate gaseous exchange, and lignification and suberization of cell walls preventing radial loss of oxygen. Sensing and signaling of lowoxygen levels in rhizosphere induces transcription of hypoxia-responsive genes and accumulation of anaerobic proteins. Group VII ethylene responsive factors are involved in low-oxygen signaling and they act as transcription factors inducing genes required for survival under anaerobic conditions. Shortage of carbohydrate availability increases the perception and transduction of secondary signaling molecules such as sucrose nonfermenting 1-related kinase 1 and target of rapamycin. Transcription factors, namely, basic leucine zipper family are also involved in inducing the expression of enzymes that utilize alternative carbon sources such as protein, structural carbohydrate, and lipids for energy. These anatomical, morphological, and biochemical adaptations in combination help the plants to sustain growth
under waterlogged condition. Genes and gene products involved in waterlogging tolerance that have been identified provide opportunities for improving flooding tolerance in crop species.
