Mechanism of waterlogging stress tolerance in pigeonpea plants: Biochemical and anatomical adaptation under waterlogging

Abstract

Pigeonpea is the most important legume grown in semiarid tropics and generally grown in low-lying areas. In low-lying areas, the chances of waterlogging are maximum. Some pigeonpea varieties are sensitive but some are quite tolerant to waterlogging. The main cause of damage is suffocation which the plant has to face due to waterlogging. Oxygen deficiency causes electrolyte leakage due to which the cell is exposed to the outside environment which can also cause peroxidation of lipid and nucleic acid and ultimately death. So any mechanism that can reinstate oxygen supply to stressed tissue can be a major trait for waterlogging tolerance. Formation of aerenchyma, adventitious roots, and lenticels is helpful in restoring oxygen to waterlogged plants. Besides the formation of these, various types of biochemical changes also occur for waterlogging tolerance in pigeonpea plants. Biochemical changes include increase in reducing sugars, activity of enzymes used in glycolysis and fermentation, and participation of antioxidants. Glycolytic enzymes include alcohol dehydrogenase and sucrose synthase. The antioxidant system includes enzymatic and non-enzymatic antioxidants. Enzymatic antioxidants include superoxide dismutase, catalase peroxidase, ascorbate peroxidase, and glutathione peroxidase, while ascorbate and glutathione fall under the category of non-enzymatic antioxidant defense system. We emphasize the attributes responsible for waterlogging tolerance in pigeonpea.