Waterlogging is a serious problem, which affects crop growth and yield in low-lying rainfed areas. Waterlogging of the soil stops air getting in. It reduces the production of dry matter in plant parts; ultimately affect the yield of grain legumes in several parts of the world. The main cause of damage under waterlogging is oxygen deprivation, which affect nutrient and water uptake, so the plants show wilting even when surrounded by excess of water. Flooding often results in leaf chlorosis, defoliation, cessation of growth and plant death. These effects have been widely attributed solely to a lack of oxygen in the root-zone. When tissues are completely submerged and O2 is exhausted by respiration, complete anoxia may occur. The tolerance of grain legumes to waterlogging may vary between and within species. During initial exposure of legumes under excess water, plants adapted to waterlogged conditions, have mechanisms to cope with this stress such as increase in ethanol fermentation, aerenchym formation, adventitious roots formation, increased availability of soluble sugars, greater activity of glycolytic pathway, increase of internode elongation rate, maintenance of high carbohydrate concentration, involvement of antioxidant defense mechanism to cope with the post hypoxia/anoxia oxidative stress. No aerenchym is observed in roots of non-flooded plants; however, it is abundant in roots of flooded plants. Aerenchym development is more abundant during vegetative growth stage than reproductive stage. Lower aerenchym formation in reproductive stage may cause lower adaptability in flooded condition. Gaseous plant hormone ethylene plays an important role in modifying plant response to oxygen deficiency. This study investigated the effects of waterlogging and the adaptive mechanisms of crops to tolerance excess water to evaluate the variation in tolerance among grain legume species.

Keyword: Legumes; Waterlogging; Hypoxia; Anoxia; Aerenchyma; Adventitious Roo