The mechanisms for the difference in waterlogging tolerance among sea barley, wheat and barley

Waterlogging is a major abiotic stress limiting crop growth and yield. There is a distinct difference among cereal crops in their responses to waterlogging stress, however, little is known about the mechanisms underlying waterlogging tolerance. Here, we investigated the influence of waterlogging stress on seedling growth and physiological traits of three cereal plants with distinct waterlogging tolerance, i.e. sea barley ( Hordeum marinum , H559), wheat ( Triticum aestivum , Chinese Spring) and barley ( Hordeum vulgare , ZU9). Sea barley is much stronger in waterlogging-tolerance than wheat, with barley being the least. Under waterlogging biomass, shoot and root length, contents of chlorophyll and soluble protein were significantly reduced, and MDA content and POD activity were significantly increased in barley and wheat seedlings in comparison with the control, but these parameters remained little change in sea barley under waterlogging in comparison with the control. Expression levels of hypoxia-responding related genes, such as ADH1 , XET1 and ERF1 were more induced under waterlogging treatment in sea barley than those in wheat and barley. Constitutive aerenchyma could be observed in the roots of sea barley under normal condition, and aerenchyma was more developed under waterlogging. However, there was no aerenchyma in the roots of barley and wheat in both control and waterlogging treatments. Obviously, higher waterlogging tolerance in sea barley could be attributed to its constitutive and induced aerenchyma.