Hydrogen sulphide and nitric oxide mitigate the negative impacts of waterlogging stress on wheat (Triticum aestivum L.)

Nitric oxide (NO) and hydrogen sulphide (H2S) are important gaseous signalling molecules that regulate key physiochemical mechanisms of plants under environmental stresses. A number of attempts have been made to improve waterlogging tolerance in plants, but with limited success. Having said that, NO and H2S are vital signalling molecules, but their role in mitigating waterlogging effects on crop plants is not well established. We investigated the efficacy of exogenous NO and H2S to alleviate waterlogging effects in two wheat cultivars (Galaxy-2013 and FSD-2008). Waterlogging produced a noticeable reduction in plant growth, yield, chlorophyll, soluble sugars and free amino acids. Besides, waterlogging induced severe oxidative damage seen as higher cellular TBARS and H2O2 content. Antioxidant enzyme activity increased together with a notable rise in Fe2+ and Mn2+ content. Proline content was higher in waterlogged plants compared with non-waterlogged plants. In contrast, waterlogging caused a substantial decline in endogenous levels of essential nutrients (K+, Ca2+ and Mg2+). Waterlogged conditions led to Fe2+ and Mn2+ toxicity due to rapid reduction of Fe3+ and Mn3+ in the soil. Exogenous NO and H2S significantly protected plants from waterlogging effects by enhancing the oxidative defence and regulating nutritional status. Besides, the protective effects of exogenous NO were more prominent as compared with effects of H2S. Further, we did not study the effect of H2S and NO on photosynthetic attributes and expression of stress-related genes. Therefore, future studies should examine the effects of H2S and NO on wheat physiology and gene expression under waterlogging.