Regulation of Na plus /H plus antiport system and nitrogen metabolism by melatonin and endogenous hydrogen sulfide confers resilience to drought and salt stress

The present study was conducted with the purpose of examining the role of endogenous hydrogen sulfide (H2S) in melatonin (Mel)-induced regulation of tolerance mechanisms to drought stress and salinity. The drought stress was induced by maintaining soil water level at 40% and salinity was induced by applying 100 mM sodium chloride (NaCl). The results demonstrate an augmentation in the degree of activation of the antioxidant defense mechanisms in response to drought stress and salinity. However, a significant decline in the K+/Na+ ratio, accompanied by an elevation in reactive oxygen species, lipid peroxidation, and electrolyte leakage, was witnessed as well. A remarkable decrease in the level of hydration and content of chlorophyll was also observed under the imposed stress. The reported findings indicate that the administration of 30 mM Mel effectively regulated the activity of the Na+-H+ antiporter and H+-ATPase. This regulation ultimately led to an increase in K+ influx and a decline in Na+ efflux, resulting in an enhanced K+/Na+ ratio. Application of Mel also demonstrated an improvement in nitrogen metabolism, as well as the enzymatic and non -enzy-matic antioxidant defense system. Additionally, Mel application caused a remarkable increase in the accumu-lation of osmolytes in drought stress and salinity-suffered plants. The synergistic effect of these characteristics resulted in the resilience of the Mel-supplemented plants to drought stress and salinity. How-ever, application of hypotaurine (a scavenger of H2S) counteracted the beneficial impact of Mel which once again resulted in the same condition that was initially created by the imposed stress. These findings imply that Mel, in coordination with H2S was remarkable in inducing plant adaptive responses to drought stress and salinity.(c) 2023 SAAB. Published by Elsevier B.V. All rights reserved.