Foliar Spraying of NaHS Alleviates Cucumber Salt Stress by Maintaining N+/K+ Balance and Activating Salt Tolerance Signaling Pathways

Abstract

Hydrogen sulfide (H2S) is involved in the regulation of plant salt stress as a potential signaling molecule. This work investigated the effect of H2S on cucumber growth, photosynthesis, antioxidation, ion balance, and other salt tolerance pathways. The plant height, stem diameter, leaf area and photosynthesis of cucumber seedlings were significantly inhibited by 50 mmol·L−1 NaCl. Moreover, NaCl treatment induced superoxide anion (O2·−) and Na+ accumulation and affected the absorption of other mineral ions. On the contrary, exogenous spraying of 200 μmol·L−1 sodium hydrosulfide (NaHS) maintained the growth of cucumber seedlings, increased photosynthesis, enhanced the ascorbate–glutathione cycle (AsA–GSH), and promoted the absorption of mineral ions under salt stress. Meanwhile, NaHS upregulated SOS1, SOS2, SOS3, NHX1, and AKT1 genes to maintain Na+/K+ balance and increased the relative expression of MAPK3, MAPK4, MAPK6, and MAPK9 genes to enhance salt tolerance. These positive effects of H2S could be reversed by 150 mmol·L−1 propargylglycine (PAG, a specific inhibitor of H2S biosynthesis). These results indicated that H2S could mitigate salt damage in cucumber, mainly by improving photosynthesis, enhancing the AsA–GSH cycle, reducing the Na+/K+ ratio, and inducing the SOS pathway and MAPK pathway.

NO and H2S Contribute to Crop Resilience against Atmospheric Stressors

“…• NO and H 2 S have become paradoxical molecules in plant biology since they have gone from being hazardous molecules to becoming essential molecules in cellular metabolism, regulating physiological processes from seed germination, root development, photosynthesis, senescence, stomatal closure, formation of flowers and fruit ripening, in addition to participating in the response mechanisms against challenging environments. Paradoxically, the available information demonstrates that the exogenous application of these molecules can be biotechnological tools that allow for promoting crop resilience [ 137 , 138 ]. In most cases, these gasotransmitters stimulate enzymatic and non-enzymatic antioxidant systems, for example, the APX activity is upregulated by S-nitrosation and persulfidation [ 139 , 140 ] which makes it possible to alleviate oxidative damage associated with atmospheric stressors, protecting the functionality of cells, and maintaining photosynthetic activity ( Figure 5 ).…”

“…Sci. 2024, 25, x FOR PEER REVIEW 9 of 14 these molecules can be biotechnological tools that allow for promoting crop resilience [137,138]. In most cases, these gasotransmitters stimulate enzymatic and non-enzymatic antioxidant systems, for example, the APX activity is upregulated by S-nitrosation and persulfidation [139,140] which makes it possible to alleviate oxidative damage associated with atmospheric stressors, protecting the functionality of cells, and maintaining photosynthetic activity (Figure 5).…”

Eugenol improves salt tolerance via enhancing antioxidant capacity and regulating ionic balance in tobacco seedlings

“…AsA, ascorbic acid; GSH, glutathione; and proline) ( Hasanuzzaman et al., 2021 ). GSSG and DHA (dehydroascorbic Acid) are the oxidized form of GSH and AsA, respectively ( Luo et al., 2023 ). The redox balance can be modulated by GSH/GSSG and AsA/DHA, which play a role in plant responses to abiotic stress ( Kumari et al., 2023 ).…”