Cyclocarya paliurus is commonly used to treat diabetes in China. However, the natural habitats of C. paliurus are typically affected by salt stress. Hydrogen sulfide (HS) is a growth regulator that is widely used to enhance plant stress tolerance, but the possible mechanism underlying HS-alleviated salt stress in C. paliurus remains unclear. C. paliurus seedlings pretreated with NaHS (an HS donor) were exposed to salt stress, and then, the leaf and total biomass, chlorophyll fluorescence parameters, nitric oxide (NO) content, oxidative damage, and proline and phenolic content were investigated to test the hypothesis that HS and NO were involved in the salt tolerance of C. paliurus. The results showed that HS pretreatment maintained chlorophyll fluorescence and attenuated the loss of plant biomass. We also found that HS pretreatment further increased the endogenous NO content and nitrate reductase activity compared with salt treatment. Moreover, HS pretreatment alleviated salt-induced oxidative damage, as indicated by lowered lipid peroxidation, through an enhanced antioxidant system including more proline and phenolic accumulation and increased antioxidant enzyme activities. However, C. paliurus leaves treated with the NO scavenger significantly diminished HS-mediated NO production and alleviation of membrane lipid peroxidation. Thus, we concluded that HS-induced NO was involved in C. paliurus salt tolerance.
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