Hydrogen sulfide counteracts chlorophyll loss in sweetpotato seedling leaves and alleviates oxidative damage against osmotic stress

In this paper, effect of NaHS, a hydrogen sulfide (H2S) donor on chlorophyll and antioxidant metabolism in seedling leaves of sweetpotato under osmotic stress was investigated. With the enhancement of osmotic stress, which was mimicked by PEG-6000, chlorophyll in seedling leaves of sweetpotato (Ipomoea batatas) decreased dramatically. At 15% PEG (w/v), chlorophyll concentration reached only 50% compared with that of the controls. The osmotic-induced decrease in chlorophyll concentration could be alleviated by spraying exogenous H2S donor, NaHS in a dose-dependent manner, while little visible symptoms were observed in leaves sprayed with NaHS under control conditions. It was also shown that H2S or HS- rather than other sulfur-containing components derived from NaHS contributed to the protective role against chlorophyll degradation during osmotic stress. Further studies showed that NaHS spraying dramatically promoted the activities of superoxide dismutase, catalase, ascorbate peroxidase and decreased that of lipoxygenase and the concentrations of hydrogen peroxide (H2O2) and malondialdehyde. In addition, concentrations of endogenous H2S in NaHS-sprayed seedlings were higher than that in water-spraying control under osmotic stress. These data indicated that H2S plays a protective role in sweetpotato seedlings during osmotic stress.