Hydrogen sulfide delays leaf yellowing of stored water spinach (Ipomoea aquatica) during dark-induced senescence by delaying chlorophyll breakdown, maintaining energy status and increasing antioxidative capacity

• H2S can delay the chlorophyll degradation of Ipomoea aquatica.
• H2S maintains the energy status and inhibits the respiration rate.
• H2S increases the antioxidant capacity in I. aquatica.

During dark-induced senescence at 12–14 °C, changes of endogenous hydrogen sulfide (H2S) metabolism, chlorophyll degradation, energy status, and antioxidant capacity of Ipomoea aquatica fumigated with or without exogenously applied H2S donor sodium hydrosulfide (NaHS) were assessed. Compared to the control, NaHS treatment brought about higher contents of endogenous H2S and chlorophyll, both of which were matched with increased activities of H2S synthetic enzymes and decreased activities of chlorophyll-degrading enzyme. Electron microscopy confirmed that the breakdown of chloroplasts was reduced by NaHS. H2S not only sustained the energy status, but also decreased the respiration rate and increased antioxidant capacity. The inhibition of H2S production caused by the application of its synthetic inhibitor (dl-propargylglucine) aggravated the yellowing of I. aquatica, and this response could be rescued by exogenously applied NaHS. Nevertheless, no obvious differences were observed between treatment of hypotaurine (a scavenger of H2S) and control. These results suggest that NaHS fumigation-induced endogenous H2S might improve the energy status, leading to enhancement of antioxidant capacity and inhibition of the respiration rate, and consequently, reducing the senescence of I. aquatica.