A B S T R A C T During dark-induced senescence at 12-14 °C, changes ofendogenous hydrogen sulfide (H25) metabolism chlorophyll degradation, energy status, and antioxidant capacity of lpomoea aquatica fumigated with ot without exogenously applied H25 donor sodium hydrosulfide (NaHS) were assessed. Compared to the control, NaHS 'treatment brought about higher contents of endogenous H25 and chlorophyll, both of Which Were matched With increased activities of'H25 synthetic enzymes and decreased activities of chlorophyll-degrading enzyme. Electron microscopy confirmed that the breakdown of chloroplasts was reduced by NaHS. H25 not only sustained the energy status, but also decreased the respiration rate and increased antioxidant capacity. The inhibition of H25 production caused by the application ofits 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 H25) and control. These results suggest that NaHS fumigation- induced endogenous H25 might improve the energy status, leading to enhancement of antioxidant Capacity and inhibition of the respiration rate, and consequentl
y, reducing the senescence of l.aquatica