Signaling Mechanism Of Hydrogen Sulfide Delaying Strawberry Postharvest Senescence And Regulating Cut Flower Refreshing In Plant

Hydrogen sulfide （H₂S） is an important signaling molecule to regulate manyphysiological processes in animal. In recent years, accumulating evidence showsthat hydrogen sulfide plays various physiological roles in plants, such as seedgermination, root organogenesis and abiotic stress tolerance. However, whetherH₂S participates in the regulation of senescence in plants remains unknown. In thepresent study, the effect of H₂S on postharvest shelf life and antioxidantmetabolism in strawberry fruits was investigated. The results showed thatfumigation with H₂S gas released from the H₂S donor NaHS, prolonged postharvestshelf life of strawberry fruits in a dose-dependent manner. Strawberry fruitsfumigated with various concentrations of H₂S sustained significantly lower rotindex than controls, and the impact of0.8mmol L-1NaHS was obvious. Moreover,H₂S donor treatment tended to maintain strawberry fruits firmness and externalcolour and elevate the contents of reducing sugars, soluble proteins and free aminoacids in strawberry fruits, and thus improve the anti-aging properties of strawberryfruits.Further investigation showed that H₂S donor treatment maintained higheractivities of catalase （CAT）, guaiacol peroxidase （POD）, ascorbate peroxidase（APX）, glutathione reductase （GR） and lower activities of lipoxygenase （LOX）relative to untreated controls. H₂S also reduced hydrogen peroxide （H₂O₂）,superoxide anion （O₂） and malondialdehyde （MDA） to levels below control fruitsduring storage. We interpret these data as indicating that H₂S plays an antioxidativerole in prolonging postharvest shelf life of strawberry fruits.This article also isolated and identified the main pathogenic bacteria ofstrawberry gray mould, such as saccharomyces cerevisiae, penicillium citreovirideand pear-shaped mucor. The bacteriostasis experiment showed that depressioneffects of H₂S on saccharomyces cerevisiae, penicillium citreoviride andpear-shaped mucor were obvious, indicating that H₂S have the function of inhibitthe main pathogenic bacteria of strawberry gray mold in order to extend the shelflife of Strawberry. In addition, we investigated the effects of H₂S on flower senescence in variousspecies of cut flowers. H₂S was found to delay flower opening and senescence incut flowers and branches from Erigeron annuus （L.）, Euonymus maackii Rupr.,Hibiscus syriacus L., Liriope spicata （Thump.）, Loropetalum chinense （R. Br.）,Punica granatum L., Rosa chinensis Jacq., and Salix matsudana Koidz. Cutexplants of these plants were cultured in solution containing differentconcentrations of the H₂S donor, NaHS. H₂S donor treatment prolonged the vasetime of cut flowers and prevented senescence in a dose-dependent manner. Wemeasured the levels of MDA as an indicator of oxidative damage to cells andshowed that it was inversely related to endogenous H₂S concentration in explants.Flowers that had senesced showed higher levels of MDA and lower amounts of H₂S.Furthermore, NaHS treatment increased the activities of SOD, CAT, APX and POD,and sustained much lower levels of H₂O₂and O₂in cut flowers of E. annuus andexplant leaves of S. matsudana. The present study implies that H₂S is involved inimproving longevity of cut flowers and functions in activity of antioxidant enzymesin plants.