Study On The Role Of AsA, H₂O₂ And Ethylene In Breaking The Dormancy Of Xinjiang Wild Apple Seed Embryos

Seed dormancy is a very complex physiological process,involving the interaction of plant hormones,and subject to strict regulation signals.Ascorbic acid(ascorbic acid,AsA)since it was discovered,has been considered an antioxidant.In recent years,it was found to play an important role in breaking seed dormancy and germination process.AsA as an antioxidant in plants can remove excess hydrogen peroxide(H2O2),and the AsA can also serve as 1-aminocy lopropane 1-carboxyl oxidase(ACO)coenzyme involved in the biosynthesis of ethylene.But their effect and relationship in breaking Malus sieversii embryo dormancy has not been elucidated fully yet.It was the aim of the study that the role and the relationship of AsA,H2O2,ethylene in embryo dormancy of Malus sieversii the embryos were treated with different concentrations of exogenous AsA,H2O2,ethylene and their synthpsis or action inhibitors.Then the germination rate of the embryos was statisticed,and the endogenous AsA,H2O2 content and ethylene release of the embryos were detected in the training process;and the change of endogenous AsA,H2O2,ACC contents,ethylene release and the activity of ACS,ACO in the embryos were detected during the stratification process.The results as follows:1.With the stratification process of Malus sieversii embryo,embryo endogenous AsA,H2O2 and ethylene were increased with the extension of stratification process,H2O2 in the upstream of AsA,and they both worked at the upstream of the ethylene.The activity of ACO was significantly increased.2.Exogenous AsA could break the Malus sieversii embryo dormancy and improve the germination rate significantly,the optimum AsA concentration was 6 mM;AsA treatment could increase the endogenous AsA level of the embryo significantly,Lycorine(Lyc)can significantly inhibit the seed L-galactose 1,4-lactone dehydrogenase(GLDH)activity,decreased the levels of endogenous AsA,and extend the seed dormancy.These results showed that the endogenous AsA was necessary for the embryo to break dormancy.3.Exogenous H2O2 could break the dormancy of Malus sieversii embryo,and improve the germination rate significantly,the optimnum concentration was 1 mM.H2O2 synthesis inhibitors DPI could reduce the role of H2O2.These results indicated that endogenous H2O2 involved in the breaking of embryo dormancy.4.ACC,ethephon treatments could break the dormancy of Malus sieversii embryo,the optimum concentration was 0.5 mM and 2 mM;ethylene biosynthesis inhibitor AOA,Aib,ethylene action inhibitor 1-MCP,STS treatments could inhibit embryo germination,indicating that endogenous ethylene involved in releaseing of embryo dormancy.5.H2O2 as a upstream signaling molecule affected As A in breaking the Malus sieversii embryo dormancy.Lyc can significantly reduce the role of H2O2,exogenous H2O2 treatment could significantly improve embryo endogenous AsA content.6.AsA as a upstream signaling molecule affected ethylene in breaking the Malus sieversii embryo dormancy.AsA enhanced ACC oxidase(ACO)activity in order to promote the biosynthesis of ethylene,which participate in the breaking of embryo dormancy.but the ethylene action inhibitor 1-MCP,STS could not inhibit the effect of AsA completely,indicating that AsA may break embryo dormancy not only by ethylene pathway,but also by other ways.7.H2O2 as a upstream signaling molecule affected ethylene biosynthesis in breaking the Malus sieversii embryo dormancy.Exogenous H2O2 treatment could increase the release rate of ethylene in the embryo significantly.H2O2 in promoting relations with the AsA on both ethylene synthesis is also linked to independent.H2O2 is not only to promote the synthesis of ethylene to the increase of AsA content,that is to say H2O2 can promote the synthesis of ethylene alone,AsA could enhance ACC oxidase activity to promote the biosynthesis of ethylene.They both increased the content of embryo internal ethylene,eventually breaking the embryo dormancy.8.According to the experimental results,the signals relations of AsA,H2O2,ethylenein breaking the dormancy of Malus sieversii embryos was proposed:H2O2 as the upstream signaling molecules affected ethylene biosynthesis in embryo;AsA was at the downstream of H2O2,at the upstream of ethylenesignaling pathway in breaking Malus sieversii embryo dormancy,that was H2O2 promote AsA accumulation in the embryos.AsA could enhance the activity of ACO to promote ethylene production,and ultimately break embryo dormancy.AsA and H2O2 involved in ethylene to break embryo dormancy,but AsA may be involved in breaking Malus sieversii embryo dormancy by other ways.