Physiological Basis Of Freezing-resistance Of Poplar And Low-temperature-induction Occurrence Of Valsa Sordida

The seedings of Yinzhong poplar,A5 poplar and Zhongsui poplar were test material,the relationships of the content changes of these seedings' secondary metabolites and hypothermia stress was main line in the research.Determined the content of condensed tannin,lignin,total phenols and flavonoid in the seedings,and analyzed associativity of the above four index and resisting freezing.Then claritied improvement of the ability of resisting freezing and the possible mechanism of freezing injury.As well as vaccinated pathogenic bacteria to the three seedings which had obtained frost resistance ability,then analyzed Valsa sordida incidence of poplar seedings.Otherwise,by means of the relationship of phenols content change of poplar in germination,budding and leaves beginning opening in spring,and according to the determination of several physiological index of cell resist freezing and membrane stability, analyzed dynamic state of membrane permeability,content of total phenol and flavonoid in poplar which was in differet temperature pelter degree.The main consequences of the research are as follow.(1)The low temperature induction condition of cutting poplar seedings was researched. It indicated that -4℃was the stagnation temperature which could caused freezing injury of Yinzhong poplar,and -4℃was the optinmal temperature to induce resist freezing of Yinzhong poplar,3 days exercise was suitable.-3℃was the stagnation temperature which could caused freezing injury of A5 and Zhongsui poplar,3 days exercise was suitable.The ability of resisting freezing of the three poplars was all influenced at -1℃.(2)Temperature strikingly drop induced the increase in the relative membrane permeability and the content of MDA,the change trend was almost identical.Generally,the effect of temperature drop on cell membrane of HeilinⅢwas larger than others,Xiaohei Huang was least.(3)The content of phenols was accompany to the extent of temperature strikingly,the relationship is direct proportion.The range ability of phenols content was greatest in germination stage.From the phenols classification point of view,lignin content change of Xiaohei poplar which had strong frost resistance ability was significant.The content of condensed tannin and total phenols had significant change in HeilinⅢwhich had weaker frost resistance ability and HeilinⅤwhich had general frost resistance ability.The content change of flavonoid in diffrernt poplar had tiny discrepancy.(4)The content change of phenols in poplar seeding organ from big to small was root,skin, leaf.The content change of flavonoid in A5 and Zhongsui seedings from big to small was skin, leaf,root.The content change of phenols in seedings leaf from big to small was Yinzhong,A5, Zhongsui poplar.The content change of phenols in skin and root from big to small was Yinzhong and A5,Zhongsui poplar.Following temperature strikingly drop,the content of phenols had significant change in poplar seedings,the content of condensed tannin and flavonoid has slightly change,the content change of lignin was quiet.(5) The result of vaccinating pathogenic bacteria experiment indicated that Valsa sordida rate of aquired inducing frost resistance poplar and comparison poplar were all decreasing in different level.Only the seeding had lowest disease rate which was processed with three stages cryogenic exercises.Different strain poplar with frost resistance had different disease rate,the disease rate of Yinzhong was lower than A5 and Zhongsui.Therefore,freeze injury was the important factor to cause the disease.Elevating frost resistance of poplar could decrease the rate of Valsa sordida.