Study On Cold Resistance Of Salix ’Zhuliu’ Varieties In Harbin Area

This study is the research content of Harbin Science and Technology Project.’Zhuliu’is a superior variety which is domesticated.It is a good plant material for landscaping.But because of cold tolerance limit,yet’Zhuliu’is not applied widely in Harbin area.Currently resistance studies of’Zhuliu’involve only salt resistance,study on cold hardiness is not reported.So studies of’Zhuliu’No.3and No.5’s cold hardiness have important significance for scientific applications of cold areas.The research is under natural and artificial low temperature stress.Relative electric conductivity,SOD activity,POD activity,soluble sugar content,soluble protein content and dissociation proline content of’Zhuliu’No.3and No.5which were introducted to Harbin area for two years and three years were determined as contrast of Salix matsudana.Then the cold resistance of selected materials was comprehensively evaluated by the method of variance analysis,multiple comparison,subordinate functionan and correlative analysis.Combined with the the natural overwintering morphology and biological observation,investigation on the growth in Heilongjiang Province.The test results are as follows:1With natural and artificial low temperature stress,’Zhuliu’No.3,’Zhuliu’No.5and Salix matsudana are evaluated by the method of subordinate functionan through determining relative electric conductivity,SOD activity,POD activity,soluble sugar content,soluble protein content and dissociation proline content.The integrated assess to the cold resistance of the three varieties is as follows:Salix matsudana>’Zhuliu’no.5>’Zhuliu’no.3.2Conductance method combined with Logistic equation can get that the semi-lethal temperature of’Zhuliu’no.3,’Zhuliu’no.5,Salix matsudana are-31.60℃,-37.27℃,-42.87℃.3Under natural low temperature stress,with the decrease and increase of natural temperature,relative electric conductivity,SOD activity,POD activity,soluble sugar content, soluble protein content of selected materials presented the trend of the first increase and then drop.Dissociation proline content of’Zhuliu’have no regularity.4Under artificial low temperature stress,relative electric conductivity of selected materials increased with the decrease of temperature,SOD activity,POD activity,soluble sugar content,soluble protein content presented the trend of the first increase and then drop. Dissociation proline content of’Zhuliu’have no regularity.5Through correlation analysis,relative conductivity and SOD activity,POD activity, soluble sugar content,soluble protein content,dissociation proline content were negatively correlated. SOD activity,POD activity,soluble sugar content,soluble protein content, dissociation proline content were positively correlated.Thus it can be seen,there is a close relationship among plasma membrane permeability.activity of protective enzyme.osmotic adjustment substances of the three selected materials.6After natural overwintering morphology and biological observations.the overwintering survival rate of ’Zhuliu’No.5’s annual cutting seedling is higher than’Zhuliu’No.3.Willow natural overwintering plants have no freezing phenomenon,the plants of ’Zhuliu’No.3and ’Zhuliu’No.5have varying degrees of frost injury during winter in Harbin. Winter frost damage of three cultivars from low to high is Salix matsudana,’Zhuliu’no.5,’Zhuliu’no.3.7The phenophase of ’Zhuliu’No.3in Harbin area is close to ’Zhuliu’ No.5.But the budding period and leaf-expansion period of Salix matsudana are earlier than ’Zhuliu’No.3and’Zhuliu’No.5,the defoliation is later than ’Zhuliu’ No.3and ’Zhuliu’No.5.The above result can reflect that cold resistance of Salix matsudana is higher than that of’Zhuliu’No.3and ’Zhuliu’No.5plants.The plants of ’Zhuliu’No.5overwintered successfully in Harbin City,Daqing City,Qiqihar City and Heihe City of Heilongjiang Province.