Physiological Investigations On The Drought And Cold Resistance Of The Ornamental Arbor Sophora Japonica Linn.,Sophora Japonica Var.Pendula Hort.,sophora Japonica 'Golden Stem' And Sophora Japonica 'Honghua'

In this thesis the drought and cold resistance of Sophora japonica Linn.and its three varieties,including Sophora japonica ' Honghua ',Sophora japonica 'Golden Stem' and Sophora japonica var.pendula Hort,are investigated.Sophora japonica Linn.and its varieties are common plants in landscape architecture.In northern China,it is dry in summer and cold in winter.Therefore,investigating the drought and cold resistance of the Sophora japonica Linn.is of great importance not only for the application in landscape architecture but also for the data support in relevant molecular mechanism study.The PEG-6000 drought stress simulating method was used in the drought stress tests.While the artificial low temperature stress and natural cooling methods were performed in the cold stress tests.The detailed contents are as follows:1.In the study of drought resistance,five key parameters including the relative water content,relative permeability,chlorophyll content,the ratio of chlorophyll a/b and malondialdehyde content were measured.The water content and chlorophyll content show positive correlation with the drought resistance,while the relative permeability,chlorophyll a/b and malondialdehyde content show negative correlation with the drought resistance.Through the variance analysis,the results under different stress conditions show obvious difference.The comprehensive subordination function analysis suggests that the drought resistance of the four varieties follows the order of Sophora japo,nica Linn.>Sophora japonica ' Honghua'>Sophora japonica var.pendula Hort.>Sophora japonica'Golden Stem'.2.In the study of artificial low temperature stress,the relative permeability,soluble sugar content and malondialdehyde content were measured.The relative permeability and malondialdehyde content show negative correlation while the soluble sugar content shows positive correlation with the cold resistance.By fitting the Logistic equation,the semilethal temperature LT50 of the Sophora japonica Linn.,Sophora japonica 'Honghua',Sophora japonica 'Golden Stem' and Sophora japonica var.pendula Hort.are determined to be-24.89?,-25.37?,-21.87?,-20.10? respectively.The temperature lower than LT50 will result in irreversible damage or even death to the plants.3.In the study of the natural cooling stress,the relative conductivity of the one,two and three-years-old branches of the four plants were measured respectively.It was found that the older branch shows higher cold resistance due to the sufficient lignifications.The branches were significantly influenced by the temperature lower than 0?,but not by that higher than 0?.The influence of natural cooling stress on the cold resistance is in accordance with that of the artificial low temperature stress,indicating the reliability of the latter method.The comprehensive subordination function analysis suggests that the drought resistance of the four plants follows the order of Sophora japonica Linn.>Sophora japonica 'Honghua'>Sophora japonica 'Golden Stem'>Sophora japonica var.pendula Hort.4.Clustering analysis was performed based on the subordination function values of the drought and cold resistance of the Sophora japonica Linn.and its three varieties.The results indicate that the Sophora japonica Linn,and Sophora japonica 'Honghua' are suitable for landscape architecture since the good stress resistance.Owing to the poor drought resistance,the Sophora japonica 'Golden Stem' needs additional irrigation in the dry seasons.As for the Sophora japonica var.pendula Hort,winter protection measures are necessary in the regions lower than the LT50 considering the poor cold resistance.