Physiological Responses And Resistance Assessment Of Several Introduced Landscape Trees And Shrubs To Drought And Saline Alkali Stress

The arid and semi-arid regions and the secondary saline areas in China are wide.It is necessary to rationally repair and develop these arid and saline areas to promote regional economic development and improve the ecological environment.Popularization and application of adversity resistant plants can provide more materials for ecological restoration.In this study,10 new excellent tree species(cultivars)were subjected to natural drought stress to study drought tolerance mechanism and 7 new excellent tree species(cultivars)were subjected to mixed salt and alkali stress(contains neutral salt stress,salt-alkali mixed stress and alkaline salt stress)to study the mechanism of salt and alkali resistance.The identification indexes of plant stress resistance were determined by regression analysis,and the garden greening tree species(cultivars)suitable for Beijing and the surrounding drought and saline alkali were elected by fuzzy membership function analysis and principal component analysis.The main research results in this study are as follows:(1)With the time extension and degree deepening of natural drought stress,the REC,MDA content of 5 kinds of trees and 5 shrubs were increased and the RWC was decreased.Their osmotic substance content like Pro,SSC and SPC were increased.Their activity of SOD,POD and CAT in enzyme protection system was significantly increased drought stress 14 days before,then were decreased.Their activity of SOD was first significantly increased,and the activity of POD and CAT increased subsequently.Their photosynthetic gas exchange parameters of Pn,Gs and Tr were decreased,and C,was decreased.Their Chl and chlorophyll fluorescence parameters of Fv/Fm,Y(?),qP,ErR were decreased,and qN was increased.(2)Drought tolerance sequence of 5 kinds of trees was obtained by fuzzy membership function and the principal component analysis as following:Gleditsia triacanthos var.inemis>Prunus virhiniana'Shubetr Select'>Celtis occidenlis>Acersaccharinum 'Silver Queen'>Acer×freemanii 'Jeffersred'.Drought tolerance sequence of 5 kinds of shrubs was obtained by fuzzy membership function and the principal component analysis as following:Syringa chinensis 'Saugeana'>Syringa × hyacinthiflora'Excel'>Weigela florida>Weigela florida 'Variegata'>Syringa ×hyacinthflora 'Asessippi'.(3)Ci and Pn were selected as drought tolerance identification index of 5 kinds of trees by regression analysis,and Chl was selected as drought resistance identification index of 5 kinds of shrub by regression analysis.(4)Under salt alkali stress,the REC,MDA content,Pro content,SSC and SPC of 4 kinds of trees were increased with the increase of salt concentration and pH value,and RWC was decreased.SOD activity was only detected in enzyme protection system,which was Expressed as low concentration promoted,high concentration inhibited in two Acer plants and increased in other two cultivars.Photosynthetic gas exchange parameters Pn,Gs,Tr were showed varying degrees of decline with the increase of salt concentration,and C;was increased.Chlorophyll content increased Under low salt concentration and decreased under high salt concentration.Chlorophyll fluorescence parameters Y(?),qP,ETR were decreased slightly,and qN was increase with the change of salt concentration and pH.(5)Under salt alkali stress,the REC and MDA content of 3 shrubs were increased with the increase of salt concentration,and the RWC was decreased.The content of Pro was increased with the increase of salt concentration in mixed neutral salt.It was increased in low concentration and decreased in high concentration under mixed neutral and alkaline salt,mixed alkaline salt.The SSC of 3 shrubs was increased with the increase of salt concentration under 3 salt stress combinations,while the SPC was decreased.The activity of SOD,POD and CAT in Enzyme protection system were increased in low concentrations,while decreased in high salinity.Photosynthetic gas exchange parameters of Pn,Gs and Tr were decreased with the increased concentration of salt and pH,and Ci was decreased.Chl and chlorophyll fluorescence parameters Fv/Fm,Y(?),qP,ETR were decreased,and qN was increased with the increased concentration of salt and pH.(6)The salt tolerance of 4 kinds of trees and 3 kinds of shrubs in 3 salt stress combinations were in the same order by using fuzzy membership function analysis and principal component analysis method.Salt and alkali tolerance of 4 kinds of trees were as following:Gleditsia triacanthos var.inemis>Prunus virhiniana 'Shubetr Select'>Acer saccharinum 'Silver Queen'>Acer x freemanii 'Jeffersred'.Salt and alkali tolerance of 3 kinds of shrubs were as following:Syringa chinensis'Saugeana'>Syringa ×hyacinthiflora 'Asessippi'>Weigela florida>Weigela florida 'Variegata'>Syringa × hyacinthiflora'Excel'.(7)Through regression analysis,Y(?),MDA content and SSC were selected as resistance identification indexes of mixed neutral salt of 4 kinds of trees.Y(?),qN,ETR were selected as mixed neutral and alkaline salt tolerance of 4 kinds of trees.Pro content,SSC,Gs were selected as alkaline salt tolerance identification indexes of mixed 4 kinds of trees(8)Through regression analysis,Tr and RWC were selected as identification indexes of mixed neutral salt of 3 kinds of shrubs.RWC and Y(?)were selected as identification indexes of mixed neutral and basic salt of 3 kinds of shrubs.Pn and SOD were selected as identification indexes of mixed alkali salt of 3 kinds of shrubs.