Study On Salt Tolerance Of Six Species Of Landscape Plants

Salt tolerance ability of plants is the main basis of plant landscape planning and design in saline-alkali land.There is a large area of saline-alkali land in China,lack of landscaping plant resources.At present,the evaluation index and evaluation system of plant salt tolerance are not perfect.The salt-tolerance mechanism and response characteristics of plants are different due to the salt-alkali composition,test materials,treatment methods and research content.By observing the growth and physiological indicators of 6 landscape plants under mixed salt stress,the key indicators of salt-tolerance evaluation were screened,and then the salt-tolerance mechanism of different plants in different growth stages was discussed,which is of great significance to the selection and cultivation of salt-alkali plants.A research has been carried out on 6 species of landscape plants—Prunus mume‘Zaohua Lve’,Prunus mume‘Meiren’,Chionanthus retusus Lindl.et Paxt.Lindl.et Paxt.,Acer rubrum L.,Koelreuteria paniculata Laxm.,Acer truncatum Bunge on the basis of the survey and transplantation,Na Cl and Na HCO₃were prepared into a mixed salt solution according to the molar mass ratio of 1:1,and set the gradient to 0（CK）,100（S1）,200（S2）,300（S3）,400（S4）,500（S5）mmol·L^-1.The morphology,growth,physiological status and photosynthetic response of plants under different salt concentration stress were observed.multiple comparisons,correlation analysis,principal component analysis and fuzzy membership function analysis were employed to evaluate the salt resistance size of 6 plants.The aim is to study the response characteristics of 6 plants and understand the mechanism of the tested species under salt stress,which provided a scientific basis for the application of landscape plants on saline-alkali land.The main results and conclusions were as follows:（1）With the increase of salt concentration,the salt damage index,salt damage grade and salt damage rate of 6 species of plants showed an upward trend,and the number of fibrous roots of the plants also gradually decreased.Combined with the Logistic equation,the salt tolerance threshold（when their salt injury index is 50%）of 6 plants was calculated.The mixed saline-alkaline tolerance of 6species of plants were as following:Chionanthus retusus Lindl.et Paxt.(361.224 mmol·L^-1)>P.mume‘Zaohua Lve’(330.189 mmol·L^-1)>Koelreuteria paniculata Laxm.(303.774 mmol·L^-1)>Acer truncatum Bunge(295.833 mmol·L^-1)>P.mume‘Meiren’(292.453 mmol·L^-1)>Acer rubrum L.(230.435mmol·L^-1).（2）With the increase of salt concentration,the leaf growth,leaf width and ground diameter growth under different treatments were mostly showed a gradually decreasing trend,but under the low salt treatments（S1 and S2）,P.mume‘Zaohua Lve’,Chionanthus retusus Lindl.et Paxt.and Koelreuteria paniculata Laxm.showed an upward trend in individual treatments,and the range of the change were different.Salt treatment had different effects on plant growth.（3）With the increase of salt concentration,the water content of the 6 plants showed a downward trend as a whole,and the relative conductivity showed an upward trend.The MDA content continued to increase except for Chionanthus retusus Lindl.et Paxt.showed a"fall-rise-fall"trend.Enzyme activities（SOD,POD,CAT and APX）and osmotic adjustment substances（SS,SP and Pro）didn’t show a single trend.The content of ABA in P.mume‘Zaohua Lve’,P.mume‘Meiren’,Acer rubrum L.and Koelreuteria paniculata Laxm.generally increased first and then decreased;Chionanthus retusus Lindl.et Paxt.and Acer truncatum Bunge generally showed a decreasing trend.（4）With the increase of salt concentration,the chlorophyll content of P.mume‘Zaohua Lve’and P.mume‘Meiren’and Acer truncatum Bunge increased first and then decreased on the whole,showing the phenomenon of low concentration promotion and high concentration inhibition.Chionanthus retusus Lindl.et Paxt.increased at first then decreased,the increased again,while the other two plants showed a downward trend.Pn,Gs and Tr showed a downward trend as a whole,and the change of Ci was inconsistent.In general,Chionanthus retusus Lindl.et Paxt.Ci values increased under mixed salt stress,mainly due to non-stomatal limitation;P.mume‘Zaohua Lve,Koelreuteria paniculata Laxm.,Acer truncatum Bunge,P.mume‘Meiren’,Acer rubrum L.decreased,mainly due to stomatal limiting factors.Fv/Fm,Yield,and q P showed a downward trend.（5）The salt tolerance of 6 plants under mixed salt stress combinations were in the same order by using fuzzy membership function analysis and principal component analysis method,and the results were as following:Chionanthus retusus Lindl.et Paxt.>P.mume‘Zaohua Lve’>Koelreuteria paniculata Laxm.>Acer truncatum Bunge>P.mume‘Meiren’>Acer rubrum L.,which was consistent with the morphological evaluation conclusion.（6）Four main components of salt tolerance were proposed by the principal component analysis of22 individual indicators.The first principal component mainly included leaf growth,electrical conductivity,MDA,SOD,SP,Pn,Gs,Tr,Fv/Fm,Yield and q P,the second principal component mainly included POD,CAT,APX,Pro,and Ci,the third main component mainly included SS,diameter growth and leaf water conten,and the fourth main component mainly included ABA.（7）Through regression analysis,q P,CAT and POD activity,Yield and relative conductivity were selected as resistance identification indexes of mixed salt of 6 species of plants.