| In view of the shortage of green plant resources in the coastal area of Hebei Province,this paper selects Tanghai County as the representative of the coastal area of Hebei Province,investigates and analyzes its existing greening plant resources by the methods of field investigation,salt tolerance evaluation and salt tolerance appraisal.Select the plants with good value in salt tolerance and view through consulting a large number of data across the country,while evaluate and classify them by the analytic hierarchy process(AHP).It provides a reference for the import of excellent species in the coastal area of Hebei Province and its surrounding areas.The results are as follows:(1)There are 98 species of green plants in Tanghai County,belonging to 41 families and 62 generas.There are 46 species of trees,34 species of shrubs and 18 species of herbs.The following problems exist in street greening: the species and quantity of evergreen trees are obviously insufficient,the proportion of evergreen trees and deciduous trees is not proper,and deciduous trees are much more than evergreen trees on some roads.Because of the regional limitation,there are so few evergreen plants in Tanghai County that there is often no view to enjoy in winter.The main applied tree species are holly spear,cypress,juniper,privet,golden leaf privet and so on,the road landscape is too depressed in winter.The types of street trees are too single and lack of functionality.(2)According to the climatic and soil conditions,112 species which were both green plant resources and salt-tolerant plant resources were selected and evaluated by the Analytic Hierarchy Process(AHP).Finally,112 species of plants were classified into 4 categories according to the comprehensive evaluation scores,which can be used for reference and selection in coastal areas of Hebei Province and areas with similar climate and soil environment.It provides a reference for improving the greening situation and enriching the greening plant resources in the coastal area of Hebei Province.(3)This paper did salt tolerance identification to Tamarix and ground-cover chrysanthemum that selected from the excellent green salt-tolerant landscape plants.It measured and analyzed their growth indexes such as the survival rate,fresh weight,plant height increment and physiological indexes such as cell membrane permeability,chlorophyll,malondialdehyde(MDA),proline and soluble sugar,observed the growth regularity under salt stress and its reason,and obtained their threshold value of salttolerance,and the salt tolerance was further confirmed.Inrich the information of green and salt-tolerant plant resources.(4)The salt tolerance of four species of Tamarix chinensis was analyzed and compared in order to provide scientific basis for using Tamarix chinensis to improve urbangreening and soil salinization in Hebei coastal areas and other similar coastal areas.Four species of Tamarix chinensis were selected as materials.Through pot experiment,six salt concentrations arrange from 0(CK)to 3.0% were set up respectively,and the changes of morphological and physiological indexes under different salt concentrations were analyzed.The results showed that the survival rate of the four species of Tamarix chinensis seedlings was not affected after salt stress,indicating that the salt tolerance limit of the four species of Tamarix chinensis was higher than 3.0%.There was a significant negative correlation between plant height increment and salt stress degree.When the salt concentration was 3.0%,the influated degree of increment of Tamarix chinensis plant height was in the order of N3 >N7 >N1 >N16.With the increase of salt concentration,the electrical conductivity of Tamarix chinensis N1 and N16 were greatly influenced and showed an upward trend,and the electrical conductivity of Tamarix chinensis N3 and N7 were not affected by salt stress.With the increase of salt concentration,the total chlorophyll(ChlT)content of Tamarix N1,N7 and N16 showed a trend of firstly increasing and then decreasing,and the content of ChlT reached the maximum value at salt concentration of 1.0%,and the ChlT content of Tamarix chinensis N3 changed basically the same trend with salt concentration.The content of malondialdehyde in Tamarix chinensis N7 was not affected with the increase of salt concentration;the content of malondialdehyde in N1,N3 and N16 decreased rapidly and significantly at salt concentration of 1.0%,then gradually stabilized.With the increase of salt concentration,the content of proline in N3 and N16 increased rapidly and significantly when the salt concentration was 3.0%.The content of proline in N7 increased rapidly and significantly when the salt concentration was 2.5%.The content of proline in N1 was not affected.With the increase of salt concentration,the content of soluble sugar in N1 was not affected.The soluble sugar content of N3 and N7 reached the maximum rapidly at salt concentration of 1.0%,and the soluble sugar content of N16 reached the maximum at salt concentration of 2.0%.Considering the changes of all these growth and physiological indexes after salt stress,the salt tolerance of Tamarix chinensis N7 was superior than that of the other three species,except that the influenced degree in increment of plant height,and the salt tolerance mechanism could be started quickly when the salt concentration was about 1.0%.(5)In order to study the salt tolerance of seven ground-cover chrysanthemums introduced from Nanjing,the seedlings of ground cover chrysanthemum were treated with six soncentrations of NaCl solution range from 0(CK)to 1.5%.The survival rate,plant height increment,flower diameter,fresh weight,cell membrane permeability,chlorophyll content,malondialdehyde content,proline content and soluble sugar content were determined after 30 days.The results were as follows: 1.All the seven kinds of ground cover chrysanthemum had strong salt tolerance,and the deatn of plant occurred until the salt concentration of 0.9%.2.The responses to salt stress were different in the same physiological index of each variety.The electrical conductivity of seven cultivars increased with the increase of salt stress,which was positively correlated with salt concentration,and the total chlorophyll content of chrysanthemums increased firstly and then decreased with the increase of salt stress.Except N1,there was no significant difference in the malondialdehyde content of the other six cultivars under different salt concentrations.The MDA content of N1 increased significantly in concentration of 0-0.6%,and decreased significantly in0.6%-1.5% range.The proline content of N1?N2?N4 and N8 increased and N3?N5?N6 increased firstly and then decreased with the increase of salt stress.With the increase of salt stress,the content of soluble sugar in the other six cultivars increased firstly and then decreased except for N8.The content of proline of N8 was significantly lower than that of the control among the stress concentrations,and there was no significant difference in the content of proline at different concentrations.3.There were great differences in salt tolerance among different varieties.The order of salt tolerance from high to low was N6 > N2 >N4 >N3 >N1 >N8 >N5. |
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