| Saline-alkali soil is a widely distributed soil on the earth severely harmed the plant, hampered the growth of agriculture and influent the ecological construction, this is especially true in Tianjin coastal area. The purpose of this research is to afforestation on the saline-alkali soil, study on the Tianjin coastal area, the poplar was chosen as research object. Firstly, through the introduction to establish the genetic resources of salt tolerant poplars, and on this basis, the salt tolerance of poplar clones was researched by use of the pots and the hydroponics simulation experiments, the physiological and biochemical indexes were determined, comprehensive appraisal the salt tolerance of clones, these undoubtedly proide important basis for the salt-tolerant poplars extension in the coastal area. The main contents and results are as follows.(1) Fifty poplar clones were preliminary screened and introduced. Analysis of the salt content(1.216g-1·kg), pH(7.83), organic matter(17.795g-1·kg) of the soil in the genetic resources of salt tolerant poplars revealed that each index satisfys the normal growth of poplar. Now the introduction of the fifty clones have succeeded, Each of spporting facilities in the genetic resoureces have finished, the genetic resources of salt tolerant poplars in Tianjin coastal area has been initially eastablished.(2) By means of hydroponics simulation experiment, 25 clones were treated with sodium chloride solution with concentrations of CK, 3, 4, 5, 6, 8g-1·L, the new branches length, biomass, root/shoot dry weight ratio, chlorophyll and salt injuries grade were measured, the results showed that: JY-18,33,26,13,24,14,44 were selected as higher salt-tolerant and the salt-tolerant threshold were 6g-1·L; JY-12,32,7,10,37,36,9,17 were lower than others and belonged to medium strains and the salt-tolerant threshold were between 4 and 5g/L; JY-15,31,35,22,23 had lower salt-tolerant and the salt-tolerant threshold were between 3 and 4g-1·L; JY-43,11,50,49,45 were high sensitive to salt and failed in salt tolerance.(3) 18 clones were cultivated in pots, they were treated with sodium mixed-mode salt solution with concentrations of CK,0.3%,0.4%,0.5%,0.6%, the survival rate ,growth, new branches length were measured, the comprehensive evaluation of salt tolerance based on fuzzy mathematics indicated that JY-36,13,18,26 showed the higher salt-tolerant and the salt-tolerant threshold were 0.4%; JY-9.7,24,14,33,31 had medium salt-tolerant and the salt-tolerant threshold were between0.3% and 0.4%; JY-44,15,17,11,22 had lower salt-tolerant and the salt-tolerant threshold were below 0.3%; JY-40,23,12 were high sensitive to salt and failed in salt tolerance.(4) As the laboratory test, there are some difference in the results between the pots and the hydroponics simulation experiments and field test, but they can be the important basis for field test. With the two simulations, the liquid substance of hydroponics simulation experiment is different from real soli media and the nutrition is idealistic, so the results of hydroponics simulation experiments are higer than the pots. Therefore, the substance, entertainment and so on are taken into comprehensive consideration, take the results of pots as the primary basis, the results of hydroponics simulation as the supporting basis, we can conclude that JY-36,13,18,26,9,7,24,14,33 show higher salt-tolerant, they can be tested in the salt concentration of 0.3% in the field, JY-36,13,18,26 can even tolerant above 0.4%. The salt concentration below 0.4% area of Tianjin takes up 91%, the research is important to ecological construction of Tianjin coastal area.
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