Physiological Response And Evaluation Of Three Hibiscus Varieties To Salt-alkali Stress

Soil salinization is becoming more and more serious,which has an important effect on the development of economy society and ecology of our country.The Salt-Tolerance Plants are worth of spreading.It is of great significance to improve saline-alkali soil and this conducive to the sustainable development of our economy,society and ecoloy.Hibiscus syriacus L.has a certain ability of salt and alkali tolerance.In this paper,three hibiscus varieties were selected as research objects,and three artificial saline-alkali stresses were used to treat their cuttings,and the growth and physiological changes were measured.Through the analysis of principal component and membership function,the saline-alkali tolerance was comprehensively evaluated,and the varieties with strong saline-alkali tolerance were selected to provide more choices and theoretical references for saline-alkali tolerant plants in China.The main results are as follows:（1）Under Na Cl stress,the leaf salt damage level,salt damage index and plant height of three hibiscus species increased with the extension of stress time and the increase of stress concentration,but the increase of salt damage level and salt damage index was small,the increase of plant height slowed down,and there was no plant death;the leaf water content and chlorophyllin content decreased with the extension of stress time and the increase of stress concentration;the relative conductivity and MDA content increased generally,soluble protein content first increasedand then decreased,the content of proline had no significant change,the content of Cl^-,Na⁺increased with the increase of stress concentration.（2）Under the stress of Na₂CO₃,the salt damage grade,salt damage index and plant height of three hibiscus species increased with the prolongation of stress time and the increase of stress concentration.The plants with the highest concentration died on the 50th day of stress,and the growth of plant height slowed down.The leaf water content and chlorophyll content decreased with the prolongation of stress time and the increase of stress concentration,the relative conductivity,MDA content and proline increased totally,soluble protein content first increasedand then decreased,the change trend of content was different,and the change trend of Na⁺content was the same.The lethal concentration of 3 hibiscus cultivars under Na₂CO₃stress was 10g/L.（3）Under the mixed stress of Na Cl and Na₂CO₃,the salt damage grade,salt damage index and plant height of three hibiscus species increased with the extension of stress time and the increase of stress concentration,and the increase of plant height slowed down,and there was no plant death;the water content and chlorophyll content of leaves decreased with the extension of stress time and the increase of stress concentration,and the relative conductivity and MDA content and proline content increased totally,soluble protein content first increasedand then decreased,The content of Cl^-,Na⁺increased with the increase of stress concentration,while the content of CO₃^2-changed differently.（4）The comprehensive evaluation results of principal component analysis and membership function showed that the average membership function value of the three hibiscus species under Na Cl stress was between 0.483 and 0.573,and the tolerance was ranked ass cv.Qiancenghong>cv.Huaban>f.Paeoniflorus;.Under Na₂CO₃stress,the average membership function value was between 0.504 and 0.525,and the order of tolerance was cv.Huaban>f.Paeoniflorus>cv.Qiancenghong.The average membership function value of Na Cl and Na₂CO₃under mixed stress was between0.525 and 0.542,and the order of tolerance was cv.Qiancenghong>f.Paeoniflorus>cv.