Physiological Responses Of Salix Psammophila Seedlings To Complex Saline-alkali Stress

This paper,taking seedlings of Salix psammophila ‘Yanliu NO.1' as testing material,studied the dynamic changes of the growth and physiological indices under complex saline-alkali stress,and made clear the leading factors of complex saline-alkali stress affecting Yanliu NO.1 seedlings through statistical methods.The seedlings were treated with 12 types of saline-alkali stress with different salinity and alkalinity levels,simulated by two neutral salts?NaCl and Na₂SO₄?and two alkali salts?NaHCO₃ and Na₂CO₃?mixed in various proportions and concentrations.The main research results are as follows:1.Under complex saline-alkali stress,the growth of Yanliu NO.1 was subject to different degrees of inhibition.With increasing salt concentration and proportion of alkaline salts,the plant height increment and leaf water content of Yanliu NO.1 were decreased.And the leaves of Yanliu NO.1 withered at salinity > 150 mmol/L and pH > 9.51.2.At salinity 50,and 100 mmol/L,the contents of Chla,Chlb,and ChlT in leaves of Yanliu NO.1 were increased.The contents of Chla,Chlb,and ChlT in leaves of Yanliu NO.1 decreased rapidly at salinity 150,and 200 mmol/L.3.Under the stress of low salinity?50 mmol/L?or low alkalinity?pH: 8.04?,the leaf MDA content in Yanliu NO.1 did not differ significantly.With increasing salt concentration and proportion of alkaline salts,the leaf MDA content increased rapidly,indicating that the degree of membrane lipid peroxidation increased.And the leaves of Yanliu NO.1 withered under the high saline-alkali stress,indicating that Yanliu NO.1 has lost the ability to tolerate complex saline-alkali stress.4.In the range of salt concentration below 150 mmol/L,the activities of SOD,POD,and CAT in leaves of Yanliu NO.1 increased with the increase of salt concentration,so as to prevent and decrease the damage of free radicals to the cells.When the salt concentration was higher than 150 mmol/L,the activities of SOD,POD,and CAT in leaves of Yanliu NO.1 were decreased to some extent,which indicated the decrease of capacity of eliminating free radicals.5.Under the stress of low salinity?50 mmol/L?or low alkalinity?pH: 8.04?,the contents of proline,soluble sugar,and soluble protein in leaves of Yanliu NO.1 showed a small variation.With the increase of salt concentration and proportion of alkaline salts,the contents of proline,soluble sugar,and soluble protein in leaves of Yanliu NO.1 showed a significantly increasing trend.It indicated that Yanliu NO.1 increased the cell concentration by increasing the content of osmotic adjustment substances,and maintained the normal water potential of the leaves in order to improve the ability of saline-alkali resistance.6.[HCO₃^-] and salt concentration were the leading factors of complex saline-alkali stress affecting Yanliu NO.1,and the ability to tolerate complex saline-alkali stress of Yanliu NO.1 could be evaluated by indices like SOD activity,CAT activity,POD activity,proline content,leaf water content,MDA content,and soluble sugar content and so on.