Evaluation Of Salt Tolerance In Cowpea Germplasm Resources And Study It Differences Of Changes Under Isotonic NaCl And Ca（NO₃）₂ Stress

With the expansion of the facility cultivation area, the secondary salinization of soil is an important problem for threaten world food production. Cowpea（Vigna unguiculata.）, as one of the facility cultivation of crops, has been planted widely.Thus,the cowpea salt resistance has a realistic significance.This study adopts the method of salt water irrigation.42 genotypes of cowpea（Vigna unguiculata.） were evaluated for salt-tolerance in the germination and seedling stage,screened out two typical materials: GD-02（the NaCl tolerant cultivar） and GD-41（the NaCl sensitive cultivar）.Then,with two cultivars as experimental materials, analyzing the dynamic changes of biomass, chlorophyll fluorescence parameters and plant nutrients in two species under isotonic NaCl and Ca（NO₃）₂stress.The aim was to explore the damage degree and mechanism of two kinds of salt to the cowpea, and to provide theoretical basis for breeding of NaCl tolerant varieties and improving salinized soil.The main research results were showed as following:1. Two typical germplasm resources with different salt tolerance were screened out.75mmol/LNaCl as screening concentration, by comprehensive consideration of the mean of subordination index value in the germination and seedling stage, screened out GD-02（the NaCl tolerant cultivar） and GD-41（the NaCl sensitive cultivar）.2. Clear NaCl and Ca（NO₃）₂ these two kinds of salt stress on the physiological and biochemical effects of the obvious differences.Differences between NaCl and Ca（NO₃）₂ stress. The effects of two kinds of salt on the effects of NaCl were different, NaCl stress decreased the length of old leaves, fresh weight of each organ, chlorophyll of new leaf, Fv/Fm of new and old leaf, Y（II） of new and old leaves, q P of old leaves, N of new leaf, K of root, the NO₃^- contents of each organ, and the decline of NaCl sensitive varieties was greater than that of NaCl Tolerance Varieties. Ca（NO₃）₂stress had no significant effect on the length of old leaf, Fv/Fm of new leaf and old leaf, q P of new leaf, Y（II） of new leaf, N of new leaf and K of root, NO₃^-content of various organs, and the Ca（NO₃）₂ stress increased the chlorophyll content of new leaf. Therefore, NaCl salt stress on physiological and biochemical damage of asparagus is greater than Ca（NO₃）₂ stress.3. The similarities and differences of physiological and biochemical responses to salt stress in different cultivars of asparagus bean were explored. Under NaCl stress, the two cultivars have great difference, GD-41 is more severe than GD-02 by salt stress, may be due to the sensitivity of NaCl varieties accumulated more Na in leaves, lost more Ca2+; as well as the root lost more NO₃^-, so that it was significantly less than NaCl tolerant varieties in photosynthetic efficiency and biomass.while under Ca（NO₃）₂ stress, the difference between the two varieties is relatively small. The main difference is the dry weight of leaf higher than the control in dragon fly, while GD-41 had no significant difference with the control; the increase in the leaves chlorophyll of GD-41 is less than that of GD-02, and q N was significantly higher than that of GD-02. The dry weight of the new and old leaves in GD-02 was significantly higher than that in the control under Ca（NO₃）₂ stress, this may be due to the new leaf chlorophyll is far greater than the control and the old leaves Y（II） is also significantly greater than the control. The increase in the leaves chlorophyll of GD-41 is less than that of GD-02, and q N was significantly higher than that of GD-02 This may be owed to the GD-41 accumulated more NO3- in leaves than in GD-02. Under 75mmol/LNaCl stress, the difference between cultivars was much greater than that under 50mmol/L Ca（NO₃）₂ stress, resulting in differences between species may be a major cause of different genotypes of cowpea to ion toxicity tolerance and salt rejection ability is different.