Study On Salt Tolerance At Different Growth Periods In Fall Dormancy Standard Varieties Of Alfalfa (Medicago Sativa)

Salt tolerance of the different fall dormancy alfalfa in geminating period has been studied by measuring the germination energy,the germination rate,the seedling early growth,the germination index,the activity index under NaCl stress.In order to elucidate mechanism of reactive oxygen species(ROS) regulation and the relevance to salt-tolerance in the different fall dormancy alfalfa,we used Maverick,Vernal,Pioneer5446,Legend,Archer,ABI700,Dona Aan,Pierce,CUF101,Zhongmu No.1 to investigate the effects of increasing NaCl on ROS,anti-oxidative enzymes, malondialdehyde(MDA) and membrane permeability(MP)in shoots and/or roots.In addition,we designed experiments to clarify the response of photosynthetic indexes(Pn,Gs and Ci) under NaCl stress.The conductivity of different growth stages has been determined,and MDA content in the leaves of seedling stage.1.Seed germination of the different fall dormancy alfalfa has not been promoted under 50 mM NaCl.the length of root,the germination index,the activity index and NaCl concentration declined with NaCl concentration increasing when NaCl concentration was greater than 50 mM.The percentage of recovery were lower than 10%under 50 mM NaCl.The percentages of recovery were maxmium when NaCl concentration was 150 mM NaCl.Under the treatments with 100 mM,150 mM and 200 mM NaCl.2.The salt tolerance abilities of alfalfa in geminating period were evaluated comprehensively by subordinate function value method.The results showed that Dona Aan,Pierce,Pioneer5446,CUF101 had the most salt tolerance,that Maverick,Vernal,Legend had the weakest salt tolerance,that ABI700,Zhongmu No.1,Archer had medium salt tolerance.Subordinate degree of alfalfa in the activity index indicated that Aan,Pierce,Pioneer5446,CUF101 had the most salt tolerance,that Maverick,Vernal,Legend had the weakest salt tolerance,that ABI700,Zhongmu No.1,Archer had medium salt tolerance.So the activity index can be taken as the indexes of salt tolerance for alfalfa during germination.3.The correlation between the O₂^- production rate and NaCl concentration was significantly positive during seedling stage.In shoots of the different fall dormancy alfalfa,the degree of ROS damage has increased with the increase of NaCl concentration.The antioxidant capacity of the different fall dormancy alfalfa in seedling stage was evaluated comprehensively by subordinate function value method.The results showed that Dona Aan,Pierce,Zhongmu No.1 had the best antioxidant capacity,that CUF101,ABI700,Legend,Vernal had the weakest antioxidant capacity, that Archer,Pioneer5446,Maverick had the medium antioxidant capacity.4.The photosynthetic response of the different fall dormancy alfalfa consisted of alarm phase, phase of resistance or phase of restoration,phase of exhaustion under 50 and 100 mM NaCl.5.With the increase of NaCl concentration,the conductivity of the different fall dormancy alfalfa seed has increased during different growth stages.Subordinate degree of alfalfa in the conductivity during different growth stages indicated that Dona Aan,Pierce,Pioneer5446,CUF101 had the most salt tolerance,that Maverick,Vernal,Legend had the weakest salt tolerance,that ABI700,Zhongmu No.1,Archer had medium salt tolerance.So the conductivity can be taken as the indexes of salt tolerance for alfalfa during different growth stages.