Influence of 6 Alfalfa Varieties on Free Proline Content and SOD Activity in Salt Stress

The salt tolerance of 6 alfalfa varieties was studied by measuring the free proline content and SOD activity under the treatments with the different salt stress.The results show that the free proline content and SOD activity of the varieties were significantly different in the different salt concentrations.For most varieties,the two peak values of the free proline content could be observed in a salt concentration of 0.20%～0.30% and a salt concentration of 0.50%～0.60% separately.In addition,the enzyme activities of SOD reached the peak under the concentration of 0.30%～0.40% and then decreased under serious stress.In conclusion,there are two kinds of mechanisms of free proline content to enhance the salt tolerance of alfalfa in the different salt concentrations,and SOD can effectively avoid the injury of the oxidative stress for alfalfa from the reactive oxygen in some salt concentrations.Furthermore,the salt tolerance of alfalfa varieties should be evaluated by measuring multi-indices.