In order to determine the optimal concentration of salt tolerance standard and confirm the effect of different concentration of NaC1 on alfalfa （Medicago sativa ） seed germination, seeds of 11 approved al falfa cuhivars were germinated at different concentrations of NaCl solution. The differences of germination potential, germination rate, seedling height and root length were also compared. The results showed that there were significant differences （P〈0.01） on above indexes among the 11 cuhivars when the seeds were treated with the 1. 25% NaCl concentration; and the differences were the largest compared with other treatments. By cluster analysis of three indexes of seed germination rate, seedling height and root length of alfalfa, it could conclude that 1.25% of NaCl concentration should be the optimal concentration for determining the salt tolerance in seed germination of alfalfa. In additional, by analysis the relationship between root length and salt stress, it seemed that root growth of alfalfa could be promoted with 0.30% salt concentration treatment, but stopped with 1. 00% salt concentration treatment. 1. 25% salt concentration treatment inhibited root growth of alfalfa.%为确定苜蓿（Medicago sativa）种子萌发期耐盐性鉴定的质量分数标准，明确不同盐质量分数对苜蓿种子萌发的影响规律，从而科学、准确、快速地鉴定我国苜蓿品种的耐盐性，分析比较了不同NaCl质量分数下的11个苜蓿审定品种的发芽势、发芽率、苗高、根长等指标的差异。结果表明，在NaCl质量分数1．25％时各品种间的发芽势、发芽率、苗高、根长差异均极显著，且品种间各指标差异最大。聚类分析表明，1．25％可作为苜蓿种子萌发期耐盐性鉴定的最佳NaCl质量分数。NaCl质量分数为0．30％时促进苜蓿根的生长，质量分数为1．00％时促进作用消失，1．25％时则抑制苜蓿根的生长。
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