Abstract: Alfalfa (Medicago sativa) was taken as research material. Saline stress was simulated by mixing NaCl and Na₂SO₄ in different molar ratios. Similarly, alkaline stress was simulated by mixing NaHCO₃ and Na₂CO₃ with different molar ratios. Six groups (A to F) with different Na⁺ concentrations and pH values were designed. Results showed that the germination rate of alfalfa seed was promoted by lower concentration. The germination indices of alfalfa seed (germination rate, germination energy, germination index and vigor index) were all decreased with the increase of salinity and the decreasing degree were more obvious with increasing the proportion of alkaline salt, whereas mean germination days were increased. Radicle was more tolerant to saline and alkaline stresses compared with embryo. These data indicated that the mixed salinity-alkalinity stresses were different from either saline or alkaline stress. The interactions of saline and alkaline stresses increased with the increase of salt concentration. Plant was damaged severely by the synergy of both stresses.

Key words: Medicago sativa, Seed, Salt and alkaline stress, Germination rate, Germination potential

摘要： 以紫花苜蓿（Medicago sativa）为材料，在实验室内模拟土壤复杂盐碱逆境条件，将2种中性盐NaCl, Na₂SO₄与2种碱性盐NaHCO₃, Na₂CO₃以不同的摩尔比例混合，按碱性盐比例递增的顺序共设置A～F组，同时每个组又设置6种盐浓度（24～168 mM），涵盖Na⁺浓度为32～192 mM，pH为7.03～10.68范围的盐碱生境，试验共模拟出36种盐度和碱度（pH值）各不相同的盐碱条件，并对胁迫下苜蓿种子发芽指标进行了测定。结果表明：低浓度胁迫对苜蓿种子发芽有一定的促进作用，在各胁迫处理组下苜蓿种子的发芽指标（发芽率、发芽势、发芽指数和活力指数）均随着盐浓度的增加不断下降，且碱性盐比例越大下降越明显，而平均发芽天数逐渐增加。胚根与胚芽生长表现出与发芽相似的变化规律，并且胚根适应盐碱能力更强。因此，复合盐碱胁迫不同于单独的盐或碱胁迫，一旦浓度较高时，盐和碱的交互作用更明显，二者存在明显的协同作用，加剧了对植物的伤害。

关键词: 紫花苜蓿, 种子, 盐碱胁迫, 发芽率, 发芽势