Synergistic Effects of Salt and Alkaline Stresses on the Seed Germination of Medicago sativa

Alfalfa(Medicago sativa) was taken as research material.Saline stress was simulated by mixing NaCl and Na_2SO_4 in different molar ratios.Similarly,alkaline stress was simulated by mixing NaHCO_3and Na_2CO_3 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.