Salt tolerance of Elaeagnus macrophylla and Frankia Ema1 strain isolated from the root nodules of E. macrophylla

Effects of NaCl on the seed germination and growth of Elaeagnus macrophylla seedlings and multiplication of Frankia Ema1 strain isolated from the root nodules of E. macrophylla were examined. The germination rate of seeds was not reduced by NaCl at 50 mill, but was reduced with further increase of t he concentration, and germination did not occur at 200 mM NaCl. Root nodule s were formed in the seedlings treated with 100 mM NaCl. The fresh and dry weight of the seedlings slightly decreased by the increase of the concentra tion of NaCl and the rate of decrease was 10-20% at NaCl concentrations hig her than 100 mill. However, Na+ concentrations in the shoot increased up to 300 mill by treatment with NaCl at a concentration above 50 mill for 30 d and in some plants the lower leaves fell. The growth of free-living Frankia was markedly suppressed and the hyphae became thick and short in the solut ion at 100 mM NaCl, This trend was more obvious at 200 mM NaCl. Na+ concent ration in the cells in the medium with 200 mill NaCl was lower than 20 mM a nd the cells underwent multiplication again when they were transferred to t he medium which did not contain NaCl. These results indicate that the salt tolerance of E, macrophylla seedlings was not very high and the threshold f or NaCl ranged between 50 and 100 mM, whereas Frankia Ema1 strain was able to survive in a much higher salt environment.