Environmental stress tolerance in non-leguminous nitrogen fixing plants and symbiont Frankia

点击翻译按钮获取中文摘要

Salt tolerance of non-leguminous nitrogen fixing plants (actinorhizal plants) and the symbiont Frankia was investigated. Actinorhizal plants used in this experiment were Casuarina equisetifolia, Elaeagnus macrophylla, Alnus sieboldiana and Alnus hirsuta, which are growing in Japan naturally. One effective Frankia strain was isolated from the root nodules of C. equisetifolia and 3 Frankia strains (Ceql, Emal and Anil) whose host range is different were used in this experiment. The growth of Frankia strains was markedly suppressed by NaCl concentration higher than 100 mM, although the magnitude of salt tolerance considerably differed among strains. However, when the cells depressed their growth by high NaCl concentration were transferred to the medium which did not contain NaCl, they underwent multiplication again. Accordingly, we judged that salt tolerance of Frankia is generally considerably high. Seed germination of 4 actinorhizal plants was markedly inhibited by NaCl and germination did not occur at 200 mM NaCl. These results suggested that sowing of actinorhizal plant seeds is not effective for the recovery of the vegetation in salt-accumulated lands. A. sieboldiana and A. hirsuta seedlings was extremely weak against salt stress. On the other hand, E. macrophylla possessed a pretty high salt tolerance, and C. equisetifolia showed was very strong salt tolerance. The upper limit of Nad concentration for nodulation was 300 mM in C. equisetifolia, 100 mM in E. macrophylla and 50 mM in A. sieboldiana and A. hirsuta.From these results, we concluded that C. equisetifolia-Ceql symbiotic system and E. mocrophrylla-Emal symbiotic system are useful for the recovery of the vegetation in salt-accumulated lands.