中文摘要：

为探索水土保持禾草的固氮能力，利用乙炔还原法（ARA）对类芦（Neyraudia reynaudiana）和狗牙根（Cynodondactylon）植株内生固氮菌的固氮酶活性进行研究。结果表明：在类芦茎部和狗牙根叶片中存在高固氮酶活性的内生固氮菌群；这些菌群在无氮培养基上经划线分离纯化得到40个菌株，其中26株有微弱固氮酶活性，14株检测不到固氮酶活性；从类芦茎部和狗牙根叶片中筛选到的固氮菌群在兼性厌氧的环境中有较高的固氮酶活性，且在石蜡油密封条件下，两者的固氮酶活性均最高；在不改变自然界微生物之间的协同关系情况下，混合菌群均具有较高的固氮酶活性，而人为组配混合得到的菌群固氮酶活性较低。

英文摘要：

The nitrogenase activities of endophytic diazotrophs in Neyraudia reynaudiana and Cynodon dactylon, which are the pioneer grasses for soil and water conservation, were studied by acetylene reduction assay （ARA）. The results showed that the communities of the endophytic diazotrophs isolated from the stems of Neyraudia reynaudiana and the leaves of Cynodon dactylon showed high nitrogenase activities. Forty strains were isolated and purified on nitrogen-free medium, in which twenty-six strains showed weak nitrogenase activities, and fourteen had no nitrogenase activities. The natural communities of endophytic diazotrophs showed high nitrogenase activity under facultative anaerobic conditions or covered by paraffine. The communities of endophytic diazotrophs under laboratory-cultured showed lower nitrogenase activity than that of the natural communities.