中文摘要：

采用乙炔还原法对从圆果雀稗（Paspalum orbiculare）根、茎中分离到的5株内生固氮菌（POJy11、POG12、POay22、POGy612、POG4）的固氮特性进行了研究。结果表明，POGy612、POG4固氮的pH适应范围是6．0—10．0，其余3株菌为6．0—8．0：POGy22固氮的最适温度为35℃，其余4株菌为30℃：随着NH4^＋浓度和NaCl浓度的升高，菌株固氮活性总体呈下降趋势，其中POGy22的固氮活性受NH4^＋抑制最明显，NH4^＋浓度为1．0mmol／L时，已无固氮活性，但POGy612在NH4^＋浓度为2．5mmol／L时的固氮活性最高，达到1045．0 nmol ml^-1h^-1，POJy11、POGy22在NaCI浓度为0．5％时的固氮活性最高，分别达到735．5nmolml^-1h^-1、703．0nmol ml^-1h^-1。

英文摘要：

Five endophytic diazotroph strains, including POJyll, POG12, POGy22, POGy612 and POG4 from rhizosphere and stalks of Paspalum orbiculare, were studied in acetylene reduction activity （ARA）. ARA was maximal at pH 6,0-10.0 in POGy612 and POG4 strains and did at pH 6.0-8.0 in POJyl 1, POG12 and POGy22 strains. The maximum activity occurred at 35℃ in POGy22 strain and did at 30℃ in the other strains. The activity in those strains remarkably declined as NH4^＋ or NaCl concentration increased. ARA was mostly inhibited by NH4^＋ in POGy22 strain and lost over 1.0 mmol/L NH4^＋. ARA showed a peak of activity at 2.5 mmol/L NH4^＋ in POGy612 strain and did at 0.5% NaCl in POJy11 and POGy22 strains.