毛萼田菁茎瘤菌共生状态下吸氢与固氮关系的研究

Relationship between the hydrogenase and nitrogenase activities in Azorhizobium caulinodans symbiotic nitrogen fixation

不同瘤龄、不同光照和生长周期的毛萼田菁，其茎瘤的吸氢活性和固氮活性均呈正相关。绿色的茎瘤，无论在数量上还是固氮及吸氢活性上均为最高。Ａ．ｃａｕｌｉｎｏｄａｎｓＯＲＳ５７１菌（Ｈｕｐ＋）、Ｈｕｐ－突变株和含Ｂ．ｊａｐｏｎｉｃｕｍ５．９ｋｂｈｕｐ结构基因质粒的转移接合子回接实验的结果表明，Ａ．ｃａｕｌｉｎｏｄａｎｓ具吸氢活性的菌株对植株生长有益，茎瘤的固氮活性高于根瘤的２倍以上；吸氢活性亦高。转移接合子在无选择压力的条件下连续培养，其带有外源ｈｕｐ基因片段的质粒会缓慢丢失，最终从茎瘤中分离的Ｒ－３０９１１和Ｒ－４９１１已经完全丧失了Ｔｃ抗性。

The hydrogenase and nitrogenase activities of stem nodules from different nodule ages or growth circles in one day are relative. Green stem nodules not only in numbers but also in hydrogenase and nitrogenase activities are higher than others. The hydrogenase and nitrogenase activities of green stem nodules are lowest in day than at night. Plants inoculated with ORS571 (Hup +) exhibited higher dry weight than those inoculated Hup _ mutants. The hydrogenase and nitrogenase activities in stem nodules are higher than those in root nodules. The transconjugants with a plasmid containing B. japonicum hup structural gene are unstable in the absence of selection pressure.