杨梅硝酸还原酶活性与根瘤固氮活性的研究

离体根瘤的固氮活性的测定采用乙炔还原法,硝酸还原酶的测定采用改进活体法,测试杨梅各器官硝酸还原酶活性的差异和温度、化合态氮对硝酸还原酶活性和固氮活性的影响,研究结果表明:①确定1%的正丙醇为活体法测定杨梅硝酸还原酶时所使用的渗透剂的最佳浓度。②杨梅NO3- 还原的主要部位在叶片,根瘤的硝酸还原酶活性受到宿主植物和内生菌的影响。③温度对植物体内硝酸还原酶和根瘤固氮活性水平影响很大,温度太高抑制酶活性,20℃时杨梅各器官的硝酸还原酶活性均达最高点,根瘤的固氮活性也达最高点。④用含10mmol/LNO3-的Hogland营养液培养的植株各部位的硝酸还原酶活性均高于对照,10mmol/L的NH4+ 对植株的硝酸还原酶活性未见明显影响,但能抑制根瘤的固氮活性,其抑制程度高于NO3-。⑤硝酸还原酶活性和根瘤固氮活性之间没有直接关系。 

Nitrate Reductase Activity and Nodule Nitrogen Fixation Activity in Myrica rubra

Nitrogenase activity of detached nodules of Myrica rubra was assayed by acetylene reduction, and nitrate reductase activity (NRA) was determined by the modified in viwo method.The NRA in the leaves, roots and nodules were compared, and the effects of temperature and compound nitrogen upon the NRA and nitrogen fixation activity were studied. The results showed the optimum propanol concentration was 1 for Myrica rubra when NRA was assayed using the in vivo method. This woody plant reduced nitrate mainly in the leaves, and the nodules with active nitrogenase showed higher NRA than the roots, which implied the microsymbiote also reduced nitrate. Temperature had similar effect on NRA and nitrogenase activities which all reached the highest point when plants were grown under 20 C, a suitable temperture for the growth of Myrica rubra. Nitrate (10 mmol/ NO3") induced nitrate reductase, and ammonia (10 mmol/ NH.") had no significant effect on NAR but inhibited the nitrogenase activity