木麻黄和桤木离体根瘤和立地土壤的固氮酶与N_2O还原酶活性的研究

Nitrogenase and N_2O Reductase Activities of Detached Nodules and Site Soils of Casuarina cunninghamiana and Alnus trabeculosa

为了解非豆科固氮树种的固氮酶和N_2O还原酶(Nos)活性,采用乙炔还原法和乙炔抑制技术对细枝木麻黄(Casuarina cunninghamiana)和江南桤木(Alnus trabeculosa)离体根瘤及立地土壤的两种酶活性进行了研究。结果表明,离体根瘤只在厌氧条件下有固氮酶活性,在好氧条件下有Nos活性。根瘤区根际土和非根瘤区根际土的固氮酶活性在好氧条件大于厌氧条件,Nos活性只表现在厌氧条件下。在好氧条件下,根瘤区根际土和非根瘤区根际土的固氮酶活性无显著差异;根瘤区根际土的Nos活性显著大于非根瘤区根际土。除离体根瘤在好氧条件下不表现固氮酶活性外,细枝木麻黄和桤木的离体根瘤、根瘤区根际土和非根瘤区根际土的固氮酶活性均都大于Nos活性。好氧条件下根瘤区根际土的固氮酶活性与非根瘤区根际土的呈极显著正相关,而厌氧条件下根瘤的固氮酶活性与好氧条件下根瘤区根际土和非根瘤区根际土固氮酶活性、好氧条件下根瘤的Nos活性与厌氧条件下根瘤区根际土和非根瘤区根际土Nos活性均呈极显著负相关。这为研究弗兰克氏菌结瘤植物共生固氮体系对N2O汇强度的影响和调控奠定基础。

To understand the activities of nitrogenase and N2O reductase(Nos) for non-legume nitrogen-fixing tree species, the detached nodules, rhizospheric soil in nodule root grown area(RSI) and rhizospheric soil near nodule root grown area(RSN) were collected from Casuarina cunninghamiana and Alnus trabeculosa in Fujian Province, southeastern China, and the nitrogenase and Nos activities were determined by acetylene reduction method and acetylene inhibition technique, respectively. The results showed that the nitrogenase activity of detached nodules could be detected only under anaerobic condition, and the Nos activity only in aerobic condition.The nitrogenase activity in RSI and RSN under aerobic conditions was higher than those under anaerobic condition, and the Nos activities could be detected only under anaerobic condition. In aerobic condition, there was no significant difference in nitrogenase activity between RSI and RSN, while Nos activity of RSI was significantly larger than that of RSN. The nitrogenase activity were greater than Nos activity for the two tree species, except that there were no nitrogenase activity for the detached nodules under aerobic condition. The nitrogenase activity in the RSI under aerobic condition was significantly positively correlated with that in RSN.However, the nitrogenase activity in nodules under anaerobic condition was negatively correlated with that in RSI and RSN under aerobic condition, and the Nos activity in nodules under aerobic condition was also negatively correlated with that in RSI and RSN under anaerobic condition. These would lay a foundation for studying the effect and regulation of symbiotic nitrogen fixation system of tree species nodulated with Frankia on N2 O sink intensity.