咪唑乙烟酸抑制大豆根瘤固氮酶活性的机理研究

【目的】探索咪唑乙烟酸抑制大豆根瘤固氮酶活性的关键机制，为解决咪唑乙烟酸长期大量应用对根瘤固氮的毒害提供依据。【方法】采用田间试验方法，研究咪唑乙烟酸茎叶处理对根瘤固氮酶活性的影响与根瘤豆血红蛋白含量、根瘤类菌体和细胞浆中氨含量的关系。【结果】咪唑乙烟酸施用后21 d内，固氮酶活性受到显著抑制。112.5和225.0 g a.i./hm2施药量下，对豆血红蛋白含量的抑制峰值分别出现在第7、14天，抑制率分别为30.52%和35.41%，抑制作用分别在第21、28天得到解除。根瘤类菌体中氨含量抑制峰值均出现在第14天，抑制率分别为35.33%和48.96%，第28天氨含量均恢复正常。细胞浆中氨含量显著增高，且分别在第 21、28天恢复正常。【结论】咪唑乙烟酸茎叶处理后，豆血红蛋白含量降低是导致固氮酶活性降低的1个重要原因，同时细胞浆中氨积累也造成了对固氮酶活性的反馈抑制。

Research on the Inhibitory Mechanism of Imazethapyr to Nodule Nitrogenase Activity in Soybean

【Objective】The objective of this study is to discover the key inhibitory mechanism of imazethapyr to nodule nitrogenase activity in soybean for providing methods to resolve the toxity on nodule nitrogen fixation after imazethapyr being over used.【Method】A field experiment was conducted to determine the relationship between inhibited nodule nitrogenase activity and leghemoglobin content, ammonia content in nodule rhizobium and in nodule cytoplasm after imazethapyr pre-emergence used.【Result】Nodule nitrogenase activity was inhibited more pronounced during 21 days after treatment (DAT). One the 7 and 14 DAT, the inhibited ratio of leghemoglobin content peaked 30.52% and 35.41%, respectively at 112.5 and 25.0 g a.i./hm2 imazethapyr and then recovered to the levels of non-treated plants on the 21 and 28 DAT, respectively. The inhibited ratio of ammonia content in nodule rhizobium peaked 35.33% and 48.96%, respectively, on the 14 DAT and recovered to the levels of non-treated plants on the 28 DAT. Ammonia content in nodule cytoplasm increased more pronounced and recovered to the normal levels respectively on the 21 and 28 DAT.【Conclusion】It is an important reason that leghemoglobin content significantly decreased after imazethapyr pre-emergence applied leads to nodule nitrogenase activity inhibited, and ammonia accumulation in nodule cytoplasm also causes feedback inhibition to nodule nitrogenase.