共生固氮体系仅限于豆科植物，涉及多样性根瘤菌和植物信号识别及互接种族。联合固氮菌在甘蔗、水稻等粮食和经济作物中广泛存在，开辟了生物固氮新途径。最近研究表明白杨等速生植物氮素主要来源叶内生物固氮，拓展了生物固氮新路径。项目拟选取泓森槐(豆科)、竹子(禾本科)等速生植物进行共生固氮、联合固氮的集成研究。采用宏基因组技术、基因组测序技术、用固氮酶nifH-RNA转录组分析等手段，尤其是对未（难）培养微生物分离培养，阐明泓森槐、竹子等固氮种类多样性和未知新类群，其高效氮素来源于哪些种类菌群及固氮机理。尤其是泓森槐豆科植物能够共生结瘤固氮（在根部），其叶部是否有叶内联合固氮菌存在，效率如何。与禾本科竹子比较，叶内固氮菌（FENFB）网络多样性异同。探究不同类群叶内固氮微生物在不同速生植物中固氮贡献和共生-联合固氮演替网络。对于森林植物自然氮素来源及农业生产生物固氮研究具有重要理论和实践意义。

The highly effective symbiotic nitrogen fixation systems are only limited to legumes, involving the interaction of complex rhizobia and plant signal recognition and cross inoculation group. The associated nitrogen-fixing bacteria were found widely existing in sugarcane, rice and other food crops and cash crops, which opened up a new way of biological nitrogen-fixing. The nitrogen sources of fast-growing plants in forests have received little attention in the past years. Recent studies have shown that nitrogen in fast-growing plants mainly comes from biological nitrogen fixation rather than soil. The project intends to integrated study the diversity of foliar endophytic nitrogen-fixation bacteria obtained from fast-growing plants-Sophora japonica (symbiotic nitrogen fixation), bamboo (associated nitrogen fixation) and others. By means of metagenome technology, genome sequencing technology, combined with transcriptome analysis of nifH-RNA technology, especially the isolation and cultivation of uncultured microorganisms, we try to obtained the nitrogen-fixing bacteria from leaves of fast-growing plants-Sophora japonica, bamboo and other plants and elucidate the contribution and succession network between symbiotic nitrogen-fixing and associated nitrogen-fixing microorganisms in leaves of different fast-growing plants. The predicted results have important theoretical and practical significance for the study of natural nitrogen sources of forest plants and the application of biological nitrogen fixation in agricultural production.