Abstract: Mycorrhiza is the most common symbiosis in nature, which can greatly promote the nitrogen uptake and utilization by host plants. In the
 function of the mutualistic symbiosis, mycorrhizal fungi play an important role. This paper summarized the research progress in the mechanisms of mycorrhizal fungi in promoting the nitrogen uptake and utilization by plants from the aspects of mycorrhizal anatomical structure, physiology, biochemistry, and molecular biology, with the focus on the available nitrogen forms and the factors affecting their utilization, the nitrogen metabolic pathways GS-GOGAT in mycorrhzal fungi, and the ornithine cycle in mycorrhizal fungi. It was pointed out that arginine was the main nitrogen translocation form within the hyphae, and NH₃ could be the main nitrogen translocation form in the interfacial apoplast.

Key words: adaptive strategy, clonal plant, environmental heterogeneity, physiological integration, resource sharing.