Application of

Biological nitrogen fixation (BNF) is an important nitrogen source in terrestrial ecosystems. Accurate estimation of BNF rate is essential to accurately quantify atmospheric nitrogen input to natural ecosystems. 15N natural abundance is commonly used to measure the BNF in symbiotic and associative nitrogen fixing plants, but are highly dependent on the choice of the reference plants. In contrast, the 15N isotope labeling technique allows precise determination of BNF rates of symbiotic, free-living, and associative N-fixing types, and surpasses the previous methods in studying plant nitrogen fixation strategies, nitrogen transfer processes, and carbon-nitrogen trading between nodules and hosts. The 15N isotope dilution method is mainly used for plant nitrogen fixation research. Although the 15N stable isotope probe technique is technically challenging and expensive, it enables the detection and study of N-fixing microorganisms by labeling DNA or RNA, and provides an effective way for assessing asymbiotic microorganism nitrogen fixation rates. The development of 15N stable isotope technique provides a strong technical guarantee for biological nitrogen fixation research.