解磷真菌能够分泌有机酸促进土壤中难溶性钙磷的磷素释放，提高土壤磷的有效性。前期研究发现，氮素形态对解磷真菌活化难溶性钙磷的能力有较大差异，但究其与有机酸分泌的关系及作用机制尚不清楚。本项目以一株高效解磷的黑曲霉为材料，拟采用15N标记的方法，研究铵态氮和硝态氮等氮素对黑曲霉溶解土壤难溶性钙磷的影响；利用高效液相色谱技术，分析不同形态氮素影响黑曲霉分泌有机酸的种类及剂量和时间效应关系；采用酶学分析方法，探究不同形态氮素调控黑曲霉分泌有机酸过程中异柠檬酸脱氢酶和草酰乙酸水解酶等相关酶活性的变化特征；利用qPCR技术，解析不同形态氮素对有机酸分泌相关酶oahA等基因的表达差异，阐明氮素形态影响黑曲霉解磷能力的有机酸分泌与酶学和分子生物学特征，揭示氮素形态调控黑曲霉有机酸分泌及其对土壤磷素活化的作用机制。研究结果为提高土壤难溶性钙磷的活化和利用提供理论依据。

Phosphate solubilizing fungi (PSF) can promote the release of phosphorus from calcium phosphate in soil, which related to the pathway of organic acid secretion. Nitrogen forms could significantly influence the dissolution of calcium phosphate by PSF. However, the mechanisms of phosphate dissolution by PSF under different nitrogen forms still unclear. In this research, the PSF Aspergillus niger (A. niger) was used as a fungi material. The effects of ammonium and nitrate nitrogen on calcium phosphate dissolution by A. niger were studies by l5N isotope labeling. HPLC technique was used to analyses the organic acid secretion by A. niger. The enzymatic technique was used to explore the isocitrate dehydrogenase and oxalyl acetate hydrolase activities, which related to the organic acid secretion by A. niger. The expression of oahA and other genes related to organic acid were analyzed by Q-PCR technique. This research aims to clarify the enzymatic and molecular biological characteristics of calcium phosphate dissolution by A. niger under different nitrogen forms. More importantly, the mechanisms of calcium phosphate dissolution by A. niger induced by nitrogen forms were exposed. This research provides a theoretical basis for improving the efficient utilization of insoluble calcium phosphate in the soil.