玉米/大豆套作既能提高资源利用效率，又能维持和改善土壤肥力，在西南地区得到大面积推广应用。该区域光照弱且土壤磷有效性低，前期研究发现，套作大豆相对单作显著提高土壤磷的有效性，但影响其活化磷的机理尚不明确。为了揭示在套作大豆相对单作“前弱后强”的变化光环境中，叶片光合特性、光合产物转运、分配影响根系生长、活化吸收利用土壤磷的过程，本项目以玉米/大豆套作模式为对象，研究不同磷水平处理和不同磷效率大豆植株光合特性、光合产物在叶片和根系中分配积累影响根系生长、分泌小分子有机酸总量与组成、酸性磷酸酶活性进而影响土壤磷有效性；研究编码磷转运蛋白和酸性磷酸酶活性、小分子有机酸分泌总量与组分、根系增殖生长的基因表达差异，验证、解释相关生理生化过程。从而阐明套作光环境中大豆响应低磷胁迫、提高土壤磷有效性的生理生化机制，为间套作种植减肥增效技术研发和低磷生态区农业资源高效利用提供理论支持。

Maize/soybean intercropping is beneficial for efficient using natural resources, maintenance and improving soil fertility, which leaped into a dominant cropping system in southwest of China. In previous research we found intercropping soybean improving soil availability phosphorus (P) and use efficiency in southwest of China, even though where is low light intensity and soil availability P, but we know the mechanisms poorly. In this project, maize/soybean relay-strip intercropping system was used to study the photosynthetic characteristics, photosynthetic products accumulate in leaves and roots affecting root growth, root morphology, total amount and composition of small molecule organic acids and phosphatase activity affects soil P availability in the treatments of different P application rates or/and P use efficiency soybean genotypes. At the same time, analysis the gene expression difference associated with coding P transporter, acid phosphatase, amount and composition of small molecule organic acids, and root proliferation to explain and verify the mechanisms of intercropping soybean increasing soil availability P. This research will helpful for understanding physiological and biochemical mechanisms of intercropping soybean increasing soil availability P in special light environment. Provide theoretical support for decreasing fertilizer application and increasing use efficiency technology R&D in intercropping system, and improving agricultural resource using efficient technology R&D in low P region.