Mycorrhiza Inoculation and Soil-Available Phosphorus Modulate Phosphorus Acquisition Strategies of Alfalfa
Xinya Pan, Haotian Li, Jiahua Wu, Qian Li, Yi Zhou, Peizhi Yang
Abstract
The comprehensive understanding of how arbuscular mycorrhizal fungi (AMF) and phosphorus (P) application affect P uptake by alfalfa roots is poorly understood. We analyzed the effects of AMF inoculation and P application levels on the trade-offs and variations in P acquisition strategies of alfalfa by assessing plant growth, root morphology, organic acid contents, phosphatase activity, root transcriptome, and soil P forms. AMF inoculation increased five organic acid contents (glutaric acid, 3-hydroxymethylglutaric acid, gallic acid, 2-hydroxyphenylacetic acid, and fumaric acid) and phosphatase activity synthesized by alfalfa and secreted by the roots and hyphae, which activated soil Ca 2 -P, Fe-P, and organic P, promoting root growth for P absorption and biomass. Without AMF inoculation, plant biomass, P accumulation, and root growth increased with increasing P application, and organic acid contents were higher at P20 and P40 (20 and 40 mg P kg –1 dry soil). AMF colonization and phosphatase played a crucial role in P acquisition under P-limiting conditions.