AMF-mediated root redistribution decreases Cd uptake in rice while enhancing phytoremediation in the S. nigrum/rice...

Harnessing arbuscular mycorrhizal fungi (AMF) in hyperaccumulator-crop intercropping holds promise for Cd remediation and food safety, yet its roles in root distribution and Cd dynamics remain unclear. Therefore, we employed a multi-compartment pot system (0, 1, 5 mg·kg^-1 Cd levels) to examine how AMF alters root allocation and Cd availability in S. nigrum-upland rice intercropping. AMF altered root distribution under Cd stress: it increased S. nigrum root allocation to the rice zone by 10.90% at 28 days, while AMF-inoculated rice allocated more roots to the S. nigrum zone under 5 mg·kg^-1 Cd (via increased root length/biomass). AMF boosted total Cd accumulation of the intercropping system by 30.76% (28 d) and 18.93% (56 d) (p < 0.05), and significantly reduced Cd concentrations in rice shoots at 1 and 5 mg·kg^-1 Cd levels (p < 0.05), associated with lower soluble Cd in the rice rhizosphere (measured by in-situ suction samplers). AMF also enhanced the variation of soluble Cd across different time points and root compartments, increasing concentrations in the S. nigrum rhizosphere, indicating distinct rhizospheric processes. A negative correlation was identified between the soil extract pH and soluble Cd concentration. These findings demonstrate that AMF-enhanced intercropping can increase phytoextraction while protecting crop safety in Cd-contaminated fields.