Extraradical Hyphae of Arbuscular Mycorrhizal Fungi Reduce Cadmium Accumulation in Maize by Altering Root Economic Strategies and Soil Solution Cadmium Speciation

Arbuscular mycorrhizal fungi (AMF) can mitigate plant cadmium (Cd) uptake through their extraradical hyphae, yet the underlying eco-physiological mechanisms remain unclear. Using a growth-core system with nonsterilized Cd-contaminated soil, we investigated how indigenous AMF extraradical hyphae influence maize Cd accumulation by either maintaining (static cores) or disrupting (rotated cores) hyphal networks. Hyphal disruption caused a 67.9% rise in Cd concentration within the rhizosphere solution, elevated the fractions of Cd2+ and CdSO4(aq), and shifted root economic strategies toward “acquisitive” ones, leading to 69.9% and 55.4% increases in shoot and root Cd contents, respectively. Structural equation modeling revealed that root forks and crossings exerted the strongest negative effects on maize Cd accumulation, while CdSO4(aq) in rhizosphere and leachate solutions showed the strongest positive effects. These findings provide novel insights into AMF-mediated Cd immobilization and lay a theoretical foundation for safe agricultural production.