抄録
Water and nitrogen constraints jointly limit the productivity and resource-use efficiency of irrigated dryland spring wheat, yet how arbuscular mycorrhizal fungi (AMF) coordinate plant carbon–nitrogen metabolism to stabilize yield under simultaneous resource limitation remains unresolved. Using a split–split plot field experiment with Funneliformis mosseae inoculation under contrasting irrigation and nitrogen regimes, this study disentangled the AMF-mediated regulatory pathway from symbiosis establishment to yield formation. AMF maintained functional symbiosis with wheat roots under moderate resource reduction, whereas severe water and nitrogen limitation suppressed colonization. Under moderate water-saving and nitrogen-reduction conditions, AMF alleviated resource constraints by enhancing rhizosphere resource acquisition, sustaining photosynthetic capacity, promoting nitrogen assimilation, and improving water- and nitrogen-use efficiency, thereby maintaining biomass accumulation and grain yield. These benefits diminished under excessive nitrogen reduction, revealing a resource-availability threshold for effective mycorrhizal regulation. Integrative analysis further showed that yield stabilization arose from a coordinated cascade linking stable symbiosis with resource acquisition, physiological compensation, photosynthetic maintenance, nitrogen assimilation, and carbon–nitrogen metabolic coordination, rather than from any single trait. This study establishes an AMF-mediated water–nitrogen synergistic regulation framework that explains how mycorrhizal symbiosis reorganizes plant resource allocation under coupled resource constraints and provides a mechanistic basis for optimizing low-input, resource-efficient wheat production.
