Abstract: Glyphosate is the most widely used herbicide in global agriculture and can affect adjacent non-target plants by altering rhizosphere microbial communities. Root-mediated transport may occur more rapidly than spray drift or soil diffusion, highlighting a potentially important exposure pathway. However, the mechanisms by which glyphosate exuded from weed roots influences non-target plants remain poorly understood. In this study, we examined the effects of glyphosate exuded from the roots of the weed Eleusine indica on the growth of non-target plant Stylosanthes guianensis under different weed densities. Three rhizosphere segregation models were employed to investigate glyphosate transfer through soil-root-hyphae pathways and to elucidate the ecological processes underlying belowground risk transmission. Glyphosate herbicide weeding significantly inhibited the growth of S. guianensis in a density-dependent manner, resulting in a negative net effect. Under high weed density, glyphosate herbicide weeding significantly increased shikimic acid accumulation in S. guianensis by 45.03–96.63% compared with mechanical weeding. At 20 days, glyphosate herbicide weeding significantly reduced microbial biomass carbon and acid phosphatase activity in the rhizosphere of S. guianensis, while decreasing the relative abundance of beneficial microbial taxa. Null model analysis indicated that deterministic processes dominated rhizosphere community assembly. Furthermore, treatments permitting common mycorrhizal networks (CMNs) consistently exhibited stronger glyphosate-induced physiological responses in non-target plants than CMNs-blocking treatments, indicating that CMN connectivity is associated with enhanced belowground glyphosate exposure. Our results demonstrate that CMN connectivity is linked to intensified glyphosate-induced responses within plant communities. These findings provide novel insights into how belowground connectivity modulates herbicide-associated responses in agroecosystems.

Key words: common mycorrhizal networks, belowground connectivity, glyphosate, non-target plant, rhizosphere microbial assembly, shikimic acid