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rice (Oryza sativa L.) is one of the most impor - tant staple food crops. Its cultivation requires a relatively high input of N fertilizers; however, rice plants do not absorb a significant proportion of added fertilizers, resulting in soil and water pol - lution. The use of diazotrophic (N-fixing) endo - phytes can provide benefits for rice cultivation by reducing the demand of N fertilizers. Diazo - trophic endophytes from the early successional plant species poplar ( Populus trichocarpa Torr. & A. Gray) and willow ( Salix sitchensis C. A. San- son ex Bong.) were added to rice seedlings. Inoculated rice plants were grown in N-limited conditions in the greenhouse, and plant physical characteristics were assessed. Endophyte-inoc - ulated rice plants had greater biomass, higher tiller numbers, and taller plant stature than mock- inoculated controls. Endophyte populations were quantified and visualized in planta within rice plants using fluorescent microscopy. The endo - phytes colonized rice plants effectively in both roots and foliage. These results demonstrated that diazotrophic endophytes of the eudicots poplar and willow can colonize rice plants and enhance plant growth in N-limited conditions.