A selection of endophytes isolated from poplar and willow species growing in nutrient poor river beds served as inoculum in a series of studies to elucidate their role in plant growth promotion, improved plant nutrition and carbon gain.  A series of inoculation trials has been conducted with a hybrid sweet corn inoculated with individual or combinations of mixed endophyte species, including bacteria and yeast.   We conducted two experiments: a greenhouse study and a field trial.  In both experiments, plant growth was monitored through silking.  Sterilized kernels were incubated in nitrogen free media with endophytic inoculums then planted in a sterilized sand:perlite mix (1:1). The greenhouse experiment investigated the effects of five individual endophyte species under two nitrogen levels.  The field study consisted of two mixed endophyte inocula, two single species inocula and an uninoculated control grown under three nitrogen fertilization levels.  Greenhouse plants receiving endophytic inocula demonstrated a significant increase in total biomass during the first 4 weeks after planting regardless of the nitrogen level.  The difference in total biomass was largely due to increased root mass.  This increase diminished as the plants matured.  A similar observation was made in the field study demonstrating significantly enhanced early growth response to endophytic inoculations.   The variation in growth within each nitrogen level was attributable to endophyte treatments.  Further, the rate of net CO₂ assimilation under saturating light (A_max) increased with endophytic inoculation.  These results have beneficial implications for crop production on nutrient poor sites.  The immediate increase of root mass observed in endophyte inoculated plants has the potential to improve resource use efficiencies (e.g. water and nutrients) and stress avoidance.  Our results also indicate that the beneficial effect from endophytes isolated from poplar and willow species are not host specific.