Effect of nitrogen-fixing bacteria on resource investment of the root system in an invasive clonal plant under low nutritional environment

Nitrogen-fixing bacteria (NFB) converts nitrogen from the air into a nitrogen source to support plants' requirements. However, the importance of NFB for invasive plants under nitrogen (N) limitation is not well understood. In this study, we investigated the response of Solidago canadensis, an invasive clonal plant, to low nitrogen conditions with the colonization of two NFB strains, using a completely sterile culture system. We found that under very low nitrogen, the addition of both NFB strains significantly increased the investment of belowground biomass and total biomass, and greatly promoted the development of the root system (p < 0.05). Importantly, the significant decrease of anthocyanin and significant increase in root volume and root average diameter indicated that NFB reduced nutritional stress and promoted roots under extreme nitrogen deficiency. Our findings suggest that the interaction with NFB may contribute to the invasiveness of S. canadensis through investing more resources into the root system in a resource-poor environment.