AUTHOR=Zhang Peng , Dumroese R. Kasten , Pinto Jeremiah R. 

TITLE=Organic or Inorganic Nitrogen and Rhizobia Inoculation Provide Synergistic Growth Response of a Leguminous Forb and Tree

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01308

DOI=10.3389/fpls.2019.01308

ISSN=1664-462X

ABSTRACT=<p>Our objective was to better understand how organic and inorganic nitrogen (N) forms supplied to a tree, <italic>Robinia pseudoacacia</italic>, and a perennial forb, <italic>Lupinus latifolius</italic>, affected plant growth and performance of their symbiotic, N-fixing rhizobia. In one experiment, we tested five sources of N [none; three inorganic forms (ammonium, nitrate, ammonium-nitrate); and an organic form (arginine)] in combination with or without rhizobia inoculation. We measured seedling morphology, allometry, nodule biomass, and N status. A second experiment explored combinations of supplied <sup>15</sup>N and inoculation to examine if inorganic or organic N was deleterious to nodule N-fixation. Plant growth was similar among N forms. A positive response of nodule biomass to N was greater in <italic>Robinia</italic> than <italic>Lupinus</italic>. For <italic>Robinia</italic>, inorganic ammonium promoted more nodule biomass than organic arginine. N-fixation was concurrent with robust supply of either inorganic or organic N, and N supply and inoculation significantly interacted to enhance growth of <italic>Robinia</italic>. For <italic>Lupinus</italic>, the main effects of inoculation and N supply increased growth but no interaction was observed. Our results indicate that these important restoration species for forest ecosystems respond well to organic or inorganic N forms (or various forms of inorganic N), suggest that the nodulation response may depend on plant species, and show that, in terms of plant growth, N supply and nodulation can be synergistic.</p>