Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota
Mucilage was generated from aerial roots and inoculated with A. brasilense Sp7. 15N2 gas was pumped in and, after incubation mucilage, was separated from the aerial roots. Mucilage alone and aerial roots alone were subjected to analysis by IRMS. Results revealed a significant enrichment of 15N2 in mucilage alone and aerial roots alone (left y-axis). Since the inoculated aerial roots may contain A. brasilense Sp7 attached to the surface, we extracted pheophytin from these aerial roots to test 15N2 incorporation in pheophytin. Results revealed a significant enrichment of 15N2 in these aerial roots, indicating that aerial roots are indeed the sites for transfer of fixed nitrogen to the plants (right y-axis). 14N2 samples were used as negative controls. n = 4 (aerial roots and mucilage), n = 3 (pheophytin). The asterisk (*) indicates a statistically significant difference (p < 0.05). (Data at DOI: 10.6084/m9.figshare.6534545) IRMS, isotope-ratio mass spectrometry.