Artificial associations between Daucus and nitrogen-fixing Azotobacter cells in vitro

Symbiotic associations were established between nitrogen-fixing Azotobacter zettuovii (CRS-H6) cells and carrot ( Daucus carota L. cv. 'Rother' Half Long) tissues based on the induced carbon and energy dependency of diazotrophs on plant metabolic activity. Symbiotic associations were grown on nitrogen-free media for four years. Plant regeneration was achieved from callus-bacterium associations on nitrogen-containing media. Light and electron micrographs are used to show the localization of bacteria in intercellular spaces of callus and regenerated plant tissues. The nitrogen-fixing ability of the partnership was proved on nitrogen-free media.