Use Of ¹³N to Study N₂ Fixation and Assimilation by Cyanobacterial-Lower Plant Associations

Abstract

Symbiotic associations involving nitrogen-fixing cyanobacteria and eucaryotes are of general interest because, in a manner analogous to interactions between rhizobia and legumes, the cyanobacteria provide fixed nitrogen for growth of the associations (Stewart et al. 1980). We are interested in identifying the chemical interactions between partners of these associations that influence cyanobacterial growth, heterocyst differentiation, and N2 fixation as well as other metabolic processes. We reasoned that such a study must utilize relatively rapidly growing material in pure culture that is also amenable to experimental manipulation. Accordingly, we established pure cultures of gametophyte tissue of the bryophyte Anthoceros punctatus L. for growth submerged in liquid medium and defined conditions for reconstitution of the association with various wild-type and mutant strains or species of Nostoc (Enderlin, Meeks, 1983). These experimental manipulations are not currently achievable with the Azolla-Anabaena association (Peters, Calvert, 1983).