POTENTIAL AND PITFALLS OF TRYING TO EXTEND SYMBIOTIC INTERACTIONS OF NITROGEN-FIXING ORGANISMS TO PRESENTLY NONNODULATED PLANTS, SUCH AS RICE

It has been a long-standing goal in the field of biological nitrogen fixation to extend nitrogen-fixing symbioses to presently non-nodulated cereal plants, such as rice. A number of researchers have recently described the induction of ''nodule-like'' structures on the roots of cereals primarily by rhizobia, in either the presence or absence of plant cell-wall-degrading enzymes or plant hormones. We briefly review this research and discuss the potential problems associated with the introduction of nitrogen-fixing microbes in novel physiological environments, such as rice roots. The results of experiments carried out in China on the induction of ''nodule-like'' structures on rice roots by rhizobia are highlighted. In addition, we present preliminary results of a series of experiments designed to repeat and evaluate these results using a variety of microscopic techniques and molecular genetic approaches.