ROLES OF FLAVONOIDS IN SYMBIOTIC AND DEFENSE FUNCTIONS IN LEGUME ROOTS

The roles of flavonoids in roots of legumes in the symbiotic relations hips with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi ar e compared with defense functions, using examples from three legume ge nera, Lotus, Medicago, and Glycine. Pathways leading to proanthocyanid ins and isoflavonoids are emphasized. The localization of flavonoids i n nodules involved in nitrogen fixation and in the apoplastic compartm ent of mycorrhizal associations is briefly described, with emphasis on the need for more information concerning their precise localization. Also emphasized are the limits of our knowledge about the regulatory g enes of the flavonoid pathway involved in both exogenous and endogenou s regulation of these complex interrelationships.