Abstract: The relationship between Eichhornia crassipes and its rhizospheric bacteria is markedly influenced by nutritional condition. The root exudates of the plant growing on sucrose containing medium have little effect on the dynamics of bacteria growth, but on phenol containing and inorganic media, the root exudates can respectively promote two- and three- fold growth of bacteria. Under phenolic condition, there exists a stronger rhizospheric effect: the metabolites of rhizospheric bacteria can promote the polyphenoloxidase activity of Eichhornia crassipes, but inhibit its peroxidase activity and decrease its phenol content. Eichhornia crassipes inoculated with bacteria has a higher activity of polyphenoloxidase and peroxidase and a higher content of phenol.

Key words: Eichhornia crassipes, Rhizospheric bacteria, Rhizospheric effect, Polyphenoloxidase, Peroxidase, Phenol-concentration