Hormesis effect of organophosphorus pesticide glyphosate- isopropy lammonium on Heterosigma akashiwo

The growth, chlorophyll a contents, protein contents of Heterosigma akashiwo under different concentrations ofglyphosate-isopropylammonium (0, 0.001, 0.01, 0.1, 1 and 10 mg·L-1) were investigated. The results showed thatglyphosate-isopropylammonium caused significantly toxic effect on microalgae. The cell density, chlorophyll a contents and proteincontents were decreased significantly under 10 mg·L-1 concentration(p'0.05). Low dose of glyphosate-isopropylammonium hadsignificantly stimulated effect on microalgae. The growth and chlorophyll a contents of H. akashiwo were significantly increased ascompared to the control group under low concentrations ('1 mg·L-1) at 72 h (p'0.05). At latter period of the experiment (7th, 9th, 11thday), the stimulated effect gradually disappeared, with no significant difference in physiological characteristics between treatments andthe control group.