ALLELOPATHIC EFFECTS OF EICHHORNIA CRASSIPES ROOTS ON ALEXANDRIUM TAMARENSE

Allelopathic effects of dry powder and extract of acetone/ethyl acetate of Eichhomia crassipes roots on Alexandrium tamarense ( HK strain) were evaluated 0.1g, 0.5g, 1.0g, 1.5g and 2.0g,/L of E.crassipes root powder were added, respectively. Due to low solubility of extracts, a control of slide was used as cartier to measure the actual concentration of extracts in the cultures. At first,0.01g,0.03g,0.05g,0.07g,/L of extracts were put into the weighted slides.Then the slides were added to the flasks containing 100mL of A. tamarense. At the end of the experiment, the slides were taken out, dried and weighted. The actual concentration of extracts in the cultures was obtained from the loss in weight. The results showed that the growth of A. tamarense was absolutely inhibited when the algae was expesured to dry powder of E.crassipes roots at above 1.5g,/L. When the concentration of dry powder of E.crassipes roots were 0.5g,/L and 1.0g,/L, the growth of algae increased after 3 days. The growth of A. tamarense was also inhibited at the actual concentration of 0.038g,/L and 0.022g,/L extract of acetone and ethyl acetate of E.crassipes roots, respectively. It suggested that E crassipes could be a potential algaecide to control harmful algal blooms.