Effects of Indole Derivatives on the Growth of Chlamydomonas spp. as Causal Green Algae in the Hydroponics System

Some Indole derivatives were examined for their algicidal activity to Chlamydomonas reinhardtii and the isolate of Chlamydomonas sp. which was isolated from the green algae-generating hydroponic solution in the hydroponic trough of the greenhouse. Of nine compounds tested, 3-indolepropionic acid, 3-indoleacrylic acid and 3- (3-indolyl) butanoic acid could suppress multiplication of C. reinhardtii cells. Although the first one exhibited the strong phytotoxicity, the latter two compounds were effective at lower concentrations which did not cause any toxic effect on the growth of tomato seedlings. In addition, 3-indoleacrylic acid and 3- (3-indolyl) butanoic acid inhibited the multiplication of Chlamydomonas green algae which were actively growing in our hydroponic facilities, and suppressed the algal emergence on the synthetic sponge cubes soaked in the hydroponic solution which had been inoculated with green algae. The present study suggests that these compounds have a potential to be used as an algicide for the hydroponics of crop plants.