ACTION SPECTRA FOR PHOTOTAXIS IN ZOOSPORES OF THE BROWN ALGA PSEUDOCHORDA-GRACILIS

Action spectra for phototaxis in zoospores of brown alga, Pseudochorda gracilis (Laminariales), were examined in the wavelength range between 300 and 600 nm using the Okazaki Large Spectrograph and a video tracking system. The direction of swimming (both in percent cells swimming in parallel with the stimulating light, and in mean angle of cell movement) was dependent on the wavelength. The action spectra had two peaks at 420 and 460 nm, while light above 500 nm was not effective in changing the swimming direction of the cells.