International Journal on Algae

Effect of ultraviolet radiation on photomovement of two species of Dunaliella Teod.

ABSTRACT

Experiments on studying the effect of ultra-violet (UV) radiation on photomovement parameters of two species of green alga of the genus Dunaliella Teod., D. salina Teod. and D. viridis Teod., had demonstrated that the velocity of forward movement of both species does not depend on the intensity and wavelength of UV radiation and duration of the irradiation, which is in contrast to phototopotaxis and the relative motility of the cells. This fact testifies to some possible difference in mechanisms governing these parameters of movement (velocity of forward movement on the one hand, and phototopotaxis and relative motility on the other hand) at the cell level. The conversion of positive phototopotaxis of algae into the negative under UV irradiation has been observed for the first time with further inhibition of phototopotaxis induced by increased duration of irradiation. The greatest inhibitory effect on phototopotaxis of algae is provoked by the radiation of 248-334 run. The maxima of absorption spectra of proteins related to the motor apparatus and photoreceptor system of the alga are probably located here. The effect of UV radiation on photomovement of both species of Dunaliella had a reversible character: photo-orientation of the cells were restored to the control value at each wavelength (except 248 nm) in two hours after stopping of irradiation of 2 W/m² intensity. The dependence of phototopotaxis and motility of the cells of algae on the intensity, wavelength of UV radiation, and duration of irradiation testify to the possibility of using these algae as biotests of natural ultra-violet radiation.