Effect of visible light on superoxide dismutase (SOD) activity in the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

Superoxide dismutase (SOD) was studied in the agarophyte Gracilariopsis tenuifrons. Similar SOD activity (130 plus or minus 9 U mg super(-1)) was observed in material from different regions of South America, from different phases of the life cycle (gametophytes and tetrasporophytes), and from apical and basal sections of the thallus. In alga grown under a light-dark cycle, SOD activity in samples taken at different times exhibited a diurnal rhythm. The activity measured during the day phase was twice as much as during the night phase. This rhythm did not persist under constant light, indicating light regulation of SOD activity. SOD activity was tested in algae submitted to different light intensities and different wavelengths. It increased with the light intensity. The blue light wavelength exerted a greater induction of SOD activity than other specific wavelengths.