Antioxidant response of Messastrum gracile (Chlorophyceae) to light-induced stress

Resumo

The antioxidant enzymes activities during the Messastrum gracile growth period under two different light intensities were evaluated. The light intensities were designated as: control at 60 µmol photons m^-2 s^-1 and two cultivations under light-induced stress at 120 µmol photons m-2 s^-1, during 24 and 72 hours. The maximum cell density in all treatments was achieved on the 21st growth day with 140x105 cells mL^-1 (control), 382x105 cells mL^-1 (24 hours) and 236x105 cells mL^-1 (72 hours). The antioxidant enzymes activities were more elevated in the control, however, GSH-Px, CAT and SOD activities were higher on the 7^th growth day, while GPOX and GR activities were higher on the 28^th and 21^st growth day, respectively. The microalgae displayed lower MDA content, which indicates low stress levels. In terms of growth, biomass production and chlorophyll-a, the best results occurred under light-induced stress (120 µmol photons m-2 s^-1). Light-induced stress decreased antioxidant activity during M. gracile growth, and the results revealed a higher activity for glutathione peroxidase, catalase and superoxide dismutase.