Evaluation of active oxygen effect on photosynthesis of Chlorella vulgaris

The relationship between O-2 and an active oxygen scavenging system in Chlorella vulgaris var.vulgaris (IAM C-534) was investigated. When Chlorella vulgaris was exposed to 2% O-2, only traces of-active oxygen scavenging enzymes were found. When the Chlorella vulgaris was treated with 20% or 50% O-2, it was shown that the level of enzyme activity increased as the O-2 concentration increased. An increase in enzyme activity was not found in any specific enzyme but in all of the enzymes, but the level of glutathione and ascorbate remained the same in all the cases. In addition, the photosynthetic efficiency also decreased as the concentration of O-2 was increased. These results suggest that an O-2 enriched environment can lead to an increase in the production of active oxygen species such as O-2(.-), and H2O2 and to a decrease in the photosynthetic efficiency in Chlorella vulgaris. The hydroxyl radical (. OH) was detected directly in the Chlorella vulgaris suspension with a spin trapping reagent. It was also clear that the increase in the . OH intensity as the visible light intensity increased was unrelated to the O-2 concentration. It was suggested that the conditions for producing . OH and the other active oxygen species were different, and that two types of oxygen stress should exist in the Chlorella vulgaris.