| Abstract: | Cultures of a blue-green alga Spirulina maxima (Setch. et Gard. ) Geitler with vari-ous concentrations of Se in Zarrouk's medium showed that not higher than 40 mg/L Se could promote itsgrowth. The present experiments showed that S. maxima grown under normal conditions, has an oxidanstress defence system for hydrigen perovide (H_2O_2) removal, which is the Halliwell-Asada pathway.When 4 to 20 mg/L Se was added to the algal medium, this pathway was replaced by a so-called Se-stressed pathway containing GSH peroxidase (GSH-POD). As a result of the occurrence of both higheractivity of GSH-POD and lower levels of hydroxy radical (OH), the Se-stressed pathway scavengedH_2O_2 so effectively that the growth of S. maxima was promoted by 4 to 20 mg/L Se. While GSH-PODactivity of the alga disappeared at 40 mg/L Se, the recovery of ascothae peroxidase was observed. Thelower levels of ascorbic acid and GSH made the Hajliwell-Asada pathway for scavenging H_2O_2 less effec-tive, wlile the highest activity of catalase might be responsible in part for the H_2O_2 removal, causing thelevel of OH' in S. maxima grown at 40 mg/L Se to be much higher than the OH. level in this algagrown at 4 to 20 mg/L Se, hut lower than that in the control. The OH' level changes caused the growthof S. maxima cultured at 40 mg/L Se to increase slighil to close to that of the contrl. |
