Dose And Time Phase Dependent Effects On Selenium-enriched Culture Of Spirulina And Its Responses To Water Stress

Spirulina is an old cyanobacterium which has been existing on earth for 3.5 billion years. It possesses a strong tolerance to environmental stresses. Moreover, Spirulina is also an economic microalgae in industries and proved to be a good carrier for selenium biotransformation. In this paper, the bioeffects of water stress on Spirulina were investigated. The dose and time phase dependent effects on Se-enriched culture of Spirulina were also studied. Some meaningful results were obtained.1. The effects of water stress on S. platensis were studied by dehydration treatment under room temperature. The results show that phycocyanin is most sensitive to water stress, and then are chlorophyll a and carotenoid. The activity of SOD keep unchanged during dehydration, while POD decreases during dehydration. CAT and APX have fast response to desiccation stress with the activity increasing to twice as high as control. So the activity of CAT and APX are possible sensitive indicators for the dehydration tolerance of S. platensis. The content of MDA changes slightly. The absorption of phycocyanin drops with dehydration, its fluorescence emission peak has blue-shift from 656nm to 644nm. Under the water loss rate of 90%, S. platensis are able to retune to normal growth condition gradually after rehydration. The critical water loss rate of S. platensis could be 70% -80%.2. The effects of Se stress on the antioxidase system and lipid peroxidization of S. platensis were studied. Se was added from the 5^th to 10^th day respectively. The accumulative concentrations of Se in test sets are all 1000 mg·L^-1, but the time of Se addition was different. Stimulative effects of Se(IV) on biomass of S. platensis were observed in two test sets which Se addition time were from the 7^th to 9^th day and the 8^th to 10^th day. The results showed that the activities of antioxidase in S. platensis under Se stress were higher than those in the control group or as high as them. The ability of S. platensis to scavenge hydroxy radical had a negative correlation with the MDA content. Their changes indicated the dual effects of Se on the antioxidant system of S. platensis. The concept of Se stress intensity can give a good explanation...