In the present study, the effects of pretreatment of time (24 and 96 hours) and pH (7 and 9) at extremely limited carbon dioxide concentration were studied on the exponential growth phase, photosynthetic pigments per cell, absorption shift of chlorophyll, structure and
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In the present study, the effects of pretreatment of time (24 and 96 hours) and pH (7 and 9) at extremely limited carbon dioxide concentration were studied on the exponential growth phase, photosynthetic pigments per cell, absorption shift of chlorophyll, structure and function of phycobilisome, the ratio of light harvesting to reaction center pigment, and the ratio of photosystem 1 to photosystem 2 in stigonematalean cyanobacterium Fischerella sp.FS 18. Results showed that pretreatments kept the exponential growth phase at both 24 and 96 hours and also under pHs 7 and 9. Contrary to the absorption peak of chlorophyll, cellular pigments showed no stable pattern regarding pretreatments. Phycobilisomes were the main point of treatment affects. The pattern of the rode part of phycobilisomes was the same at pretreatment reactions. The shift of phycocyanin was about 1 and phycoerythrin about 3. The highest rate of photosystem 1 to photosystem 2 ratio was observed at 24 hours and under neutral condition. This changed by the time and led to decreased efficiency of energy transport in photosynthesis system. The change in the phycobilisome operation may be a compensation mechanism to mitigate the degree of such a decrease.
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