Morphological Variation of Paddy Field Cyanobacterium Fischerella sp. from Iran under Combined Influence of pH and Irradiance

In current research morphological variations and growth of Fischerella sp., collected from paddy fields of Golestan province, have been studied under combination effects of different irradiances and pHs. Soil samples were cultured in BG-11 medium and formed colonies were isolated. Fischerella sp. was identified and treated with different pHs (5, 6, 7, 8, 9) and irradiances (2, 11, 24, 107, 300 ?E m-2s-1) in same solid medium. Results showed that morphological variations of Fischerella sp. can be related with both acidity and light. Variations were seen in pHs 5 and 9. In low light intensities, there is no hormogonium production in each acidic condition. Biometrical statistical analysis showed that it seems hard to reach a unique pattern in morphological variation analysis in vegetative cells and heterocysts of this strain, especially comparing the pattern of expanding width of main axes with the length and width of branches and even main axes too. High light intensity (300 ?E m-2 s-1), caused noticeable morphological variations especially in pH5. It seemed that in this condition, organism tends seriously to get a new or at least different topological configuration. In other light intensities, this pattern seemed relatively variable and possibly localized. In alkaline condition (pH9), the patterns of growth in low and medium light intensities were completely the same.