The effect of salinity on morphological and molecular characters and physiological responses of Nostoc sp. ISC 101

Taking into account the high potential of cyanobacteria to tolerate salinity stress, researches have evaluated the morphological and physiological behavior of these microorganisms in recent years. This study is conducted to investigate the impact of different concentrations of NaCl on the morphological and physiological traits of Nostoc sp. ISC 101. Biometrical and morphological observations are carried out by light and scanning electron microscopy. Results indicated that vegetative cells and heterocysts were wider in control treatment in comparison with samples under different amounts of salinity. Akinete formation began in 3% NaCl and reached to highest level in 5%. The relative degeneration of structure of the cells in 5% salt was demonstrated. According to physiological impresses of salt it was found that growth rate decreased with increasing salinity. Total chlorophyll content stimulated in 1% salinity, but in the higher concentration it decreased vice versa. The rate of APC, PE, PC increased in 1% salinity, although in high level concentration they would be diminished. Photosynthesis rate was also decreased with increasing salinity but it was stimulated slightly in 1% NaCl. All in consequence, despite of acclimation of this strain to marine environment, not much tolerance was seen in the mentioned treatments, and increasing salinity to upper than 1% NaCl had destructive effects, and cyanobacterium maintained its growth rate at slightly saline environments.