THE EFFECT OF SALT STRESS ON SOME PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF NOSTOC SPHAEROIDES Kütz. (CYANOBACTERIUM)

In the colonies of Nostoc sphaeroides kütz.which suffered salt stress, the efficiency of excitation capture by open photosystem II (PSII) reaction centers (expressed as Fv/Fm) decreased with increased salinity.When treated with high salinities, the algal colonies lowered the Fv/Fm after prolonged treatment.The exogenous proline had little function in preventing the lowering of Fv/Fm on the salt stressed colonies.Meanwhile, the endogenous proline contents of the colonies didn' t increase with the increased salinities, whereas malondialdehyde (MDA) increased when the salt stress became more serious.In addition, the graphes of the SOD activities in the colonies have a typical "V" shape with treating salinities, presumably the changing was related to the real stresses that the colonies experienced .