EFFECT OF LOW TEMPERATURE ON NITROGENFIXING ACTIVITY OF BLUE-GREEN ALGAE ANABAENA 7120 UNDER SODIUM CHLORIDE THE MITIGATIVE EFFECT OF CALCIUM ON NITROGENFIXATION OF BLUE-GREEN ALGAE ANABAENA 7120UNDER SODIUM CHLORIDE STRESS AND ITSRELATION TO PHYSIOLOGICAL CONDITIONS Effects of seeds irradiation with 60Coγ-ray on shoot growth and physiological status of Carthamus tinctorius NITROGEN FIXATION OF BLUE-GREEN ALGAE Anabaena 7120 UNDER OSMOTIC STRESS COMDITION