PHYSIOLOGICAL BASIS OF MITIGATIVE EFFECT OF KNO3 ON NaCl STRESS IN NITROGEN FIXATION OF BLUE-GREEN ALGAE ANABAENA 7120

Abstract:

The NaCl-induced inhibition of nitrogen-fixing activity of blue-green algae Anabaena 7120 was removed to a certain degree by the introduction of appropriate KNO3 into the culture medium.When the preincubation of algae cells was done in dark before experiment for 24 hours or in the presence of photosynthetic inhibitors,such as DNP or CCCP, the benefical effect of KNO₃ on the nitrogen-fixing activity of Anabaena treated with NaCl stress weakened or disappeared.In the addition of O₂ together with H₂ the mitigative effect of KNO₃on nitrogen-fixing activity of Anabaena was reinforced under NaCl stress.But a marked inaction in nitrogen-fixing activity of Anabaena occurred under NaCl stress when O₂was introduced into the test system alone.When algae cells treated with NaCl stress were incubated in the aerobic condition(in air)the benefical action of KNO₃ was higher than that in anaerobic condition(in Ar).The KNO₃supported nitrogen-fixing activity of Anabaena was more evident under NaCl stress in the prensence of the exogenous sucrose or CO₂.The migatative effect of KNO₃ on nitrogen-fixing activity of Anabaena was accelerated under NaCl stress in the addition of N₂ together with CO₂, while it was depressed by adding N₂ alone.