Abstract:The paper deals with the mitigative effect of calcium on NaCl stress upon nitrogenfixation of Anabaena 7120 under different physiological conditions.The followingobservations have been made:1.The nitrogen-fixing activity of Anabaena under NaCl stress was mitigated with theincrease of calcium chloride in culture solution.Over 5×10-4 mol/L CaCl2,there was amarked weakness in mitigative effect of calcium on nitrogen-fixing activity of Anabaenaunder NaCl stress.2. Under dark condition or in the presence of photosynthetic inhibitors, such as DNPand CCCP, the mitigative effect of calcium on NaCl stress upon nitrogen fixation byAnabaena was diminished,but enhancing effect occurred when exogenous sucrose wasadded to the culture solution.3.The mitigative effect of calcium on NaCl stress upon nitrogen fixation by Anabaenaunder anaerobic condition(in Ar or N2)was lesser than that under aerobic condition.4.The addition of H2 together with O2 could accelerated nitrogen-fixing activity ofAnabaena under NaCl stress, while further depress was observed by adding oxygen alone.5.The mitigative effect of calcium on NaCl stress upon nitrogen fixation by Anabaenawas slightly enhanced to a certain degree by the preincubation of 5% CO2 or of 5% CO2 with40% N2 respectively,but was abated by the addition of N2 alone.The mitigative effect of calcium on NaCl stress upon nitrogen fixation by Anabaenaand its regulatory mechanism were discussed.
