受固氮活性制约的蓝藻固氮去铵阻抑及其与生理条件的关系

在不同气体环境中培养的蓝藻Ａｎａｂａｅｎａ７１２０固氮活性各异，Ａｒ＋ＣＯ２中最大，空气中次之，Ａｒ中最小。固氮活性高者去铵阻抑速率大，反之则小。它们对各种生理条件的反应不一样，固氮活性高者，其去铵阻抑速率受氧和氮的抑制小。在氢和氧加合条件下，三种活性的蓝藻去铵阻抑均加快，但活性低者慢而小些。光强减弱或加光合抑制剂时，固氮活性低者去铵阻抑速率显著小于活性高者，而添加外源的蔗糖或丙酮酸时，也是固氮活

NH4+-DEKEPRESSION OF NITROGEN FIXATION IN BLUE-GREEN ALGAE Anabaena 7120 RESTRICTED BY NITROGEN-FIXING ACTIVITY AND ITS RELATION TO PHYSIOLOGICAL CONDITIONS

Under an atmosphere containing 97% Ar and 3% CO₂ or containing 100% Ar, the nitrogenase activity of Anabaena 7120 was much higher or lower, respectively, than that in air. When the treatment was done in the above listed atmosphere considerable variation in the NH₄⁺-derepression of nitrogen fixation in Anabaena occurred. Moreover, the response of NH₄⁺-derepression of nitrogen fixation in Anobaena to physiological conditions differed. When algae was incubated in O₂ or N₂, Respectively, the extent of inhibition of NH₄⁺-derepression in Anobaena with a lower nitrogen-fixing activity was greater than that in one with a higher activity. A great acceleration of NH₄⁺-derepression of nitrogen fixation by hydrogen in Anabaena with a higher nitrogen-fixing activity was observed. The rate of NH₄⁺-derepr;.ssion of nitrogen fixation in Anabaena with a higher nitrogen-fixing activity was significantly faster when the hydrogen was added with oxygen or added only with exogenous carbonhydrates, such as sucrose or pyruvate, to the test system. Under weak light or in the presence of phtosynthetic inhibitors in the reaction system, the NH₄⁺-derepression of nitrogen fixation was more pronounced in Anabaena with a lower nitrogen-fixing activity.