Effect of Nitrification Inhibitor Dicyandiamide on Growth,Physiological and Biochemical Characteristics of Aliinostoc sp.(Diazotrophic Cyanobac-teria)
In order to elucidate the effects of nitrification inhibitor dicyandiamide(DCD)on physiological and biochemical characteristics of paddy diazotrophic cyanobacteria and provide a theoretical basis for reasonable application of DCD and diazotrophic cyanobacteria in paddy fields,the variations of growth,photosynthesis,nitrogenase activity,activities of antioxidative enzymes,and oxidative damage characteristics of a paddy diazotro-phic cyanobacterium Aliinostoc sp.YYLX235 under DCD stress were investigated.The results showed that the growth of Aliinostoc sp.YYLX235 was inhibited by DCD at concentrations of 100～300 mg·L-1.The activities of cellular vitality and N2-fixation significantly decreased at a DCD concentration of 50 mg·L-1.The photosystem Ⅱof Aliinostoc sp.YYLX235 exhibited hormetic effects under DCD stress,with characteristics of increasing cellular pigment contents and improvement of electron transfer efficiency.The activities of superoxide dismutase(SOD)and catalase(CAT)in cells of Aliinostoc sp.YYLX235 were positively correlated with DCD concentration in the medium.The oxidative-antioxidative system in cells of Aliinostoc sp.YYLX235 lost balance when DCD concentration ranged from 200 mg·L-1 to 300 mg·L-1,resulting in oxidative damage to algal cells.The results of this study indi-cate that DCD has strong negative effects on growth,cellular vitality,and N2-fixation activity of paddy diazotrophic cyanobacteria.Thus,the application of diazotrophic cyanobacteria-based bio-fertilizer and DCD should be staggered.
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