Study on azolla productivity and its relation to the change of several nutrients in different liquid media

The productivity was measured when Azolla grew in different soluble media including artificially mixed Hoagland Azolla medium, naturally originated well water and pond water in which some nutrients were monitored. The capacity of Azolla growth in three liquid media varied with the time and the trend simulated significantly a quadratic curve showing bloom and decline. In artificial medium, Azolla had a significantly higher productivity, nitrogenase and peroxidase(POD) activity than in two natural water media but the superoxide dismutase(SOD) activities had little difference. The correlation analysis revealed that three tested enzymes had a significant correlation with Azolla productivity while nitrogenase and POD indicated the positive correlation and SOD indicated the negative correlation. With the growth of Azolla in liquid medium, almost all tested parameters for water nutrient except pH demonstrated the same dynamic trend in three liquid systems as the conductivity, the contents of nitrate and phosphate decreased, the ammonia kept in low content and the chemical oxygen demand(COD) increased. A correlation between Azolla productivity and liquid parameter showed a low influence of the fluctuation in nitrogen ion, COD on Azolla productivity that was significantly affected by pH, conductivity and phosphorus content.