Nitrogen assimilating enzyme of azolla as influenced by potassic fertilizer

S.Muruganayaki and A.Jeyachitra

Association between the Azolla and Anabena azollae resulted in fixation of atmospheric nitrogen through a process of reduction of atmospheric di-nitrogen mediated by the enzymes, glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) both under symbiotic and free-living conditions. The activity of these enzymes is increased by enrichment of nutrients especially K which usually applied to rice crop and improve the biological nitrogen fixation by Azolla. An incubation experiment was conducted by growing Azollae filiculoides with the agriculturally important potassic fertilizers (Potassium Chloride, Potassium shulphate) as main plot in seven concentrations (0, 5, 10, 20, 30, 40 and 50 ppm of K) as sub-plots laid down in split-plot design replicated thrice to study the impact of these fertilizer on the activities of nitrogen-fixing enzymes. The activity of glutamate synthase enzyme was predominant in azolla than other enzymes. The maximum activity of glutamate synthase (1.567 n mole min-1 mg-1), glutamate dehydrogenase activity (0.158 n mole min-1 mg-1) and glutamine synthatase (0.908 n mole min-1 mg-1) was observed under the 40 ppm K solution especially on 30th day after incubation. The potassium sulphate fertilizer was superior than the potassium chloride in influencing the growth and maintaining higher enzyme activity in azolla.

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