Activity of Nitrogenase and Nitrogen Assimilation Enzymes in Wheat Inoculated with Azotobacter chroococcum

Abstract

Summary Activity of nitrogenase in the rhizosphere, and nitrate reductase, glutamine synthetase and glutamate dehydrogenase in the leaves was determined in wheat plants inoculated with Azotobacter chroococcum. The plants were grown in sand culture with the supply of nutrient solutions containing 7.5 (N-l) and 15.0 mmol 1-1 NH4NO3 (N-2) or without N compound (N-0). It was found that nitrogenase activity was inhibited by the addition of nutrient solution N-l and N-2. After cutting off the nutrient supply, nitrogenase activity increased and reached its maximum of 22-378 nmol H2H4 g-1 dry root h-1. The effect of Azotobacter inoculation on the activity of nitrate reductase, glutamine synthetase and glutamate dehydrogenase was dependent on the strain of the bacteria and N level in the nutrient solution. The inoculation with Azotobacter A-1 strain was more effective than with A-2 and A-3 on the increase in activity of nitrate reductase and glutamine synthetase. The greatest effect of the inoculation on the activity of nitrate reductase and glutamine synthetase was observed when the plants were grown on N-1 and N-0 nutrient solution, respectively.