In vivoNitrate Reductase (NR) Activity in the Leaves and Nitrogen Fixing Efficiency of Root-Nodules and Rhizobia Isolated from Certain Cover-Legumes Growing Wild in Tripura

Abstract

It has been noticed that in the tropical condition of Tripura, a number of leguminous weed plants are growing luxuriantly wild in various localities. Leguminous weed plants can be used as cover crop that can reduce soil erosion, soil degradation and can provide several benefits to other plants. In the present paper in vivo nitrate reductase (NR) activity in the leaves and detached root nodules and rhizobia (isolated from root nodules of four weed legumes viz., Mucuna bractecata, Desmodium triflorum, Pueraria phaseoloides and Mimosa pudica), and nitrogen fixing efficiency (in terms of nitrogenase activity) in the root nodules and rhizobia isolated from root nodules the above weed legumes were studied. The nitrate reductase (NR) activity was present in high amount in the leaves and rhizobial samples of these weed legumes. Among these four legumes, leaves of Mimosa pudica showed the highest amount of NR activity (0.133μ mol NO2−produced h−1g−1 leaf fr. Wt.), whereas Mucuna bracteata showed lowest amount (0.050μ mol NO2 produced h−1g−1 leaf fr. wt.). The NR activity in the rhizobial samples isolated from root nodules of Mimosa pudica was found highest (2.63μ mol NO2−produced h−1 ml−1 rhizobial suspension) on the 5th day after inoculation and it gradually decreased with increase in incubation period of the rhizobial culture. The nitrogen fixing efficiency, expressed in terms of nitrogenase (N2-ase) activity, was found maximum in the case of Pueraria phaseoloides and it was minimum in the case of Desmodium triflorum on the 4th day after inoculation.