NITROGENASE ACTIVITY OF RICE PLANT ROOT SYSTEMS

Field experiments were conducted to determine the N2ase activity of washed rice (Oryza saliva L.) roots grown under cultural practices common to Arkansas. Using the C2H2 reduction technique, the magnitude of N2ase activity of rice roots was shown to be similar to published data. The pattern of root N2ase activity as a function of time showed a midseason maximum. When cultivars of different introduction dates were compared, the N2ase activities of older cultivars introduced before the advent of inorganic N fertilization were higher than, or equal to, the N2ase activities of those cultivars introduced later. The application of midseason fertilizer N caused an initial depression in N2ase activity followed by an enhancement in N2ase activity. © 1978.