Abstract: The nitrogenase activity of root nodules from Sesbania cannabina plants treated with Na2S2O4, DTT and trypsin was increased by 108%–114%, 106%–117% and 103%–119%, respectively. EM observation showed that the density of ATP-hydrolase as the marker of lead phosphate particles which were distributed on the peribacteroid membrane was much more significant than that of the control, but the bacteroids in peribacteroid membrane did not have ATP-hydrolase particles present. Dark treatment of the same age plants accelerated the nodule senescence and the ATP-hydrolase particles most densified on the peribacteroid membrane of the nodules, meanwhile, dense ATP-hydrolase particles also appeared in a number of degenerative bacteroids. This again confirms the conformation change of ATP-ase in bacteroids from ATP synthetase to ATP-hydrolase and its relation to nitrogen fixation with the senescence of nodules. The comparison of ATP-hydrolase particle density on the peribacteroid membrane of the nodule cells with different treatmemts are carried out and the role of the ATP-hydrolase on the peribacteroid membrane in substance transportation are discussed.

Key words: Nitrogen fixation, ATP ase, Root nodule, Sesbania cannabina