CLOSED-SYSTEM O-2 UPTAKE - A SIMPLE TECHNIQUE OF NODULE OXYGEN PERMEABILITY ESTIMATION

Regulation of nitrogen fixation in response to various environmental c onditions often involves an adjustment in nodule permeability and, bec ause of the importance of nodule permeability in nitrogen fixation, se veral methods to estimate it have been developed, In the present study , these methods are reviewed and their limitations are highlighted, A simple, rapid and inexpensive technique that can be used to estimate p ermeability of nodules and respiration of other plant tissues is descr ibed, The technique was evaluated by comparing it to the lag-phase tec hnique as an independent and reliable method for estimating nodule per meability, Over a wide range of nodule permeability estimates, the clo sed system O-2 uptake technique was linearly related to lag-phase perm eability estimates. The technique was tested further by studying the r esponse to sub- and supra-ambient pO(2) in the root environment, and t he responses agreed well with published reports on the effect of O-2 o n nodule permeability, The technique was found to be very satisfactory in estimating nodule permeability and may be used to measure the abil ity of other plant tissues to take up O-2.