| Abstract: | Regulation of nitrogen fixation in response to various environmentalconditions often involves an adjustment in nodule permeabilityand, because of the importance of nodule permeability in nitrogenfixation, several methods to estimate it have been developed.In the present study, these methods are reviewed and their limitationsare highlighted. A simple, rapid and inexpensive technique thatcan be used to estimate permeability of nodules and respirationof other plant tissues is described. The technique was evaluatedby comparing it to the lag-phase technique as an independentand reliable method for estimating nodule permeability. Overa wide range of nodule permeability estimates, the closed systemO2 uptake technique was linearly related to lag-phase permeabilityestimates. The technique was tested further by studying theresponse to sub- and supra-ambient pO2 in the root environment,and the responses agreed well with published reports on theeffect of O2 on nodule permeability. The technique was foundto be very satisfactory in estimating nodule permeability andmay be used to measure the ability of other plant tissues totake up O2. Key words: Soybean, Glycine max, nitrogen fixation, root, respiration |
