| Abstract: | Analysis of the distribution of enzymes of carbohydrate, carboxylicacid and nitrogen metabolism in nodule tissues prepared by protoplastisolation techniques has led to some confusion about their whereabouts.In this study nodule cortical and central (infected) tissuewas separated manually using a scalpel blade. Protein contents of whole nodules, central region and cortexwere found to be 19, 25 and 5-0 mg g–1 fresh weight, respectively.Specific activities of glutamine synthetase (GS), phosphoenolpyruvatecarboxylase (PEPC), invertase (INV) and sucrose synthase (SS)were higher in the central region than in the cortex. The reversewas true for UDP glucose pyrophosphorylase (UDPGPP), phosphoglucomutase(PGM) and phosphoglucose isomerase (PGI). The central (infected) region represented a minimum of 65% ofthe nodule fresh weight. Calculations based on this estimateand on the activities per gram fresh weight indicate that thebulk of the potential enzyme activity is located in the centralregion. This was particularly so for SS, INV and GS where greaterthan 96% of the relevant activity was located in the centralregion. Even the enzymes which had greater specific activitiesin the cortex (UDPGPP, PGM and PGI) were, in fact, predominantlyfound in the central region (86, 81, and 85%, respectively).The conclusion from this data must be that most metabolism inthe nodule is likely to occur in the central region, althoughthis does not negate the importance of the cortex in carbonand nitrogen flux. Key words: Glycine max, soybean, nodules, cortex, infected region, enzymes |
