Carbon metabolism in chickpea nodules

We describe biochemical changes that take place in developing and senescing chickpea (Cicer arietinum L.) nodules that have been formed with Rhizobium sp. (Cicer) CC 1192. Essentially all of the capacity for sucrose catabolism was in the host cytosol of the nodules, with the bacteroids lacking several key enzymes. In a time-course study, using plants grown in a glasshouse, the specific activities of enzymes involved in sucrose breakdown increased in parallel with the acetylene-reducing activity (ARA) of the nodules and the total N content of the plants until approximately 7 wk after planting, when flowering generally occurred. Subsequently, the size of the nodules and the total N content of the plants continued to increase, but there was a sharp decrease in the ARA and the specific activities of the enzymes in the nodule extracts. The starch content of the nodules also showed a similar increase, followed by a decrease, whereas malate accumulated as the nodules aged.