Appearance of different phosphatase forms and phosphorus partitioning in nodules of chickpea (Cicer arietinum L.) during development

Acid and alkaline phosphatase and phytase activities were determined in the bacteroid free fractions of chickpea (Cicer arietinum L.) nodules at 15 days intervals, from 40 days after sowing (DAS) to 85 DAS. In general, the activities and specific activity of both the acid and alkaline phosphatases declined at 55 DAS. Out of the various substrates studied, ATP was the best substrate for both phosphatases. Activities of phosphatases with glucose-6-phosphate and fructose-6-phosphate were low in comparison to these with fructose 1,6 bisphosphate. The efficiency of acid phosphatase for utilizing fructose 1,6 bis phosphate as a substrate increased with nodule development. A fructose 1,6 bis phosphate specific acid phosphatase with elution volume to void volume (Ve/Vo) ratio of around 2.0 was observed in mature nodules (80 DAS). Acid phosphatase at 40 DAS was resolved into two peaks which were eluted at Ve/Vo of about 1.5 and 1.8. However, at 60 DAS the peak with Ve/Vo of 1.5 could not be detected. With ATP as substrate, a high (Ve/Vo of 1.2) and low MM form (Ve/Vo of 2.1) alkaline phosphatases were observed at 40 DAS however at 60 DAS stage only one peak with Ve/Vo of 1.7 was detected. Although, a low activity of acid phytase was observed in nodules at all stages of development but neither alkaline phytase nor phytic acid could be detected. It appears that the nodules acquire inorganic phosphate from the roots. The higher content of water soluble organic phosphorus in mature nodules could be due to the low activities of phosphatases at maturity.