Adjunctive nodule enzyme activities associated with tripartite symbiosis in Astragalus cicer L.

Abstract

Cicer milkvetch (Astragalus cicer L.) is a productive forage legume adapted to a wide range of soil types. It is a long‐lived, nonbloating rhizomatous perennial with tolerance for low soil fertility, unfavorable acid pH and salinity. It has much value for soil fertility improvement and soil erosion control. Objectives of this study were to determine soil fertility influencing growth, nodulation, cytosol reductases, and nitrogenase activity with effective mycorrhizal colonization. Significant increases in growth, nodulation, nitrogenase activity and seed yield resulted for mycorrhizal plants. Increases in nitrogenase levels were also congruent with increased nodulation for soil K amendments. Differences were not significant for N transformation enzyme activity levels for aspartate transaminase (AST), glutamate dehydrogenase (GDH), glutamine synthetase (GS), and glutamate‐oxoglutarate transaminase (GOGAT). However, highly significant differences were apparent for greater nonmycorrhizal nitrate reductase and cytosol nitrate N with an inverse higher cytosol pyruvate and thiosulfonate reductase (TSR) of mycorrhizal colonized plants. Definitive histological microscopy was highly correlated with both explicative enzyme cytochemistry and fluorescence parameters for nodule cytosol (reductase) enzyme transformations.