Effect of nitrate and aminoethoxyvinylglycine on Cicer arietinum L. nodules

Abstract

The chickpea (Cicer arietinum L.) cv. HC-1 was raised in earthen pots filled with dune sand in screenhouse. At vegetative stage, i.e. 40 - 45 d after sowing, 10, 20 and 40 mM NO3- was applied through rooting medium. After 24 h of NO3- treatments an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG) in concentration 5 μM was given. A conspicuous increase in (5 - 9 fold) ethylene evolution in nodules was noticed after NO3- treatments. This rise was parallel to the increase in 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC oxidase activity. On the contrary, a sharp decline in ACC content, ACC oxidase activity and ethylene evolution was observed when AVG was given. A decrease of in acetylene reduction assay (ARA) with NO3- treatments was associated with decline in cytosolic pH (from 6.12 to 5.45), leghemoglobin (Lb) content, accumulation of H2O2 and with the loss of membrane integrity. The lipid peroxidation, followed as MDA production and electrolyte leakage increased with NO3- treatments, however, the level of MDA was brought down in AVG-treated nodules. Results confirm that ethylene might be involved in mechanism by which the functioning of nodules is adversely affected by NO3-.