Ethylene evolution, H2O2 scavenging enzymes and membrane integrity of Cicer arietinum L. nodules as affected by nitrate and aminoethoxyvinylglycine

Nitrate induced changes on ethylene evolution, H2O2 scavenging enzymes and membrane integrity in chickpea (Cicer arietinum L.) cv. HC-1 nodules were studied under green house conditions. Plants were exposed to 10, 20 and 40 mmol/L NO−3 at vegetative stage (40-45 DAS). Aminoethoxyvinyl-glycine (5 μmol/L, AVG) was added to nodules 24 h after NO−3 treatment. An increase in ethylene evolution (388 % to 832 %) was noticed 3 d later in NO−3 treated nodules. However, this declined 58-69 % with addition of AVG. The H2O2 scavenging enzyme i.e. catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.11.1.9) increased by 9-27 %, 155-227 %, 33-117 % and 53-109 %, respectively. Despite the increase in the activity of these enzymes H2O2 content increased by 116 to 168 %. Superoxide dismutase (EC 1.15.1.1) decreased from 32 % to 63 % with NO−3. Application of AVG to NO−3 treated nodules also showed a decline in activity of catalase (16-23 %), peroxidase (21-30 %), ascorbate peroxidase (25-49 %) and glutathione reductase (46-53 %) with simultaneous depletion of H2O2 content (29-34 %). Lipid peroxidation and electrolyte leakage increased 5-9 fold and 2-4 fold, respectively. However, these effects were also overcome to some extent by added AVG, showing a reversible loss in membrane integrity. It is concluded that ethylene production is increased in nodules on NO−3 application. H2O2 content increased significantly even on the activation of H2O2 scavenging enzymes. The membrane integrity was adversely affected. AVG treatment showed partial recovery in above parameters showing the involvement of ethylene directly or indirectly in the functioning of nodules on NO−3 application.