Cd- and Cu-induced phytotoxicity on 2–3 leaf stage of Cyamopsis tetragonoloba and its regulation by nitrate reductase and ROS quenching enzyme

Abstract

The present study focused on Cd- and Cu-induced nitrate reductase activity and its relation to ROS scavenging enzyme in C. tetragonoloba. Hydroponically adapted seedling treated with different metal concentration (Cd and Cu) in the series from 10 to 100 µM. Seedlings were harvested after 96 h of metal treatment and analyze cellular homeostasis and metal tolerance mechanism by determining growth, stress and enzymatic parameters. The nitrate reductase activity was observed to be highest at 70 µM Cd and 50 µM Cu in cyamopsis roots, i.e., 2.31 and 2.59 times higher than control. Exogenous supplementation of SNP (100 µM) enhanced the NR activity in roots of C. tetragonoloba. Polymorphism between different metal treated leaves and roots were also observed. Higher polymorphism was observed in metal-treated roots in comparison to metal-treated leaves. The activity of other antioxidants except catalase (ascorbate peroxidase, guaiacol peroxidase and nitrate reductase was also recorded to be highest at 70 µM Cd and 50 µM Cu. Increased activity of Nitrate reductase and other antioxidants were directly associated with reduction in MDA and H2O2 level at 70 µM Cd and 50 µM Cu. The present investigation is highlighted the defensive role of Nitrate reductase in mitigating Cd and Cu induced toxicity by regulation of antioxidants and ROS metabolism. The study is important as this is the first report exemplifying the protective role of Nitrate reductase in detoxifying ROS in C. tetragonoloba under Cd and Cu stress.