Zinc Effects on Antioxidative Enzymes and Nitrate Reductase Activity in Phaseolus vulgaris (Common Bean) Seedling

The present study analyses antioxidative enzymes and in vitro NR activity in common bean seedlings in response to ZnCl2 supply over the range of 0 – 1 mM concentrations. Bean seedlings were grown in plastic pots containing acid washed sand for 10 days and watered daily with ½ Strength Hoagland’s Solution containing 5 mM NH4NO3 as nitrogen source and desired concentration of ZnCl2. Zn supply increased seedling weight and shoot length at 0.001 mM whereas root length decreased at all concentrations.

Amongst the antioxidative enzymes, super oxide dismutase (SOD) activity increased up to 0.1 mM significantly and then decreased at 1 mM in leaf tissue whereas in root tissue it decreased at 0.001 mM and then increased significantly. The catalase (CAT) activity increased at all the concentration being more prominent at 0.1 mM in leaf whereas in roots it increased substantially at 0.1 and 1 mM Zn. Ascorbate peroxidase (APX) activity in leaf increased at 0.1 mM but decreased at 0.001 and 1 mM, whereas in roots it decreased at all the concentration. Various in vitro activities of NR were analysed in response to Zn supply. The effect of Zn on NADH-NR is more substantial than MVH-NR at all the concentrations. Also NRmax and NRact increased at all the concentration of Zn being most prominent at 0.1 mM in leaf and at 1 mM in root tissue.