Nitric Oxide (no)-Dependent Alleviation of Copper-and Zinc-Induced Toxic Effects on Hordeum Vulgare L. Seedlings

The aim of present study was to examine whether SNP (sodium nitroprusside, an NO donor) could alleviate the Cu and Zninduced suppression of seedling growth of Hordeum vulgare. Both Cu (0–100 μM) and Zn (0–1000 μM) inhibited the seedling growth in terms of root length, shoot length and seedling fresh weight in a concentration-dependent manner. Metal-and organspecific differences were evident. Thus, the magnitude of Cu-induced suppression was more as compared to Zn and root elongation was affected invariably more than the shoot length. α-amylase activity in the seeds was reduced due to treatment with higher Cu or Zn-concentrations. The activity of two antioxidative enzymes namely, ascorbate peroxidase (APX) and catalase (CAT) was enhanced in the Cu and Zn-stressed seedlings implying the involvement of redox metabolism. SNP pretreatment of seeds prior to the exposure to Cu or Zn led to a substantial alleviation of the HM-induced toxic effects on seedling growth. The SNP-dependent alleviation was accompanied by specifically altered activities of α-amylase, APX and CAT. The findings suggest a role of NO in alleviation of toxic effects of surplus Cu and Zn on H. vulgare seedling growth via altered hydrolytic and redox metabolism.