Anthropogenic activities have resulted in severe environmental degradation. Untreated wastewater from tanneries is hazardous to all kinds of life on earth. Effluent from tanning industries, containing large amount of Cr, is used to irrigate the crops in Pakistan. The current experiment was carried out to study the effects of tannery wastewater on spinach and the role of lysine-Zn in mitigating the severity of stress. The plants were grown in soil and the following treatments were used: irrigation with 0%, 33%, 66%, and 100% wastewater (ww) along with two doses (0 mM, 10 mM) of Zn-lysine. Foliar application of zinc-lysine enhanced the plant growth, biomass, Zn contents, photosynthesis, and enzyme activities in different tissues of plant. Zinc-lysine (10 mM) considerably decreased the Cr content in roots and shoots, along with ameliorating the oxidative stress by enhancing the activities of antioxidant enzymes in plants. Addition of Zn-lys (10 mM) improved the plant height by 19%, root length by 57%, leaf dry weight by 19%, and root dry weight by33% under 100% Cr treatment. Zn-lys significantly reduces the oxidative stress and concentration of Cr as compared with the Cr treatments alone. Application of Zn-lys (10 mM) reduced the Cr contents in roots by 27 and 22 under 33 and 66% Cr treatment, respectively. Taken together, Zn-lys chelates efficiently ameliorated the toxic effects of chromium. Zn-lysine has the extravagant potential of mitigating the heavy metal toxicity without harming the normal growth and development of the plants.
Keywords: Antioxidant enzymes; Chromium stress; Growth attributes; Oxidative stress; Tannery wastewater irrigation; Zn-lysine.