Combined application of zinc and iron-lysine and its effects on morpho-physiological traits, antioxidant capacity and chromium uptake in rapeseed (Brassica napus L.).

Environmental contamination of chromium (Cr) has gained substantial consideration worldwide because of its high levels in the water and soil. A pot experiment using oil seed crop (rapeseed (Brassica napus L.)) grown under different levels of tannery wastewater (0, 33, 66 and 100%) in the soil using the foliar application of zinc (Zn) and iron (Fe)-lysine (lys) has been conducted. Results revealed that a considerable decline in the plant growth and biomass elevates with the addition of concentrations of tannery wastewater. Maximum decline in plant height, number of leaves, root length, fresh and dry biomass of root and leaves were recorded at the maximum level of tannery wastewater application (100%) compared to the plants grown without the addition of tannery wastewater (0%) in the soil. Similarly, contents of carotenoid and chlorophyll, gas exchange parameters and activities of various antioxidants (superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)) were also reduced significantly (P < 0.05) with the increasing concentration of tannery wastewater (33, 66 and 100%) in the soil. In addition, a combined application of Zn and Fe-lys reduced the accumulation and uptake of toxic Cr, while boosting the uptake of essential micronutrients such as Zn and Fe in different tissues of the plants. Results concluded that exogenous application of micronutrients chelated with amino acid successfully mitigate Cr stress in B. napus. Under field conditions, supplementation with these micronutrient-chelated amino acids may be an effective method for alleviating metal stress in other essential seed crops.

Zinc-lysine Supplementation Mitigates Oxidative Stress in Rapeseed (Brassica napus L.) by Preventing Phytotoxicity of Chromium, When Irrigated with Tannery Wastewater.

Contamination of soil and water with metals and metalloids is one of the most serious problems worldwide due to a lack of a healthy diet and food scarcity. Moreover, the cultivation of oilseed crops such as rapeseed (Brassica napus L.) with tannery wastewater could contain a large amount of toxic heavy metals [e.g., chromium (Cr)], which ultimately reduce its yield and directly influence oilseed quality. To overcome Cr toxicity in B. napus, a pot experiment was conducted to enhance plant growth and biomass by using newly introduced role of micronutrient-amino chelates [Zinc-lysine (Zn-lys)], which was irrigated with different levels [0% (control), 33%, 66%, and 100%] of tannery wastewater. According to the results of present findings, very high content of Cr in the wastewater directly affected plant growth and composition as well as gas exchange parameters, while boosting up the production of reactive oxygen species (ROS) and induced oxidative damage in the roots and leaves of B. napus. However, activities of antioxidants initially increased (33% of wastewater), but further addition of tannery wastewater in the soil caused a decrease in antioxidant enzymes, which also manifested by Zn content, while the conscious addition of wastewater significantly increased Cr content in the roots and shoots of B. napus. To reduce Cr toxicity in B. napus plants, exogenous supplementation of Zn-lys (10 mg/L) plays an effective role in increasing morpho-physiological attributes of B. napus and also reduces the oxidative stress in the roots and leaves of the oilseed crop (B. napus). Enhancement in different growth attributes was directly linked with increased in antioxidative enzymes while decreased uptake and accumulation of Cr content in B. napus when cultivated in wastewater with the application of Zn-lys. Zn-lys, therefore, plays a protective role in reducing the Cr toxicity of B. napus through an increase in plant growth and lowering of Cr uptake in various plant organs. However, further studies at field levels are required to explore the mechanisms of Zn-lys mediated reduction of Cr and possibly other heavy metal toxicity in plants.

Interactive role of zinc and iron lysine on Spinacia oleracea L. growth, photosynthesis and antioxidant capacity irrigated with tannery wastewater.

ABSTRACT: Untreated wastewater contains toxic amounts of heavy metals such as chromium (Cr), which poses a serious threat to the growth and physiology of plants when used in irrigation. Though, Cr is among the most widespread toxic trace elements found in agricultural soils due to various anthropogenic activities. To explore the interactive effects of micronutrients with amino acid chelators [iron-lysine (Fe-lys) and zinc-lysine (Zn-lys)], pot experiments were conducted in a controlled environment, using spinach (Spinacia oleracea L.) plant irrigated with tannery wastewater. S. oleracea was treated without Fe and Zn-lys (0 mg/L Zn-lys and 0 mg/L Fe-lys) and also treated with various combinations of (interactive application) Fe and Zn-lys (10 mg/L Zn-lys and 5 mg/L Fe-lys), when cultivated at different levels [0 (control) 33, 66 and 100%) of tannery wastewater in the soil having a toxic level of Cr in it. According to the results, we have found that, high concentration of Cr in the soil significantly (P < 0.05) reduced plant height, fresh biomass of roots and leaves, dry biomass of roots and leaves, root length, number of leaves, leaf area, total chlorophyll contents, carotenoid contents, transpiration rate (E), stomatal conductance (gs), net photosynthesis (PN), and water use efficiency (WUE) and the contents of Zn and Fe in the plant organs without foliar application of Zn and Fe-lys. Moreover, phytotoxicity of Cr increased malondialdehyde (MDA) contents in the plant organs (roots and leaves), which induced oxidative damage in S. oleracea manifested by the contents of hydrogen peroxide (H2O2) and membrane leakage. The negative effects of Cr toxicity could be overturned by Zn and Fe-lys application, which significantly (P < 0.05) increase plant growth, biomass, chlorophyll content, and gaseous exchange attributes by reducing oxidative stress (H2O2, MDA, EL) and increasing the activities of various antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) catalase (CAT) and ascorbate peroxidase (APX). Furthermore, the supplementation of Zn and Fe-lys increased the contents of essential nutrients (Fe and Zn) and decreased the content of Cr in all plant parts compared to the plants cultivated in tannery wastewater without application of Fe-lys. Taken together, foliar supplementation of Zn and Fe-lys alleviates Cr toxicity in S. oleracea by increased morpho-physiological attributes of the plants, decreased Cr contents and increased micronutrients uptake by the soil, and can be an effective in heavy metal toxicity remedial approach for other crops.