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.

Graphic abstract

中文翻译：

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锌和赖氨酸铁对菠菜生长、光合作用和抗氧化能力的交互作用与制革废水灌溉

摘要

未经处理的废水含有有毒量的重金属，如铬 (Cr)，在用于灌溉时对植物的生长和生理构成严重威胁。然而，由于各种人为活动，Cr 是在农业土壤中发现的最普遍的有毒微量元素之一。为了探索微量营养素与氨基酸螯合剂 [赖氨酸铁 (Fe-lys) 和赖氨酸锌 (Zn-lys)] 的相互作用，在受控环境中进行盆栽实验，使用菠菜 ( Spinacia oleracea L.) 植物灌溉与制革废水。年代。甘蓝在没有 Fe 和 Zn-lys（0 mg/L Zn-lys 和 0 mg/L Fe-lys）的情况下进行处理，并且还用（交互式应用）Fe 和 Zn-lys（10 mg/L Zn-lys 和5 mg/L Fe-lys)，当在土壤中以不同水平 [0 (对照) 33、66 和 100%) 培养时，土壤中含有有毒水平的 Cr。根据结果​​，我们发现，土壤中高浓度 Cr 显着 ( P < 0.05) 降低的株高、根叶新鲜生物量、根叶干生物量、根长、叶数、叶面积、总叶绿素含量、类胡萝卜素含量、蒸腾速率（E）、气孔导度（gs）、净光合作用 (PN) 和水分利用效率 (WUE) 以及未叶面喷施 Zn 和 Fe-lys 的植物器官中 Zn 和 Fe 的含量。此外，Cr的植物毒性增加了植物器官（根和叶）中丙二醛（MDA）的含量，从而诱导了S的氧化损伤。甘蓝表现为过氧化氢（H ₂ O ₂）含量和膜渗漏。Cr 毒性的负面影响可以通过 Zn 和 Fe-lys 的应用来逆转，这显着（P < 0.05) 通过减少氧化应激（H ₂ O ₂、MDA、EL）和增加各种抗氧化酶如超氧化物歧化酶（SOD）、过氧化物酶（POD）的活性来 增加植物生长、生物量、叶绿素含量和气体交换属性) 过氧化氢酶 (CAT) 和抗坏血酸过氧化物酶 (APX)。此外，与未施用 Fe-lys 在制革废水中培养的植物相比，补充 Zn 和 Fe-lys 增加了植物各部分中必需营养素（Fe 和 Zn）的含量并降低了 Cr 含量。总之，叶面补充 Zn 和 Fe-lys 可减轻S中的 Cr 毒性。甘蓝通过增加植物的形态生理属性，降低铬含量和增加土壤对微量营养素的吸收，可以成为其他作物重金属毒性的有效补救方法。

图形摘要