Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0795, Japan; Department of Agroforestry and Environmental Science, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka 1207, Bangladesh.
Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka 1207, Bangladesh.
Ecotoxicol Environ Saf. 2018 Jan;147:990-1001. doi: 10.1016/j.ecoenv.2017.09.045. Epub 2017 Oct 7.
Cadmium (Cd) is a serious environmental threat because it accumulates in plants from soil and is subsequently transported into the food cycle. Increased Cd uptake in plants disrupts plant metabolism and hampers crop growth and development. Therefore, remediation of Cd from soil and enhancing plant tolerance to metal toxicity is vital. In the present study, we investigated the function of different doses of citric acid (CA) on Cd toxicity in terms of metal accumulation and stress tolerance in mustard (Brassica juncea L.). Brassica juncea seedlings (12-day-old) were treated with Cd (0.5mMCd and 1.0mM CdCl) alone and in combination with CA (0.5mM and 1.0mM) in a semi-hydroponic medium for three days. Cadmium accumulation in the roots and shoots of the mustard seedlings increased in a dose-dependent manner and was higher in the roots. Increasing the Cd concentration led to reduced growth, biomass, water status, and chlorophyll (chl) content resulting from increased oxidative damage (elevated malondialdehyde, MDA content; hydrogen peroxide, HO level; superoxide, O generation; lipoxygenase, LOX activity; and methylglyoxal, MG content) and downregulating of the major enzymes of the antioxidant defense and glyoxalase systems. Under Cd stress, both doses of CA improved the growth of the plants by enhancing leaf relative water content (RWC) and chl content; reducing oxidative damage; enhancing the pool of ascorbate (AsA) and glutathione (GSH) and the activities of the antioxidant enzymes (ascorbate peroxidase, APX; monodehydroascorbate reductase, MDHAR; dehydroascorbate reductase, DHAR; glutathione reductase, GR; glutathione peroxidase, GPX; superoxide dismutase, SOD; catalase, CAT); improving the performance of the glyoxalase system (glyoxalase I, Gly I and glyoxalase II, Gly II activity); and increasing the phytochelatin (PC) content. Exogenous CA also increased the root and shoot Cd content and Cd translocation from the roots to the shoots in a dose-dependent manner. Our findings suggest that CA plays a dual role in mustard seedlings by increasing phytoremediation and enhancing stress tolerance through upregulating the antioxidant defense and glyoxalase systems.
镉（Cd）是一种严重的环境威胁，因为它会从土壤中积累在植物中，随后被运输到食物链中。植物对 Cd 的吸收增加会破坏植物的新陈代谢，阻碍作物的生长和发育。因此，从土壤中修复 Cd 并提高植物对金属毒性的耐受性至关重要。在本研究中，我们研究了柠檬酸（CA）的不同剂量对芥菜（Brassica juncea L.）中 Cd 毒性的功能，从金属积累和胁迫耐受方面进行了研究。用 0.5mM 和 1.0mM CdCl 单独以及与 0.5mM 和 1.0mM CA 组合处理 12 天大的芥菜幼苗 3 天，在半水培培养基中。芥菜幼苗的根和地上部分的 Cd 积累量呈剂量依赖性增加，在根部更高。随着 Cd 浓度的增加，生长、生物量、水分状态和叶绿素（chl）含量降低，这是由于氧化损伤增加（丙二醛、MDA 含量升高；过氧化氢、HO 水平升高；超氧化物、O 生成；脂氧合酶、LOX 活性升高；甲基乙二醛、MG 含量升高）和抗氧化防御和糖氧酶系统的主要酶下调所致。在 Cd 胁迫下，两种剂量的 CA 通过提高叶片相对含水量（RWC）和 chl 含量、降低氧化损伤、增强抗坏血酸（AsA）和谷胱甘肽（GSH）池以及增强抗氧化酶（抗坏血酸过氧化物酶、APX；单脱氢抗坏血酸还原酶、MDHAR；脱氢抗坏血酸还原酶、DHAR；谷胱甘肽还原酶、GR；谷胱甘肽过氧化物酶、GPX；超氧化物歧化酶、SOD；过氧化氢酶、CAT）的活性、改善糖氧酶系统（糖氧酶 I、Gly I 和糖氧酶 II、Gly II 活性）的性能以及增加植物螯合肽（PC）的含量，从而促进植物的生长。外源 CA 还以剂量依赖的方式增加了根和地上部分的 Cd 含量以及 Cd 从根部向地上部分的转运。我们的研究结果表明，CA 在芥菜幼苗中发挥双重作用，通过上调抗氧化防御和糖氧酶系统来增加植物修复并增强胁迫耐受性。
