Nickel Toxicity in Plants

Nickel (Ni) is an essential micronutrient at low concentrations and becomes phytotoxic when it exceeds threshold levels. Ni plays a pivotal role in various physiological mechanisms in plants; nevertheless, the toxic effects of Ni could alter the plant physiological functions, activate plant defensive mechanisms, and interfere with plant mineral nutrition, plant-soil-water relations, growth and development, photosynthesis, and yield. Plants develop various adaptive strategies to counter and/or to acclimate to the low to high levels of Ni concentration in the soil, i.e., formation of phytochelatins, metallothioneins, proline, organic acids, and amino acid accumulation at the cell level. Moreover, various types of chelating agents, such as EDTA and citric acid, can be applied exogenously to the plants to enhance the phytoextraction of Ni from the soil to different plant organs. In sum, Ni is required by the plants as a trace element; however, its high concentration may be damaging to crop plants and requires sustainable solutions. Plant properties, including metal uptake, accumulation, detoxification, and transport of different organic pollutants, can be improved by genetically modified fast-growing plants and inserting the gene of interest from the various hyper-accumulator species of plants, as well as over expression of metal chelating transporter, metal-associated proteins, and antioxidant genes led to promising outcomes in alleviating nickel induce oxidative stress improve plant growth toxic conditions. Genetically modified plants can be developed as an inexpensive, simple, and controllable way to reduce these contaminants for global food biosafety and security.