Current Assessment and Future Perspectives on Phytoremediation of Heavy Metals

Heavy metals such as zinc, manganese, nickel, cobalt, copper, iron, and molybdenum are required in minute quantities to maintain optimal biological functions. However, most other heavy metals are not required for living cells; thus, their accumulation within cells and tissues poses a serious threat to human health and the environment. Phytoremediation can offer a safe, inexpensive, and ecologically sustainable technique to clean habitats contaminated with heavy metals. Several herbaceous and woody plants have been identified and utilized as potential candidates for phytoremediation, and the technique has transformed from being in the formative stage, where it was confined to laboratories and greenhouses, to becoming a widely applied technology involving field trials across the globe. However, recently, several field studies have shown promising results that can propel the large-scale implementation of this technology at industrial sites and in urban agriculture. The commercialization of this technique is possible if an interdisciplinary approach is employed to increase its efficiency. Identification of the genetic mechanisms and the cell signaling pathways involved in phytoremediation may support biotechnological intervention through OMICS and CRISPR approaches, resulting in an improvement in the efficiency of the process. This review presents a comprehensive overview of phytoremediation with a focus on the current assessment and future perspectives of the technique. It illustrates the concept of phytoremediation, the ecological and commercial benefits, and the types of phytoremediation. The candidate plants and factors that influence phytoremediation are discussed. The physiological and molecular mechanisms, along with perspectives on the future of the technique, are also illustrated. This review presents clear and updated information on this rapidly evolving technology, thus providing the public and private sectors with essential knowledge on phytoremediation mechanisms. This may assist in policy development for the management of heavy metals while accelerating the development of transgenic plants or other tools that might be more efficient in phytoremediation.