Research Progress in Soybean by Phytohormone Modulation and Metal Chelation over the Past Decade

Phytohormones have been acknowledged as an eco-friendly and alternative source for plant growth promotion and abiotic stress tolerance. Heavy metal stress has attained considerable attention worldwide because of its serious effects. Globally, it is a major cause of crop yield loss. Soybean is an important legume crop that continuously faces environmental stress, such as heavy metal stress. The application of plant growth regulators, such as phytohormones, enhances plant tolerance toward heavy metals. Phytohormones augment the interaction with plants. They improve plant productivity under stress due to the potential of phytostabilization. They are capable of enhancing metal stress tolerance by reducing oxidation stress. In the present review, an attempt has been made to summarize the role of phytohormones in metal chelation in a model plant, soybean. The results suggest that among the phytohormones, ABA, JA, SA ET, GA, and IAA are synergistic with metal chelation, whereas cytokinins are antagonistic. The application of phytohormones and corresponding microbes enhances the production of glutathione (GSH), which enhances metal tolerance by metal sequestration.