ABSTRACT
Heavy metals are known as important natural and non-biodegradable constituents of the Earth’s crust. Due to anthropogenic activities, these heavy metals can accumulate and persist for an indefinite time in the ecosystem. The high concentration of heavy metals in an ecosystem leads to a major yield loss in plants. They can interrupt plant metabolic activities by enhancing ROS accumulation and reducing the level of antioxidant enzymes. The removal of these heavy metals has become an essential concern of scientific interest. In recent years, researches marked that plant hormones have the potential to provide metal stress tolerance to plants. To sustain life, plant hormones can regulate all the physiological and biochemical parameters of the plant and ultimately enhance the growth responses against various heavy metal stresses. These specific plant hormones can boost internal antioxidant machinery thereby releasing different toxic oxidative radicles which are vigorously formed during heavy metal stresses. Additionally, they can also promote genetic modifications and programmed cell death to cope with adverse situations by modulating different signaling pathways that ultimately provide a better crop yield to the growing population. Interaction of plant growth hormones with other signaling molecules showed their defensive-signalling strategies to cope up with stressful environments. In the present study, we have gathered all the current information about the role of natural and synthetic plant growth hormones like auxins, gibberellins, cytokinins, abscisic acid, ethylene, jasmonic acid, salicylic acid, brassinosteroids, and 5-aminolevulinic acid in defense mechanisms, signalling pathways, and lessening of heavy metal toxicity.
