Role of Plant Growth Regulators (PGRs) in Mitigation of Heavy Metal Phytotoxicity in Plants

Abstract

Metal ions are the natural components of earth’s crust. At low concentrations, metal ions are really essential to the plant system, but their excessive amounts lead to toxicity. Industrial revolution and anthropogenic activities are critically disturbing the level of metal ions in the ecosystem, like soil, water, and plant resources. Elemental and chemically combined forms of these metal ions such as Cd, As, Pb, Hg, Cr, and Zn are toxic to plant system, leading to loss in yield. Also, the heavy metal toxicity hinders the efficacy of photosynthetic apparatus, and causes oxidative stress and abnormal plant growth. Plants overcome such toxicity by assimilating these toxic metals into the root system or transforming these complexes into physiologically tolerant forms. Plants have adopted a series of physiological and molecular mechanisms to mitigate these stress responses that might enable them to withstand higher metal ion levels in soil. Scientific community is highly concerned to understand these mechanisms. Researchers are also keen to know the roles of plant growth regulators auxins, gibberellins, brassinosteroids, ethylene, cytokinin, jasmonic acid, salicylic acid, etc. in signaling pathways associated with the heavy metal tolerance in plants. Recent research has possible evidences of PGR’s role in the mitigation of heavy metal toxicity, as well as shows that it can regulate and integrate the factors associated with growth and development. In this chapter, we have discussed the role of PGRs in alleviating heavy metal stress, their mechanism of action, and cross talk.