Cereals and Phytohormones Under Heavy Metal Stress

This book chapter addresses the contribution of phytohormones in the moderation of heavy metal (HM) stress in cereal crops. Cereals like rice, wheat, rye, corn, barley, oat, and millet are stapled foods in different areas around the world, contributing to about half of human energy necessities. HMs such as Fe, Mn, Co, Cu, Ni, Zn, Cd, Hg, and As are accrued in soils for a long time via sewage disposal and industrial waste. Though some of them are essential micronutrients accountable for many steady processes in plants, however, their excess can have deleterious effects and can directly impact the growth, physiology, and metabolism of the plant. The central defense system stimulates the signalling actions, dependent on the type of metalloid stress, which further leads to cascade events, involving activation of kinases and production of reactive oxygen species along with the accumulation of phytohormones. Phytohormones are chemical messengers imparting tolerance to HM stress in plants, letting them sustain healthy growth and progressive developments in the life cycle. The well-designed phytohormone signalling systems and their cross-talk with each other render them perfect candidates for facilitating defense responses. Moreover, their exogenic supplementation along with alteration of the endogenic concentrations via specifically aiming at their biosynthetic and signalling machineries is an effective method of imparting defensive safeguards to cereal crops in order to tolerate stressful environments. Henceforth, the present book chapter primarily analyses the concrete advances in the contributions of plant hormones to the moderation of metal/metalloid stress in cereal crops.