Switching role of hydrogen sulfide in amelioration of metal stress in plant

One of key issues for concern is metal toxicity from common metals beings poured above threshold levels and toxic metals which hampers plant’s physiological as well as metabolic pathways at stake. The main sources for non-toxic metal’s affluence are industrial wastes, fertilizers, herbicides, pesticides. Whereas, the toxic metal’s sources include mining, industrial affluent wastes, exhaust emissions, sewage irrigation practices, metal products usage, pesticides and cheap chemical fertilizers. Furthermore, anthropogenetic activities have enormously elevated metal levels in lands above threshold/admissible value thus demolishing environmental hygiene and ecosystem health. Excess amount of essential as well as non-essential metals affects seed germination, seedling growth, inactivation of antioxidant enzymes, disruption of membrane systems, chromosomal fragmentation, growth inhibition, limiting photosynthesis, thus chlorosis, internal water imbalance, altered nutrient accumulation, nutrient imbalance, free radical production, oxidative stress and increment in senescence. These factors alone or in the combination affect the plant growth and development and ultimately lead to plant death. These toxicity responsive metals are aluminum (Al), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), mercury (Hg), Nickel (Ni), and zinc (Zn). The main characteristic of metals stress causes accumulation toxicity and prominent damage to roots. It has been proven that the hydrogen sulfide (H2S) molecule is not only a key contributor to the signal transduction pathway to various biotic and abiotic stresses but also contribute toward the alleviation of different abiotic stress. In spite of numerous reports published till present, there is emerging need to understand the role of H2S in metal stress tolerance and physiological and molecular mechanisms behind H2S action in surpassing and lowering metal toxicity. In this chapter, we have tried to mention the latest advancement and progress in H2S metabolism and switching/multifunctional roles in plants against metal stress. These insights may pave path for novel strategies in genetic improvement of plant’s tolerance towards overcoming metal stress.