Biostimulants and regulation of Cr, Pb, Fe, Zn, Hg, Cu, Mn, and Ni stress in plants

With expansion of industrialisation, anthropogenic activities and natural calamities, amount of heavy metals such as Chromium (Cr), Nickel (Ni), Mercury (Hg), Lead (Pb) etc in soil as well as water bodies has increased many folds in the last few decades. Also because these metals are non-biodegradable, they have high probability of entering the food chain and accumulating in human body. This has started directly impacting the human health, which makes heavy metal toxicity a matter of concern for scientists. Studies on bioremediation through the use of biostimulants have never been so critical as they are today. Biostimulants is a broad category of substances that stimulate plant nutrient use efficiency, improve quality features and somehow induce stress tolerance too. These biostimulants have now been established to have a role in reducing heavy metal toxicity by activating the antioxidant response through multiple studies. Focussing on strategies that involve the usage of heavy metal stress alleviating agents like plants, microbes, biochar, humus, chelators etc have now become indispensable. Plants that have the ability to accumulate and s+tore these heavy metals (superaccumulators) are one of the best bet that we can explore to deal with this issue as they are not only eco-friendly and low cost option, but they also provide added benefits like prevention of soil erosion and metal leaching. Many studies have been done on the role of biostimulants in reducing metal stress but there is still possibility of progressing the research work in the area of identifying more bioactive substances from agricultural wastes/by-products as this would provide dual benefit. Future research can be oriented towards better understanding of action mode of these biostimulants and using them for cleaner environment.