Role of Nickel & Zinc in Crop Plants

Due to the consequences of urbanization and industrialization, heavy metal contamination in the environment is a world wide problem, threatening to the plants, animals, and human beings. Most heavy metals occur naturally in soils as trace elements, the biota-require some of these elements as essential micronutrients. These heavy metals at their higher concentrations, found toxic in living organisms. Their release into the environment in biologically available forms, as a result of human activity, may damage or alter both natural and man-made ecosystems. The most obvious sources of metal pollution are the process of extraction and purification, mining, smelting and refining, use of metal containing agricultural sprays, pesticides, fertilizers, industrial effluents, automobile combustion, municipal incinerators, sewage sludge and industrial effluents etc. The soils derived from ultra-basic igneous rocks, particularly serpentine, contain high nickel content. There is greater concern about nickel toxicity in crop plants regarding, for example, the application of sewage sludge (Pandey, 2006), which is often high in nickel.