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Heavy metals are the elements that are present in the environment naturally, with the development of industries in the world, there is a drastic increase of heavy metals in the biosphere. Among the heavy metals, lead (Pb) is the most toxic metal that easily gets accumulated in the soil and sediments. Lead is not an important element for plant growth but it gets easily absorbed and accumulated in different parts of the plant. In this study, Setaria italica (foxtail millet - CO (Te) 7) is treated with different concentrations of lead to evaluate the changes in the morphological growth parameters such as rate of percentage of germination, Tolerance Index (TI) and phytotoxicity. The germination percentage is comparatively greater in the control plant and gradually decreases as the concentration of Pb increases. The length of root and shoot, the amount of fresh weight and dry weight also decrease with the increase in the concentration of heavy metals. The root length and shoot length in the control on the 45th day were 20.2±0.16 and 48.7±0.24 whereas in the maximum concentration of metal (250 mg/kg) it showed a minimum reading of 11.1±0.43 and 27.3±0.33 respectively. The percentage of phytotoxicity increases as the concentration of the metal increases. Tolerance indices decrease as the percentage of phytotoxicity increases.

Heavy metals are elements that are naturally present in the environment. However anthropogenic activities such as the production of industrial wastes and domestic effluents, dumping of sewage waste, urban storm, water runoff, and atmospheric sources can give rise to the concentration of these metals relative to the normal background values. Any metal or metalloid with a density exceeding 5g /cm−3 is termed as “heavy metal”. These metallic ions are always associated with pollution and toxicity, although some of these elements are required by organisms at low concentrations. Some of the heavy metals such as zinc, iron and copper are essential for the physiological functioning of living organisms. The same essential elements become toxic when their concentration increases from their initial value. The present review article features the occurrence and toxicity of various heavy metals and compiles the sources, effects and the treatment of heavy metals with reference to cadmium, chromium and lead. This work also investigates the abilities of plants in terms of tolerance and degradation of these metals. It also reviews deeply about the heavy metal uptake mechanisms and several research studies associated with the topics. An evaluation of the present status of technology exploitation and the capability of some cultivated plants to reduce the contaminant is also reported and suggested for future work.