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Cadmium (Cd) toxicity is highly detrimental for the human and largely originated from faulty industrial and agricultural practices. Cadmium toxicity can be observed in minute concentration and highly mobile in the soil–plant system and availability in soil is mainly governed by various physio-chemical properties of the soil. Cereals and vegetables cultivated in peri-urban areas, former mining and industrial areas accumulate Cd in toxic limit as they receive Cd from multiple ways. In general, when the total cadmium (Cd) concentration in soil exceeds 8 mg kg−1, or the bioavailable Cd concentration becomes >0.001 mg kg−1, or the Cd concentration in plant tissue reaches 3–30 mg kg−1most plants exhibit visible Cd toxicity symptoms. The impacts of Cd toxicity are seed germination, growth, photosynthesis, stomata conductance, enzyme activities and alteration in mineral nutrition. The major source of Cd in human is food chain cycle and causes disorders like “itai-itai” disease, cancer, and nephrotoxicity. Cadmium harms kidney, liver, bone and reproductive body parts and may be fatal in serious condition. WHO recommended the tolerable monthly Cd intake are 25 μg kg−1 body weights and in drinking water Cd concentration should not exceed 3 μg L−1. It is hard to remove these potent and hazardous metals from the environment as they have long mean residence time but, can be converted into less toxic form through bioremediation. This chapter focuses on the effect of Cd toxicity in soil–plant-human continuum and its bioremediation techniques to mitigate the Cd- toxicity.

Heavy metal (HM) stress is threatening agricultural crops, ecological systems, and human health worldwide. HM toxicity adversely affects plant growth, physiological processes, and crop productivity by disturbing cellular ionic balance, metabolic balance, cell membrane integrity, and protein and enzyme activities. Plants under HM stress intrinsically develop mechanisms to counter the adversities of HM but not prevent them. However, the exogenous application of abscisic acid (ABA) is a strategy for boosting the tolerance capacity of plants against HM toxicity by improving osmolyte accumulation and antioxidant machinery. ABA is an essential plant growth regulator that modulates various plant growth and metabolic processes, including seed development and germination, vegetative growth, stomatal regulation, flowering, and leaf senescence under diverse environmental conditions. This review summarizes ABA biosynthesis, signaling, transport, and catabolism in plant tissues and the adverse effects of HM stress on crop plants. Moreover, we describe the role of ABA in mitigating HM stress and elucidating the interplay of ABA with other plant growth regulators.