Toxicity of cadmium and its competition with mineral nutrients for uptake by plants: A review

Cadmium (Cd) is a toxic heavy metal occurring in the environment naturally and is also generated through various anthropogenic sources and acts as a pollutant. Human health is affected by Cd pollution in farmland soils because food is the main source of Cd intake in the non-smoking population. For crops, Cd toxicity may result from a disturbance in uptake and translocation of mineral nutrients and disturbance in plant metabolism, inhibiting plant growth and development. However, plants have Cd tolerance mechanisms, including restricted Cd uptake, decreased Cd root-to-shoot translocation, enhanced antioxidant enzyme activities, and increased production of phytochelatins. Furthermore, optimal supply of mineral nutrients is one of the strategies to alleviate the damaging effects of Cd on plants and to avoid its entry into the food chain. The emerging molecular knowledge contributes to understanding Cd uptake, translocation, and remobilization in plants. In this review, Cd toxicity and tolerance mechanisms, agricultural practices to minimize Cd accumulation, Cd competition with essential elements (calcium, copper, iron, zinc, and manganese), and genes associated with Cd uptake are discussed in detail, especially regarding how these mineral nutrients and genes play a role in decreasing Cd uptake and accumulation in crop plants.