The Role of Zinc in Grain Cadmium Accumulation in Cereals

Zinc (Zn) and cadmium (Cd) are chemically similar. Therefore, Cd may be taken up by plant roots and it may be accumulated in edible parts. A high Cd concentration in plant parts disturbs the vital functions of Zn and other metal nutrients. Moreover, even the trace levels of Cd are toxic for plants, animals and humans. The accumulation of Cd in cereal grains may cause widespread oral exposure to Cd in human populations. This is more probable when cereals are grown in Cd-contaminated soils having low phyto-availability of Zn. On the other hand, the optimum supply of Zn to cereal crops may decrease root uptake and grain accumulation of Cd. Surprisingly, a few studies have also suggested a synergistic relationship between Zn and Cd for their uptake by plant roots. This chapter summarises Zn-induced changes on Cd behaviour in soils along with accumulation and mobility of Cd in rhizosphere, roots, xylem, leaves, phloem and grains of cereals. The reported synergistic relationship in a few studies is also discussed.