Roles of root and shoot tissues in transport and accumulation of cadmium, lead, nickel, and strontium

The review considers the roles of root and shoot tissues in transport and accumulation of heavy metals in plants of two contrast groups, i.e., excluders and hyperaccumulators. The regularities in distribution of cadmium, lead, nickel, and strontium are summarized. Effects of other cations, calcium in particular, on accumulation and distribution of heavy metals are analyzed. Specific patterns of metal distribution in hyperaccumulator plants are discussed together with morphological and functional features underlying the ability of plants to accumulate heavy metals in the aboveground organs. Based on the data available, the root and shoot tissues are classified according to their roles in transport and distribution of the metals examined.