Subcellular Accumulation of Different Concentrations of Cadmium, Nickel, and Copper in Indian Mustard and Application of a Sigmoidal Model

Abstract

Certain plant species can tolerate and even detoxify metallic elements. This detoxification ability has been shown to depend on how plants distribute the metallic elements in their tissues. In turn, this distribution may have an important impact on phytoremediation. Here, we investigated the effects of different single-metal concentrations (10, 50, 100, and 300 μmol L) of cadmium (Cd), nickel (Ni), and copper (Cu) on their subcellular distribution in L. var. (Indian mustard). At the applied concentration of 300 μmol L, 98% of the Cu and 79% of Cd were retained in the roots, while Ni was distributed between leaves (32%), stems (29%), and roots (39%). The cell wall and soluble fractions were the dominant storage compartments for Cd and Cu in the stems and leaves, whereas the soluble fraction was the dominant storage compartment for Ni in stems and leaves. Scanning electron microscopy (SEM) X-ray micrographs showed a breakdown of epidermal, palisade, and spongy parenchyma cells following the 300 μmol L Cd, Ni, and Cu treatment. A sigmoidal model is a powerful tool to describe the subcellular accumulation and tissue concentrations of Cd, Ni, and Cu following exposure to various concentrations of metals. The coefficients of determination () values for the description of the accumulation were high, although the membrane subcellular fraction did not fit the equation. Both the maximum accumulation capacity and the critical concentrations of metals were well described by the model. The results indicate that the use of a sigmoidal model is a promising method that could improve the understanding of metal accumulation at the subcellular level in Indian mustard.