Anatomical changes due to uptake and accumulation of Zn and Cd in Indian mustard (Brassica juncea)

Anatomical and physiological changes in Indian mustard (Brassica juncea) plants due to uptake and accumulation of Zn and Cd were investigated. Potted plants were exposed to metal treatments of Zn and Cd for 15 and 16 days, respectively. Leaves, stems and roots were harvested for studying anatomy and analyzing metal accumulation. Anatomical changes were documented using light microscopy, scanning, and transmission electron microscopy. Accumulation of Zn and Cd in all parts of the plant increased significantly with an increase in applied metal concentration. Microscopic studies revealed clotted depositions in roots and stems, break down of parenchyma cells, and a decrease in starch content in leaves of plants treated with high concentrations of Zn. Physiological and morphological changes of Zn-treated plants included a significant decrease in relative water content, dry weight and plant height. Cd at higher concentrations resulted in structural changes only in stems and roots. Mustard plants accumulated significant amounts of Zn and Cd without exhibiting symptoms of phytotoxicity. However, higher Zn (ZnT3 and ZnT4) and Cd (CdT4) concentrations resulted in structural changes in roots, stems and leaves and altered physiological and morphological characteristics. Our results systematically illustrate the physiological implications of structural alterations caused by Zn and Cd at higher concentrations.