Long-distance transport of cadmium from roots to leaves of Solanum melongena.

In this study, the characteristics of cadmium (Cd) uptake by roots and translocation from roots to leaves of two eggplant species ( Solanum melongena and Solanum torvum) under relatively low Cd concentrations were investigated using stable Cd isotope through a number of hydroponic experiments. The uptake and translocation of Cd was compared with those of Zn and N. The results showed more Cd was loaded to the vascular channels and translocated upward to the leaves in S. melongena than in S. torvum, while the Cd concentrations were significantly lower in the roots of S. melongena than in S. torvum. When the phloem and xylem were wounded by grafting treatments, the foliar Cd concentrations were decreased by more than 66 % regardless of the rootstock species, whereas the uptake of Cd in the root was not inhibited by grafting. Similar grafting effects were observed for Zn. Hence, wounding phloem and xylem by grafting disturbed the upward transport of Cd and Zn to the eggplant leaves. Similarly, interruption of the phloem by the girdling treatment reduced the concentrations of Cd in the leaves of S. melongena by approximately 51 %, though the uptake of Cd by roots was not reduced by the interruption of phloem. In contrast, neither Zn concentrations nor stable N isotope ratio (δN) values in the roots and leaves of S. melongena were significantly influenced by the interruption of phloem. In conclusion, the phloem played a dominant role in the long-distance transport of Cd from the root to the leaf of S. melongena, whereas the xylem was the main channel for the translocation of Zn and N. [ABSTRACT FROM AUTHOR]