ACCUMULATION, DISTRIBUTION AND REDISTRIBUTION OF Cd-109 AND Zn-65 IN WHEAT (TRITICUM AESTIVUM L.) AND BEAN (PHASEOLUS VULGARIS L.) PLANTS ON NUTRIENT MEDIA WITH ELEVATED ZINC OR CADMIUM

Abstract

The aim of the work was to identify the effects of elevated zinc or of cadmium on the dynamics of previously introduced Zn-65 and Cd-109, considering especially the effects of high zinc supply on Cd-109 and of cadmium on Zn-65 transport and redistribution in the whole plant. The translocation of radiolabelled zinc (Zn-65) and cadmium (Cd-109) was compared in wheat (Triticum aestivum L.) and in bean (Phaseolus vulgaris L.) plants, considering the root-to-shoot transport and further redistribution within the shoots. Visible symptoms of heavy metal toxicity were observed in both plant species. Dry matter was reduced by increased Cd, but not by increased Zn. At day 12 (but not before), the dry matter of bean roots and of trifoliate 1 was significantly lower in plants subjected to increased Cd in the nutrient medium than in control plants, while other bean organs were not significantly affected. In contrast, dry matter in wheat was significantly lowered by increased Cd supply only in the youngest (4th) leaf at day 3 (but not afterwards and not in roots or other leaves). Zn-65 was translomited more rapidly than Cd-109 from roots to the aerial parts in both species, but this transport was more efficient in wheat than in bean. Strong accumulation in the roots was observed for Cd-109. An increased Zn concentration in the nutrient medium, but not Cd, negatively influenced the root-to-shoot transfer of Zn-65 in bean plants. The redistribution of Zn-65 from primary leaves to the youngest trifoliate leaves was also negatively affected by an increased Zn supply. In wheat plants, an increased Zn concentration in the nutrient medium also negatively influenced the root-to-shoot transfer of Zn-65, as well as the redistribution of this radionuclide from the oldest to the youngest leaves. Transport and distribution of zinc and cadmium differed clearly between bean and wheat, but effects of increased zinc on cadmium transport and vice versa were less pronounced than expected.