The effects of some environmental factors on the partitioning of zinc and cadmium between roots and tops of rice plants

The effects of physico‐chemical property (electronegativity) of the metals, temperature, light intensity (shading), metal concentration in the medium and the depth of the soil layers in which the metals were placed on the partitioning of the metals between roots and tops in rice plants have been investigated. The results can be summarized as follows: 1. Metals of large electronegativity were mainly accumulated in roots and only a small quantity of them was translocated to tops.2. The increase in the metal concentration in the medium decreased the ratio of the translocation to tops. X‐ray micro‐analysis of the root revealed that the metal concentration around the stele was greatly increased when the metal was applied in high concentrations.3. Shading and low temperature reduced the ratio of the translocation of the metals to tops. Cd and Zn were translocated as organo‐metal complexes in xylems.4. Reduction of Eh of the soil by flooding decreased the metal translocation but not the uptake into roots. These results suggest that the metabolic dependent transformation of free metalions to organo‐metal complexes is involved in the efficient translocation of the metals from roots to tops.