UPTAKE AND DISTRIBUTION OF CADMIUM IN MAIZE INBRED LINES

Genotypic variation in uptake and distribution of cadmium (Cd) was stu died in 19 inbred lines of maize (Zea mays L.). The inbred lines were grown for 27 days on an in situ Cd-contaminated sandy soil or for 20 d ays on nutrient solution culture with 10 mug Cd L-1. The Cd concentrat ions in the shoots showed large genotypic variation, ranging from 0.9 to 9.9 mug g-1 dry wt. for the Cd-contaminated soil and from 2.5 to 56 .9 mug g-1 dry wt. for the nutrient solution culture. The inbred lines showed a similar ranking for the Cd concentrations in the shoots for both growth media (r2 = 0.89). Two main groups of inbreds were disting uished: a group with low shoot, but high root Cd concentrations (shoot : 7.4 +/- 5.3 mug g-1 dry wt.; root: 206.0 +/- 71.2 mug g-1 dry wt.; ' shoot Cd excluder') and a group with similar shoot and root Cd concent rations (shoot: 54.2 +/- 3.4 mug g-1 dry wt.; root: 75.6 +/- 11.2 mug g-1 dry wt.; 'non-shoot Cd excluder'). The classification of the maize inbred lines and the near equal whole-plant Cd uptake between the two groups demonstrates that internal distribution rather than uptake is causing the genotypic differences in shoot Cd concentration of maize i nbred lines. Zinc (Zn), a micronutrient chemically related to Cd, show ed an almost similar distribution pattern for all maize inbred lines. The discrepancy in the internal distribution between Cd and Zn emphasi zes the specificity of the Cd distribution in maize inbred lines.