EVALUATION OF STRUCTURAL AND PHYSIOLOGICAL PLANT CHARACTERISTICS IN RELATION TO THE DISTRIBUTION OF CADMIUM IN MAIZE INBRED LINES

To establish the structural and physiological characteristics related to the genotypic variation in Cd distribution between maize inbred lin es ('shoot Cd excluders' and 'non-shoot Cd excluders'), shoot and root morphological parameters were studied on plants grown in nutrient sol ution. Furthermore, the xylem sap composition and the desorbability of Cd from roots of these inbreds have been compared. No relationship be tween the morphological characteristics of either shoot (specific leaf area and leaf area ratio) or. root (specific root length, specific su rface area, and average diameter) and Cd distribution could be assesse d. Cadmium concentrations in the xylem exudates from 'non-shoot Cd exc luders' were higher than those from 'shoot Cd excluders', but not rela ted to citrate and malate concentrations. The absolute and relative am ounts of Cd desorbed from roots of 'shoot Cd excluders' were about twi ce as high compared to those of the 'non-shoot Cd excluders', especial ly at the lowest Cd concentration in solution. The absence of a relati onship between shoot or root morphological parameters and Cd partition ing and the differences between both groups in the amounts of Cd desor bed, even at similar root Cd concentrations, indicate that the differe ntial Cd distribution between 'shoot Cd excluders' and 'non-shoot Cd e xcluders' may be related to the observed differences in root Cd concen tration, desorption characteristics and binding capacity of Cd inside and/or outside the root and its distribution within the roots.