Mapping Cadmium distribution in roots of Salicaceae through scanning electron microscopy with x-ray microanalysis

A screening in hydroponics was carried out to assess the potential of Cd uptake and metal accumulation in roots of 4 poplar and 2 willow clones. Rooted cuttings were exposed for 3 weeks to 50 mu M Cd sulphate in a growth chamber. Salicaceae clones were discriminated in their potential to absorb and distribute Cd in root tissues considering the interaction between metal and macronutrients. SEM-EDXMA was useful to investigate structural modifications and to identify in situ concentration and distribution of elements in roots, establishing indirect correlations between accumulation and localization of the metal. Overall, observations suggested differential patterns between species and clones in accumulating Cd within the root profile. In conclusion, Cd accumulation in root levels would hardly be a useful indicator of the ability of plants to translocate metal, independently from other parameters, while Cd location in the root cross-section levels could suggest clone-specific control mechanism to mineral uptake.