Aims This study investigated the possible source organs delivering several trace elements to seeds (root uptake versus net remobilization), by studying changes in biomass and element contents in the plant organs. Methods Sunflowers were grown in a greenhouse using a nutrient solution enriched with Cd. Four samplings were performed from the early flowering to the seeds physiological maturity. Results The low grain Ca indicated that phloem was likely the main route for transporting the elements to seeds. Excluding roots, the mass balance of the elements indicated the following contribution of the net remobilization to the total quantities in seeds at maturity: Mg = 50%, Cd = 14%, Cu = 35%, Fe = 29%, Mn = 19%, Zn = 12%. Source organs were mainly the receptacle and the stem. No significant net remobilization was observed for Ca, K and Mo. Conclusions The amount of trace elements accumulated in vegetative parts can be redistributed to seeds in an extent that depended on the element. Due to the important contribution of root uptake to the content in seeds at maturity, the availability of elements in soil during the reproductive stages is an important point to consider.