Abstract: The soluble sugar, starch and invertase of the roots, stems and ovaries of Ceratoides arboresens during seed development were measured periodically to determine carbohydrate in relation to low seed set in this plant. During seed development, the soluble sugar and starch contents in roots and stems continuously decreased; the starch content in roots fell by 48% from the flowering stage to maturity, but there was a smaller decline in the stems; At the same time, invertase activity in the two organs gradually reduced and had reached the lowest value by the end of seed development. Simultaneously, the soluble sugar and starch contents in developing fruits continuously increased and the invertase activity in them also increased. Although the root and stem are usually considered as the metabolic “sink” organs, during the period of seed growth and development, root and stem become “source” organs and their large amount of assimilates were transported to the reproductive organs. However, from the aspect of assimilate flow, the proportions of assimilate losses from the root and stem of C. arboresens were far less than those of annual crops.