Sand culture using radish (Raphanus sativus L.) and hydroponics using carrot (Daucus carota L.) were conducted to examine root-uptake of carbon and its assimilation in the form of 14C-acetic acid. 14C-acetic acid (1, 2-14C, radioactivity: 74 kBq) was added to each pot. Radishes were grown under the dark conditions or the light conditions for 24 h. Carrot were grown under the light conditions after 14C-acetic acid addition (radioactivity: 19 kBq). The 14C radioactivity in each plant part was determined. The distribution of 14C in the plants was visualized using autoradiography. For a comparison, autoradiography was also done using 22Na. The results indicated that the root vegetables absorbed 14C through the roots and assimilated it into the shoots and edible parts. However, the amount of 14C-acetic acid absorbed by plants through the roots was considered to be very small. Absorption and assimilation of 14C seemed to be carried out not because of uptake of 14C-acetic acid but because of uptake of 14C in inorganic forms with very low concentration. 14C dominantly transferred to the plant parts where were physiologically active. 14C movement in the plant did not have a close relation to water movement unlike 22Na movement.