Abstract
Hydroponic experiments were conducted to examine root-uptake of 14C in the form of acetic acid by 3 kinds of plants (marigold, tall fescue, and paddy rice) based on buried transuranic (TRU) waste disposal. Also, chamber experiment was conducted to examine loss of 14C as vaporized carbon dioxide (CO2) from the experimental tessera (spatially heterogeneous environment). The distribution of radioactivity in the plant, mediums, and carbon dioxide (14CO2) in the chamber were determined, and the distribution of 14C in the plant was visualized by the autoradiography. The plants absorbed and assimilated 14C through the roots. The amount of 14C in marigold and tall fescue were higher than that of paddy rice. However, the amounts of 14C-acetic acid absorbed by all the plants through their roots were considered to be very small. More so, 14CO2 gas was released from the culture solution to the atmosphere; however, it was not enough for the plant to perform photosyn-thesis. Assimilation of 14C in the plant shoots would be because of 14C movement of inorganic forms such as CO2 and HCO3-via the roots. Thus, the results indicated that the plants absorbed 14C through the roots and assimilated it into the shoots or edible parts not because of uptake of 14C-acetic acid but because of uptake of 14C in inorganic forms.
