[en] Translocation of ¹³¹I to ears of rice plant at the end of milky stage was investigated. A small piece of absorbent cotton wool containing 185 kBq (5 μCi) of Na¹³¹I solution was placed on the flag leaf (n-th leaf) surfaces. Three days after that, ¹³¹I was detected in the ears autoradiographically. In the same way, the cotton was placed on the lower leaf surfaces. More than 10 days were needed to find ¹³¹I in the ears. A 20 μl of Na¹³¹I solution (3.7 kBq (0.1 μCi)) was administered to the basal part of the flag leaf by using micropipet. Only two days after administration, ¹³¹I was clearly found in the ears also autoradiographically though the dose was only one-fiftieth for foliar administration. It can be supposed that the translocation of ¹³¹I to the ears from basal part of the flag leaf is faster than that from the leaf surfaces. Rice plants were grown in the beaker containg 25 ml of deionized water with 740 kBq (20 μCi) of Na¹³¹I for 0.2, 1 and 2 days. Iodine-131 was detected almost all parts of the plants. In general, there are two transport systems in the plants, that is, xylem system and phloem system. Foliar and basal part uptake-translocations are taken place through the phloem system, while root uptake-transport is through the xylem system. It was observed that ¹³¹I in the xylem system was transported to hull, while that in the phloem system more to brown rice than to hull. (author)