Cadmium transport in young soybean plant using a positron-emitting Cd

Ito, Sayuri; Suzui, Nobuo; Kawachi, Naoki; Ishioka, Noriko; Fujimaki, Shu

Recently, Cd accumulation in soybean seed is considered one of the acute agricultural problems in Japan. However, characteristics of Cd transport and accumulation in soybean plants are unclear so far. In this study, the mechanism of Cd transport in young soybean plants was characterized using tracer of a positron-emitting Cd (half-life: 6.5 hours) and the positron-emitting tracer imaging system (PETIS). Soybean (Glycine max [L.] Merr. cv. Williams) seeds were grown hydroponically for 3 weeks after sowing. The test plants were placed between a set of the PETIS detector heads in another growth chamber. Cd and was added to the hydroponic solution with non-radioactive Cd. The imaging with PETIS was performed for 36 hours. In the field of view of PETIS, Cd was observed very weakly. Cd appeared in the shoot base at about 10 hours after Cd feeding, which timing was 10 times later compared with the results of rice. Cd was not reached the leaves within 36 hours. These results may indicate that Cd transport might be particularly slow in soybean plants.