Tracing cadmium from culture to spikelet; Noninvasive imaging and quantitative characterization of absorption, transport, and accumulation of cadmium in an intact rice plant

培地から籾までカドミウムを追跡; 生きたままのイネ植物体におけるカドミウムの吸収,移行,蓄積の非侵襲的画像化及び定量的解析

藤巻 秀; 鈴井 伸郎; 石岡 典子; 河地 有木; 伊藤 小百合; 茅野 充男*; 中村 進一*

Fujimaki, Shu; Suzui, Nobuo; Ishioka, Noriko; Kawachi, Naoki; Ito, Sayuri; Chino, Mitsuo*; Nakamura, Shinichi*

We characterized the absorption and translocation of cadmium (Cd) in rice using serial images observed with a positron-emitting tracer imaging system (PETIS). We fed a positron-emitting Cd tracer to the hydroponic culture. The absorption rates by the root were proportional to Cd concentrations in the culture within the tested range below 100 nM. It was estimated that the radial transport from the culture to the xylem in the root tissue was completed in less than 10 min. Cd moved up through the shoot with velocities of a few centimeters per hour, which was obviously slower than the bulk flow in the xylem. Cd reached the panicles 7 h after feeding and accumulated there constantly. The nodes exhibited the most intensive Cd accumulation in the shoot and Cd transport from the basal nodes to crown root was observed. We concluded that the nodes are the central organ where xylem-to-phloem transfer occurs and play a pivotal role in the half-day travel of Cd from the soil to the grains.