Real-time imaging and analysis of differences in cadmium dynamics in rice cultivars () using positron-emitting Cd tracer

Ishikawa, Satoru*; Suzui, Nobuo; Ito, Sayuri*; Ishii, Satomi; Igura, Masato*; Abe, Tadashi*; Kuramata, Masato*; Kawachi, Naoki; Fujimaki, Shu

In this study, we have visualized and quantitatively analysed the real-time Cd dynamics from roots to grains in typical rice cultivars that differed in grain Cd concentrations. We used positron-emitting Cd tracer and an innovative imaging technique, the positron-emitting tracer imaging system (PETIS). In particular, a new method for direct and real-time visualization of the Cd uptake by the roots in the culture was first realized in this work. Imaging and quantitative analyses revealed the different patterns in time-varying curves of Cd amounts in the roots of rice cultivars tested. Three low-Cd accumulating cultivars (japonica type) showed rapid saturation curves, whereas three high-Cd accumulating cultivars (indica type) were characterized by curves with a peak within 30 min after Cd supplementation, and a subsequent steep decrease resulting in maintenance of lower Cd concentrations in their roots. Moreover, the PETIS analyses revealed that the high-Cd accumulating cultivars were characterized by rapid and abundant Cd transfer to the shoots from the roots, a faster transport velocity of Cd to the panicles, and Cd accumulation at high levels in their panicles, passing through the nodal portions of the stems where the highest Cd intensities were observed.