Non-invasive imaging of sodium dynamics in common reed using positron-emitting tracer imaging system

Suzui, Nobuo; Maruyama, Teppei*; Kawachi, Naoki; Miwa, Eitaro*; Higuchi, Kyoko*; Fujimaki, Shu

Common reed, which is classified to the same family as rice, is a salt-tolerant plant. In this study, we conducted non-invasive imaging of Na dynamics in intact common reed plants by using Na tracer and a positron-emitting tracer imaging system (PETIS) in order to understand the salt-tolerant mechanism in common reed. Common reeds and rice plants were cultivated in a nutrient solution containing 50 mM NaCl. After Na was fed into the solution, we observed the Na movement from the solution to the shoot for 24 h using PETIS. As a result, Na was strongly accumulated in the shoot base but not transported to the upper shoot in common reed, whereas Na was continuously transported to the upper shoot in rice plant. Furthermore, we replaced the original solution with a fresh nutrient solution without Na and traced the Na movement inside the plants for 18 h. Detailed quantitative analysis of the image data revealed that Na migrated downward from the shoot base to the root tip in common reed. These results indicate that common reed has constitutive ability of Na exclusion only in the direction of root tips, and consequently keeps low Na concentration in the upper shoot.