Noninvasive imaging of zinc dynamics in an intact plant using the positron-emitting tracer Zn

Suzui, Nobuo; Yamazaki, Haruaki*; Kawachi, Naoki; Ishii, Satomi; Ishioka, Noriko; Fujimaki, Shu

Zn (half-life: 244 days) is commercially available and frequently used as a zinc tracer in plants. Zn decays with 98.6% by electron capture and 1.4% by positron emission to stable 65Cu. Because of its weak positron emission, Zn was thought to be unsuitable for positron imaging, but there has been no verification of the possibility. In this study, we examined whether positron imaging of zinc is possible using Zn and a positron-emitting tracer imaging system (PETIS). The tracer solution containing 400 kBq Zn was fed to a rice plant ( L.) and the dynamics of Zn in plant was monitored by PETIS. As a result, serial images of Zn distribution were successfully obtained every 5 minutes for 48 hours. In addition, the uptake kinetics (m/max) and the translocation velocity of zinc in plant were determined from the image data. These results indicate that Zn is a suitable radioisotope for noninvasive imaging by PETIS. By taking advantage of the long half-life, Zn translocation can be visualized all through the life of plants. Furthermore, the commercial availability of Zn makes it possible to conduct noninvasive imaging of zinc in facilities without cyclotron, accelerating the research of zinc dynamics in plants.