Autoradiography system with phosphor powder (ZnS:Ag) for imaging radioisotope dynamics in a living plant

Abstract

Radioisotope tracer imaging is useful for studying plant physiological phenomena. In this study, we developed an autoradiography system with phosphor powder (ZnS:Ag), “Live-autoradiography”, for imaging radioisotope dynamics in a living plant. This system visualizes the element migration and accumulation in intact plants continuously under a light environment. An imaging test was performed on point sources of 137Cs, with radioactivity of 10–100 kBq of being observed; this indicates satisfactory system linearity between the image intensity and the radioactivity of 137Cs. Moreover, dynamics imaging of 137Cs was performed on an intact soybean plant for four days. The serial images indicated 137Cs accumulation in the node, vein, and growing point of the plant. The developed system can be used for studying plant physiological phenomena and can be employed for the quantitative measurement of radionuclides.

“Live-Autoradiography” Technique Reveals Genetic Variation in the Rate of Fe Uptake by Barley Cultivars

“…Live-autoradiography has been previously reported to successfully detect 37 Cs in a plant body [ 15 ], but the luminescence efficiency was not sufficient to detect smaller amounts of radioactive tracers in plants, which is necessary for future high-throughput applications. Therefore, the original system was modified prior to phenotyping.…”

“…The original system can obtain an image of only one plant at a time using an L-shaped dark box [ 15 ]. The extension of the detection field using a T-shaped black box equipped with two fluorescent plates enabled us to observe the two plants simultaneously ( Figure 1 b).…”

“…To examine whether the Fe-deficiency-tolerant cultivars had a great ability to localize the Fe newly acquired by roots to the newest leaves, which have a high demand for Fe to construct photosystems under Fe-deficient conditions, 59 Fe tracer experiments were performed. Using live-autoradiography [ 15 ], we estimated the influx rate of 59 Fe into each leaf of living barley under light conditions and thus measured the actual rate of Fe absorption ( Figure 3 a); 0.5 MBq of 59 Fe as 1.24 nM Fe-citrate was applied to one plant without non-radioactive Fe. Because active Fe transport systems in roots were not induced under Fe-sufficient conditions, radioactivity in Fe-sufficient leaves was detected only at trace levels (data not shown).…”

“…The β-rays emitted from the tracers were converted to light by a CsI scintillator, and the light was detected by a highly sensitive cooled charge-coupled device (CCD) camera. The dynamics of various β-ray-emitting nuclides in living Arabidopsis plants were visualized in a previous study using RRIS [ 14 ], and a new β-ray imaging system called “live-autoradiography” has been developed recently [ 15 ]. This system has the advantage of flexibility in the shape of the field of view, because it uses ZnS:Ag phosphor powder as the scintillator.…”

“…In this study, the rate of Fe uptake from a nanometer-order Fe solution was compared among the three barley cultivars using live-autoradiography. The system was equipped with a 100 × 100 mm imaging field, as originally described [ 15 ]. In the current study, two 200 × 200 mm fluorescent plates were used to improve the throughput.…”