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This study investigated the effect of Cs-137 absorbed from the upper part (surface of leaves and husk) of rice plants and its accumulation in grains. Cesium-137 content in brown rice plants sprayed with Cs-137 onto the plant surface before ear emergence, flowering, and grain filling stages were 5, 109, and 76 Bq/kg, respectively. Comparison of Cs-137 concentration between mature and immature grains revealed that brown rice can easily absorb Cs-137 at the beginning of grain filling.

Using the real-time radioisotope imaging system (RRIS), we present the carbon dioxide gas fixation process of a soybean plant applying the 14C-labeled gas. When 14CO2 gas was supplied to the selected mature leaf, the fixed carbon, photosynthate, was transferred and accumulated to the younger leaves preferentially within 24 h. When 14CO2 gas was supplied to the younger leaves, fixed carbon was hardly moved. In the case of the pods, fixed 14CO2 gas in the leaf was preferentially transferred to the closest pod.

We updated real-time radioisotope imaging system (RRIS) to study photosynthate movement in a large-size plant. Earlier, we used a CsI (Tl) scintillator attached to a fiber optic plate (FOS) to convert radiation into light. However, the scintillator size was fixed as 10 cm × 10 cm, which was too small to observe the entire plant. Moreover, the high cost of FOS makes it hard for other researchers to introduce the system in their facilities. Here, we investigated six types of low-priced plastic scintillators, and demonstrated the movement of 14C-labeled photosynthates in a living plant using the most efficient scintillator instead of FOS.

Contamination of agricultural products by resuspended matter remains a concern in the highly contaminated areas. Radiocesium concentration of spinach cultivated with non-contaminated soil was low in the decontaminated areas, but high in the contaminated areas. The washed plants had relatively lower radiocesium concentration than the unwashed plants. Furthermore, the plants cultivated closer to the ground surface tended to have a higher radiocesium concentration than those cultivated farther from the ground. Therefore, it can be concluded that radiocesium found in the spinach leaves derived from resuspended matter in the air. With further analysis, radiocesium in the resuspended matter was confirmed to be present as particles.

We developed a real-time radioisotope imaging system (RRIS) technique that can nondestructively visualize the element absorption and transport process in plants, using not only positron emitters but also commercially available radioisotopes. In this study, we applied RRIS to analyze light effects on ion movement in rice plants. As tracers, 28Mg, 32P, and 45Ca were used. During the first 5 h, dark/light cycle of 3/7 min were set up; the RRIS needs dark conditions during capturing. When the light was ceased 5 h after supplying each tracer, 32P transport from root to shoot decreased immediately. In contrast, 28Mg and 45Ca transport did not change with light conditions. These results suggest that the P transport is dependent on water flow, whereas Mg and Ca transport are independent of water flow.

We selected and re-categorized the monitoring data opened by the government of Fukushima prefecture focusing on the radiocesium concentrations in four agricultural products, from the data on 90,000 samples analyzed during 3 years. Radioactivity was found to be high during 3 months after the accident because of direct fallout. The internal exposure in the area with the highest contamination area of rice during the first 3 months was calculated and estimated to be 0.75 mSv year−1. The radioactivity in foods products rapidly decreased after 3 months later, but in the case of some forestry products and fish, there are still some products in which radioactivity was above the regulated value, 100 Bq kg−1.

The concentrations of radiocesium in different organs of wild boar inhabiting Iitate, Fukushima were measured, after the Fukushima Daiichi nuclear power plant accident. After dissection, about 24 parts were collected and measured using a NaI gamma ray counter. In 2012, the radiocesium concentration (134Cs and 137Cs) was highest in muscle (approximately 15,000 Bq kg−1) and low in ovary, bone and thyroid gland, indicating large variation among tissues. Radiocesium concentrations in 24 different organs revealed the pattern of distribution of radiocesium in wild boar and indicated its availability in the ecosystem of the forests and villages where the boars matured.

The physiological effects of critical nutrient deficiencies (K, P, N) on the uptake of caesium (Cs) and impact on plant growth has been investigated in rice plants. Growth defects were observed after 2 weeks of a state of nutrient starvation (K, P, or N). However, only K starvation produced increased Cs content in the shoot and the intensive transport to young leaves. These observations support that modification of Cs uptake and transport in rice plants was achieved based on the distinctive physiological effect of K.

We have developed a real-time radioisotope imaging system (RRIS) that can nondestructively trace 14C-labeled chemicals in plants. In an experiment, after feeding 14CO2 to a plant, the plant was fixed inside a box where lighting was regulated, and beta rays emitted from the 14C in the plant were intermittently imaged using the developed system. As a first step, using a series of standard sources of 14C, the data depth and detection limits of the 14C images captured by the RRIS were evaluated for various integral times. As a result, the linearity between the 14C activity and signal intensity was determined for the range 103. Next, the linearity was validated using plant (Arabidopsis thaliana) organs, resulting that the linearity was shown in the case of young leaf, but was not maintained in the thick organs, such as a flower, mature leaf, siliques, and stem. Considering the good correlation between the intensity by RRIS and the PSL value by an imaging plate (IP) as well as the relative low energy of beta rays emitted from 14C, the thickness of the organs would easily affect the quantitativity of the RRIS as well as an IP. Our findings prove that sequential images of 14C in a living plant sample in a regulated light and air environment can be nondestructively analyzed using the developed system, whose quantitativity is similar to that of an IP.

We present how radioactive Cs was deposited on wheat, rice, peach tree and soil after nuclear accident in Fukushima. The deposition of radioactive Cs was found as spots at the surface of the leaves, branch or trunk of the trees, as well as in soil using one of the imaging method, autoradiography. The deposited radioactive Cs was not easily washed out, even with the treatment of acid solution. When the wheat was harvested 2 months after the accident, high radioactivity of Cs was found only on the leaves developed and expanded at the time of the accident. In the case of the rice grain, most of the radioactivity was found in bran and the radioactivity was drastically reduced in milled rice. Most of the radioactive Cs accumulation in rice plants was estimated from the absorption of the Cs ion dissolved in water, rather than Cs adsorbed in soil.

A new real-time radioisotope imaging system (RRIS) to study the kinetics of nutrient uptake and transfer of photosynthetic products in a living plant was developed and evaluated through a test run. 14C is a common radioisotope of carbon and useful to trace the photosynthetic products as well as a low energy beta emitter. The rationale of this study was to develop a RRIS that has the ability to detect low energy beta emitters, such as 14C, 35S, and 45Ca. To achieve compatibility between the detection of low energy beta emitters and irradiation of the test plant, an intermittent lighting system was added to the RRIS. Furthermore, a commercially available digital camera was added to the RRIS for acquisition of photographic images of the test plants. The capabilities of the new RRIS were evaluated through a test run by using seedlings of rice plants and 35S-labeled sulfate. It was shown that the new RRIS was able to detect 35S absorbed by rice plant seedlings, and it was able to acquire photon-counting images and photographic images of the test plants simultaneously. Despite some limitations, the new RRIS provides a means to study the kinetics of elements in plants by utilizing low energy beta emitters.

As an approach to increased production of rape seed oil from Brassica napus L., Arabidopsis thaliana, a species from the same Brassicaceae family, was used to investigate transport behavior and distribution of matter in the plant body. In this study, sucrose, an initial metabolic product of photosynthesis, labeled with carbon-14 was used. The sucrose was applied to A. thaliana via the surface of a rosette leaf. Using the real time radioisotope imaging system we developed and an imaging plate (IP), images of whole or part of the sample were obtained. The sucrose assimilation products were accumulated in maturing tissue such as flowers and fruits, and in a joint part. From the comparison among branches and stems, it was indicated that there were different patterns of demand and distribution of sucrose assimilation products depending on the tissue and its growing stage. This might be caused by either morphological reason such as diameter and location of the sieve tube, or genetic factors such as an activity of a membrane transport protein. Because of self-absorption of carpels, it was difficult to observe the accumulation of carbon-14 in the seeds inside the fruits; however, an IP image of a frozen section of a fruit revealed that carbon-14 transport to seeds was higher than that of carpels. These methods will help us gain insight into matter transport and strategies to improve the production of rape seed oil.

The magnesium (Mg) uptake of rice seedlings treated with different pH solutions was investigated using tracer of 28Mg. The application of 28Mg enabled the determination of Mg uptake amount within 15 min of the different pH treatments. The uptake amount of 28Mg and its distribution in rice plants were determined by using the imaging plate. The result demonstrated that the Mg uptake amount was approximately 3 mu mol/15 min per plant in 0.27 mM Mg solution at pH 5.6, and this uptake decreased by 30 % at lower pH conditions (pH 4.5). On the contrary, the pH 6.5 condition induced the Mg uptake activity to 4.4 mu mol/15 min. The inverse relationship found between proton concentration in nutrient solution and the Mg uptake amount within 15 min of treatment demonstrated that the low pH condition could inhibit the Mg uptake activity as a consequence of the competition between Mg2+ and proton. It is concluded that under low pH conditions, regardless of other factors, there is a decrease of Mg uptake activity in rice roots.

The mineral composition of frozen food of taro [Colocasia esculenta (L.) Schott] was analyzed to categorize the geographical production place of taro. The concentrations of Co and H2PO4− were found to be useful to separate the producing place between Japan and China. The analysis was performed by instrumental neutron activation analysis (INAA) and ion chromatography (IC). In the case of INAA, the samples were dried and sealed in a vinyl bag and irradiated with thermal neutrons from JRR3M, installed at Japan Atomic Energy Agency (JAEA). The activated samples were cooled down for a few weeks and the elements (Co, Cr, Fe, Rb, Zn) were determined. Cobalt concentration of frozen taro from China was higher than that from Japan. The tendency was the same in the fresh sample of taro. When concentration of H2PO4− of frozen sample was measured, taro from Japanese product was higher than that of Chinese one, contrary to fresh sample. This result might be caused by the leakage of H2PO4− during freezing process, indicating that we should be careful to apply the discrimination indicators. In addition to Co, there was a significant difference of Rb and Fe concentrations between frozen taro from Japan and China.

We present the real-time RI imaging and analyzing system to study the kinetics of nutrient uptake manner in a living plant. The system allowed light condition for the up-ground part of the plant and continuous dark condition for the root part, therefore, light/dark cycles was set as 16/8 h. There was 9,000 lx of LED lights in an aluminum container where the plant was set. The container was shielded well so that there was no light leakage to damage highly sensitive CCD camera which detected beta-rays from the sample. With this system, RI imaging was able to perform for 6 days without damaging the activity of the plant.

We present real-time imaging of 32P-phosphate within a living plant as well as that in culture solution toward roots. The above-ground part of the plant was irradiated with light from LED and roots were kept in dark. The plant was Lotus japonicus, cv. Miyakojima MG20 and real-time 32P-phosphate uptake manners in young, flowering and adult phase were visualized. In the case of young plant, there was a preferential translocation of 32P in younger leaves. When the sample was treated with phosphate deficient condition, 32P uptake amount was much higher. In an adult phase, 32P uptake was high at pods.

We carried out instrumental neutron activation analysis (INAA) as well as k 0-based prompt gamma-ray analysis (k 0-PGA) to measure the amount of the elements in onions and studied whether the onions collected from different sites can be categorized based on the elemental concentration profile. Six elements (Na, Mg, Cl, K, Ca, Mn) and 3 elements (B, S, Cl) were measured by INAA and PGA in the onions grown in two districts, Hokkaido and Saga, in Japan, respectively. After principal component analysis, it was found that Cl was an important element to feature the producing districts of onions.

We present chemometric study to identify the provenance of agricultural product, beef. Combination of instrumental neutron activation analysis (INAA) and prompt gamma-ray analysis (k 0-PGA) were performed to determine 10 elements, C, H, N, S, Sm, Br, Mg, Na, K, Cl, nondestructively. We measured elemental profiles in beef samples produced from different districts in Japan, Australia and USA. In the case of PGA, k 0-method was employed to determine the elemental concentrations. There was a difference in elemental profiles between Japanese black cattle beef and that produced in USA through principal component analysis (PCA). However, Holstein beef of Japan and that of Australia was not sufficiently grouped by the PCA modeling with the elemental data set. This is the first study to identify the provenance of beef through elemental analysis.

To study the effect of rhizosphere pH condition on the cadmium uptake movement, 109Cd, was applied as a radioisotope tracer to a soybean plant grown in a water culture at pH 4.5 or pH 6.5. The distribution of 109Cd in the soybean plant was observed radiographically with an imaging plate (IP). The amount of Cd transported from the root to the upper part of the plant at pH 4.5 was approximately two times higher than that at pH 6.5. However, the movement of Cd in the upper part of the plant was similar under both pH conditions. The distribution of Cd inside the internodes at pH 4.5 also showed similar pattern to that at pH 6.5, suggesting that once Cd reached to the vessel of the root, the movement of Cd was not dependent on rhizosphere pH conditions.

We developed a quantitative, real-time imaging system of labeled compounds in a living plant. The system was composed of CsI scintillator to convert β-rays to visible light and an image intensifier unit (composed of GaAsP semiconductor and MCP; micro channel plate) to detect extremely weak light. When the sensitivity and resolution of the image of our system was compared with that of an imaging plate (IP), the sensitivity of our system (with 20 minutes) was higher than that of an IP, with similar quality to that of an IP. Using this system, the translocation of 32P in a soybean plant tissue was shown in successive images.

Elemental concentration in each tissue of Japanese morning-glory (Pharbitis nil) during the growth was analyzed by INAA. Plants were grown in water culture for 4 days under 12-hour light and 12-hour dark condition. During the growth, 10 plants in the same developmental stage were periodically harvested. Then the plants were separated into 9 tissues to determine elemental concentration and water content. There was an elemental specific profile within the plant tissue, for example, Na and K concentrations were high in root whereas Mg and Ca concentrations were high at the upper part of the plants. Among the elements studied, Ca and Mg showed rhythmical change in concentration, increased during the day and decreased during the night. This tendency was especially noted at shoot apex. However, water content in all of the tissue was increased about 6 hours prior to the light period and showed maximum in the middle of the light period. About 6 hour difference of water content movement to those of Ca and Mg concentration suggested that water movement drives more dynamic change of each elemental concentration within a plant.

We present a new trial to measure real time water movement in a living plant using the positron emitting radionuclide, 15O. 15O was prepared by 14N(d,n)15O reaction and 10 ml of 15O labeled water (2 GBq) was supplied from the root of a soybean plant. To detect activity, an imaging plate (IP) as well as a BGO detector system were used. Since the half-life of 15O is extremely short, (T1/2= 122 s), water uptake measurement was performed only for 20 minutes. In order to get [15O]waterimage, an IP was exposed to the plant for 1 minute for two times. Since the exposure to an IP requires dark condition, a BGO detector system was developed to measure [15O]waterunder light condition. A couple of BGO probes was set at the lowest stem and the gamma-rays (0.511 MeV) emitted from the radionuclide were measured through coincidence counting and compared with the radioactivity measured from an IP image. Using this system, we have found that the water uptake activity of the plant was drastically reduced under high humidity (99%) and dark condition.

We present water imaging of a plant sample both by neutron beam and positron emission tracer imaging system (PETIS). The former method provided static water profile in a plant sample as well as that in the vicinity of a root imbedded in soil. Not only X-ray film but also CT method using a cooled CCD camera is presented. Through non-destructive water image in an X-ray film, root development as well as 2-dimensional water movement toward the root was analyzed. Spatial water image was constructed from 180 CT projection images, taken at an interval of one degree while rotating the sample, through a CCD camera. In the case of a soybean root, there was a water gradient toward a root in soil and gave minimum value at about 1 mm far from the surface of a root. The water absorbing part in a root was gradually shifted downward with the root development. We also present real time water movement by PETIS, where water was labeled with a positron emitting nuclide, 15O. The transportation of 15O-water within a plant was relatively slow and water uptake was observed only at the lowest internode, between a root and the first leaf, during 20-minute measurement.

We have analyzed 16 elements and the radioactivity of 210Pb in a wood disk, across the annual rings to find out a promising tool for dendrochronology (chronology of wood) both for a Japanese wood, Cryptomeria japonica, and for an Indonesian rain forest wood, Alstonia, which does not form annual rings because of the relatively constant climate of the rain forest. As a result, only Mg concentration showed similar, smooth decreasing tendency in both wood species. The smooth change of the Mg concentration across the annual rings along with the growth suggested the possibility of the Mg concentration determination as a promising dendrochronological tool.

The time course of Mg uptake and release using intact rice plants and 28Mg as a tracer is presented. Since there is no conventional Mg tracer available, 28Mg was produced via 27Al(alpha, 3p)28Mg reaction using a cyclotron. Using the purified 28Mg tracer, it was found that the uptake amount of 28Mg by the rice plants increased linearly during 30 min of application. After 28Mg treatment for 90 min, the roots were sequentially washed with iced solution for 120 min. Within about 10 min, almost all of the 28Mg, that was thought to be weakly bound to the apoplast, was washed away.

In the study of aluminum toxicity for plant, it is important to analyzethe behavior of Al in cells. We present how Al is taken up by tobacco cellsthrough lumogallion staining method developed by our laboratory. The fluorescenceintensity from the cell was increased rapidly between 4 and 8 hours of 1 mMAl treatment. To calibrate the fluorescence intensity from Al-lumogallioncomplex, Al amount in the cell was determined by NAA. When the same samplewas analyzed by ICP-AES, Al amounts in all the samples were 13% lower thanthose measured by NAA.

We present real time vanadate (V5+ ) uptake imaging in acowpea plant by positron emitting tracer imaging system (PETIS). Vanadium-48was produced by bombarding a Sc foil target with 50 MeV α -particlesat Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) AVFcyclotron. Then 48 V was added to the culture solution to investigatethe V distribution in a cowpea plant. The real time uptake of the 48V was monitored by PETIS. We measured the distribution of 48Vin a whole plant after 3, 6 and 20 hours of V treatment by Bio-imaging AnalyzerSystem (BAS). After the 20 hour treatment, vanadate was detected at the up-groundpart of the plant. To know the effect of V uptake on plant activity, 18F-labeled water uptake was analyzed by PETIS. When a cowpea plantwas treated with V for 20 hours before 18 F-labeled water uptakeexperiment, the total amount of 18F-labeled water absorption wasdrastically decreased. Results suggest the inhibition of water uptake wasmainly caused by the vanadate already moved to the up-ground part of the plant.