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論文

Imaging of radiocesium dynamics in soybean by using a high-resolution gamma camera

尹 永根; 河地 有木; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 112, 2016/02

Large areas of agricultural fields were contaminated with radiocesium ($$^{134}$$Cs and $$^{137}$$Cs) in Japan by the accident of The Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station in March 2011. Many agricultural studies, such as fertilizer management and plant breeding, are undertaken for reducing radiocesium uptake in crops or enhancing of uptake and transportation via phytoremediation. These studies examine the control of radiocesium transport into/within plant bodies from the viewpoint of plant physiology. Radiotracer imaging is one of the few methods that enable the observation of the movement of substances in a living plant, like a video camera, without sampling of the plant tissues. In this study, we performed the imaging of $$^{137}$$Cs uptake and transport from root to aerial part by using a new gamma camera in intact soybean plants because contamination of soybean by radiocesium has currently become a major problem in agriculture in Fukushima.

論文

Development of a gamma camera system for high-energy gamma photon for quantitative observation of $$^{137}$$Cs movement in a plant body

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 94, 2016/02

We developed an original gamma camera system to image radiocesium in a plant. The gamma camera was designed for high-energy gamma photons from $$^{137}$$Cs radiocesium (662 keV). We performed tests to evaluate the position resolution and quantitative linearity of the gamma camera. The best spatial resolution of this gamma camera was determined to be 19.1 mm in full width at half maximum at the center of the field-of-view. And a result shows a quantitative linearity of the image data with a correlation of ${it r$^{2}$}$ = 0.9985 between the source activity and the count rate. We conclude the gamma camera system has sufficiently high capability to obtain quantitative and dynamic images of $$^{137}$$Cs movement in intact plants.

論文

Evaluation of the effect of elevated concentrations of CO$$_{2}$$ in a greenhouse for tomato cultivation

石井 里美; 山崎 治明*; 鈴井 伸郎; 尹 永根; 河地 有木; 島田 浩章*; 藤巻 秀

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 93, 2016/02

Tomato is popularly grown in environmentally controlled system such as a greenhouse for improvement of bioproduction. It is important to control the condition in the greenhouse for increasing the translocation of fixed carbon from the leaves to the growing fruits. Elevation of CO$$_{2}$$concentration is widely employed for that purpose; however, it is difficult to estimate its effect quantitatively because tomato plants have too large inter-individual variations with developing fruits. In this study, we employed a PETIS which is a live-imaging system of nutrients in plant body using short-lived radioisotopes including $$^{11}$$C. We also established a closed cultivation system to feed a test plant with CO$$_{2}$$ at set concentrations of 400, 1,500 and 3,000 ppm and a pulse of $$^{11}$$CO$$_{2}$$.

論文

Imaging of radiocesium uptake dynamics in a plant body by using a newly developed high-resolution gamma camera

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

Journal of Environmental Radioactivity, 151(Part 2), p.461 - 467, 2016/01

 被引用回数:5 パーセンタイル:55.17(Environmental Sciences)

We developed a new gamma camera specifically for plant nutritional research and successfully performed live imaging of the uptake and partitioning of $$^{137}$$Cs in intact plants. The gamma camera was specially designed for high-energy $$gamma$$ photons from $$^{137}$$Cs (662 keV). To obtain reliable images, a pinhole collimator made of tungsten heavy alloy was used to reduce penetration and scattering of $$gamma$$ photons. The array block of the GAGG scintillator was coupled to a high-quantum efficiency position sensitive photomultiplier tube to obtain accurate images. The completed gamma camera had a sensitivity of 0.83 count s$$^{-1}$$ MBq$$^{-1}$$ for $$^{137}$$Cs, and a spatial resolution of 23.5 mm. We used this gamma camera to study soybean plants that were hydroponically grown and fed with 2.0 MBq of $$^{137}$$Cs for 6 days to visualize and investigate the transport dynamics in aerial plant parts. $$^{137}$$Cs gradually appeared in the shoot several hours after feeding, and then accumulated preferentially and intensively in growing pods and seeds; very little accumulation was observed in mature leaves. Our results also suggested that this gamma-camera method may serve as a practical analyzing tool for breeding crops and improving cultivation techniques resulting in low accumulation of radiocesium into the consumable parts of plants.

論文

Live-imaging evaluation of the efficacy of elevated CO$$_{2}$$ concentration in a closed cultivation system for the improvement of bioproduction in tomato fruits

山崎 治明*; 鈴井 伸郎; 尹 永根; 河地 有木; 石井 里美; 島田 浩章*; 藤巻 秀

Plant Biotechnology, 32(1), p.31 - 37, 2015/04

 被引用回数:2 パーセンタイル:79.96(Biotechnology & Applied Microbiology)

To maximize fruit yield of tomatoes cultivated in a controlled, closed system such as a greenhouse or a plant factory at a limited cost, it is important to raise the translocation rate of fixed carbon to fruits by tuning the cultivation conditions. Elevation of atmospheric $$^{11}$$CO$$_{2}$$ concentration is a good candidate. In this study, we employed a positron-emitting tracer imaging system (PETIS), which is a live-imaging technology for plant studies, and a short-lived radioisotope $$^{11}$$C to quantitatively analyze immediate responses of carbon fixation and translocation in tomatoes in elevated CO$$_{2}$$ conditions. We also developed a closed cultivation system to feed a test plant with CO$$_{2}$$ at concentrations of 400, 1500 and 3000 ppm and a pulse of $$^{11}$$CO$$_{2}$$. As a result, we obtained serial images of $$^{11}$$C fixation by leaves and subsequent translocation into fruits. Carbon fixation was enhanced steadily by increasing the CO$$_{2}$$ concentration, but the amount translocated into fruits saturated at 1500 ppm on average. The translocation rate had larger inter-individual variation and showed less consistent responses to external CO$$_{2}$$ conditions compared with carbon fixation.

論文

Evaluation of velocity of $$^{11}$$C-photoassimilate flow using positron-emitting tracer imaging system

鈴井 伸郎; 河地 有木; 石井 里美; 尹 永根; 岩崎 郁*; 小川 健一*; 藤巻 秀

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 105, 2015/03

In this study, we developed an analytical method to evaluate velocity of photoassimilate flow using $$^{11}$$C-tracer and the positron-emitting tracer imaging system (PETIS). $$^{11}$$CO$$_{2}$$ gas tracer was fed to the compound leaves of the soybean plant, and serial images of $$^{11}$$C distribution were obtained by PETIS. Regions of interests (ROIs) were set in the node of the first compound leaf (ROI-1) and the stem base (ROI-2). Time course of $$^{11}$$C-radioactivity (Time-Activity Curve: TAC) in each ROI was generated from the serial images. Initial slope of the rising $$^{11}$$C-radioactivity was estimated by a linear least-square method using the TAC data. The value of the intercept of approximated line to the background line (X-intercept) was defined as "$$^{11}$$C-arrival time" to the ROIs. In order to determine X-intercept with a fair criterion, we developed an analytical program. The velocities of $$^{11}$$C-photoassimilate flows of 18 individual soybean plants were estimated by the values of $$^{11}$$C-arrival time and the distance between ROI-1 and ROI-2. As a result, the average value of the velocity was 113 cm h$$^{-1}$$ and the standard deviation was 20 cm h$$^{-1}$$. This result indicates the newly developed method is a reliable tool for the quantitative analysis of photoassimilate flow through the phloem.

論文

Effects of glutathione concentration in the root zone and glutathione treatment period on cadmium partitioning in oilseed rape plants

中村 進一*; 近藤 ひかり*; 鈴井 伸郎; 尹 永根; 石井 里美; 河地 有木; 頼 泰樹*; 服部 浩之*; 藤巻 秀

Molecular Physiology and Ecophysiology of Sulfur, p.253 - 259, 2015/00

 被引用回数:1 パーセンタイル:37.03

Glutathione is a sulfur-containing peptide involved in various aspects of plant metabolism. Glutathione is also known to have effects on heavy metal responses in plants. In our previous work, we have found glutathione, applied to roots site- specifically, inhibited cadmium (Cd) translocation from roots to shoots and Cd accumulation in shoots in oilseed rape plants. In addition, we succeeded in visualizing inhibition of root-to-shoot translocation of Cd by using a positron-emitting tracer imaging system (PETIS). In this work, the effects of glutathione concentration in the root zone (hydroponic solution) and the glutathione treatment period on Cd partitioning in oilseed rape plants were investigated. Our experimental results demonstrated that glutathione, exceeding a certain concentration in the root zone, is needed to trigger inhibition of Cd translocation, and that treatment time from the start of glutathione application had different effects on Cd partitioning in oilseed rape plants.

論文

From laboratory to field; ${it OsNRAMP5}$-knockdown rice is a promising candidate for Cd phytoremediation in paddy fields

高橋 竜一*; 石丸 泰寛*; Shimo, H.*; Bashir, K.*; 瀬野浦 武志*; 杉本 和彦*; 小野 和子*; 鈴井 伸郎; 河地 有木; 石井 里美; et al.

PLOS ONE (Internet), 9(6), p.e98816_1 - e98816_7, 2014/06

 被引用回数:12 パーセンタイル:32.61(Multidisciplinary Sciences)

Previously, we reported that OsNRAMP5 functions as a manganese, iron, and cadmium (Cd) transporter. The shoot Cd content in ${it OsNRAMP5}$ RNAi plants was higher than that in wild-type (WT) plants, whereas the total Cd content (roots plus shoots) was lower. For efficient Cd phytoremediation, we produced ${it OsNRAMP5}$ RNAi plants using the natural high Cd-accumulating cultivar Anjana Dhan (A5i). Using a positron-emitting tracer imaging system, we assessed the time-course of Cd absorption and accumulation in A5i plants. Enhanced $$^{107}$$Cd translocation from the roots to the shoots was observed in A5i plants. To evaluate the phytoremediation capability of A5i plants, we performed a field experiment in a Cd-contaminated paddy field. The biomass of the A5i plants was unchanged by the suppression of ${it OsNRAMP5}$ expression; the A5i plants accumulated twice as much Cd in their shoots as WT plants. Thus, A5i plants could be used for rapid Cd extraction and the efficient phytoremediation of Cd from paddy fields, leading to safer food production.

論文

A Kinetic analysis of cadmium accumulation in a Cd hyper-accumulator fern, ${it Athyrium yokoscense}$ and tobacco plants

吉原 利一*; 鈴井 伸郎; 石井 里美; 北崎 真由*; 山崎 治明*; 北崎 一義*; 河地 有木; 尹 永根; 七夕 小百合*; 橋田 慎之介*; et al.

Plant, Cell & Environment, 37(5), p.1086 - 1096, 2014/05

 被引用回数:11 パーセンタイル:39.28(Plant Sciences)

Cadmium (Cd) accumulations in a Cd hyper-accumulator fern, ${it Athyrium yokoscense}$ ($$Ay$$), and tobacco, ${it Nicotiana tabacum}$ ($$Nt$$), were kinetically analysed using the positron-emitting tracer imaging system under two medium conditions (basal and no-nutrient). In $$Ay$$, maximumly 50% and 15% of the total Cd accumulated in the distal roots and the shoots under the basal condition, respectively. Interestingly, a portion of the Cd in the distal roots returned to the medium. In comparison with $$Ay$$, a little fewer Cd accumulations in the distal roots and clearly higher Cd migration to the shoots were observed in $$Nt$$ under the basal condition (maximumly 40% and 70% of the total Cd, respectively). The no-nutrient condition down-regulated the Cd migration in both species, although the regulation was highly stricter in $$Ay$$ than in $$Nt$$ (almost no migration in $$Ay$$ and around 20% migration in $$Nt$$). In addition, the present work enabled to estimate physical and physiological Cd accumulation capacities in the distal roots, and demonstrated condition-dependent changes especially in $$Ay$$. These results clearly suggested occurrences of species-/condition-specific regulations in each observed parts. It is probable that integration of these properties govern the specific Cd tolerance/accumulation in $$Ay$$ and $$Nt$$.

論文

Whole-plant imaging of $$^{107}$$Cd distribution using positron-emitting tracer imaging system

鈴井 伸郎; 尹 永根; 井倉 将人*; 石井 里美; 河地 有木; 石川 覚*; 藤巻 秀

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 101, 2014/03

We have conducted noninvasive imaging of cadmium (Cd) in intact plants using a positron-emitting tracer imaging system (PETIS) and $$^{107}$$Cd for the purpose of understanding the mechanism of Cd translocation in plants. In our typical imaging experiment, $$^{107}$$Cd tracer has been fed to the root of large plants such as rice, and obtain the serial images of $$^{107}$$Cd distribution in the underground parts (roots and culture solutions) or the aerial parts (shoots or grains). However, whole-plant images of $$^{107}$$Cd distribution in both underground and aerial parts have not been obtained because the field of view (FOV) of PETIS is limited. In this study, we fed $$^{107}$$Cd to dwarf plants, ${it Sedum plumbizincicola}$ and visualized Cd dynamics in a whole plant within the FOV of PETIS. As a result, the whole physiological process, i.e., uptake from culture solution, translocation from root to shoot and accumulation in shoot, were successfully visualized in the single imaging experiment. The time courses of Cd amounts demonstrated that the half amount of Cd fed to the solution was taken up by the root within 2 hours, and the two-thirds amount was accumulated in the shoot after 30 hours. These results imply the whole-plant imaging represents a reliable tool for the quantitative analysis of Cd dynamics.

論文

Production of $$^{13}$$N-labeled nitrogen gas tracer for the imaging of nitrogen fixation in soybean nodules

石井 里美; 井倉 将人*; 尹 永根; Hung, N. V. P.*; 鈴井 伸郎; 河地 有木; 小柳 淳*; 大山 卓爾*; 藤巻 秀

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 98, 2014/03

Nitrogen is the most important nutrient for the plants. Soybean can utilize nitrogen from atmospheric N$$_{2}$$ fixed by nodules which are symbiotic organs of leguminous plants with rhizobia. In the beginning of this research project, we set our methodological goal to visualize and analyze the nitrogen fixation in the nodules and subsequent nitrogen transport to the aerial part in a plant using $$^{13}$$N and PETIS. Previously, we have developed a method of production of highly purified $$^{13}$$N-labelled nitrogen gas tracer using gas chromatography and successfully visualized nitrogen fixation in intact nodules. However, the yields of the tracer were only a few ten megabecquerels and too low to visualize the transport of fixed nitrogen to the aerial part. Therefore, we have been trying to improve the production method to gain much higher radioactivity with consideration of the very short half-life of [$$^{13}$$N]N$$_{2}$$. In this study, we tested a new technique to turn the main by-product [$$^{13}$$N]N$$_{2}$$O into the desired product [$$^{13}$$N]N$$_{2}$$ directly.

論文

Analysis of the effect of O$$_{2}$$ partial pressure on nitrogen fixation in soybean plant using positron-emitting tracer

Hung, N. V. P.; 石井 里美; 鈴井 伸郎; 河地 有木; 尹 永根; 小柳 淳; 大山 卓爾*; 藤巻 秀

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 99, 2014/03

ダイズの根粒における共生的窒素固定に対する周辺空気の組成、とくに酸素分圧の及ぼす影響について解析するために、ポジトロンイメージング(PETIS)による画像化と解析を行った。窒素13ガスを製造、精製し、所定の酸素分圧となるようにトレーサガスを調製した。これをダイズ根粒に10分間投与し、PETISによりイメージングを行った。減衰を待ち、同一個体を対象に、酸素分圧を変えて(0%, 10%, 20%)実験を繰り返し、合計3回の実験を行った。各実験回において根粒が窒素を固定する動画像が得られ、これらのデータを解析したところ、酸素分圧が通常の20%から10%に低下した場合、窒素固定活性も顕著に低下するが、その程度は0%の場合とさほど変わりないことが明らかになった。

論文

RI imaging method to analyze a process of radiocesium contamination of plants and to develop phytoremediation techniques

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 渡部 浩司*; 山本 誠一*; 藤巻 秀

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 100, 2014/03

Because of the accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company, Inc., an extensive area of agricultural fields was contaminated with radioactive materials. Cs-137 is the most of soil contaminant, which was reported to have a 16 - 18 years half-life in agricultural fields affected by physical decay and soil erosion. Therefore, further research is required on the behavior of radiocesium and its transfer from contaminated soil to agricultural products. In this study, we have developed a gamma camera for $$gamma$$ ray imaging of Cs-137 emitting at 662 keV. A pinhole collimator was fabricated with heavy metal of tungsten to avoid the penetration and scattering of $$gamma$$ rays, since high-energy incident $$gamma$$ ray originates from Cs-137 tracer inside a test plant. A gadolinium oxyorthosilicate (GSO) scintillator and a flat panel position sensitive photomultiplier tube were adapted to the gamma camera to obtain adequate high sensitivity. Giant knotweed, which has potential as a cleanup plant with high uptake capacity for cesium, was grown in hydroponic solutions. After exposed to approximately 400 kBq of Cs-137, images were taken for 15 h. Sequential images reveal the changing distribution of cesium into the plant from the hydroponic solutions via the root system. We have indicated real-time visualization of uptake of radiocesium within an intact plant in the first time successfully.

論文

Quantitative analysis of the initial transport of fixed nitrogen in nodulated soybean plants using $$^{15}$$N as a tracer

Hung, N. V. P.*; 渡部 詩織*; 石川 伸二*; 大竹 憲邦*; 末吉 邦*; 佐藤 孝*; 石井 里美; 藤巻 秀; 大山 卓爾*

Soil Science and Plant Nutrition, 59(6), p.888 - 895, 2013/12

 被引用回数:2 パーセンタイル:86.52(Plant Sciences)

The quantitative analysis of the initial transport of fixed $$^{15}$$N in intact nodulated soybean plants was investigated at the vegetative stage and pod-filling stage by the $$^{15}$$N pulse-chase experiment. The nodulated roots were exposed to N$$_{2}$$ gas labeled with a stable isotope $$^{15}$$N for 1 hour. Plant roots and shoots were separated into three sections with the same length of the main stem or primary root. Approximately 80% and 92% of fixed N was distributed in the basal part of the nodulated roots at vegetative and pod-filling stage the end of 1 hour of $$^{15}$$N$$_{2}$$ exposure, respectively. In addition, about 90% of fixed $$^{15}$$N was retained in the nodules and 10% was exported to root and shoot after 1 hour of $$^{15}$$N$$_{2}$$ exposure at pod-filling stage. The percentage distribution of $$^{15}$$N in the nodules at pod-filling stage decreased from 90% to 7% during the 7 hours of the chase-period, and increased in the roots (14%), stems (54%) leaves (12%), pods (10%), and seeds (4%). The $$^{15}$$N distribution was negligible in the distal root segment, suggesting that nitrogen fixation activity was negligible and recycling fixed N from the shoot to the roots was very low in the initially short time of the experiment.

論文

Imaging of root exudates secreted from soybean root to soil by using carbon-11-labeled carbon dioxide and PETIS

尹 永根; 鈴井 伸郎; 河地 有木; 石井 里美; 山崎 治明; 小柳 淳*; 藤巻 秀

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 92, 2013/01

The root of higher plant has important role in absorb essential nutrients critical to life. On the other hand, the root evolved special abilities to uptake of nutrients from the rhizosphere environment because that is fixed in the soil. As one example, the roots secrete organic acids to surrounding of rhizosphere for solubilization of the insoluble mineral in soil and absorb directly or indirectly of the nutrition. Previously, our group has reported that imaging of cadmium (Cd) uptake from hydroponic culture solution to root for study the mechanism of mineral metabolism by using a positron-emitting tracer imaging system (PETIS) in plant. In this study, we performed the imaging of organic matter which is exudate from root to soil cultivation by using carbon-11-labeled carbon dioxide ($$^{11}$$CO$$_{2}$$) gas tracer with PETIS.

論文

A New method to analyze individual photosynthetic abilities of young plant seedlings using positron-emitting tracer imaging system (PETIS)

河地 有木; 小柳 淳*; 鈴井 伸郎; 石井 里美; 尹 永根; 山崎 治明; 岩崎 郁*; 小川 健一*; 藤巻 秀

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 93, 2013/01

We had employed the positron emitting tracer imaging system (PETIS) in combination with carbon-11- labeled carbon dioxide ($$^{11}$$CO$$_{2}$$) as the tracer gas. In the present study, we have developed a new method based on PETIS and $$^{11}$$CO$$_{2}$$ to evaluate individual photosynthetic abilities of young seedlings planted collectively on a petri dish with agar culture medium and thus investigate the effect of genetic modification or treatment on plant biomass enhancement. We report for the first time a method based on the use of PETIS and tracer gas of $$^{11}$$CO$$_{2}$$ for the quantitative and statistical evaluation of carbon fixation by small plant individuals. We plan to extend this method to the analysis of the relationship between the individual carbon fixation ability and gene expression, which is probably related to photosynthesis.

論文

Real-time imaging and analysis of differences in cadmium dynamics in rice cultivars (${it Oryza sativa}$) using positron-emitting $$^{107}$$Cd tracer

石川 覚*; 鈴井 伸郎; 伊藤 小百合*; 石井 里美; 井倉 将人*; 安部 匡*; 倉俣 正人*; 河地 有木; 藤巻 秀

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 91, 2013/01

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 $$^{107}$$Cd tracer and an innovative imaging technique, PETIS. 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 showed rapid saturation curves, whereas three high-Cd accumulating cultivars were characterized by curves with a peak within 30 min after $$^{107}$$Cd supplementation, and a subsequent steep decrease resulting in maintenance of lower Cd concentrations in their roots. This difference in Cd dynamics may be attributable to OsHMA3 transporter protein, which was recently shown to be involved in Cd storage in root vacuoles and not functional in the high-Cd accumulating cultivars. 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.

論文

NaI(Tl) spectrometerとガンマカメラを駆使した農地汚染問題への取り組み

尹 永根; 鈴井 伸郎; 河地 有木; 山口 充孝; 田野井 慶太朗*; 石井 里美; 中西 友子*; 茅野 充男*; 中村 進一*; 渡部 浩司*; et al.

放射線と産業, (133), p.45 - 48, 2012/12

東京電力福島第一原子力発電所事故から飛散した放射性セシウム(Cs-134, Cs-137)による農地の汚染が深刻な問題となっている。生産者, 消費者双方からの極めて強い関心に伴い、土壌や肥料, 農産物などの放射性セシウムの計測や、農作物における放射性セシウムの追跡と、その動態解明といった研究の取り組みが必要である。そこで本稿では、(1)タリウムヨウ化ナトリウムシンチレーションスペクトロメーター(NaI(Tl) spectrometer)を利用した試料中のCs-134及びCs-137の弁別と定量分析の手法の開発や、(2)Cs-137のイメージングが可能なガンマカメラの開発について、われわれが取り組んできた研究やその成果の内容を紹介する。

論文

作物の窒素栄養獲得機構の研究

石井 里美

放射線と産業, (132), p.17 - 20, 2012/06

「放射線と産業」誌の「RIイメージング技術の環境・農業分野への展開」と題した特集号に掲載されるもので、植物の栄養獲得機構のうち、最も植物の成長に関与する窒素栄養について、これまでにわれわれの研究グループで行われてきた研究を紹介するものである。ポジトロンイメージング技術と$$^{13}$$N標識化合物を用いたさまざまな研究のうち、(1)$$^{13}$$N標識窒素ガストレーサの開発とこれを用いたダイズの共生的窒素固定の画像化及び定量的解析、(2)$$^{13}$$N標識硝酸, $$^{13}$$N標識アンモニアの製造とイネにおけるアンモニア吸収の画像化及び定量的解析、(3)寄生植物オロバンキによる窒素栄養収奪率に関する成果を解説している。

論文

Dose optimization of $$^{107}$$Cd for direct imaging of Cd uptake from culture to root

鈴井 伸郎; 河地 有木; 石井 里美; 山崎 治明; 藤巻 秀

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 95, 2012/01

In an effort to understand the mechanism of cadmium (Cd) accumulation in grains, we have conducted noninvasive imaging of Cd in intact rice plants using a positron-emitting tracer imaging system (PETIS) and $$^{107}$$Cd. Recently, we attempt to obtain the serial images of $$^{107}$$Cd in underground parts, i.e., roots and culture solutions. In this case, the dosage of $$^{107}$$Cd should be optimized because the presence of high radioactivity in the field of view (FOV) of PETIS induces the counting loss of annihilation $$gamma$$-rays, resulting the underestimation of radioactivity. Thus, in this study, we determined the optimal dosage of $$^{107}$$Cd for direct imaging of Cd uptake. $$^{107}$$Cd solution was infused into a flat "phantom" container. This phantom was measured by PETIS for 24 hours while the radioactivity of $$^{107}$$Cd in FOV decayed to 1/13 of its initial value. In the $$^{107}$$Cd phantom, the counting loss was diminished after the radioactivity of $$^{107}$$Cd in FOV decayed to below 8 MBq. On the other hand, we should allow some degree of counting loss at the initial period of imaging in order to obtain the images for kinetic analyses over the longer time period. When 5% of counting loss was allowed, the optimal dosage of $$^{107}$$Cd for the purpose was determined to be 15 MBq.

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