Atsunori Tsuji

Visualization of 15O-water flow in tomato and rice in the light and dark using a positron-emitting tracer imaging system (PETIS)

Abstract 15P-water flow from the roots to the top in tomato (Lycopersicon esculentum Mill.) and rice (Oryza sativa L.) plants was visualized with time using a positron-emitting tracer imaging system (PETIS). The 15O-water flow was switched on by light and completely stopped in the dark. The flow rate in the stem of tomato and the shoot of rice at a light intensity of 500 μmol·m−2·s−1 was 1.9 and 0.4 cm min−1, respectively.

Production of positron emitters and application of their labeled compounds to plant studies

The positron emitters11C,13N and18F and their labeled compounds have been produced for studies on plants using a newly developed positron emitting tracer imaging system. Although this system covers, at present, a limited area in a plant, the distribution of the positron emitter fed into the plant can be visualized dynamically. Further development of positron-emitter-labeled compounds is expected to elucidate the physiological function of plants in vivo.

13N-nitrate uptake sites and rhizobium-infectible region in a single root of common bean and soybean

Abstract The positron emitting tracer-imaging system (PETIS) was used to determine whether it was possible to obtain on image of 13N-distribution in common bean in which a single root was fed with a liquid medium containing nitrate at different concentrations with different 13N specific activities. The distribution of the images of the 13N atoms in the root could be obtained over a wide range of nitrate concentrations and 13N specific activities in the medium. As for nitrate stress on leguminous root nodulation, the positional relationship between the nitrate uptake sites and root hair just elongating area, where rhizobia capably initiate their infection, was studied in common bean and soybean. PETIS gave direct evidence that single roots of both common bean and soybean showed one or two dense 13N-distribution areas after 2 min pulse-feeding of 13N03 -. These areas remained stable over 30 min, and the first dense site, which was common in all the examined roots, extended over ca. 1 cm above the root apex....

Effects of anion channel blockers on xylem nitrate transport in barley seedlings

Abstract The effects of anion channel blockers, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and anthracene-9-carboxylic acid (A-9-C), on the uptake and xylem transport of nitrate were investigated in intact barley (Hordeum vulgare L.) seedlings using 13NO3 − and 15NO3 − as tracers. The seedling roots were pretreated with either blocker for 1 h and then 13NO3 − or 15NO3 − was supplied to the medium. Real-time images of 13N accumulation in shoots were monitored during the first 30 min using Positron Emitting Tracer Imaging Systems (PETIS). The radioactivity in the shoots of the plants treated with either blocker was about half of that in the shoots of the control plants. Analysis of the distribution of 13N in whole seedlings using a Bioimaging Analyzer System (BAS) showed a 13N-accumulation in both shoots and roots of the control plants but reduced 13N-levels in the shoots of the plants treated with either blocker. Nitrate concentrations in the xylem sap were significantly reduced by the application of either blocker while the net uptake of 15NO3 − was not or slightly influenced by the treatment with blockers. The translocation and uptake of chloride were also significantly reduced by the treatment with A-9-C but not with DIDS. These results suggested that anion channels contributed to xylem loading of nitrate in barley plants.

Uptake and transport of positron-emitting tracer in irradiated plants

The transport of l8F-water introduced into irradiated plants was followed dynamically by the detection of annihilation γ -rays from a positron emitter using a “Positron-Emitting Tracer Imaging System”. Tracer activities at the vein of top leaf of unirradiated soybean (Glysine max) were observed in a short time, whereas those in plants irradiated with a doses up to 100 Gy were delayed with increase in dose. In the case of rose (Rosa sp. Rote Rose), radiation using a dose of 800 Gy for disinfestation as a quarantine procedure inhibited flowering. Uptake and transport of 18F-water through the cut stem was changed significantly by irradiation. These results show that the system is effective in observing the damage of irradiated plants and is useful for the study of physiological functions of plants.