Visualization of Uptake of Mineral Elements and the Dynamics of Photosynthates in Arabidopsis by a Newly Developed Real-Time Radioisotope Imaging System (RRIS)

Abstract

Minerals and photosynthates are essential for many plant processes, but their imaging in live plants is difficult. We have developed a method for their live imaging in Arabidopsis using a real-time radioisotope imaging system. When each radioisotope, 22Na, 28Mg, 32P-phosphate, 35S-sulfate, 42K, 45Ca, 54Mn and 137Cs, was employed as an ion tracer, ion movement from root to shoot over 24 h was clearly observed. The movements of 22Na, 42K, 32P, 35S and 137Cs were fast so that they spread to the tip of stems. In contrast, high accumulation of 28Mg, 45Ca and 54Mn was found in the basal part of the main stem. Based on this time-course analysis, the velocity of ion movement in the main stem was calculated, and found to be fastest for S and K among the ions we tested in this study. Furthermore, application of a heat-girdling treatment allowed determination of individual ion movement via xylem flow alone, excluding phloem flow, within the main stem of 43-day-old Arabidopsis inflorescences. We also successfully developed a new system for visualizing photosynthates using labeled carbon dioxide, 14CO2. Using this system, the switching of source/sink organs and phloem flow direction could be monitored in parts of whole shoots and over time. In roots, 14C photosynthates accumulated intensively in the growing root tip area, 200–800 µm behind the meristem. These results show that this real-time radioisotope imaging system allows visualization of many nuclides over a long time-course and thus constitutes a powerful tool for the analysis of various physiological phenomena.

Plastic Scintillators Enable Live Imaging of ³²P-labelled Phosphorus Movement in Large Plants

“…[6][7][8][9][10][11] Real-time radioisotope imaging system (RRIS), previously developed by us, can detect many types of radioisotopes, allowing us to observe the movement of various elements. 6 14,15) and the whole body of plants with larger dimensions have not been tested. Plants are supposed to have absorption and transportation dynamics unique to their growth stages; therefore, it is necessary to build a new system to observe the whole plant body.…”

“…K. Sugahara et al : Plastic Scintillators Enable Live Imaging of 32 P-labelled Phosphorus Movement in Large Plants of14 C, whose energy (mean: 49.5 keV, maximum:…”

Agricultural aspects of radiocontamination induced by the Fukushima nuclear accident — A survey of studies by the Univ. of Tokyo Agricultural Dept. (2011–2016)

“…29–31) Using this real-time radioisotope imaging system, a discrepancy was observed between the radiocesium absorption of plants growing in water culture and that of plants growing in soil culture. In water culture, plants absorbed high amounts of 137 Cs within hours, whereas in the paddy soil, 137 Cs was trapped firmly by the soil and was unavailable for absorption by the plants (Fig.…”

Research with radiation and radioisotopes to better understand plant physiology and agricultural consequences of radioactive contamination from the Fukushima Daiichi nuclear accident

“…Development of radioisotope imaging (RI) systems [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] Two types of the real-time RI imaging system, namely macroscopic and microscopic, were developed. Both systems are designed to use conventional RI so that it is possible to perform imaging in our laboratory and not at special laboratory with special facilities.…”