JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Carbon Translocation in a Whole Plant Body by Using
Positron Emitting Tracer Imaging System (PETIS) and
Carbon-11-labeled Carbon Dioxide ( 11 CO2)
N. Kawachi a) , N. Suzui a) , S. Ishii a) , S. Ito a) , N. S. Ishioka a) ,
H. Yamazaki a, b) c, d) c, d) a)
, A. Iwasaki , K. Ogawa and S. Fujimaki
a) Radiation-Applied Biology Division, QuBS, JAEA, b) Faculty of Science and Technology,
Tokyo University of Science, c) Plant Redox Regulation Research Group, Research Institute for
Biological Sciences Okayama, d) Core Research for Evolutional Science and Technology, JST
Elucidation of carbon kinetics in a plant is important
from viewpoint of environmental reduction in the amounts
of atmospheric carbon dioxide (CO 2) and from an
agricultural viewpoint in terms of the growth and
development of the plant body. In particular
photosynthetic CO 2 fixation and photoassimilate
translocation are important topics for understanding the
mechanisms underlying carbon kinetics. In this study, we
have developed a new method to investigate the carbon
kinetics in a whole body by using one of the most powerful
radionuclide-based imaging techniques for plant study, that
is, the positron emitting tracer imaging system (PETIS).
Carbon-11-labeled carbon dioxide ( 11 CO 2) and PETIS
enable video imaging of tracer dynamics of carbon fixation,
photosynthesis, and translocation 1, 2) . Because of a large
field of view (FOV; 120.8 mm width, 186.8 mm height)
provided by the PETIS and the sufficiently small size of
soybeans (G. max cv. Jack) that fit in the FOV, dynamic
quantitative PETIS data of gradual changing in 11 C activity
and 11 C distribution throughout the entire intact plant body
after pulse-chase 11 CO 2 treatment was acquired. Figure
1(a) shows an experimental setup of this method. All
aerial part of the soybean was covered by a large exposure
cell, and was positioned between two opposite detectors of
PETIS.
The treatment of the 11 CO 2 exposure and air containing
JAEA-Review 2010-065
an ambient concentration (~ 350 ppm) of nonradioactive
carrier CO 2 gas led to the cell at flow rate of 1,000 mL/min.
The positron emitting 11 C-radioisotope was produced by
bombarding a nitrogen gas target with approximately
10 MeV protons from AVF cyclotron at TIARA. The
11 CO2 gas was synthesized 20 MBq at the time when PETIS
began acquiring images. The noninvasive imaging
experiments were repeatable to scan at fertilizer application
level and various environmental conditions of temperature,
light intensity, and humidity from a single individual.
Figure 1(b) shows an example of serial PETIS images of
carbon dynamics re-sorted in the sequence from 0–5 to
35–40 min in a soybean of whole plant. All the images
were corrected for 11 C radioactive decay (half life = 1,223.1
sec). Total activity of the 11 C in the images was stable over
the acquisition, so that the image data followed the law of
carbon nutrient conservation in a plant body. This
conservation in serial images indicates the successful
imaging of CO 2 photoassimilate translocation from the time
of infusion into leafs to that of distribution of the whole
plant body; further, carbon kinetics is analyzable to
understand plant physiology and nutrition.
References
1) N. Kawachi et al., IEEE TNS 2991 (2006) 53.
2) K. Kikuchi et al., J. J. S. Horti. Sci. 199 (2008) 77.
Fig. 1 (a) Photograph of an experimental setup. (b) The PETIS image data re-sorted in the sequence from 0 – 5 to
35 − 40 min (from left to right).
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