JXB Advance Access originally published online on April 4, 2005
Journal of Experimental Botany 2005 56(415):1419-1425; doi:10.1093/jxb/eri143
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RESEARCH PAPER |
Input–output analysis of in vivo photoassimilate translocation using Positron-Emitting Tracer Imaging System (PETIS) data
1Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Gunma 370-1207, Japan
2Department of Radioisotopes, Japan Atomic Energy Research Institute, Gunma 370-1207, Japan
3Central Research Laboratory, Hamamatsu Photonics Co., Shizuoka 434-0041, Japan
* Present address and to whom correspondence should be sent: Institute of Agricultural Chemistry, Carl-Sprengel-Weg 1, D-37075 Göttingen, Germany. Fax: +49 551 395570. E-mail: Akeutge{at}gwdg.de. For correspondence on PETIS, please contact Dr S Matsuhashi; E-mail: Shinpei{at}taka.jaeri.go.jp
The Positron-Emitting Tracer Imaging System (PETIS) is introduced for monitoring the distribution of 11C-labelled photoassimilates in Sorghum. The obtained two-dimensional image data were quantitatively analysed using a transfer function analysis approach. While one half of a Sorghum root in a split root system was treated with either 0, 100, or 500 mM NaCl dissolved in the nutrient solution, tracer images of the root halves and the lower stem section were recorded using PETIS. From the observed tracer levels, parameters were estimated, from which the mean speed of tracer transport and the proportion of tracer moved between specified image positions were deduced. Transport speed varied between 0.7 and 1.8 cm min–1 with the difference depending on which part of the stem was involved. When data were collected in the lowest 0.5–1 cm of the stem, which included the point where the roots emerge, transport speed was less. Rapid changes in NaCl concentration, from 0 to 100 mM, resulted in short-term increases of assimilate import into the treated root. This response represented a transient osmotic effect, that was compensated for in the medium-term by osmotic adaptation. Higher concentrations of NaCl (500 mM) resulted in distinctly less photoassimilate transport into the treated root half. The present results agree with earlier observations, showing that transport of 11C-labelled photoassimilates measured with the PETIS detector system can be quantified using the method of input–output analysis. It is worth noting that with the PETIS detector system, areas of interest do not need to be defined until after data collection. This means that unexpected behaviour of a plant organ will be seen, which is not necessarily the case with conventional detector systems looking at predefined areas of interest.
Key words: 11C carbon, short-lived radioisotope, transfer function analysis