title: Input-output analysis of in vivo photoassimilate translocation using Positron-Emitting Tracer Imaging System (PETIS) data.
abstract: The Positron-Emitting Tracer Imaging System (PETIS) is introduced for monitoring the distribution of (11)C-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 (11)C-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.
authors.affiliation: Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Gunma 370-1207, Japan.
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Keutgen
authors.forename: Norbert
authors.initials: N
authors.lastname: Keutgen
authors.forename: Shinpei
authors.initials: S
authors.lastname: Matsuhashi
authors.forename: Chizuko
authors.initials: C
authors.lastname: Mizuniwa
authors.forename: Takehito
authors.initials: T
authors.lastname: Ito
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujimura
authors.forename: Noriko-Shigeta
authors.initials: NS
authors.lastname: Ishioka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Watanabe
authors.forename: Akihiko
authors.initials: A
authors.lastname: Osa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sekine
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uchida
authors.forename: Atsunori
authors.initials: A
authors.lastname: Tsuji
authors.forename: Shoji
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D001692:Biological Transport; D002250:Carbon Radioisotopes; D004583:Electrons; D010710:Phosphates / Q000378:metabolism*; D010781:Photography; D011865:Radioisotope Dilution Technique; D012588:Scintillation Counting / Q000295:instrumentation / Q000379:methods; D045868:Sorghum / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D010710:Phosphates