Evaluation of velocity of
C-photoassimilate flow using positron-emitting tracer imaging system
Suzui, Nobuo; Kawachi, Naoki; Ishii, Satomi; Yin, Y.-G.; Iwasaki, Aya*; Ogawa, Kenichi*; Fujimaki, Shu
In this study, we developed an analytical method to evaluate velocity of photoassimilate flow using
C-tracer and the positron-emitting tracer imaging system (PETIS).
CO
gas tracer was fed to the compound leaves of the soybean plant, and serial images of
C distribution were obtained by PETIS. Regions of interests (ROIs) were set in the node of the first compound leaf (ROI-1) and the stem base (ROI-2). Time course of
C-radioactivity (Time-Activity Curve: TAC) in each ROI was generated from the serial images. Initial slope of the rising
C-radioactivity was estimated by a linear least-square method using the TAC data. The value of the intercept of approximated line to the background line (X-intercept) was defined as "
C-arrival time" to the ROIs. In order to determine X-intercept with a fair criterion, we developed an analytical program. The velocities of
C-photoassimilate flows of 18 individual soybean plants were estimated by the values of
C-arrival time and the distance between ROI-1 and ROI-2. As a result, the average value of the velocity was 113 cm h
and the standard deviation was 20 cm h
. This result indicates the newly developed method is a reliable tool for the quantitative analysis of photoassimilate flow through the phloem.