UPTAKE AND TRANSPORT OF POSITRON-EMITTING TRACER (F-18) IN PLANTS

The transport of a positron-emitting isotope introduced into a plant w as dynamically followed by a special observation apparatus called 'Pos itron-Emitting Tracer Imaging System' to observe the damage and recove ry functions of plants in vivo. in the system, annihilation gamma-rays from the positron emitter are detected with two planar detectors (5 x 6 cm(2)). The water containing ca. 5 MBq/ml of F-18 was fed to the cu t stem of soybean for 2 min and then the images of tracer activity wer e recorded for 30-50 min. When the midrib of a leaf near the petiole w as cut just before measurement, the activity in the injured leaf was d ecreased but detected even at the apex. This result suggests that the damaged leaf recovered the uptake of water through the lamina. Maximum tracer activities in leaves of unirradiated plant were observed withi n 10 min, whereas those of irradiated plant at 100 Gy were observed af ter over 25 min. The final activity of irradiated plant after 30 min w as lower than that of unirradiated plant. In case of beans, there was a difference in the absorption behavior of the F-18-labeled water betw een unirradiated and irradiated samples. These results show that the s ystem is effective to observe the uptake and transportation of water c ontaining positron emitting tracer for the study of damage and recover y functions of plants. (C) 1997 Elsevier Science Ltd.