UPTAKE OF ~(14)C-ACETIC ACID BY RICE PLANT AS RELATED TO ROOT FUNCTION AND MICROBIAL ACTIVITY ON THE ROOT SURFACE

摘要

Experiments using rice plants (Oryza sativa L.) were conducted to examine uptake of ~(14)C-acetic acid via the root and ~(14)C behavior on the root surface. For hydroponics, three types of rice plants were cultured with ~(14)C-acetic acid solution: complete plant, half-rooted plant, and non-rooted plant. Also, for the root incubation experiment, sterilized root and non-sterilized root were incubated with ~(14)C-acetic acid solution. The ~(14)C radioactivities in the plant parts and solution were measured. Non- and half-rooted plant had ~(14)C radioactivity in their aerial part, but the complete plant did not. The trends of radioactivity levels in the solution were directly opposite to those of plant root biomass. A high level of ~(14)C radioactivity was observed on the entire root surface of non-sterilized root in the incubation experiment, and ~(14)C radioactivity in the solution also remarkably decreased from 7 h to 96 h after the ~(14)C addition. These results suggest that the amount of ~(14)C-acetic acid absorbed by the plant through the roots is very small. However, the plant absorbs ~(14)C-acetic acid through breaks in the roots. Once ~(14)C-acetic acid is inside the plant, it immediately transfers to the shoots. Degradation of ~(14)C radioactivity in the solution and ~(14)C fixation on the root surface arise from the context of microbial activities.