Estudo do metabolismo do ácido 2(131 I), 3,5 triiodo benzóico em soja (Glycine max)

Resumo

2 (131 I), 3,5 triiodobenzoic acid (TIBA) was applied on field and greenhouse grown soybeans (Harosoy-63) by spraying and by leaf brushing, respectively. Time of application corresponded to the onset of flowering, exception for the late spray experiment when it coincided with the pod filling stage. The TIBA photodecomposition was tested by protecting one field treated plant against sunlight.  A single extraction with 95% ethanol yielded 70% for the treated leaves and almost 90% for the control, an homogenate of non treated leaves to which labelled TIBA was added. A declining and apparently exponential relationship was obtained when the yield of the alcoholic extraction was plotted against the time elapsed from spraying, what indicated that time was an important variable in the soluble activity "fixation" or mobilization to other plant parts. The acid-base purification study showed that the radioactivity of the treated leaves and of the control extracts partitioned differently between the organic and the aqueous phases, seeming to indicate the existence of compounds others than TIBA, mainly iodide, in the treated leaves. The radiochromatograms of the leaf extracts revealed the presence of 4 main radioactive spots: TIBA, iodine and 2 unknowns X1 and Xz. TIBA deiodination at position 2 became evident” by the increased iodide and decreased TIBA levels in the treated leaves as compared with the control. X; and X; contents also rose. The sunlight UV radiation action, as shown by the photosensitivity test, was the main, if not the only cause, appearing to be time dependent. Iodide, Xj and X2 are thought to be TIBA light degradation products rather than true metabo- lites.