Root absorption and translocation of 5-substituted analogs of the imidazolinone herbicide, imazapyr
1994
In preparation for assessing quantitative structure-activity relationships (QSAR) for root absorption and translocation of imidazolinones herbicides, 13 radiolabeled analogs of imazapyr (2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) nicotinic acid) substituted in the 5-position of the pyridine ring were evaluated in corn (Zea mays L.) and sunflower (Helianthus annuus L.). The compounds (10 micromolar) were supplied to the roots through a hydroponic solution for 8 h and, following harvest, plant tissues were either combusted to measure total uptake of radiolabeled material or were extracted for determination of the extent of degradation of the parent compound. Root absorption in both species varied by two orders of magnitude among analogs while translocation, expressed as a percentage of absorption, varied by only three- or four-fold. Few differences were observed for translocation of radioactivity from sunflower stems to leaves. Although six of the analogs were partially metabolized in corn, little metabolism of the imidazolinone analogs occurred in sunflower. These data indicate that meaningful models of root absorption and subsequent translocation to shoots may be developed for 5-substituted analogs of imazapyr, particularly when applied to sunflower.
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