ABSORPTION AND FATE OF IMAZAPYR IN LEAFY SPURGE (EUPHORBIA-ESULA)

Imazapyr absorption, translocation, root release and metabolism were e xamined in leafy spurge (Euphorbia esula L.). Leafy spurge plants were propagated from root cuttings and [C-14]imazapyr was applied to growt h-chamber-grown plants in a water + 28% urea ammonium nitrate + nonion ic surfactant solution (98.75 + 1 + 0.25 by volume). Plants were harve sted two and eight days after herbicide treatment (DAT) and divided in to: treated leaf, stem and leaves above treated leaf, stem and leaves below the treated leaf, crown, root, dormant and elongated adventitiou s shoot buds. Imazapyr absorption increased from 62.5% 2 DAT to 80.0% 8 DAT. Herbicide translocation out of the treated leaf and accumulatio n in roots and adventitious shoot buds was apparent 2 DAT. By the end of the eight-day translocation period only 14% of applied C-14 remaine d in the treated leaf, while 17% had translocated into the root system . Elongated and dormant adventitious shoot buds accumulated 3.2- and 1 .8-fold more C-14, respectively, 8 DAT than did root tissue based on B q g(-1) dry weight. Root release of C-14 was evident 2 DAT, and by 8 D AT 19.4% of the C-14 reaching the root system was released into the ro oting medium. There was no metabolism of imazapyr in crown, root or ad ventitious shoot buds 2 DAT; however, imazapyr metabolism was evident in the treated leaf 2 and 8 DAT. Imazapyr phytotoxicity to leafy spurg e appears to result from high imazapyr absorption, translocation to un derground meristematic areas (roots and adventitious shoot buds), and a slow rate of metabolism.