ABSTRACT
In greenhouse experiments, additions of 0.5% (v/v) ethylan or 5.0% (w/v) ammonium sulfate increased the permeability of quackgrass (Elytrigia repens) leaf-cell membrane treated with a solution containing 250 mg 1−1 of technichal-grade glyphosate-isopropylamine salt (MON 0139) [N-(phosphonomethyl)glycine] or formulated Roundup® (hereafter, glyphosate). Permeability reached a plateau at different times, depending upon the treatment. Rhizome bud viability was bioassayed using a 0.1% solution of 2,3,5-triphenyl tetrazolium chloride. Mean bud viability was reduced more by glyphosate than MON 0139, regardless of the concentrations (250, 750, and 1250 mg l−1). All treated and untreated plants had increasing bud viability with increasing distance from the treated shoot, but the viability in untreated plants and those treated with 250 mg 1 −1 MON 0139 increased at a greater rate than the ones treated with glyphosate with increasing distance from the treated shoot. Additions of 0.5% (v/v) ethylan or 5.0% (w/v) ammonium sulfate increased by about 25% the phytotoxicity to quackgrass of sprays containing 250 mg l−1 glyphosate. Neither adjuvant modified the distribution of glyphosate in rhizomes, compared to glyphosate alone, but rhizome growth subsequent to glyphosate treatment was less with the addition of ammonium sulfate or ethylan than with glyphosate alone.
