The uptake and translocation of14C labelled acetochlor and EPTC herbicides were followed in experiments with maize /Zea mays L./ and mustard /Sinapis alba L./ in nutrient solutions. Radioactivity data were comparatively evaluated for approaching the origin of the different phytotoxicity of these herbicides to the plants used. Results obtained are in good agreement with the extent and symptoms of herbicide injury on maize and mustard plants grown in acetochlor or EPTC treated sand.
Effect of acetochlor placement on the uptake and distribution of carbonyl-14C labelled compound in maize /Zea Mays L./ was followed in time-course experiments by using charcoal barrier to separate the roots from shoot in sand culture. The results confirm that the main entrance of acetochlor to maize is through the roots but the uptake by coleoptile also plays an important role in the selectivity of acetochlor. Phytotoxic symptoms caused by acetochlor show good correlation with the site of uptake.
The labelled compound was prepared by chlorination of [2-14C]acetone obtained from the barium salt of [1-14C]acetic acid by pyrolysis. The reaction product 1,1-dichloro [2-14C]acetone was converted to 2-dichloromethyl-2-methyl [2-14C]-1,3-dioxolane by condensation with ethylene glycol in the presence of thionyl chloride. Radiochemical yield: 62% based on [1-14C]acetic acid.
Metabolism of acetochlor /2-chloro-N-/2-ethyl-6-methyl-phenyl/-N-/ethoxymethyl/acetamide/ herbicide was traced in tolerant corn /Zea mays L./ and sensitive wheat /Triticum aestivum L./. Both resistant and susceptible plant species were found to have the ability to metabolize acetochlor absorbed. However, a faster metabolism of the herbicide was observed in the tolerant plants.
The fate of acetochlor herbicide was investigated in corn /Zea mays L./ in nutrition solution culture experiments with and without R-25788 antidote. The antidote was found to slightly stimulate tthe absorption but retard the translocation of acetochlor labelled with14C in the carbonyl group. The degradation of the herbicide and the formation of the acetochlor GSH conjugate were faster in the antidote treated plants than in the untreated controls.
Absorption and translocation of acetochlor /2-chloro-N/2-ethyl-6-methylphenyl/-N-/ethoxymenthyl/acetamide/ herbicide were followed in experiments with tolerant corn /Zea mays L./ and sensitive wheat /Triticum aestivum L./ plants by using carbonyl-14C labelled compound. Tolerant plant species absorbed more radioactivity from the nutrient solution than susceptible plant species. However, the root-absorbed radioactivity was translocated to the shoot more readily in the sensitive plants.