Selective Action of Chloroxuron on Soybean and Tall Morningglory

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Abstract
The selective action of chloroxuron [3-(p-(p-chlorophenoxy)phenyl)-1,1-dimethylurea] on tolerant soybean [Glycine max(L.) Merr. ‘Kent’] and susceptible tall morningglory [Ipomea purpurea(L.) Roth] was studied using root and foliar applications. In root uptake studies with carbonyl-14C-chloroxuron, soybean roots contained greater than 90% of the total absorbed radioactivity; whereas tall morningglory roots contained approximately 60% of the total absorbed radioactivity. Leaves of 1, 2, and 3-wk old soybean plants contained 0.8, 3.7, and 3.5% of the total radioactivity, respectively; whereas leaves of tall morningglory plants of corresponding age contained 29.1, 33.0, and 37.4% of the total radioactivity. Metabolism from root uptake of both species was similar; and metabolites were identified as approximately 85% chloroxuron, 13% 3-(p-(p-chlorophenoxy)phenyl-1-methylurea (Compound II), and 2.5% 3-(p-(p-chlorophenoxy)phenylurea (Compound III) in 3-wk old plants. In a nutrient solution containing 5.6 × 10−6M chloroxuron, soybean plants with roots intact were tolerant; whereas plants with roots detached were susceptible indicating the importance of differential translocation for selective action from root uptake. Following foliar spray and washing of 2-wk old plants, tall morningglory foliage absorbed about two times more radioactivity than soybean foliage. Further, 18 hr after foliar application, chloroplasts isolated from tall morningglory contained twice as much14C-chloroxuron as soybean chloroplasts. Metabolite concentrations recovered from foliar treatment of both species were similar; and metabolites were identified as 88.1 to 92.2% chloroxuron, 6.4 to 8.6 % Compound II and 0.5 to 1.7% Compound III.