Leaf discs of cotton (Gossypium hirsutum L.), broadleaf plantain (Plantago major L.), soybeans (Glycine max Merrill), and corn (Zea mays L.) were incubated 1 hr in aqueous solutions of methyl- or ring-labeled 3-(p-chlorophenyl)-l,l-dimethylurea-14C (monuron) or carbonyl-labeled 3-(3,4-dichlorophenyl)-l,l-dimethyl-urea-14C (diuron). The loss of herbicide and formation of metabolites were determined at approximately 1-hr intervals up to 7 hr. Cotton leaf discs actively metabolized monuron to l-(p-chlorophenyl)-3-methylurea (monomethylmonuron), l-(p-chlorophenyl)urea (p-chlorophenylurea), and p-chloroaniline. Plantain leaf discs strongly metabolized diuron to l-(3-,4-dichlorophenyl)-3-methylurea (monomethyldiuron) and l-(3,4-dichlorophenyl)urea (3,4-dichlorophenylurea). Plantain degraded monuron less actively than diuron and cotton degraded diuron less rapidly than monuron. In soybean leaf discs, metabolism did not progress beyond the first demethylation, and corn leaf discs were unable to metabolize the herbicides in short-term studies.

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Simultaneous treatment with certain carbamate insecticides inhibited degradation of 3-(p-chlorophenyl)-1,1-dimethyrurea (monuron) in cotton (Gossypium hirsutumL.) leaf discs. Monuron degradation was strongly inhibited by 1-naphthyl methylcarbamate (carbaryl) and 4-benzothiophene-N-methylcarbamate, but 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate was ineffective. Effective carbamates did not prevent the metabolism of monuron to 1-(p-chlorophenyl)-3-methylurea (hereinafter referred to as monomethylmonuron), but they inhibited subsequent degradation of monomethylmonuron.

Discs of potato (Solanum tuberosum L.) tuber tissue were immersed in buffered (pH 4.0 to 8.0) solutions of 4-amino-3,5,6-trichloropicolinic acid (picloram) (5 × 10−4M to 5 × 10−3M) for 1 to 36 hr. Uptake of picloram during incubation, and leakage after return of the discs to untreated buffer, were determined by gas chromatographic analysis of extracts of the tissue and ambient buffer. Picloram absorption increased with concentration and with time up to 24 hr. Maximum uptake occurred at pH 4.0 and very little picloram was absorbed at pH 7.0 and 8.0. Both absorption and leakage were temperature dependent. The rate and extent of leakage was greatest at the highest concentration. Typically, more than 90% of the picloram absorbed from 5 × 10−3M was lost to fresh buffer within 12 hr.