Barry L. Hoffer

Metabolism of diclofop-methyl in susceptible and resistant biotypes of Lolium rigidum

Abstract Differential metabolism and detoxication of the postemergence graminicide diclofop-methyl (DM) [methyl 2-(4-(2′,4′-dichlorophenoxy)phenoxy)propanoate] is not the basis for selectivity between the DM resistant (R) and susceptible (S) biotypes of Lolium rigidum. Metabolism of DM did not differ significantly between the two biotypes. DM metabolism in Lolium sp. resembled that of susceptible oat and wild oat (Avena sp.) and not resistant wheat (Triticum aestivum). Metabolism of DM was assayed in excised shoots, roots and leaves (leaf surface-applied DM) of R and S Lolium biotypes. Higher concentrations of phytotoxic diclofop (acid) remained in shoots and roots of R and S Lolium biotypes (42 to 47% of absorbed DM after 72 hr in roots), than was found in susceptible oat. Conjugates of both diclofop (ester conjugate) and aryl hydroxylated diclofop (phenolic conjugate) were formed in Lolium sp. Aryl hydroxylation may be slightly higher in roots than in shoots of both biotypes but hydroxylation was less than in resistan wheat. The mode of action of DM in the S biotype of Lolium is probably similar to that in susceptible Avena sp. since the phytotoxicity of DM in both species is reversed by 2,4-dichlorophenoxyacetic acid.

Photolysis of 3‐(3,4‐dichlorophenyl)‐1, 1 ‐Dimethylurea (Diuron) in dilute aqueous solution

Diuron samples at 40mg/L concentration were photolyzed with ultraviolet lamps and with natural sunlight to determine if data from ultraviolet lamp photolysis could be used to predict results from sunlight photolysis. Seven photoproducts were identified from the photolysis experiments. The identified photoproducts and the photoproduct yields were essentially the same for the two light sources.

Photolysis of 3‐(3,4‐dichlorophenyl)‐1‐methoxy‐1 ‐Methylurea (Linuron) in dilute aqueous solution

Linuron samples at 75mg/L concentration were photolyzed with ultraviolet lamps or with natural sunlight. Ten photoproducts were identified and yields were determined for the more significant photoproducts resulting from either sunlight or ultraviolet lamp photolysis.

A Regiospecific Photoreaction for Synthesis of 3-Phenylpyridines

Abstract The regiospecific photocoupling of 3-(4-chloro-phenyl)-1,1-rdimethylurea with pyridine to afford 3-(4-dimethyl-ureidophenyl)pyridine was used to develop a synthetic scheme for the preparation of 3-phenylpyridine.

The absorption, translocation, and metabolism of difenopenten-ethyl in soybean and wheat

Abstract The postemergence graminicide, difenopenten-ethyl [ethyl 4-(4-(4′-trifluoromethylphenoxy)-phenoxy)-2-pentenoate], was rapidly hydrolyzed to its acid, difenopenten, in both susceptible wheat and resistant soybean followed by hydroxylation of the pentenoic acid side chain to a 3-hydroxy metabolite and subsequent conjugation to water-soluble polar metabolite(s). Metabolism of the herbicide did not differ greatly between the two species. A minor decarboxylation product of the 3-hydroxy metabolite, isolated from soybean cell suspension culture, was identified as a substituted 2-butanone metabolite. Difenopenten-ethyl is rapidly absorbed by both species through the roots and leaf surfaces but apoplastic and symplastic translocation is very limited. Differential absorption, translocation, and metabolism may not be major factors in the selective action of difenopenten-ethyl.

Test for photosynthetic inhibition by bis(N′,N′-dimethylureido)biphenyl photoproducts of monuron

Abstract Five substituted biphenyl photoproducts were identified from the photolysis of 3-(4-chlorophenyl)-1, 1-dimethylurea (monuron) under varying solution conditions. These photoproducts contained functional groups that conferred phytotoxic properties to phenylurea herbicides. Therefore, a study was conducted to determine if these biphenyl photoproducts at 1, 10 and 100 μM concentrations could exhibit phytotoxic effects using the Hill reaction as the biological assay. The results show that virtually no inhibitory effects were observed from the bis-(N′,N′-dimethylureido)biphyenyl photoproducts at any of the above concentrations.