Uptake, Translocation, and Metabolism of Propham by Wheat(Triticum aestivum), Sugarbeet(Beta vulgaris), and Alfalfa(Medicago sativa)

Abstract

Uptake, translocation, and metabolism of propham (isopropyl carbanilate) were ascertained for wheat(Triticum aestivumL., ‘Neepawa’) sugarbeet(Beta vulgarisL., ‘HH-10’), and alfalfa(Medicago sativaL., ‘Cherokee’) when grown in either liquid culture or in soil. Three-week-old wheat and 5-week-old sugarbeet and alfalfa plants were treated with14C-propham in liquid culture for 1, 2, and 4 days. Other plants were placed in treated soil at 10 weeks after germination and grown for 15 weeks. Wheat absorbed 98%, sugarbeet 93%, and alfalfa 81% of the propham from solution after 4 days. Propham was translocated in all species. Under liquid culture, three polar metabolites of propham were isolated from wheat and alfalfa extracts and one was isolated from sugarbeet extracts. The agylcone moiety of the two most polar wheat metabolites was isopropyl-4-hydroxycarbanilate and that of the least polar metabolite was isopropyl-2-hydroxycarbanilate. The aglycone of all alfalfa and sugarbeet polar metabolites was isopropyl-4-hydroxycarbanilate. Only one polar metabolite was isolated from all soil-treated plants. The aglycone moiety was determined to be isopropyl-4-hydroxycarbanilate. Of the propham absorbed 95, 91, 89, and 36% was metabolized by sugarbeet roots, sugarbeet leaves, wheat leaves, and alfalfa leaves, respectively, after a 4-day liquid culture treatment. Propham was 100% metabolized when applied to plants via soil application.

Metabolic Detoxification of Phenmedipham in Leaf Tissue of Tolerant and Susceptible Species

“…This metabolism is unusual because bacteria and mammals hydrolyze ^-carbamates (11,16), and plants typically ringhydroxylate carbanilate herbicides (2,17,21). N-hydroxylations are known to occur in plants (4, 7), but the carbamate herbicide chlorpropham (isopropyl-m-chlorocarbanilate) is not metabolized in this way (8).…”

Expression of a bacterial gene in transgenic plants confers resistance to the herbicide phenmedipham

“…In a glycosylation step the hydroxy derivative is transformed into the herbicidally inactive glucoside [4,7]. Whereas in plants carbamates are typically metabolized either by ring hydroxylation [3,33,37] or by N-hydroxylation [6,13], bacteria and mammals prefer hydrolytic cleavage [17]. We have recently characterized an enzyme from the soil bacterium Arthrobacter oxidans P52 which is capable of hydrolysing phenmedipham and isolated the corresponding gene [24].…”