Metabolism of¹⁴C-Pronamide in the Soil and in Lettuce (Lactuca sativa) under Field Conditions

Abstract

Metabolism of14C-pronamide [N-(1,1-dimethylpropynyl)-3,5-dichlorobenzamide, carbonyl-14C] was studied in silt loam soil (located in Louvain-la-Neuve, Belgium) and in lettuce (Lactuca sativaL., ‘Appia′, Clause3) from a crop planted in soil that had been treated before planting. During the experiment, most of the14C remained in the 0- to 6-cm soil layer. The percentage of14C-pronamide degraded to14CO2during the experiment was less than 10%. The soil-extractable14C was made up of pronamide and its first ketone metabolite [N-(1,1-dimethylacetonyl)-3,5-dichlorobenzamide]. About 30% of the pronamide present in the soil was bound to the soil. The bound residue, i.e., the14C that could not be extracted by acetone, at lettuce harvest was about 80% of the14C contained in the soil at that time; 3,5-dichlorobenzoic acid was the main component of the bound residue. The harvested lettuce also contained pronamide, the ketone, and 3,5-dichlorobenzoic acid. Similar kinetics of metabolism were observed with lettuces grown on loamy sand soil (located in St. Kathelijne-Waver, Belgium). However, pronamide was not bound to this type of soil.

Absorption, translocation, and fate of propyzamide in witloof chicory (Cichorium intybus L.) and common amaranth (Amaranthus retroflexus L.)

“…Propyzamide is slowly metabolized in both sensitive and tolerant species (Weed Science Society of America, 1989). Rouchaud et al (1987) reported that lettuce slowly metabolized propyzamide to ketone and 3,5-dichlorobenzoic acid following shoot application in the field. However, the authors indicated that the metabolites might have been absorbed by lettuce from the soil.…”

“…After 112 days, the predominant metabolite of propyzamide in alfalfa was 8-(3,5-dichlorobenzamido)-8-methylbutyric acid. Similarly, field-grown lettuce metabolized propyzamide to 3,5-dichlorobenzoic acid 40 days after application (Rouchaud et al, 1987). Under field conditions, plants are exposed to propyzamide immediately after germination, and sensitive species are killed within few days.…”

Biodegradation of propyzamide by Comamonas testosteroni W1 and cloning of the propyzamide hydrolase gene camH

“…S2b, the metabolite showed a protonated molecular ion at m/z 190 [MÀH] À and characteristic fragment ion at m/z 144.90 [M-COOH-H] -. Hence, the metabolite was identified as 3, 5-dichlorobenzoic acid, which had been reported as a metabolite of propyzamide in soil (Rouchaud et al, 1987b). In this paper, it could be degraded by strain W1 and the accumulation of chloride ion proved that the total degradation of aromatic part of propyzamide (Fig.…”

“…It inhibits growth of sensitive species by disrupting the mitotic sequence in dividing cells in shoots and roots (John and Lisk, 1975;Vaughn and Lehnen, 1991). The half-life of propyzamide in soil is usually between 40 and 60 days, but can range from 10 to 120 days depending on the soil type, temperature and moisture (Rouchaud et al, 1987b;Walker, 1970;Yih et al, 1970). Propyzamide is widely used because of its high herbicidal activity and low toxicity to mammals (Viste et al, 1970).…”

Rhizosphere Ecology of Xenobiotic-Degrading Microorganisms

“…Along with being model compounds, chlorobenzoates are themselves environmental contaminants. They occur as a result of the use of chlorobenzoatebased pesticides (40,43), as breakdown products of other classes of pesticides (44) and as metabolites of polychlorinated biphenyl degradation (45). Walton, 1990 (7) TCE, trichloroethylene Increased mineralization in rhizosphere soil, but overall rates for both rhizosphere and bulk soil were slow.…”