Examination of bound (non‐extractable) residues of MCPA and flamprop in wheat straw

Abstract

The long term metabolism of [ 14C]MCPA and ['4C]flamprop in wheat (Triticurn aestivum) straw was found to involve incorporation of radioactivity as residues that were insoluble in acetone+water (1+1 by volume). A chemical and an enzymic solubilisation procedure were critically evaluated in attempts to release these residues for further examination. The chemical procedure resulted in complete solubilisation of all the radioactivity of both compounds in association with more than one cell wall fraction. However, routine quantitative analysis was found to be difficult for some fractions. Furthermore, the extracts did not appear to be suitable for investigation of the nature of the binding with the plant constituents. None of the enzymes employed in the enzymic procedures released significant amounts of the residues insoluble in the aqueous acetone. Despite these problems, the residues of MCPA that were insoluble in aqueous acetone were found to contain both the parent MCPA and its major metabolite 4-chloro-a-hydroxy-o-tolyloxyacetic acid.

Herbicide selectivity by differential metabolism: considerations for reducing crop damages

“…Secondary conjugations might also occur during Phase III, giving origin to non-phytotoxic compounds (Hatzios, 1991). Later, in Phase IV, the metabolites of the detoxification process, compartmentalized in vacuoles, may be associated with components of the cell wall (pectin, lignin, polyssacharides, and protein fractions) forming insoluble residues (Pillmoor et al, 1984;Langebartels & Harms, 1985;Cole, 1994;Edwards et al, 2005). The reactions, solubility, phytotoxicity and mobility of metabolites in plants during the herbicide detoxification process over the four Phases are listed in Table 1.…”

Application of [U-14C-phenyl]-cyprodinil on spring wheat to investigate the formation and structure of non-extractable residues within the cell wall

“…In triplicates, 1-1.5 g of the plant debris were subjected to a slightly modified cell wall fractionation procedure according to Langebartels and Harms [23]: Instead of enzymatic treatment, extraction of pectin was performed according to Pillmoore et al [15] using Na-EDTA (Titriplex III Õ , Merck, Germany). In addition to acidolysis lignin, Bjo¨rkmann lignin [24] was also extracted.…”

“…After an experimental period of 9 weeks, plants were analyzed for 14 C-labelled residues of the fungicide. Special emphasis was on non-extractable residues of cyprodinil; these were examined by a modified cell wall fractionation procedure according to Pillmoore et al [15] and Langebartels and Harms [16], and by treatment with trimethylchlorosilane utilized successfully for effective extraction of soil-bound residues of cyprodinil [17][18][19]. All portions of radioactivity mobilized by these procedures were subsequently subjected to further chromatographic analyses.…”

Metabolism and cell wall incorporation of phenoxyacetic acid in soybean cell suspension culture

“…Owing to its low phytotoxicity, POA can be applied at a much higher concentration than 2,4-D (263 lM vs 9 lM, F Laurent, unpublished observations). Another interest of POA is the relative simplicity of its metabolic pathway in plants, 5,19h21 by comparison with 2,4-D. 6 Analyses of POA metabolites in cell cultures conürmed that simplicity, since they revealed only one primary metabolite, 4-HO-POA, and two glycoconjugates : the 4-HO-POA glucoside and the 4-HO-POA glyco-ester conjugate. Surprisingly, the glycoester of POA was not detected.…”