tion. Further investigation of the dealkylation products, namely the chlorinated and hydroxylated 4,6-diamino-striazines, was hindered by extraction and partition difficulties but is in progress.

The metabolism of propachlor in corn seedlings and in excised leaves of corn, sorghum, sugarcane, and barley is similar during the first 6 to 24 hr following treatment. At least three water-soluble metabolites are produced in each species during this period.Two of these metabolites, compounds I and II, were isolated. Compound I was identified as the glutathione conjugate of propachlor. Compound II appears to be the -glutamylcysteine conjugate of propachlor. In corn seedlings compounds I and II were shown to be transitory metabolites, and they were not detected in significant concentrations 72 hr following treatment. The possibility that N,Ndiallyl-2-chloroacetamide (CDAA) and 4-chloro-2butynyl-m-chlorocarbanilate (barban) might form similar conjugates was considered.Glutathione has been the subject of many biochemical investigations, but its role in biological systems is still not completely understood. Glutathione is a substrate or coenzyme in several enzymatic reactions and is believed to protect thiol groups of proteins. In addition, it plays an important role in the detoxication of exogenous chemicals by formation of glutathione conjugates (Boyland and Chas- seaud, 1969). Mercapturic acids are believed to be formed from the corresponding glutathione conjugates by successive removal of the glutamyl and glycine residues, followed by Nacetylation of the cysteine residue (Boyland and Chasseaud, 1969). The metabolism of organic halides and related compounds to glutathione conjugates or mercapturic acids occurs in mammals (Booth et al., 1961), birds (Wit and Leeuwangh, 1969), and insects (Cohen and Smith, 1964). A similar mode of metabolism was established in plants when 2-chloro-4ethylamino-6-isopropylamino-s-triazine (atrazine) was found to be metabolized to a glutathione conjugate and a -glutamylcysteine conjugate in sorghum (Lamoureux et al., 1970); the process was shown to be enzymatic (Frear and Swanson, 1970). Glutathione transferase activity has been demonstrated in corn, sorghum, sugarcane, Sudan grass, and Johnson grass.The enzyme is capable of catalyzing the formation of glutathione conjugates with a number of herbicidal 2-chloro-s-triazines (Frear and Swanson, 1970). The report that 2-chloro-JV-isopropylacetanilide (propachlor) reacts nonenzymatically in vitro with glutathione (Frear and Swanson, 1970) indicated that glutathione conjugation may be a pathway for metabolism of the -chloroacetamide herbicides in higher plants. This paper reports on the metabolism of propachlor by this route in several species of higher plants. EXPERIMENTALGeneral Methods. Quantitative amino acid analyses were performed on a Technicon Amino Acid Analyzer using a 140-cm column of Chromobeads Type B and the standard citrate buffer gradient (Technicon Chromatography Corp., 1962). The 14C content of insoluble plant residues was determined by liquid scintillation techniques after the samples were combusted in an oxygen atmosphere (Shimabukuro, 1967). The general methods used for monitoring 14C, preparing silica gel thin-layer pl...

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Two unrelated metabolites of atrazine were isolated from sorghum. Complete N-dealkylation yielded 2-chloro-4,6-diamino-s-triazine, which no longer inhibited the Hill reaction and cyclic and noncyclic photophosphorylation in isolated pea chloroplasts. The isolation and identification of the metabolite N,Ai'-bis(4-ethylamino-6isopropylamino-s-triazinyl-2)cystine gave further support to a previous report that atrazine was metabolized by the glutathione conjugation pathway to its lanthionine conjugate. The isolation of the dimer does not necessarily indicate that this is the form of the metabolite in plants. The Ncysteine monomer may dimerize in vivo during the sequence of reactions leading to the lanthionine conjugate.The metabolism and detoxication of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in higher plants occurs via 2-hydroxylation, N-dealkylation, and glutathione conjugation, as discussed in a recent review (Shimabukuro et al., 1971b). Glutathione conjugation seems to be the key pathway responsible for the mechanism of resistance in plants such as corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], and sugarcane (Saccharum officinarum L.) (Lamoureux et al., 1970(Lamoureux et al., , 1972Shimabukuro and Swanson, 1969;Shimabukuro et al., 1971a). N-Dealkylation is significantly less active than glutathione conjugation in corn and sorghum (Shimabukuro, 1967;Shimabukuro et al., 1970). In sorghum, Ndealkylation yielded the metabolites 2-chloro-4-amino-6isopropylamino-s-triazine and 2-chloro-4-amino-6-ethylamino-s-triazine (Shimabukuro, 1967). Chloroform-soluble metabolites other than the two mono-N-dealkylated derivatives were also present in sorghum (Shimabukuro, 1967). Plimmer et al. (1971) isolated and identified 2chloro-4,6-diamino-s-triazine as one of the reaction products resulting from a free-radical oxidation of atrazine. This metabolite has not been isolated and identified in higher plants, although a metabolite with chromatographic properties similar to those of 2-chloro-4,6-diamino-s-triazine was reported to be present in resistant grasses (Hurter, 1967). Another unknown chloroform-soluble metabolite, amounting to 4.1% of the total radioactivity in sorghum shoots, was detected after a 4-day treating period with atrazine-14C (Shimabukuro et al., 1971b).This paper describes the isolation and identification of two chloroform-soluble metabolites of atrazine in sorghum. No product-precursor relationship existed between the two metabolites. The identification of the unknown metabolites indicated that one was an intermediate in the glutathione conjugation pathway, but the second was an intermediate in the N-dealkylation pathway. The structures of the metabolites, designated as XI and XIII, are shown in Figure 1. MATERIALS AND METHODSPlant Material. For small-scale herbicide treatments, sorghum seeds [Sorghum bicolor (L.) Moench var. North Dakota 104] were germinated in vermiculite for 11 days before transfer to continuously aerated Hoagland's solution. The plants in nutrient solution wer...

A compartmental model of the foliar behavior of the postemergence grass herbicide tridiphane has been developed with use of data collected in an environmentally controlled ecosystem. Rate constants for penetration, desorption, volatility, and metabolism have been determined for the chemical applied to giant foxtail as a function of temperature, spray variables, and spray adjuvants. Temperature had the most dramatic effect on the rate constants, which increased 2-5-fold with each 10 °C rise in temperature. Crop oil concentrate (COC) adjuvant significantly increased the rate of foliar penetration with no effect on the volatility rate. Spray variables such as drop size and spray volume showed smaller effects. The model was tested under the varying environmental conditions in a field experiment and found to reasonably predict the behavior of tridiphane.