Transformation of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)-acetamide] was studied with an actinomycete strain isolated from metolachlor-contaminated soil. Eight metabolites were obtained and identified by mass and NMR spectral analysis. Benzylic hydroxylation of the aralkyl side chains and/or demethylation a t the N-alkyl substituent appeared to be the only transformations involved. All metabolites had a monochlorine isotopic pattern, indicating that no dehalogenation of the chloroacetyl moiety occurred.

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Levine (8) have found mutants of C. reinhardi which have lost partial function in photosystem II. These blocks in photosystem II occur on the oxidizing side of the photoact, and many of the manifestations of this photosystem can be restored with the appropriate electron donor system. This paper presents evidence that PMA inhibits photosystem II at a site between the tris lesion and the photoact. Alternate oxidation sites for artificial donors such as hydroxylamine, hydroquinone, and diphenyl carbazide have been discerned through the use of PMA to study the complex series of reactions associated with the evolution of oxygen. MATERIALS AND METHODSThe method for the spectrophotometric measurement of the photoreduction of NADP has been described previously (15). A typical 3-ml reaction mixture contained the following components in ,umoles: sodium phosphate buffer, pH 7.8, 50: NADP, 0.5; ADP, 1: MgCl2, 10; and a saturating amount of spinach ferredoxin. If TCIP-ascorbate was to be used as a donor, 5 nmoles of DCMU, 20 ,umoles of sodium ascorbate, and 0.3 ,umole of TCIP were added. For metmyoglobin reduction NADP was replaced by 0.4 ,umole of metmyoglobin, and the light-induced absorbance change at 580 nm was measured. When ferricyanide or TCIP was used as acceptor. NADP and ferredoxin were replaced by 1.0 1lmole of potassium ferricyanide or 0.1 1Lmole of TCIP, and the light-induced change at 410 or 620 nm respectively was followed. The luminous flux for such experiments was 5 x 10°erg cm2 sec1. Methyl viologen reduction was measured by taking advantage of its autoxidizability. Oxygen uptake was measured using a Yellow Springs Instrument Company oxygen electrode. A representative 3-ml reaction mixture usually contained the following in amoles: Tricine buffer, pH 7.8, 45: methyl viologen, 2: sodium azide, 1; and NaCl, 6. When TCIP was the electron donor. 5 nmoles of DCMU, 30 nmoles of TCIP, and 15 /Lmoles of sodium ascorbate were used. The light intensity used for methyl viologen reduction was the same as noted above. Photophosphorylation was assayed according to the procedure of Krogmann and Olivero (12).The diaphorase activity of ferredoxin-NADP oxidoreductase was measured with a modification of the method of Avron and Jagendorf (2). A 3-ml reaction mixture containing 50 nmoles of TCIP, 50 ,umoles of sodium phosphate buffer, pH 7.0, and 0.04 ml of partially purified spinach flavoprotein (approximately 3 mg protein/ml) was placed in a cuvette and the absorbance measured at 620 nm. The reaction was initiated by adding 0.3 ,umole NADPH. The rate of decrease in absorbance at 620 nm is a measure of diaphorase activity.Mn2+ photooxidation was measured according to Ben-Hayyim and Avron (4). A standard reaction mixture contained exactly one-half of the amounts of components described by 376 www.plantphysiol.org on May 10, 2018 -Published by Downloaded from

The Farm Family Exposure Study should provide insights about pesticide exposure under real world conditions and thereby facilitate improved exposure assessment in epidemiologic studies of agricultural populations.

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