Studies on the absorption, translocation, and metabolism of [36Cl] Dursban, [14C] Dursban, [ W l ] 3,5,6-trichloro-2-pyridinol, and ['TI 3,5,6-trichloro-2-pyridinol in plants show that Dursban is not absorbed into the plant, although it accumulates on the surface of the roots. Once it enters the plant it appears to be metabolized to form primary hydrolysis products where the phosphorus is still attached to the 3,5,6-trichloro-2-pyridinol. The rate at which the 3,5,6-trichloro-2-pyridinol enters the plant depends on the p H of the solution. The sodium salt enters the plant more than five times faster than the free pyridinol. The pyridinol undergoes metabolism with the liberation of chloride and the formation of several decomposition products.I n previous studies on the uptake and translocation of 0,O-diethyl 0-3,5,6-trichloro-2-pyridyl phosphorothioate (Dursban, trademark of The Dow Chemical Co.) in plants (Smith et al., 1967) the compound did not penetrate either the roots or leaves, but only metabolites entered the plant. In previous investigations the amount of radioactive compound found inside the plant was in the order of 0.5 to 2x of the applied dose. Under these circumstances it was difficult to determine if the plant actually metabolized the compound or if the breakdown products found were formed outside the plant by ultraviolet light, in the case of foliar treatments, or by soil bacteria.A series of experiments was conducted in which a continuous supply of Dursban was available t o the plant, with the hope of increasing the quantity of compound within the plant.Soil studies (Theigs, 1965) showed that 3,5,6-trichloro-2-pyridinol formed by the hydrolysis of Dursban was also present in the soil. The uptake and metabolism of this compound were also 9tudied.
METHODSIn these investigations, both the [ 36C1] chlorine and the [ I C ] carbon-labeled Dursban and 3,5,6-trichloro-2-pyridinol were used.The [ 36C1] chlorine-labeled Dursban and 3,5,6-trichloro-2-pyridinol were prepared by the New England Nuclear Corp., using a procedure based on the synthesis method developed by Rigterink and Kenaga (1966). The [36Cl] 3,5,6-trichloro-2-pyridinol was prepared by the direct chlorination of 6-chloro-2-pyridinol using HC136 and H202. Part of the resulting [ W l ] 6-chloro-2-pyridinol was then converted to [ W l ] Dursban. The pyridinol-[36CI] and [36C1] Dursban had a specific activity of 29 pc. per mmole and were labeled in the 3,5-position as indicated. 3, *5, *6-Trichloro-0.0-Diethyl O-3,5,6-trichloro-2-pyridinol 2-pyridyl phosphorothioate Biomechanisms Laboratory, The Dow Chemical Co., Midland, Mich. The purity of both compounds was checked by infrared analysis and paper chromatography. As far as could be ascertained, at least 97 of the radioactivity was associated with the original compounds. There were traces of impurities in both compounds. The amount of parent compound and the impurities in the samples were determined by locating the spots on the chromatographic strips by autoradiographs, removing the radioactive ar...
