Isopropyl m‐Chlorocarbanilate and Its Hydroxylated Metabolites: Their Effects on Cell Suspensions and Cell Divison in Soybean and Carrot

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AbstractHydroxylated metabolites of isopropyl m‐chlorocarbanilate (chlorpropham) are found in intact soybean plants (Glycine max Merr.). The metabolites are isopropyl 2‐hydroxy‐5‐chloro‐carbanilate (2OH) and isopropyl 3‐chloro‐4‐hydroxycarbanilate (4OH). The phytotoxicity of these metabolites and chlorpropham was tested in cell suspensions and roots of intact soybean seedlings and cell cultures of carrot (Daucus carota L.). The growth of soybean cell suspensions was inhibited with 50 μM chlorpropham. Ten μM chlorpropham usually slowed initial growth of the cultures while 5 μM and 0.1 μM chlorpropham had no effect. The 2OH and 4OH metabolites had no significant effect on dry weight over the same concentration range. Some metabolism of chlorpropham, 2OH and 4OH occurred during 6 and 48 h of incubation with soybean cells. The results are interpreted to mean that all three analogs penetrated into the cells, were metabolized, and some of the metabolites excreted back into the medium. Mitotic index studies of intact 3‐day‐old soybean roots showed that 2OH inhibited mitosis to a greater extent than chlorpropham, whereas 4OH produced only a slight and insignificant reduction compared to controls. Chlorpropham, 2OH and 4OH (at 50 μM) all reduced the growth of wild carrot cultures grown in the presence or absence of 2,4‐D. Therefore, hydroxylation of chlorpropham at the 2′ or 4′ positions of the 5′ chlorinated benzene ring is not sufficient to render the compound nonphytotoxic in all plant systems.