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The toxicity and metabolism of 2,4-dichlorophenol, with regard to the aquatic macrophyte Lemna gibba (duckweed), have been studied Toxicity is described in terms of the effect of 2,4-dichlorophenol(2,4-DCP) on the vegetative reproduction of duckweed over a 10-d growth period, the EClO and EC5O were 2.5 and 9 2 pM, respectively. Metabolism of 2,4-dichlorophenol was monitored by incubation of the plants with radiolabeled substrate, and periodic sampling and analysis by reversedphase HPLC of the plant growth medium Depending on the growth conditions, up to 95% of the 2,4-DCP was metabolized over a 6-d growth period. To analyze the metabolites, the plants were grown in the presence of sublethal concentrations of [U-I4C]-2,4-DCP. The growth medium was lyophilized and then mixed with the plants, extracted, and analyzed using reversedphase HPLC, followed by scintillation counting of the fractions The major metabolite was isolated and identified as 2,4-dichlorophenyl-~-~-glucopyranoside by high-field NMR and MS. The structure of the metabolite was confirmed by synthesis and by enzymatic cleavage of the P-glucosidic linkage to afford 2,4-DCP. An important consequence of conjugate formation IS the masking of the presence of 2,4-DCP to the usual analytical techniques used for its detection and quantitation. This finding is probably applicable to other contaminants and organisms.

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Abstract-The toxicity of a series of chlorinated phenols, from phenol to pentachlorophenol, was determined using frond reproduction in aseptically grown Lemna gibba. The toxicities of the phenols tended to increase as the number of chlorine substituents on the phenol ring increased. The plants metabolized each of the phenols in the same manner producing metabolites that were more polar than their parent compounds. The metabolite for 2,4,5-trichlorophenol was isolated and identified by nuclear magnetic resonance spectroscopy and chemical ionization mass spectroscopy. The structural identity was confirmed by comparison with synthetic material as 2,4,5-trichlorophenyl-␤-D-glucopyranoside. These results, together with previously published results, suggest that conjugation with D-glucose is a stereotypic response of duckweed to challenge by phenol and chlorinated phenols.

The hollow pseudobulbs of Schomburgkia tibicinis (Orchidaceae; Central America) serve as domatia for many species of ants. The ants pack many of the pseudobulbs with debris including dead insects, plant material, and sand. Ants were fed 14C‐labelled D‐glucose in honey, killed, and placed in the pseudobulbs for up to eight weeks. Samples of plant tissue were harvested and tested for radioactivity after 1, 2, 3, 4, 6, and 8 weeks. The labelled material had moved into various parts of the plant and demonstrated direct nutrient uptake.