Metabolism and cell wall incorporation of phenoxyacetic acid in soybean cell suspension culture

The metabolism of [ 14 C]phenoxyacetic acid (POA) was studied in cell suspension culture of soybean (Glycine max). POA was metabolized to 4-HO-POA, 4-HO-POA glucoside and 4-HO-POA glycosidic ester. A large part of the 4-HO-POA glucoside and small amounts of the glycosidic ester were recovered in the medium. POA was also converted to non-extractable residues bound to cell walls. Sequential extraction of cell-wall polymers showed that non-extractable residues, partly identified with 4-HO-POA and POA, were mainly associated with hemicelluloses and lignin. Comparison of the metabolism of [carboxy- 14 C]- and [phenyl- 14 C]POA revealed some degradation of the POA side-chain, followed in all probability by the incorporation of the aromatic moiety into cell walls. However, the sturdiness of the resulting bonds prevented precise identification of these bound aromatic structures. In summary, the degradation of POA in soybean cell culture provided a good model to study the formation of non-extractable residues of pesticides.