ALLELOPATHIC EFFECTS OF PHENOLIC-ACIDS ON NUCLEIC-ACID AND PROTEIN-LEVELS IN SOYBEAN SEEDLINGS

Experiments were carried out, in a controlled environment during a 4-h incubation period, to examine the effects of phenolic acids on uptake by soybean (Glycine max (L.) Merr cv. Maple Bell) roots of phosphate and methionine and their incorporation into nucleic acids and proteins , respectively. Benzoic, p-hydroxybenzoic, vanillic, cinnamic, p-couma ric, and ferulic acids were used in the study. Nucleic acid and protei n synthesis were assayed by the incorporation of P-32 and S-35-methion ine into soybean root. The uptake of P-32 was reduced by benzoic, cinn amic, vanillic, and ferulic acids, while p-hydroxybenzoic and p-coumar ic acids increased slightly its absorption. At 250 mu M, all alleloche micals tested reduced the incorporation of P-32 into DNA and RNA. Benz oic, cinnamic, ferulic, and vanillic acids reduced the uptake of S-32- methionine, whereas p-hydroxybenzoic and p-coumaric acids increased it s uptake. The methionine incorporation into proteins was reduced by al l phenolic acids, except for p-coumaric acid and vanillic acid at 125 mu M. These results suggest that interference with nucleic acid and pr otein metabolism by the phenolic acids is one of the main mechanisms b y which they influence plant growth.