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-coumaric, and ferulic acids were used in the study. Nucleic acid and protein synthesis were assayed by the incorporation of P-32 and S-35-methionine into soybean root. The uptake of P-32 was reduced by benzoic, cinnamic, vanillic, and ferulic acids, while p-hydroxybenzoic and p-coumaric acids increased slightly its absorption. At 250 mu M, all allelochemicals tested reduced the incorporation of P-32 into DNA and RNA. Benzoic, cinnamic, ferulic, and vanillic acids reduced the uptake of S-32-methionine, whereas p-hydroxybenzoic and p-coumaric acids increased its uptake. The methionine incorporation into proteins was reduced by all phenolic acids, except for p-coumaric acid and vanillic acid at 125 mu M. These results suggest that interference with nucleic acid and protein metabolism by the phenolic acids is one of the main mechanisms by which they influence plant growth.