IDENTIFICATION AND EVALUATION OF TOXICITY OF RICE ROOT ELONGATION INHIBITORS IN FLOODED SOILS WITH ADDED WHEAT STRAW

Rice root elongation was markedly inhibited by the solution extracted from flooded soil incubated with wheat straw. The toxicity was mainly due to the ether extractable fractions under acidic conditions. The following organic acids were detected in the ether extract of the soil solution: aliphatic acids; formic, acetic, propionic, butylic, and iso -valeric acids; aromatic acids; benzoic, 2-phenylpropionic, and 3-phenylpropionic acids. In another experiment, the soil solution from the field amended with wheat straw contained 2-hydroxybenzoic acid and the aromatic acids described above. The results of a bioassay with aromatic acids for rice seedlings showed that 2-phenylpropionic and 3-phenylpropionic acids exerted a severe inhibitory effect, which reduced rice root elongation by 73.3 and 30.7%, respectively at 4×10−5M. © 1990 Taylor & Francis Group, LLC.