Growth Inhibition by Glyphosate and Reversal of Its Action by Phenylalanine and Tyrosine

Abstract

The broad spectrum herbicide glyphosate inhibited growth of a bacterium (E. coli), an alga (Chlamydomonas reinhardi), plant cell cultures (carrot and soybean) and roots of whole plants (Arabidopsis thaliana). Inhibition was transitory, except in plant roots, suggesting breakdown of the herbicide by the test organism. Phenylalanine and tyrosine acted synergistically to reverse the growth inhibition. Addition of these alone, other amino acids and/or divalent metal ions (Fe²⁺, Co²⁺ , Zn²⁺) had no effect. The data are discussed in relation to a possible mode of action of glyphosate.