Identification of a Phytotoxic Amino Acid from Fescue Grasses

Allelopathy refers to the process by which certain plants release phytotoxic chemicals to prevent the growth of other plants nearby. Fescue grasses are known to exhibit allelopathy by releasing large quantities of an aqueous root exudate in the soil rhizosphere. A group of scientists from the Boyce Thompson Institute identified the non-protein amino acid meta-tyrosine as the major component of the grasses' phytotoxic exudate.

Toxicity studies using lettuce and Arabidopsis showed that m-tyrosine can inhibit root growth. Unlike other known root-deposited allelochemicals, m-tyrosine affected neither photosynthetic efficiency nor chlorophyll production of the target plants. Its phytotoxic effects were counteracted by exogenous application of protein amino acids, especially phenylalanine. Several other non-protein amino acids have been known to exhibit phytotoxic properties but m-tyrosine is unique in being both root-exuded and inhibitory in even micromolar concentrations. Since there is an increasing concern over the use of synthetic herbicides, the researchers hope that the identification of m-tyrosine will contribute to the development of new approaches in weed management systems.

 Read the full paper published by PNAS at http://www.pnas.org/cgi/content/full/104/43/16964 or the abstract at http://www.pnas.org/cgi/content/abstract/104/43/16964