Abstract:In recent years there has been growing interests in plant response to environmental stress via the salicylic-acid (SA)-mediated signal transduction pathway. Significant advances have been achieved on SA metabolism in relation to phenylpropanoid pathway and the process involved in the breakdown of H202 by catalase, which can be inhibited by SA. Evidence from a large body of literature suggests the role of SA as a signal molecule and provids the biochemical and molecular biological basis for the link between pathogen infection and the induction of systemic acquired resistance.