Systemic acquired resistance and salicylic acid:: current state of knowledge

Plants can induce defense reactions to a broad range of pathogens as a result of prior exposure to pathogens, various chemicals or physical stress. Induced resistance is expressed locally, at the site of the infection or systemically, at sites remotely located from the initial infection. The reactions occurring locally in the inducer leaf, the systemic signal and reactions in the upper leaf will be briefly reviewed here, with a special emphasis on the role played by salicylic acid in this process.