Systemic acquired resistance and salicylic acid: current state of knowledge

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