The Role of Salicylic Acid in the Expression of and Other Immunity-Related Genes.

The hormone salicylic acid (SA) plays a crucial role in plant immunity by activating responses that arrest pathogen ingress. SA accumulation also penalizes growth, a phenomenon visible in mutants that hyperaccumulate SA, resulting in strong growth inhibition. An important question, therefore, is why healthy plants produce basal levels of this hormone when defense responses are not activated.