Abstract: Polyamines are plant growth regulators that have been previously associated to plantresponses to abiotic stress. However there is not much information about their possible relation toplant-pathogen responses. In the present work, we demonstrated that plants overexpressingSAMDC (S-adenosylmethionin decarboxylase) and ADC2 (Arginie decarboxylase2) behavehypersensitive to Pseudomonas syringae. Accordingly, the T-DNA knockdown mutants adc2 andsamdc1 display reduced sensitivity to the bacterium. Despite these results, polyamine mutationsresult in an overcompensation by other biosynthetic genes rending unexpected polyamineprofiles. In order to better understand the roles of polyamine in plant resistance, a fast analyticalmethod for underivatized polyamines has been developed. The analysis is based on LC coupledto MS/MS by using additives to ion-pair polyamines.