Systemic acquired resistance is an important component of the disease-resistance response of plants, and is associated with an enhanced capability for activating defense responses upon pathogen attack or chemical treatment. Pretreatment with salicylic acid, when followed by inoculation with Erysiphe polygoni DC., can after specific time frames, potentiate the induction of plant defense components phenylalanine ammonia-lyase (PAL), peroxidase (PO), and total soluble phenolics in pea (Pisum sativum L.) leaves. The optimal time for pretreatment was 48 h prior to fungal inoculations. Pretreatment for longer, or shorter times, resulted in less-pronounced potentiation of responses. Also, the increase in phenolics stays constant with pretreatment of 48 h or longer, whereas optimal PAL induction was seen only with the 48-h pretreatment indicating that PAL by itself is not the sole limiting factor in the production of phenolics.