Twenty-one day- old plants of equal size were selected (eight lettuce plants in each treatment, n = 56) to be sprayed with a solution of the elicitors to be tested (1.5 mL per plant): 1 lM arachidonic acid (AA1), 100 lM arachidonic acid (AA2), 1 lM jasmonic acid (JA1), 100 lM jasmonic acid (JA2), 50 lM abscisic acid (ABA1) and 100 lM abscisic acid (ABA2) prepared in deionized water (elicitors were previously dissolved in very small amounts of ethanol (1 mL) and dispersed in appropriate volumes of water to achieve desirable concentrations).