Downstream effects of defense-related signals. Cells treated with chitosan, E-FOL, PGA, voltage, or salicylic acid (SA) were assayed for MAP kinase activation, H2O2 production, and gene induction. Five-minute samples were subjected to in-gel kinase assay. In chitosan- and E-FOL-treated cultures, H2O2 concentration had increased to 5 μm above untreated cultures within 20 min. Gene regulation was determined by northern-blot analysis with probes for Pal and Lin6.