Oxidative burst and lipoxygenase activity induced by hydroxycinnamic acids in cucumber roots

Seven-day-old seedlings of cucumber (Cucumis sativus L.) cv. 'Dar' were exposed to allelochemical stress by treating their roots with 0.5_mM solutions of ferulic and p-coumaric acids. In cucumber roots, the level of active oxygen species (hydrogen peroxide, superoxide anion and hydroxyl radical) and stable free radicals as well as lipoxygenase activity (in soluble and membrane bound fraction) were investigated. It was found that ferulic and p-coumaric acids caused a significant increase in the level of hydrogen peroxide and hydroxyl radical and enhanced the level of stable free radicals. Moreover, the induction of lipoxygenase activity was observed as a stress effect. The results indicate that the oxidative burst in cucumber roots occurred under the influence of ferulic and p-coumaric acids.