Generation of active oxygen species in roots of maize, pea and radish in response to exogenous ferulic and p-coumaric acids

Roots of sweet maize, garden pea and radish seedlings were subjected to allelopathic stress with two hydroxycinnamic acids (ferulic and p-coumaric acids). It was found that these phenolic compounds caused the generation of active oxygen species (AOS): hydrogen peroxide, superoxide anion and hydroxyl radical in seedling roots. In all three examined plant species, the allelopathic stress factors caused the generation of AOS, 30 min after the stress application. The dynamics of AOS level changes differed not only depending on the studied active oxygen form, but also on the species and on the stress factor which caused the changes. The effect of ferulic and p-coumaric acids on the changes in hydrogen peroxide and hydroxyl radical levels was particularly distinctive. The oxidative burst as a universal response of plants to allelopathic stress caused by phenolic compounds is discussed.