Oxidative stress in pea seedling leaves in response to Acyrthosiphon pisum infestation

► Oxidative stress was induced in pea seedling leaves in response to pea aphid infestation. ► The early, strong generation of hydrogen peroxide (H2O2) may be related to the function of H2O2 as a signaling molecule. ► The strong generation of superoxide anion (O2−) induced the defense potential to protect against pea aphid. ► Generation of semiquinones may contribute to build-up of a defensive barrier or activate other defense mechanisms. ► The enhanced activity of the antioxidant enzymes was one of important elements of pea protection against oxidative stress.