EN
Oxidative stress, defined as a shift of the balance between prooxidative and antioxidative reactions in favor of the former seems to be a common denominator of the action of various agents on living organisms. This review briefly presents the sources of reactive oxygen species and means of antioxidative defense in plants, means of assessment of oxidative stress and exemplary data on the induction of oxidative stress by various environmental and biological factors such as hyperoxia, light, drought, high salinity, cold, metal ions, pollutants, xenobiotics, toxins, reoxygenation after anoxia, experimental manipulations, pathogen infection and aging of plant organs.