Low doses of most stressors stimulated antioxidative protection and growth of barley shoots, reduced the concentration of O2.− and/or intensity of lipid peroxidation. Whereas an impairment of growth and intensification of oxidative stress as well as a reduction in concentration of carotenoids and further increase in activity of antioxidative enzymes were noticed when the intensity of the stressors was increased. In the cases of ozone and UV-B stress, the effects of oxidative stress on plant growth was mitigated by strong antioxidative protection—highly increased catalase (CAT) and superoxide dismutase (SOD) activities, respectively. In the cases of drought and Cu, relatively strong oxidative stress was the major cause of plant growth depression. Additionally, mitigation of oxidative stress due to increased SOD activity was likely to be one of the main causes of growth stimulation induced by low doses of UV-B, Cd and Cu stress. Possible reasons for O3-induced growth stimulation were increased CAT activity and concentration of carotenoids. Generalizing the effects of different stressors, the contribution of non-specific oxidative stress on plant growth was stronger compared with stressor-specific action mechanisms: oxidative stress determined 42% of the changes in plants’ dry biomass, whereas the contribution of stressor-specific mechanisms accounted for 35% of variability in barley growth.