Generation of reactive oxygen species (ROS) occurs in seed not only during stress conditions, but also as a result of physiological processes. ROS are produced in seed in all developmental and germination phases like embryogenesis, including desiccation, seed ageing, imbibition, mobilization of storage reserves and germination manifested in radicle protrusion. Increase in ROS level during early embryogenesis and desiccation may lead to serious damage of embryos cells and disturb developmental processes. ROS generated during prolonged storage may promote the inability of seed to germinate.