ABSTRACT
Oxygen supports aerobic life of land plants granting them with great energetic benefi ts but on the other hand challenges them through an endless formation of reactive oxygen species (ROS). ROS, namely singlet oxygen (1O2), superoxide radical (O-2), hydrogen peroxide (H2O2) and hydroxyl radical (HO.), are by-products of the energy-generating processes of photosynthetic and respiratory electron transport chains (ETC). Consequently, chloroplasts, mitochondria and peroxisomes are the main organelles of ROS producers in plant cells. ROS are highly reactive and toxic based on their ability to react indiscriminately with almost all biomolecules provoking destructive protein modifi cations, DNA strand breaks, purine oxidations, protein-DNA crosslinks and β-oxidation of lipids (Van Breusegem and Dat 2006). Thus, evolution of all aerobic organisms has been dependent on the development of effi cient enzymatic and non-enzymatic ROS-scavenging mechanisms, referred as antioxidant machinery.
