Figure 11

Model of subcellular ROS accumulation and detoxification by antioxidants and catalase during high light conditions. Line drawing proposing a model of the effects of high light stress on the subcellular accumulation of reactive oxygen species (ROS) in Arabidopsis thaliana with special focus on the compartment specific detoxification of hydrogen peroxide (H₂O₂) by ascorbate (Asc), catalase (Cat) and glutathione (GSH). High light stress (indicated by yellow thunderbold) induces the generation of ROS and H₂O₂ in chloroplasts (C) and in peroxisomes (Px) by overstraining the electron transport chain in thylakoids (green staples inside the chloroplast) and through photorespiration, respectively. Asc, Cat and GSH detoxify and suppress the accumulation of ROS and H₂O₂ in these cell compartments. With increasing light intensities H₂O₂ leaks from chloroplasts and peroxisomes into the cytosol and eventually into vacuoles. Whereas Asc, Cat and GSH detoxify H₂O₂ also in the cytosol, only Asc is involved in the detoxification of H₂O₂ in vacuoles where it helps to reduce phenoxyl radicals created by oxidation of phenols by H₂O₂[49].