PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

Photo-oxidative stress and protective mechanisms: The importance of thermal energy dissipation and tocopherol. Thomas Grasses^*,1, Bernhard Grimm², Dario Leister³, Peter Jahns¹, ¹ Heinrich Heine University of Duesseldorf, Duesseldorf, Germany² Humboldt University of Berlin, Berlin, Germany³ Max Planck Institute for Plant Breeding Research, Koeln, Germany

ABSTRACT- Photo-oxidative stress is a general and severe problem for all plants. Under unfavorable environmental conditions like drought, temperature stress or nutrient limitation, the formation of reactive oxygen species (ROS) is increased even at low light intensities. Plants have developed different strategies to control these unavoidable stress conditions. The formation of ROS can be reduced by various mechanisms, e.g. by heat dissipation of light energy or the increase of electron consuming pathways like photorespiration and the water-water cycle. In a second line of defense, oxidative damage is prevented by ROS scavenging systems consisting of redox substances such as ascorbate, glutathione, tocopherol and enzymes like ascorbate peroxidase, glutathione reductase, superoxide dismutase. The importance of tocopherol and thermal energy dissipation for the protection against photo-oxidative damage of PSII, one of the primary targets of ROS in chloroplasts, has been investigated in Arabidopsis mutants with reduced capacity of non-photochemical quenching (NPQ) of excitation energy dissipation and tobacco plants with reduced tocopherol content.

KEY WORDS: reactive oxygen species, photoinhibition, non-photochemical quenching, tocopherol