Zusammenhänge zwischen CO2-Fixierung und biotischem Stress in Mesembryanthemum crystallinum

Zbigniew Miszalski (Krakau): All aspects of aerobic life involve reactive oxygen species (ROS), antioxidants and redox regulation. Redox regulation is integrated with the redox-reactions in photosynthesis, photorespiration and respiration to achieve an overall energy balance and to maintain a reduced state necessary for the biosynthetic pathways that are reductive in nature.

Some plants shift their mode of carbon assimilation from the C3 pathway to Crassulacean acid metabolism (CAM) in response to many factors that lead to the generation of ROS at the cellular level. These factors also caused alterations in leaf cell and chloroplast morphology. C3 and CAM plants show different sensitivity to biotic stress factors. We propose that H2O2 plays crucial role in restricting pathogen-induced cell death and light is required for plant resistance in both metabolic types. In C3 plants, these changes were followed by metabolic shifts towards weak CAM-similar diurnal oscillations of malate content. Light-dependent processes related to CAM and H2O2 accumulation are in parallel with resistance to pathogens. This may explain, at least partly, why CAM plants could be less sensitive to biotic stress factors. The potential role of H2O2 will be discussed. It is hypothesized that the spatial differences within leaf blade in superoxide anions are important for the non-uniform sensitivity to biotic stress factors.