Quality of bioenergy plants under abiotic and biotic stress
Atmospheric ozone is formed by multiple reactions between nitrogen oxides and volatile organic compounds (VOCs) under the influence of UV-irradiation. The main sources for ozone formation are traffic by contributing with nitrogen oxides and plants by releasing VOCs.
Ozone is a very reactive gas which is affecting humans by causing irritation of eyes, and respiratory mucous tissues. Despite, in EU it is aimed to lower the threshold value for ozone to <120 µg m-3 until 2020, ozone concentrations are still rising. At present, ozone values of 180 µg m-3 provoke recommendations for sensitive persons to avoid exposing themselves outdoors.
Not only for human beings but also for plants, sensitivity to ozone is a matter of concern. In ozone sensitive plants, elevated ozone causes a reduction in photosynthesis and reduced growth. Additionally, physiological changes may also affect the quality of the plant tissue which is especially important for plants designated for use in biogas formation. Ozone increases the production of secondary metabolites and the formation of lignin. This altered plant tissue quality may have an influence on the biodegradability and thus the efficiency of microbial processes.
In Scheyern, free-air ozone fumigation has been established in a former fallow. In May 2009, an experiment has been established with poplar clones of differing ozone sensitivity. Poplar is very often used for bioenery production. Poplar on the one hand is growing fast, but also has the disadvantage to produce VOCs in high amounts thus even may contribute to ozone formation. To study interactions between sensitive and on-sensitive poplar clones, a planting design with different competitive pressure between the different clones was chosen.
The ozone regimes applied in the ozone plot in Scheyern are limited to 150 µg m-3 to avoid acute damage by toxic concentrations. Our interest is more in chronic elevated ozone stress, which continuously challenges the plant to regulate the production of defense compounds. Several groups are participating at this experiment, namely from the Helmholtz Center München (BIOP, IBÖ, EUS), from the Karlsruhe Institute of Technology (IMK - IFU Institute for Meteorology and Climate Research - Atmospheric Environmental Research at Garmisch), from TU München (Ecophysiology of Plants, Forest Pathology, Animal Ecology) and the University of Freiburg (Tree Physiology).
The aim is, to get insights into multiple stress reactions of plants especially in terms of quality of biomass, pest incidence, water and light use efficiency, competition. Further partners are welcome. Please contact K. Pritsch.
