XVI International Botanical Congess

Plant emissions of volatile organic compounds contribute significantly to the oxidation capacity and hence the O3 level of the atmosphere. We report on climate chamber based cuvette measurements of the aldehyde exchange between lichens and the atmosphere. Coincidentally with high thallus water content and low net photosynthesis the investigated species emitted acetaldehyde. The emission could be enhanced by anoxic cuvette conditions and was negatively correlated with light exposure. However the emission rate was found to be dependant on the pre-incubation period, enabling the lichen to assimilate. The study provides evidence that lichens are able to bypass hypoxia, due to watersaturated thallus, via the ethanolic fermentation. Remarkably, the lichens tend to release substantial amounts of the intermediate but cell-toxic acetaldehyde into the atmosphere.