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Measuring photosynthetic activity with Imaging-PAM Photosynthetic organisms contain chlorophyll, a photosynthetic pigment in the chloroplasts, absorbing photons of light to be used for photosynthetic energy. A method to study the photosynthetic activity of photosynthetic organisms is chlorophyll-fluorescence. This method is a sensitive technique to measure chlorophyll fluorescence in all physiologically relevant stages in a non-destructive way. The chlorophyll measuring technique is based on the first law of thermodynamics; the sum of energy from photosynthetic energy conservation (photochemistry, fluorescence and heat dissipation) must be equal to one. Both fluorescence and heat dissipation is measured by the measuring technique and thereby information of chemical energy can be optained. At the division of Building materials we study biological growth on rendered façades. Besides mould and (most) bacteria, which can not do photosynthesis, all other organisms growing on façades are photosynthetic; algae, lichens and mosses. Algae have for example only a positive energy balance during a few hours after sunrise. Before that it is to dark (no photosynthesis) and after a few hours in sunlight they dessicate (neither photosynthesis or respiration). We are therefore interested to study variations in the photosynthetic activity for different organisms growing on different façades on for instance on daily basis at different seasons or during night and day, and at the same time monitoring climatic variables. Status: Ongoing Duration: Continous, started 2009 Financing: Fysiografiska Sällskapet i Lund. Contact: Sanne johansson, M.Sc., Ph.D., Building Materials, Lund University P.O.Box 118, SE-221 00 Lund, Sweden Phone: +46 46 222 31 00