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- ItemSolar spectral conversion for improving the photosynthetic activity in algae reactors(London : Nature Publishing Group, 2013) Wondraczek, L.; Batentschuk, M.; Schmidt, M.A.; Borchardt, R.; Scheiner, S.; Seemann, B.; Schweizer, P.; Brabec, C.J.Sustainable biomass production is expected to be one of the major supporting pillars for future energy supply, as well as for renewable material provision. Algal beds represent an exciting resource for biomass/biofuel, fine chemicals and CO2 storage. Similar to other solar energy harvesting techniques, the efficiency of algal photosynthesis depends on the spectral overlap between solar irradiation and chloroplast absorption. Here we demonstrate that spectral conversion can be employed to significantly improve biomass growth and oxygen production rate in closed-cycle algae reactors. For this purpose, we adapt a photoluminescent phosphor of the type Ca 0.59Sr0.40Eu0.01S, which enables efficient conversion of the green part of the incoming spectrum into red light to better match the Qy peak of chlorophyll b. Integration of a Ca 0.59Sr0.40Eu0.01S backlight converter into a flat panel algae reactor filled with Haematococcus pluvialis as a model species results in significantly increased photosynthetic activity and algae reproduction rate.
- ItemNatural variation in physiological responses of tunisian hedysarum carnosum under iron deficiency(Lausanne : Frontiers Media, 2018) Abdallah, Heithem Ben; Mai, Hans Jörg; Slatni, Tarek; Fink-Straube, Claudia; Abdelly, Chedly; Bauer, PetraIron (Fe) is an essential element for plant growth and development. The cultivation of leguminous plants has generated strong interest because of their growth even on poor soils. Calcareous and saline soils with poor mineral availability are wide-spread in Tunisia. In an attempt to select better forage crops adapted to Tunisian soils, we characterized Fe deficiency responses of three different isolates of Hedysarum carnosum, an endemic Tunisian extremophile species growing in native stands in salt and calcareous soil conditions. H. carnosum is a non-model crop. The three isolates, named according to their habitats Karkar, Thelja, and Douiret, differed in the expression of Fe deficiency symptoms like morphology, leaf chlorosis with compromised leaf chlorophyll content and photosynthetic capacity and leaf metal contents. Across these parameters Thelja was found to be tolerant, while Karkar and Douiret were susceptible to Fe deficiency stress. The three physiological and molecular indicators of the iron deficiency response in roots, Fe reductase activity, growth medium acidification and induction of the IRON-REGULATED TRANSPORTER1 homolog, indicated that all lines responded to -Fe, however, varied in the strength of the different responses. We conclude that the individual lines have distinct adaptation capacities to react to iron deficiency, presumably involving mechanisms of whole-plant iron homeostasis and internal metal distribution. The Fe deficiency tolerance of Thelja might be linked with adaptation to its natural habitat on calcareous soil.
- ItemModeling of wave-induced irradiance variability in the upper ocean mixed layer(München : European Geopyhsical Union, 2012) Hieronymi, M.; Macke, A.; Zielinski, O.A Monte Carlo based radiative transfer model has been developed for calculating the availability of solar radiation within the top 100 m of the ocean. The model is optimized for simulations of spatial high resolution downwelling irradiance Ed fluctuations that arise from the lensing effect of waves at the water surface. In a first step the accuracy of simulation results has been verified by measurements of the oceanic underwater light field and through intercomparison with an established radiative transfer model. Secondly the potential depth-impact of nonlinear shaped single waves, from capillary to swell waves, is assessed by considering the most favorable conditions for light focusing, i.e. monochromatic light at 490 nm, very clear oceanic water with a low chlorophyll a content of 0.1 mg m−3 and high sun elevation. Finally light fields below irregular wave profiles accounting for realistic sea states were simulated. Our simulation results suggest that under open ocean conditions light flashes with 50% irradiance enhancements can appear down to 35 m depth, and light variability in the range of ±10% compared to the mean Ed is still possible in 100 m depth.