TY - JOUR A1 - Franck, Siegfried A1 - von Bloh, Werner A1 - Müller, Christoph A1 - Bondeau, Alberte A1 - Sakschewski, B. T1 - Harvesting the sun new estimations of the maximum population of planet Earth JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - The maximum population, also called Earth's carrying capacity, is the maximum number of people that can live on the food and other resources available on planet Earth. Previous investigations estimated the maximum carrying capacity as large as about 1 trillion people under the assumption that photosynthesis is the limiting process. Here we use a present state-of-the-art dynamic global vegetation model with managed planetary land surface, Lund-Potsdam-Jena managed Land (LPJmL), to calculate the yields of the most productive crops on a global 0.5 degrees x 0.5 degrees grid. Using the 2005 crop distribution the model predicts total harvested calories that are sufficient for the nutrition of 11.4 billion people. We define scenarios where humankind uses the whole land area for agriculture, saves the rain forests and the boreal evergreen forests or cultivates only pasture to feed animals. Every scenario is run in an extreme version with no allowance for urban and recreational needs and in two soft versions with a certain area per person for non-agricultural use. We find that there are natural limits of the maximum carrying capacity which are independent of any increase in agricultural productivity, if non-agricultural land use is accounted for. Using all land planet Earth can sustain 282 billion people. The save-forests-scenario yields 150 billion people. The scenario that cultivates only pasture to feed animals yields 96 billion people. Nevertheless, we should always have in mind that all our calculated numbers for the carrying capacity refer to extreme scenarios where humankind may only vegetate on this planet. Our numbers are considerably higher than the general median estimate of upper bounds of human population found in the literature in the order of 10 billion. KW - Maximum population KW - Human carrying capacity KW - Photosynthesis KW - Dynamical global vegetation model Y1 - 2011 U6 - https://doi.org/10.1016/j.ecolmodel.2011.03.030 SN - 0304-3800 VL - 222 IS - 12 SP - 2019 EP - 2026 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Damaraju, Sridevi A1 - Schlede, Stephanie A1 - Eckhardt, Ulrich A1 - Lokstein, Heiko A1 - Grimm, Bernhard T1 - Functions of the water soluble chlorophyll-binding protein in plants JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Functional aspects of water soluble chlorophyll-binding protein (WSCP) in plants were investigated during the courses of leaf senescence, chlorophyll biogenesis, stress response and photoprotection. The cDNA sequence encoding WSCP from cauliflower was cloned into a binary vector to facilitate Agrobacterium tumefaciens mediated transformation of Nicotiana tabacum. The resultant transgenic tobacco plants overexpressed the CauWSCP gene under the control of a 35S-promoter. Analyses of protein and pigment contents indicate that WSCP overexpression does not enhance chlorophyll catabolism in vivo, thus rendering a role of WSCP in Chl degradation unlikely. Accumulation of higher levels of protochlorophyllide in WSCP overexpressor plants corroborates a proposed temporary storage and carrier function of WSCP for chlorophyll and late precursors. Although WSCP overexpressor plants did not show significant differences in non-photochemical quenching of chlorophyll fluorescence, they are characterized by significantly lower zeaxanthin accumulation and peroxidase activity at different light intensities, even at high light intensities of 700-900 mu mol photons m(-2) s(-1). These results suggest a photoprotective function of the functional chlorophyll binding-WSCP tetramer by shielding of chlorophylls from molecular oxygen. KW - Chlorophyll metabolism KW - Non-photochemical quenching of chlorophyll fluorescence KW - Photooxidation KW - Photoprotection KW - Photosynthesis Y1 - 2011 U6 - https://doi.org/10.1016/j.jplph.2011.02.007 SN - 0176-1617 VL - 168 IS - 12 SP - 1444 EP - 1451 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Ebenhoeh, Oliver A1 - Houwaart, Torsten A1 - Lokstein, Heiko A1 - Schlede, Stephanie A1 - Tirok, Katrin T1 - A minimal mathematical model of nonphotochemical quenching of chlorophyll fluorescence JF - Biosystems : journal of biological and information processing sciences N2 - Under natural conditions, plants are exposed to rapidly changing light intensities. To acclimate to such fluctuations, plants have evolved adaptive mechanisms that optimally exploit available light energy and simultaneously minimise damage of the photosynthetic apparatus through excess light. An important mechanism is the dissipation of excess excitation energy as heat which can be measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). In this paper, we present a highly simplified mathematical model that captures essential experimentally observed features of the short term adaptive quenching dynamics. We investigate the stationary and dynamic behaviour of the model and systematically analyse the dependence of characteristic system properties on key parameters such as rate constants and pool sizes. Comparing simulations with experimental data allows to derive conclusions about the validity of the simplifying assumptions and we further propose hypotheses regarding the role of the xanthophyll cycle in NPQ. We envisage that the presented theoretical description of the light reactions in conjunction with short term adaptive processes serves as a basis for the development of more detailed mechanistic models by which the molecular mechanisms of NPQ can be theoretically studied. KW - Photosynthesis KW - Light reactions KW - Nonphotochemical quenching of chlorophyll fluorescence KW - Chlorophyll fluorescence KW - Mathematical model Y1 - 2011 U6 - https://doi.org/10.1016/j.biosystems.2010.10.011 SN - 0303-2647 VL - 103 IS - 2 SP - 196 EP - 204 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Spijkerman, Elly A1 - Wacker, Alexander T1 - Interactions between P-limitation and different C conditions on the fatty acid composition of an extremophile microalga JF - Extremophiles : life under extreme conditions N2 - The extremophilic microalga Chlamydomonas acidophila inhabits very acidic waters (pH 2-3.5), where its growth is often limited by phosphorus (P) or colimited by P and inorganic carbon (CO(2)). Because this alga is a major food source for predators in acidic habitats, we studied its fatty acid content, which reflects their quality as food, grown under a combination of P-limited and different carbon conditions (either mixotrophically with light + glucose or at high or low CO(2), both without glucose). The fatty acid composition largely depended on the cellular P content: stringent P-limited cells had a higher total fatty acid concentration and had a lower percentage of polyunsaturated fatty acids. An additional limitation for CO(2) inhibited this decrease, especially reflected in enhanced concentrations of 18:3(9,12,15) and 16:4(3,7,10,13), resulting in cells relatively rich in polyunsaturated fatty acids under colimiting growth conditions. The percentage of polyunsaturated to total fatty acid content was positively related with maximum photosynthesis under all conditions applied. The two factors, P and CO(2), thus interact in their effect on the fatty acid composition in C. acidophila, and colimited cells P-limited algae can be considered a superior food source for herbivores because of the high total fatty acid content and relative richness in polyunsaturated fatty acids. KW - Acidophilic algae KW - Cellular P quota KW - Chlamydomonas acidophila KW - Chlorophyceae KW - Colimitation KW - CO(2) KW - Fatty acid composition KW - Food quality KW - Glucose KW - Mixotrophy KW - Photosynthesis KW - Phytoplankton KW - Phosphorus limitation Y1 - 2011 U6 - https://doi.org/10.1007/s00792-011-0390-3 SN - 1431-0651 VL - 15 IS - 5 SP - 597 EP - 609 PB - Springer CY - Tokyo ER -