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The breeding sex ratio of Willow Warblers Phylloscopus trochilus in a subalpine birch forest was strongly female biased. Very few territorial males remained unmated and most became polygynous. Bigyny was the rule, but some males probably had three females. Male assistance at secondary nests varied and was probably dependent on temporal distance between the females' nests. There was no significant reduction in reproductive output for these females. Variation in the sex ratio of breeding birds can be explained, at least partly, by variation in the timing of male settlement. 相似文献
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Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides , Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season. 相似文献
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A precise potentiometric method for determination of algal activity in an open CO2 system 总被引:1,自引:1,他引:0
OLOF HOFSLAGARE GORAN SAMUELSSON† STAFFAN SJÖBERG NILS INGRI 《Plant, cell & environment》1983,6(3):195-201
Abstract. The activity of the green alga Scenedesmus obliquus was studied in simplified nutrient solutions (20 mol m−3 NaNO3 , 20 mol m−3 NH4 C1, 20 mol m−3 NH4 NO3 , and 20 mol m−3 NaCl, respectively) at 25 °C. The experiments were performed under welldefined incident photon density fluxes ranging from 10 to 200 μmol m2 s−1 , Light-dependent changes in pH and alkalinity (A) were followed by means of a potentiometric method using a glass electrode. In the experiments, carbon dioxide with known partial pressure was bubbled through the algal suspension, and during dark periods ul intervals of 1 h, the solution was allowed to equilibrate with the gas phase. This technique was applied to calculate equilibrium values of pH and alkalinity at regular intervals during a 12-h period. Results obtained in NaNO3 , solution show a linear increase in A with time, at each level of illumination studied. After an initial drop, A also increases in NH4 NO3 , solution in a similar way to that in NaNO3 solution. The change in A with time was also found to increase linearly with the photon density flux studied and no saturation level could be defined. In experiments in NaCl solution, no changes in A were registered while measurements in NH4 Cl solution showed a decrease in A with time. 相似文献
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Co-expression tools for plant biology: opportunities for hypothesis generation and caveats 总被引:1,自引:0,他引:1
BJÖRN USADEL TAKESHI OBAYASHI MAREK MUTWIL FEDERICO M. GIORGI GEORGE W. BASSEL MIMI TANIMOTO AMANDA CHOW DIRK STEINHAUSER STAFFAN PERSSON & NICHOLAS J. PROVART 《Plant, cell & environment》2009,32(12):1633-1651
Gene co‐expression analysis has emerged in the past 5 years as a powerful tool for gene function prediction. In essence, co‐expression analysis asks the question ‘what are the genes that are co‐expressed, that is, those that show similar expression profiles across many experiments, with my gene of interest?’. Genes that are highly co‐expressed may be involved in the biological process or processes of the query gene. This review describes the tools that are available for performing such analyses, how each of these perform, and also discusses statistical issues including how normalization of gene expression data can influence co‐expression results, calculation of co‐expression scores and P values, and the influence of data sets used for co‐expression analysis. Finally, examples from the literature will be presented, wherein co‐expression has been used to corroborate and discover various aspects of plant biology. 相似文献
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