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131.
132.
Summary Mutations of the homeotic gene fork head (fkh) of Drosophila transform the non-segmented terminal regions of the embryonic ectoderm into segmental derivatives: Pre-oral head structures and the foregut are replaced by post-oral head structures which are occasionally associated with thoracic structures. Posterior tail structures including the hindgut and the Malpighian tubules are replaced by post-oral head structures associated with anterior tail structures. The fkh gene shows no maternal effect and is required only during embryogenesis. The phenotypes of double mutants indicate that fkh acts independently of other homeotic genes (ANT-C, BX-C, spalt) and caudal. In addition, the fkh domains are not expanded in Polycomb (Pc) group mutant embryos. Ectopic expression of the homeotic selector genes of the ANT-C and BX-C in Pc group mutant embryos causes segmental transformations in terminal regions of the embryo only in the absence of fkh gene activity. Thus, fkh is a region-specific homeotic rather than a selector gene, which promotes terminal as opposed to segmental development.
Offprint requests to: Institut für Biologie II (Genetik), Universität Tübingen, Auf der Morgenstelle 28, D-7400 Tübingen, Federal Republic of Germany 相似文献
133.
Trait means,trait plasticity and trait differences to other species jointly explain species performances in grasslands of varying diversity 下载免费PDF全文
Christiane Roscher Marlén Gubsch Annett Lipowsky Jens Schumacher Alexandra Weigelt Nina Buchmann Ernst‐Detlef Schulze Bernhard Schmid 《Oikos》2018,127(6):865-865
Functional traits may help to explain the great variety of species performances in plant communities, but it is not clear whether the magnitude of trait values of a focal species or trait differences to co‐occurring species are key for trait‐based predictions. In addition, trait expression within species is often plastic, but this variation has been widely neglected in trait‐based analyses. We studied functional traits and plant biomass of 59 species in 66 experimental grassland mixtures of varying species richness (Jena Experiment). We related mean species performances (species biomass and relative yield RY) and their plasticities along the diversity gradient to trait‐based pedictors involving mean species traits (Tmean), trait plasticities along the diversity gradient (Tslope), extents of trait variation across communities (TCV; coefficient of variation) and hierarchical differences (Tdiff) and trait distances (absolute values of trait differences Tdist) between focal and co‐occurring species. Tmean (30–55%) and Tdiff (30–33%) explained most variation in mean species performances and their plasticities, but Tslope (20–25%) was also important in explaining mean species performances. The mean species traits and the trait differences between focal species and neighbors with the greatest explanatory power were related to plant size and stature (shoot length, mass:height ratios) and leaf photosynthetic capacity (specific leaf area, stable carbon isotopes and leaf nitrogen concentration). The contribution of trait plasticities in explaining species performances varied in direction (positive or negative) and involved traits related to photosynthetic capacity, nitrogen acquisition (nitrogen concentrations and stable isotopes) as well as structural stability (shoot carbon concentrations). Our results suggest that incorporating plasticity in trait expression as well as trait differences to co‐occurring species is critical for extending trait‐based analyses to understand the assembly of plant communities and the contribution of individual species in structuring plant communities. 相似文献
134.
Detlef Icheln Bärbel Gehrcke Yvonne Piprek Petra Mischnick Wilfried A. König Marco A. Dessoy Ademir F. Morel 《Carbohydrate research》1996,280(2):237-250
When 2,6-di-O-tert-butyldimethylsilylated cyclomalto-oligosaccharides (cyclodextrins) are treated with allyl or methyl iodide and NaH in dry tetrahydrofuran, O-2 → O-3 migration of the secondary 2-O-tert-butyldimethylsilyl groups occurs, leading to 2-O-alk(en)yl-3,6-di-O-tert-butyldimethylsilyl-cyclodextrin derivatives. The detection and identification of the reaction step during which migration occurred is described and possible mechanisms of migration are discussed. 相似文献
135.
Detlef Wilke 《FEMS microbiology reviews》1995,16(2-3):89-100
Abstract: In terms of the chemical industry most biotech products have a fine chemical or even speciality character. Nevertheless there is at least one striking example of a fermentation-derived bulk chemical, bio-ethanol, which provides an excellent case study of the economic and technological prerequisites which biotechnology has to attain as a supplier to the chemical marketplace. The competitive position of existing and new products produced from renewable resources through biotechnological conversion methods will depend on its market acceptance - overall environmental compatibility and cost performance. In order to provide significant contributions to chemical bulk production beyond 2000, biotechnologists and chemical engineers are requested to search for new products, new processes to existing products and new technologies to overcome present cost constraints in fermentation, bioconversion and downstream processing. 相似文献
136.
Werner Albig Jens Ebentheuer Gustav Klobeck Jürgen Kunz Detlef Doenecke 《Human genetics》1996,97(4):486-491
A solitary histone H3 gene encoding a novel H3 protein sequence has been isolated. This H3 gene maps to chromosome 1 (1g42), whereas we have shown previously that the majority of the human histone genes form a large cluster on chromosome 6 (6p21.3). In addition, a small cluster has been described at 1q21. The clustered histone genes are expressed during the S-phase of the cell cycle, hence their definition as replication-dependent histone genes. In contrast, expression of replacement histone genes is essentially cell-cycle independent; they are solitary genes and map outside the major clusters. The newly described H3 gene maps outside all known histone gene clusters and varies by four amino acid residues from the consensus mammalian H3 structure. In contrast to other solitary histone genes, this human H3 gene shows the consensus promoter and 3 flanking portions that are typical for replication-dependent genes. 相似文献
137.
Jérôme Metz Peter Annighöfer Peter Schall Jorma Zimmermann Tiemo Kahl Ernst‐Detlef Schulze Christian Ammer 《Global Change Biology》2016,22(2):903-920
Some forest‐related studies on possible effects of climate change conclude that growth potential of European beech (Fagus sylvatica L.) might be impaired by the predicted increase in future serious drought events during the growing season. Other recent research suggests that not only multiyear increment rates but also growth resistance and recovery of beech during, respectively, after dry years may differ between pure and mixed stands. Thus, we combined dendrochronological investigations and wood stable isotope measurements to further investigate the impact of neighborhood diversity on long‐term performance, short‐term drought response and soil water availability of European beech in three major geographic regions of Germany. During the last four decades, target trees whose competitive neighborhood consisted of co‐occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close‐by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures what is in line with the results of the stable isotope analysis. Apparently, the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. Our investigation strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatica. 相似文献
138.
Vassilis Daioglou Elke Stehfest Birka Wicke Andre Faaij Detlef P. van Vuuren 《Global Change Biology Bioenergy》2016,8(2):456-470
By‐products of agricultural and forestry processes, known as residues, may act as a primary source of renewable energy. Studies assessing the availability of this resource offer little insight on the drivers and constraints of the available potential as well as the associated costs and how these may vary across scenarios. This study projects long‐term global supply curves of the available potential using consistent scenarios of agriculture and forestry production, livestock production and fuel use from the spatially explicit integrated assessment model IMAGE. In the projections, residue production is related to agricultural and forestry production and intensification, and the limiting effect of ecological and alternative uses of residues are accounted for. Depending on the scenario, theoretical potential is projected to increase from approximately 120 EJ yr?1 today to 140–170 EJ yr?1 by 2100, coming mostly from agricultural production. To maintain ecological functions approximately 40% is required to remain in the field, and a further 20–30% is diverted towards alternative uses. Of the remaining potential (approximately 50 EJ yr?1 in 2100), more than 90% is available at costs <10By‐products of agricultural and forestry processes, known as residues, may act as a primary source of renewable energy. Studies assessing the availability of this resource offer little insight on the drivers and constraints of the available potential as well as the associated costs and how these may vary across scenarios. This study projects long‐term global supply curves of the available potential using consistent scenarios of agriculture and forestry production, livestock production and fuel use from the spatially explicit integrated assessment model IMAGE. In the projections, residue production is related to agricultural and forestry production and intensification, and the limiting effect of ecological and alternative uses of residues are accounted for. Depending on the scenario, theoretical potential is projected to increase from approximately 120 EJ yr?1 today to 140–170 EJ yr?1 by 2100, coming mostly from agricultural production. To maintain ecological functions approximately 40% is required to remain in the field, and a further 20–30% is diverted towards alternative uses. Of the remaining potential (approximately 50 EJ yr?1 in 2100), more than 90% is available at costs <10$2005 GJ?1. Crop yield improvements increase residue productivity, albeit at a lower rate. The consequent decrease in agricultural land results in a lower requirement of residues for erosion control. The theoretical potential is most sensitive to baseline projections of agriculture and forestry demand; however, this does not necessarily affect the available potential which is relatively constant across scenarios. The most important limiting factors are the alternative uses. Asia and North America account for two‐thirds of the available potential due to the production of crops with high residue yields and socioeconomic conditions which limit alternative uses. 相似文献
139.
Summary The water and potassium content and the relative vacuolar volume ( = Vvacuole/Vcell) of mesophyll cells of the needles of healthy 21-yearold spruce trees [Picea abies (L.) Karst.] were determined. In 5-year-old needles was 0.626 ± 0.178 (ovx ± SD). Potassium concentrations in the bulk tissue water ranged from about 65 to 105 mM. Simulations were made using this information and a simple two-compartmental model of the cell with the bulk cytoplasm and the vacuole and assuming that the minimum cytoplasmic and vacuolar K+ concentrations are 100–150 mM and 10–15 mM respectively. It is shown that a K+ content of needles below 50 mmol/1 tissue water would be precarious for maintenance of normal physiological and metabolic performance. 相似文献
140.
P. Agnellus Schneider Reinhard Hoppe G. Timmermann G. L. Maclean Hans Deetjen H. Deetjen F. Schmitz Detlef Robel Herbert Ringleben Vesta Stresemann Erwin R. Scherner Eckart Schwarze H. Kumerloeve Heinrich Dathe und Wolfgang Fischer 《Journal of Ornithology》1969,110(1):101-112
Zusammenfassung Die Schlußfolgerungen, dieStegmann (J. Orn. 109, 1968, p. 441–445) für die verwandtschaftliche Stellung der Flughühner auf Grund seiner eigenen Untersuchungen und an Hand anderer Quellen zieht, werden kommentiert. Es wird gezeigt, daß einige dieser Schlußfolgerungen nur auf morphologischen Merkmalen beruhen und mit den zu anderen Resultaten gelangten ethologischen und physiologischen Untersuchungsergebnissen nicht zu vereinbaren sind. Außerdem erscheint es unwahrscheinlich, daß die Flughühner, deren Ursprung von bodenlebenden Nestflüchtern unbestritten ist, auf dem Umweg über die baum- und felsbewohnenden nesthockenden Tauben erst sekundär wieder zu bodenbewohnenden Nestflüchtern geworden sind. Es gibt kein einziges Flughuhn-Merkmal, das diese Hypothese stützen könnte. 相似文献