Yearbook 2005

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Plants talk

Max Planck Institute for Chemical Ecology Paschold, Anja; Halitschke, Rayko; Kessler, André; Baldwin, Ian T.
Plants respond to herbivore attack by releasing volatile organic compounds (VOCs) that function as a defense by attracting natural enemies of the herbivore, thereby establishing defensive mutualisms with insects. The fact that plants use VOCs to communicate with insects generates the expectation that they also use VOCs to communicate with each other. Numerous studies have examined the question of whether un-attacked neighboring plants growing adjacently to attacked plants use these VOCs to anticipate future attack and preemptively activate defense responses. Most of these experiments have been carried out under experimental conditions that unnaturally amplify or distort the effects of the VOCs on neighboring plants and none have conclusively identified the active constituents of the VOC bouquet that function as signals. Scientists from the Max Planck Institute for Chemical Ecology in Jena present a new experimental approach to these challenges that allows for the study of plant-plant signaling under natural conditions. more
Insect feeding elicits the synthesis and emission of volatile compounds in the infested plants as part of the indirect defense against herbivory. By using an artificial caterpillar, MecWorm, it is possible to analyze the impact of mechanical wounding and chemical signals separately. Studies with lima bean revealed that long lasting continuous wounding of plant tissues is sufficient to induce volatile blends which are similar to those emitted after insect-feeding. Microarray techniques were used to investigate gene regulation processes on transcript levels in Arabidopsis thaliana upon insect feeding and MecWorm treatment, respectively. On the whole genome background, significant changes in transcript levels have been found locally as well as systemically in both cases for about 5700 genes. Among these genes, 4100 were identically regulated, independently from the presence or absence of insect chemical components. In contrast, the observation of about 3200 regulated genes in systemically induced leaves indicates that insect signal compounds are involved in long distance responses. more
State-of-the-art quantum-mechanical methods have been applied to determine technologically important elastic properties of iron, namely theoretical tensile strength, phonon dispersion, and thermal expansion. These methods allow an accurate and realistic description of material properties without relying on experimental/empirical input parameters. The efficiency of such an approach is demonstrated by studying two key properties of iron: The tensile strength is studied for extreme loads in two different crystallographic directions, [001] and [111]. In the second part, it will be discussed how the methods, which in principle are valid only for T = 0K, can be generalized to study finite temperature properties. more
Advanced NiAl-based high temperature materials are developed and characterized for applications in energy conversion systems. The intermetallic compound NiAl with B2 superlattice structure exhibits superior physical and high-temperature mechanical properties, and excellent oxidation resistance. Disadvantages of polycrystalline NiAl are the lack in plasticity and fracture toughness and room temperature and insufficient high temperature strength at temperatures above 800 °C. The refractory metals Cr, Mo, and Re form with NiAl quasi-binary eutectic systems which enable to produce metal fibres reinforced NiAl-based alloys by using directional solidification. These in-situ composites showing fine-grained and thermally stable microstructures possessing high-temperature strength, superior creep resistence and sufficient room temperature ductility. more
Molecular hydrogen (H2) is an important energy carrier in environmentally-friendly applications, e.g. clean fuel cells, which are under development worldwide. However, presently the large scale production of hydrogen from water and sunlight is still a major challenge. In nature anaerobic bacteria use this molecule as energy source. The two major classes of hydrogenases, the enzymes that catalyze the production or the splitting of H2, were investigated by means of EPR and FTIR spectroscopy and quantumchemical calculations to elucidate the reaction mechanism. more
Stable isotopes, in particular of nitrogen and carbon, are a new tool to study the structure of food webs in aquatic ecosystems. These isotopes show characteristic enrichment when organic material is passed from one step in the food chain to the next. Moreover, the isotopic composition of organisms provides information on the origin of their resources. Scientists in the Department of Physiological Ecology of the Max Planck Institute for Limnology used this method to show how carbon from methane produced in lake sediments is transferred through bacteria and midge larvae to spiders outside of the water. In another project, they were able to demonstrate that different morphotypes of the same fish species specialize on different habitat and food resources in a lake. more
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