Insekten-Funde aus dem Westfalium D (Ober-Karbon) des Piesberges bei Osnabrück (Deutschland) : Nachtrag 1: Palaeodictyopteroida

In diesem ersten Nachtrag zur Monographie der Insekten (ausschließlich der Odonatoptera und Blattodea) aus Schichten des Westfalium D vom Piesberg bei Osnabrück (Niedersachsen, Deutschland) werden weitere neue Angehörige der Palaeodictyoptera beschrieben: Homaloneura kiliani n. sp. (Spilapteridae) und Lithomantis meyeri n. sp. (Lithomanteidae). Neue Flügel-Funde zu bekannten Arten aus der Familie der Breyeriidae (Palaeodictyoptera) und Aspidothoracidae (Megasecoptera) ergänzen den bisherigen Fossilbericht von dieser Lokalität.In this first supplement of the monograph on the hitherto known fossil insects (exclusively Odonatoptera and Blattodea) from Westphalian D beds of the Piesberg quarry near Osnabrück (Lower Saxony, Germany) new taxa of the Palaeodictyoptera are described: Homaloneura kiliani n. sp. (Spilapteridae) and Lithomantis meyeri n. sp. (Lithomanteidae). New wing finds of species known from this locality and belonging to the Breyeriidae (Palaeodictyoptera) and Aspidothoracidae (Megasecoptera) support the fossil report

Buchbesprechung

Besprochen wird das Werk "Findlinge in Nordrhein-Westfalen und angrenzenden Gebieten" von Eckhard Speetzen (1998)

Mapping of quantitative trait loci associated with chilling tolerance in maize (Zea mays L.) seedlings grown under field conditions

The effect of low growth temperature on morpho-physiological traits of maize was investigated by the means of a QTL analysis in a segregating F2:3 population grown under field conditions in Switzerland. Chlorophyll fluorescence parameters, leaf greenness, leaf area, shoot dry weight, and shoot nitrogen content were investigated at the seedling stage for two years. Maize was sown on two dates in each year; thus, plants sown early were exposed to low temperature, whereas those sown later developed under more favourable conditions. The main QTLs involved in the functioning of the photosynthetic apparatus at low temperature were stable across the cold environments and were also identified under controlled conditions with suboptimal temperature in a previous study. Based on the QTL analysis, relationships between chlorophyll fluorescence parameters and leaf greenness were moderate. This indicates that the extent and functioning of the photosynthetic machinery may be under different genetic control. The functioning of the photosynthetic apparatus in plants developed at low temperature in the field did not noticeably affect biomass accumulation; since there were no co-locations between QTLs for leaf area and shoot dry weight, biomass accumulation did not seem to be carbon-limited at the seedling stage under cool conditions in the fiel

Salzhydratschmelzen als Lösemedien für Cellulose und Cellulosederivate

Die vorliegende Arbeit befasst sich mit Untersuchungen anorganischer Salzhydratschmelzen, wie beispielsweise LiClO4•3H2O, ZnCl2+4H2O und NaSCN/KSCN/LiSCN/H2O als Lösemedien für Cellulose und ausgewählte Cellulosederivate sowie zur Charakterisierung der durch den Lösevorgang hervorgerufenen strukturellen Veränderungen von Cellulose. Es konnten Aussagen zu Wechselwirkungen zwischen den Cellulosemolekülketten und den in den Hydratschmelzen auftretenden Spezies getroffen sowie eine Korrelation zwischen den Eigenschaften der Schmelzen und der molekularen und übermolekularen Struktur der aus den Schmelzen regenerierten Cellulosen gefunden werden. Zur Beschreibung der Wechselwirkungen wurden verschiedene NMR-spektroskopische Methoden genutzt. Die Polymerproben wurden mittels WAXS, 13C-CP/MAS-NMR-Spektroskopie, BET-, SEC-Messungen, Solvatochromie- und REM-Untersuchungen charakterisiert. Mittels experimenteller Untersuchungen wurde nachgewiesen, dass sich bestimmte Salzhydratschmelzen zum Lösen, Quellen bzw. gezielten Abbauen von Cellulose eignen

Chlorophyll fluorescence as a selection tool for cold tolerance of photosynthesis in maize (Zea mays L.)

The possibility of using quenching analysis of chlorophyll a fluorescence as a selection tool for improving the cold tolerance of maize was investigated in six genotypes differing greatly in the ability to develop a competent photosynthetic apparatus at low temperature. Upon gradual cooling, measurements of the quantum yield of electron transport (ΦPSII) indicated that leaves of tolerant genotypes, that developed at suboptimal temperature (15 °C), maintained higher rates of electron transport than leaves of sensitive genotypes. This difference was largely due to the ability of the tolerant plants to keep higher efficiency of excitation energy capture by open photosystem II reaction centres (F′v/F′m). The absence of genotypic differences in leaves that developed at optimal temperature indicates that the trait is not expressed constitutively, but relies on adaptation mechanisms. Furthermore, the genotypic difference was not expressed under increasing illumination at 15 °C and 25 °C suggesting that the trait is also low-temperature-specific and is not expressed solely in response to increasing excess light energy. Applying the method to flint and dent breeding population led to a substantial increase (up to 31%) in the photosynthetic capacity of hybrids between selected F3 inbreeding families grown at suboptimal temperature, demonstrating that the method is an efficient selection tool for improving the cold tolerance of maize through breedin

Genetic structure and history of Swiss maize ( Zea mays L. ssp. mays ) landraces

Between 1930 and 2003 with emphasis on the 1940s maize landraces (Zea mays L. ssp. mays) from all over Switzerland were collected for maintenance and further use in a new Swiss breeding program. The genetic relationship and diversity among these accessions stored in the Swiss gene bank is largely unknown. Our hypothesis was that due to the unique geographic, climatic, and cultural diversity in Switzerland a diverse population of maize landraces had developed over the past three centuries. The aims were to characterize the genetic diversity of the Swiss landraces and their genetic relationship with accessions from neighbouring regions as well as reviewing their history, collection, and maintenance. The characterization and grouping was based on analyses with ten microsatellite markers. Geographic, cultural, and climatic conditions explained a division in two distinct groups of accessions. One group consisted of landraces collected in the southern parts of Switzerland. This group was related to the Italian Orange Flints. The other group contained accessions from northern Switzerland which were related to Northern European Flints in particular German Flints. Historic evidence was found for a frequent exchange of landraces within the country resulting in a lack of region-specific or landrace-specific genetic groups. The relatively large separation between the accessions, indicated by high F ST (0.42), might be explained partly by a bottleneck during the collection and maintenance phase as well as by geographical and cultural separation of north and south of the country. Due to the high genetic diversity, the accessions here are a potential resource for broadening the European flint poo

QTL studies reveal little relevance of chilling-related seedling traits for yield in maize

Prolonged low temperature phases and short-term cold spells often occur in spring during the crucial stages of early maize (Zea mays L.) development. The effect of low temperature-induced growth retardation at the seedling stage on final yield is poorly studied. Therefore, the aim was to identify genomic regions associated with morpho-physiological traits at flowering and harvest stage and their relationship to previously identified quantitative trait loci (QTLs) for photosynthesis and morpho-physiological traits from the same plants at seedling stage. Flowering time, plant height and shoot biomass components at harvest were measured in a dent mapping population for cold tolerance studies, which was sown in the Swiss Midlands in early and late spring in two consecutive years. Early-sown plants exhibited chilling stress during seedling stage, whereas late-sown plants grew under favorable conditions. Significant QTLs, which were stable across environments, were found for plant height and for the time of flowering. The QTLs for flowering were frequently co-localized with QTLs for plant height or ear dry weight. The comparison with QTLs detected at seedling stage revealed only few common QTLs. A pleiotropic effect was found on chromosome 3 which revealed that a good photosynthetic performance of the seedling under warm conditions had a beneficial effect on plant height and partially on biomass at harvest. However, a high chilling tolerance of the seedling seemingly had an insignificant or small negative effect on the yiel

Cold Tolerance of the Photosynthetic Apparatus: Pleiotropic Relationship between Photosynthetic Performance and Specific Leaf Area of Maize Seedlings

The objective of this study was to elucidate the genetic relationship between the specific leaf area (SLA) and the photosynthetic performance of maize (Zea mays L.) as dependent on growth temperature. Three sets of genotypes: (i) 19 S5 inbred lines, divergently selected for high or low operating efficiency of photosystem II (ΦPSII) at low temperature, (ii) a population of 226 F2:3 families from the cross of ETH-DL3 × ETH-DH7, and (iii) a population of 168 F2:4 families from the cross of Lo964 × Lo1016 were tested at low (15/13°C day/night) or at optimal (25/22°C day/night) temperature. The latter cross was originally developed to study QTLs for root traits. At 15/13°C the groups of S5 inbred lines selected for high or low ΦPSII differed significantly for all the measured traits, while at optimal temperature the groups differed only with regard to leaf greenness (SPAD). At low temperature, the SLA of these inbred lines was negatively correlated with ΦPSII (r= − 0.56, p < 0.05) and SPAD (r = − 0.80, p < 0.001). This negative relationship was confirmed by mapping quantitative trait loci (QTL) in the two mapping populations. A co-location of three QTLs for SLA with QTLs for photosynthesis-related traits was detected in both populations at 15/13°C, while co-location was not detected at 25/22°C. The co-selection of SLA and ΦPSII in the inbred lines and the co-location of QTL for SLA, SPAD, and ΦPSII at 15/13°C in the QTL populations strongly supports pleiotropy. There was no evidence that selecting for high ΦPSII at low temperature leads to a constitutively altered SL

Stability of large vacancy clusters in silicon

Using a density-functional-based tight-binding method we investigate the stability of various vacancy clusters up to a size of 17 vacancies. Additionally, we compute the positron lifetimes for the most stable structures to compare them to experimental data. A simple bond-counting model is extended to take into account the formation of new bonds. This yields a very good agreement with the explicitly calculated formation energies of the relaxed structures for V6 to V14. The structures, where the vacancies form closed rings, such as V6 and V10, are especially stable against dissociation. For these structures, the calculated dissociation energies are in agreement with experimentally determined annealing temperatures and the calculated positron lifetimes are consistent with measurements.Peer reviewe