Root responses to legume plants integrate information on nitrogen availability and neighbour identity

Rhizobial symbiosis is known to increase the nitrogen availability in the rhizosphere of legumes. Therefore, it has been hypothesized that other plants’ roots should forage towards legume neighbours, but avoid non-legume neighbours. Yet, root distribution responding to legume plants as opposed to non-legumes has not yet been rigorously tested and might well be subject to integration of multiple environmental cues.In this study, wedevised an outdoor mesocosm experiment to examine root distributions of the two plant species Pilosella officinarum and Arenaria serpyllifolia in a two-factorial design. While one factor was ‘neighbour identity’, where plants were exposed to different legume or non-legume neighbours, the other factor was ‘nitrogen supply’. In the latter the nutrient-poor soil was supplemented with either nitrogen-free or with nitrogen-containing fertilizer.Unexpectedly, of all treatments that included a legume neighbour (eight different species or factor combinations), we found merely one case of root aggregation towards a legume neighbour (P. officinarum towards Medicago minima under nitrogen-fertilized conditions). In this very treatment, also P. officinarum root–shoot allocation was strongly increased, indicating that neighbour recognition is coupled with a contesting strategy.Considering the various response modes of the tested species towards the different legume and non-legume neighbours, we can conclude that roots integrate information on neighbour identity and resource availability in a complex manner. Especially the integration of neighbour identity in root decisions must be a vital aptitude for plants to cope with their complex biotic and abiotic environment in the field.     

Isolation of an Aspergillus terreus mutant impaired in arginine biosynthesis and its complementation with the argB gene from Aspergillus nidulans

Using filtration enrichment techniques, an Aspergillus terreus arginine auxotrophic strain which contains a mutation that abolishes ornithine transcarbamylase (OTCase) activity has been isolated. This mutant has been genetically transformed with the cloned Aspergillus nidulans OTCase gene. Prototrophic transformants arose at a frequency of about 50 transformants per microgram of plasmid DNA. Southern blot analysis of DNA from the transformants showed that the transforming DNA was ectopically integrated at different locations in the A. terreus genome, often in multiple tandem copies. The transformants were phenotypically stable for several mitotic divisions and retained their capacity to produce extracellular enzymes.     

Feeding ecology of common carp (Cyprinus carpio L.) in a rice–fish culture system of the Apatani plateau (Arunachal Pradesh, India)

For two years (2002, 2003) selective feeding ecology of the common carp (Cyprinus carpio L.) has been studied in carp-integrated rice fields in Apatani Plateau of Arunachal Pradesh (India). Sampling strategy was based on the water depths in the fields and on the flood phases: early flood phase (June–July), mid flood phase (July–August), and late flood phase (September–October). In 2003 the water level was higher and therefore periphyton availability was better. This resulted in larger gut contents and better growth of the carp compared with 2002 when the water levels were lower. Gut contents analyses revealed a total of 60 food items of which 22 belonged to the Chlorophycea, 12 to the Cyanobacteria, 10 to the Bacillariophycea and 16 to several zooplankton taxa. With the progress of flood phases, the fish increased its feeding on periphyton food items; simultaneously, feeding on plankton items gradually declined. This was caused by the increasing periphyton availability on the rice-stems. Selective feeding on plankton and periphyton taxa was studied, selectivity changed with the flood phases. Periphytic Chlorophycea and Cyanobacteria, especially, were strongly positively selected. Generally, periphyton was the most important resource for the common carp in the rice fields.     

Social cognitive impairment and autism: what are we trying to explain?

Early psychological theories of autism explained the clinical features of this condition in terms of perceptual and sensory processing impairments. The arrival of domain-specific social cognitive theories changed this focus, postulating a ‘primary’ and specific psychological impairment of social cognition. Across the years, evidence has been growing in support of social cognitive and social attention explanations in autism. However, there has also been evidence for general non-social cognitive impairments in representational understanding, attention allocation and sensory processing. Here, I review recent findings and consider the case for the specificity and primacy of the social cognitive impairment, proposing that we should focus more explicitly on clinically valid features for insights on the integration of ‘social’ and ‘non-social’ cognition.     

No More Foreigners? The Remaking of German Naturalization and Citizenship Law, 1990–2000

Since the beginning of the 1990s, Germany has been taking controversial policy measures that had been quite unimaginable, even in the 1980s. On the one hand, regulations for asylum seekers and ethnic Germans have gradually become restrictive in nature. On the other hand, changes to the Citizenship and Nationality Law of 1913 (Reichs und Staatsangehörigkeitsgesetz) and the Alien Act of 1965 (Ausländergesetz) have dramatically altered the naturalization process. Before the passage of the new German citizenship law in 1999, the acquisition of citizenship in Germany was solely based on the principle of descent (jus sanguinis). This paper attempts to explain why German government altered its citizenship policy and introduced birthright citizenship. It reviews the post-war contextual factors that have shaped the debate on citizenship and asks whether it is external or internal factors, that is international-level norms and institutions or domestic politics, that led to the change. If domestic politics can fully explain the adoption of the new citizenship law, what domestic forces played an important role? Was state action taken in the name of protecting “the national interest” or was it party politics? What role did societal forces play in the making of new citizenship policy? Did the act seek to mitigate anti-foreigner sentiment growing in Germany since the 1990s? Using archival and documentary research and secondary data on socio-economic and demographic trends in Germany, this paper concludes that domestic politics explain the changes in the citizenship law. I argue that granting and withholding national citizenship, including birthright citizenship, is exclusively in the hands of a nation state. Considering a purely ethnocultural understanding of nation-hood now includes legal and territorial components, the new German citizenship law is a major reform at the both theoretical and conceptual level. However, the practical consequences of the new naturalization process remain to be seen. The main question for the future research agenda is whether the new naturalization and citizenship laws will bring full integration of foreigners living in German society.     

POPULATION STRUCTURE OF A CLONAL GORGONIAN CORAL: THE INTERPLAY BETWEEN CLONAL REPRODUCTION AND DISTURBANCE

Clonality is a common feature of plants and benthic marine organisms. In some cases clonal propagation results in a modest increase in population density, while in other cases dense populations may be generated by the propagation of only a few clones. We analyzed the population structure of the clonal gorgonian Plexaura kuna across several reef habitats with a range of disturbance regimes in the San Blas Islands, Panama, and the Florida Keys, U.S.A. Using multilocus DNA fingerprinting to distinguish clones, we estimated that clones ranged in size from single individuals to 500 colonies. The number of genotypes identified on nine reefs ranged from three to 25. Population density and clonal structure varied markedly among reefs with G_O:G_E ranging from 0.03 to 1.00. On some reefs vegetative reproduction transformed P. kuna from a rare species to the numerically most abundant gorgonian. The effect of clonal propagation on P. kuna population structure was dependent on interactions between fragmentation and the reef environment (disturbance regime, substratum). We present a generalized model relating population structure of clonal species to disturbance and the mode of vegetative propagation. Disturbance promotes colony propagation and skews the size-frequency distribution of clones among P. kuna and many species that propagate via fragmentation. Propagation of these species is promoted by disturbance (disturbance sensitive), and they tend to have clones that are dispersed across local sites. Species that fragment and have dispersed clones, have high genotypic diversity in habitats with low levels of disturbance. Genotypic diversity then decreases at intermediate disturbance and increases again at the highest disturbance levels. Clonal species that do not rely on disturbance for vegetative propagation (disturbance insensitive) generally do not disperse and form aggregated clones. Among these taxa disturbance has a greater affect on individual survival than on propagation. Genotypic diversity is directly related to the level of disturbance until very high levels of disturbance, at which time genotypic diversity declines.     

The effects of X-rays on the proliferation dynamics of cells in the imaginal wing disc ofDrosophila melanogaster

Summary We report on the size distribution of clones marked by mitotic recombination induced by several different doses of X-rays applied to 72 h oldDrosophila larvae. The results indicate that the radiation significantly reduces the number of cells which undergo normal proliferation in the imaginal wing disc. We estimate that 1000 r reduces by 40–60% the number of cells capable of making a normal contribution to the development of the adult wing. Part of this reduction is due to severe curtailment in the proliferative ability of cells which nevertheless remain capable of adult differentiation; this effect is possibly due to radiation-induced aneuploidy. Cytological evidence suggests that immediate cell death also occurs as a result of radiation doses as low as 100 r. The surviving cells are stimulated to undergo additional proliferation in response to the X-ray damage so that the result is the differentiation of a normal wing.     

Intercompany Energy Integration

Reusing heat through process integration in heat exchanger networks has long been a key measure for increasing energy efficiency in energy‐intensive industries. Thermal pinch analysis is commonly used for a systematic matching of process streams and thus planning of optimal process integration in large chemical plants. The possible savings increase with the amount of heat and the number of integrated process streams. Therefore co‐ siting of several companies in a symbiotic network opens new opportunities for process integration even in small and medium‐size enterprises (SMEs), but also introduces new challenges. Thermal pinch analysis is extended here to account for piping distances and fluctuations and limited availability of energy flows by adding additional costs for the piping system and a backup utility system in the optimization function. Cooperative game theory is proposed to derive a sharing of savings between the partners of the industrial symbiosis that is optimal for each partner and should prevent partners from leaving the network because of higher benefits in a subgroup or alone. It is argued that knowledge about the optimality of a network for each partner creates trust between the partners that is a necessary base for the long‐term commitment needed in industrial symbioses. An exemplary symbiotic network combining the production of pulp and woody biomass energy carriers is used to illustrate the proposed approaches.     

Plant growth modelling without integrating mechanisms

The integration of root and shoot activity for resource acquisition and allocation is a central problem both in experimental physiology and in mathematical growth modelling. A key feature in all proposed solutions is the mechanism by which roots and shoot communicate their resource status, their needs or their demands. In experimental studies, chemical messengers (hormones or nutrients) have been central. In mathematical models, partitioning or productivity functions of one form or another have been incorporated to fill a similar role. In this paper, the central hypothesis is that growth and resource allocation can be based solely on local, internal, non-structural resource concentrations and local kinetic rules, without the need for additional mechanisms to integrate activities at the organis-mal level. The specific objective was to develop a formal model using the classical two-compartment, two-resource framework which did not include direct intercompartmental coordinating or communicating mechanisms or resource partitioning functions. The formalization effort was successful based on two criteria. First, the ‘plants’ grow at steady and balanced rates when ‘growth conditions’ are constant; and second, challenged with experimental manipulations such as pruning or limitations in resource acquisition, their growth responses mimic those of real plants. Analysis of the results indicates that the complex integrated growth patterns of the modelled plants are emergent properties – having no direct or indirect mechanistic basis – of the simple system. They imply that similar ‘mechanism-less’ integration is possible in real plants as an emergent property of strictly local, cellular-level activities.     

Variation in O-antigens, niche-specific selection and bacterial populations

Bacterial populations usually consist of distinct clones, often apparently adapted to specific niches. A formal model is developed whereby niche-specific selection maintains the polymorphisms involved in clonal adaptation. Infrequent transfer of non-adaptive alleles to a clone is balanced by the selection for the resident adaptive allele. The model can account for the extensive polymorphism in surface antigens observed in bacteria, and also for the existence of sympatric clones of pathogenic species which differ in host range and/or mode of pathogenesis. Niche-specific selection combined with low levels of genetic transfer can also account for the high level of neutral variation in bacteria, and indirectly for their ability to respond rapidly to environmental changes.