Summer drought alters plant-mediated competition between foliar- and root-feeding insects

Summer droughts are predicted to increase in severity and frequency in the United Kingdom, due to climate change. Few studies have addressed the impacts of drought on interactions between species, and the majority have focussed on increases in CO2 concentration and changes in temperature. Here, the effect of experimental summer drought on the strength of the plant-mediated interaction between leaf-mining Stephensia brunnichella larvae and root-chewing Agriotes larvae was investigated. Agriotes larvae reduced the abundance and performance of S. brunnichella feeding on a mutual host plant, Clinopodium vulgare, as well as the rate of parasitism of the leaf-miner. The interaction did not, however, occur on plants subjected to a severe drought treatment, which were reduced in size. Changes to summer rainfall, due to climate change, may therefore reduce the occurrence of plant-mediated interactions between insect herbivores.

The relation between content and structure in language production: an analysis of speech errors in semantic dementia

In order to explore the impact of a degraded semantic system on the structure of language production, we analysed transcripts from autobiographical memory interviews to identify naturally-occurring speech errors by eight patients with semantic dementia (SD) and eight age-matched normal speakers. Relative to controls, patients were significantly more likely to (a) substitute and omit open class words, (b) substitute (but not omit) closed class words, (c) substitute incorrect complex morphological forms and (d) produce semantically and/or syntactically anomalous sentences. Phonological errors were scarce in both groups. The study confirms previous evidence of SD patients’ problems with open class content words which are replaced by higher frequency, less specific terms. It presents the first evidence that SD patients have problems with closed class items and make syntactic as well as semantic speech errors, although these grammatical abnormalities are mostly subtle rather than gross. The results can be explained by the semantic deficit which disrupts the representation of a pre-verbal message, lexical retrieval and the early stages of grammatical encoding.

How do plants respond to nutrient shortage by biomass allocation?

Plants constantly sense the changes in their environment; when mineral elements are scarce, they often allocate a greater proportion of their biomass to the root system. This acclimatory response is a consequence of metabolic changes in the shoot and an adjustment of carbohydrate transport to the root. It has long been known that deficiencies of essential macronutrients (nitrogen, phosphorus, potassium and magnesium) result in an accumulation of carbohydrates in leaves and roots, and modify the shoot-to-root biomass ratio. Here, we present an update on the effects of mineral deficiencies on the expression of genes involved in primary metabolism in the shoot, the evidence for increased carbohydrate concentrations and altered biomass allocation between shoot and root, and the consequences of these changes on the growth and morphology of the plant root system.

Relation between the fatty acid composition of peripheral blood mononuclear cells and measures of immune cell function in health free-living subjects aged 25-72 y

Background: There is little information about the relation between the fatty acid composition of human immune cells and the function of those cells over the habitual range of fatty acid intakes. Objective: The objective of the study was to determine the relation between the fatty acid composition of human peripheral blood mononuclear cell (PBMC) phospholipids and the functions of human immune cells. Design: One hundred fifty healthy adult subjects provided a fasting blood sample. The phagocytic and oxidative burst activities of monocytes and neutrophils were measured in whole blood. PBMCs were isolated and used to measure lymphocyte proliferation in response to the T cell mitogen concanavalin A and the production of cytokines in response to concanavalin A or bacterial lipopolysaccharide. The fatty acid composition of plasma and PBMC phospholipids was determined. Results: Wide variations in fatty acid composition of PBMC phospholipids and immune cell functions were identified among the subjects. The proportions of total Polyunsaturated fatty acids (PUFAs), of total n-6 and n-3 PUFAs, and of several individual PUFAs in PBMC phospholipids were positively correlated with phagocytosis by neutrophils and monocytes, neutrophil oxidative burst, lymphocyte proliferation, and interferon gamma production. The ratios of saturated fatty acids to PUFAs and of n-6 to n-3 PUFAs were negatively correlated with these same immune functions. The relation of PBMC fatty acid composition to monocyte oxidative burst was the reverse of its relation to monocyte phagocytosis and neutrophil oxidative burst. Conclusion: Variations in the fatty acid composition of PBMC phospholipids account for some of the variability in immune cell functions among healthy adults.

Relation between neuronal morphology and electrophysiology in the Kainate lesion model of Alzheimer's Disease

This paper describes a computational and statistical study of the influence of morphological changes on the electrophysiological response of neurons from an animal model of Alzheimer's Disease (AD). We combined experimental morphological data from rat hippocampal CA1 pyramidal cells with a well-established model of active membrane properties. Dendritic morphology and the somatic response to simulated current clamp conditions were then compared for cells from the control and the AD group. The computational approach allowed us to single out the influences of neuromorphology on neuronal response by eliminating the effects of active channel variability. The results did not reveal a simple relationship between morphological changes associated with AD and changes in neural response. However, they did suggest the existence of more complex than anticipated relationships between dendritic morphology and single-cell electrophysiology.

Perceived competence moderates the relation between performance-approach and performance-avoidance goals

In the present research, we conducted 4 studies designed to examine the hypothesis that perceived competence moderates the relation between performance-approach and performance-avoidance goals. Each study yielded supportive data, indicating that the correlation between the 2 goals is lower when perceived competence is high. This pattern was observed at the between- and within-subject level of analysis, with correlational and experimental methods and using both standard and novel achievement goal assessments, multiple operationalizations of perceived competence, and several different types of focal tasks. The findings from this research contribute to the achievement goal literature on theoretical, applied, and methodological fronts and highlight the importance of and need for additional empirical work in this area. (PsycINFO Database Record (c) 2012 APA, all rights reserved)(journal abstract)

On the relation between explosive cyclones affecting Europe and the North Atlantic oscillation

Intense winter cyclones often lead to hazardous weather over Europe. Previous studies have pointed to a link between the North Atlantic Oscillation (NAO) and strong European windstorms. However, the robustness of this relation for cyclones of varying intensities remains largely unexplored. In this paper, the bi-directional relation between the NAO and cyclones impacting Europe is analyzed for the period 1950–2010 focusing on the sensitivity to storm intensity. Evidence is given that explosive (EC) and non-explosive cyclones (NoEC) predominantly develop under different large-scale circulation conditions over the North Atlantic. Whereas NoEC evolve more frequently under negative and neutral NAO phases, the number of EC is larger under a positive NAO phase, typically characterized by an intensified jet toward Western Europe. Important differences are also found on the dynamics of NAO evolution after peak intensity for both cyclone populations.

A tillering inhibition gene influences root-shoot carbon partitioning and pattern of water use to improve wheat productivity in rainfed environments

Genetic modification of shoot and root morphology has potential to improve water and nutrient 19 uptake of wheat crops in rainfed environments. Near-isogenic lines (NILs) varying for a tillering 20 inhibition (tin) gene and representing multiple genetic backgrounds were investigated in contrasting 21 controlled environments for shoot and root growth. Leaf area, shoot and root biomass were similar 22 until tillering whereupon reduced tillering in tin-containing NILs produced reductions of up to 60% in 23 total leaf area and biomass, and increases in total root length of up to 120% and root biomass to 24 145%. Together, root-to-shoot ratio increased two-fold with the tin gene. The influence of tin on shoot 25 and root growth was greatest in the cv. Banks genetic background, particularly in the biculm-selected 26 NIL, and was typically strongest in cooler environments. A separate de-tillering study confirmed 27 greater root-to-shoot ratios with regular tiller removal in non-tin containing genotypes. In validating 28 these observations in a rainfed field study, the tin allele had a negligible effect on seedling growth but 29 was associated with significantly (P<0.05) reduced tiller number (-37%), leaf area index (-26%) and 30 spike number (-35%) to reduce plant biomass (-19%) at anthesis. Root biomass, root-to-shoot ratio at 31 early stem elongation and root depth at maturity were increased in tin-containing NILs. Soil water use 32 was slowed in tin-containing NILs resulting in greater water availability, greater stomatal 33 conductance, cooler canopy temperatures and maintenance of green leaf area during grain-filling. 34 Together these effects contributed to increases in harvest index and grain yield. In both the controlled 35 and field environments, the tin gene was commonly associated with increased root length and biomass 36 but the significant influence of genetic background and environment suggests careful assessment of 37 tin-containing progeny in selection for genotypic increases in root growth.

Exploring the spatial relations between soil physical properties and apparent electrical conductivity

Relations between the apparent electrical conductivity of the soil (ECa) and top- and sub-soil physical properties were examined for two arable fields in southern England (Crowmarsh Battle Farms and the Yattendon Estate). The spatial variation of ECa and the soil properties was explored geostatistically. The variogram ranges showed that ECa varied on a similar spatial scale to many of the soil physical properties in both fields. Several features in the map of kriged predictions of ECa were also evident in maps of the soil properties. In addition, the correlation coefficients showed a strong relation between ECa and several soil properties. A moving correlation analysis enabled differences in the relations between ECa and the soil properties to be examined within the fields. The results indicated that relations were inconsistent; they were stronger in some areas than others. A regression of ECa on the principal component scores of the leading components for both fields showed that the first two components accounted for a large proportion of the variance in ECa, whereas the others accounted for little or none. For Crowmarsh topsoil sand and clay, loss on ignition and volumetric water measured in the autumn had large correlations on the first component, and for Yattendon they were large for topsoil sand and clay, and autumn and spring volumetric water. The cross-variograms suggested strong coregionalization between ECa and several soil physical properties; in particular subsoil sand and silt at Crowmarsh, and subsoil sand and clay at Yattendon. The structural correlations from the linear model of coregionalization confirmed the strength of the relations between ECa and the subsoil properties. Nevertheless, no one property was consistently important for both fields. Although a map of ECa can indicate the general patterns of spatial variation in the soil, it is not a substitute for information on soil properties obtained by sampling and analysing the soil. Nevertheless, it could be used to guide further sampling. (c) 2005 Elsevier B.V. All rights reserved.

Interactions between earthworms and arsenic in the soil environment: a review

Chemical pollution of the environment has become a major source of concern. In particular, many studies have investigated the impact of pollution on biota in the environment. Studies on metalliferous contaminated mine spoil wastes have shown that some soil organisms have the capability to become resistant to metal/metalloid toxicity. Earthworms are known to inhabit arsenic-rich metalliferous soils and, due to their intimate contact with the soil, in both the solid and aqueous phases, are likely to accumulate contaminants present in mine spoil. Earthworms that inhabit metalliferous contaminated soils must have developed mechanisms of resistance to the toxins found in these soils. The mechanisms of resistance are not fully understood; they may involve physiological adaptation (acclimation) or be genetic. This review discusses the relationships between earthworms and arsenic-rich mine spoil wastes, looking critically at resistance and possible mechanisms of resistance, in relation to soil edaphic factors and possible trophic transfer routes. (C) 2003 Elsevier Science Ltd. All rights reserved.

Drought impacts on above-belowground interactions: do effects differ between annual and perennial host species?

Root herbivores can have a positive or negative effect on the abundance and/or performance of foliar phytophages. In addition, abiotic factors such as drought can either strengthen or weaken this effect, depending on the system under investigation. One explanation for these varying responses lies in differences in the physiological response of host plants to drought and root herbivores. Here, the impacts of root phytophages on a leaf-mining species feeding on annual and perennial plant species (four Sonchus species) were compared. The responses of plants and leaf-miners to dtought and root herbivore treatments were not related to whether the host plant was an annual or perennial. However, where root feeders did affect foliar phytophage performance, this occurred only under a drought treatment, demonstrating the potential for climatic change to alter the outcome of plant-mediated interactions. (c) 2007 Gessellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Relationships between yield and mineral concentrations in potato tubers

There is concern that modern cultivars and/or agronomic practices have resulted in reduced concentrations of mineral elements essential to human nutrition in edible crops. Increased yields are often associated with reduced concentrations of mineral elements in produce, and a number of recent studies have indicated that, when grown under identical conditions, the concentrations of several mineral elements are lower in genotypes yielding more grain or shoot biomass than in older, lower-yielding genotypes. Potato is a significant crop, grown worldwide, yet few studies have investigated whether increasing yields, through agronomy or breeding, affects the concentrations of mineral elements in tubers. This article examines the hypothesis that increasing yields, either by the application of mineral fertilizers and/or by growing higher-yielding varieties, leads to decreased concentrations of mineral elements in tubers. It reports that the application of fertilizers influences tuber elemental composition in a complex manner, presumably as a consequence of soil chemistry and interactions between mineral elements within the plant, that considerable variation exists between potato genotypes in the concentrations of mineral elements in their tubers, and that, like in other crops, higher-yielding genotypes occasionally have lower concentrations of some mineral elements in their edible tissues than lower-yielding genotypes.