Juvenile root vigour improves phosphorus use efficiency of potato

Aims Potato (Solanum tuberosum L.) has a large phosphorus (P)-fertiliser requirement. This is thought to be due to its inability to acquire P effectively from the soil. This work tested the hypothesis that early proliferation of its root system would enhance P acquisition, accelerate canopy development, and enable greater yields. Methods Six years of field experiments characterised the relationships between (1) leaf P concentration ([P]leaf), tuber yield, and tuber P concentration ([P]tuber) among 27 Tuberosum, 35 Phureja and 4 Diploid Hybrid genotypes and (2) juvenile root vigour, P acquisition and tuber yield among eight Tuberosum genotypes selected for contrasting responses to P-fertiliser. Results Substantial genetic variation was observed in tuber yield, [P]leaf and [P]tuber. There was a strong positive relationship between tuber yields and P acquisition among genotypes, whether grown with or without P-fertiliser. Juvenile root vigour was correlated with accelerated canopy development and both greater P acquisition and tuber biomass accumulation early in the season. However, the latter relationships became weaker during the season. Conclusions Increased juvenile root vigour accelerated P acquisition and initial canopy cover and, thereby, increased tuber yields. Juvenile root vigour is a heritable trait and can be selected to improve P-fertiliser use efficiency of potato

Imaging microstructure of the barley rhizosphere:particle packing and root hair influences

Soil adjacent to roots has distinct structural and physical properties from bulk soil, affecting water and solute acquisition by plants. Detailed knowledge on how root activity and traits such as root hairs affect the three-dimensional pore structure at a fine scale is scarce and often contradictory. Roots of hairless barley (Hordeum vulgare L. cv Optic) mutant (NRH) and its wildtype (WT) parent were grown in tubes of sieved (&lt;250 μm) sandy loam soil under two different water regimes. The tubes were scanned by synchrotron-based X-ray computed tomography to visualise pore structure at the soil–root interface. Pore volume fraction and pore size distribution were analysed vs distance within 1 mm of the root surface. Less dense packing of particles at the root surface was hypothesised to cause the observed increased pore volume fraction immediately next to the epidermis. The pore size distribution was narrower due to a decreased fraction of larger pores. There were no statistically significant differences in pore structure between genotypes or moisture conditions. A model is proposed that describes the variation in porosity near roots taking into account soil compaction and the surface effect at the root surface.</p

A conditional mutation in a wheat (Triticum aestivum L.) gene regulating root morphology

Key message: Characterisation and genetic mapping of a key gene defining root morphology in bread wheat. Abstract: Root morphology is central to plants for the efficient uptake up of soil water and mineral nutrients. Here we describe a conditional mutant of hexaploid wheat (Triticum aestivum L.) that when grown in soil with high Ca 2+ develops a larger rhizosheath accompanied with shorter roots than the wild type. In wheat, rhizosheath size is a reliable surrogate for root hair length and this was verified in the mutant which possessed longer root hairs than the wild type when grown in high Ca 2+ soil. We named the mutant Stumpy and showed it to be due to a single semi-dominant mutation. The short root phenotype at high Ca 2+ was due to reduced cellular elongation which might also explain the long root hair phenotype. Analysis of root cell walls showed that the polysaccharide composition of Stumpy roots is remodelled when grown at non-permissive (high) Ca 2+ concentrations. The mutation mapped to chromosome 7B and sequencing of the 7B chromosomes in both wild type and Stumpy identified a candidate gene underlying the Stumpy mutation. As part of the process to determine whether the candidate gene was causative, we identified wheat lines in a Cadenza TILLING population with large rhizosheaths but accompanied with normal root length. This finding illustrates the potential of manipulating the gene to disconnect root length from root hair length as a means of developing wheat lines with improved efficiency of nutrient and water uptake. The Stumpy mutant will be valuable for understanding the mechanisms that regulate root morphology in wheat.</p

A conditional mutation in a wheat (Triticum aestivum L.) gene regulating root morphology

Key message: Characterisation and genetic mapping of a key gene defining root morphology in bread wheat. Abstract: Root morphology is central to plants for the efficient uptake up of soil water and mineral nutrients. Here we describe a conditional mutant of hexaploid wheat (Triticum aestivum L.) that when grown in soil with high Ca 2+ develops a larger rhizosheath accompanied with shorter roots than the wild type. In wheat, rhizosheath size is a reliable surrogate for root hair length and this was verified in the mutant which possessed longer root hairs than the wild type when grown in high Ca 2+ soil. We named the mutant Stumpy and showed it to be due to a single semi-dominant mutation. The short root phenotype at high Ca 2+ was due to reduced cellular elongation which might also explain the long root hair phenotype. Analysis of root cell walls showed that the polysaccharide composition of Stumpy roots is remodelled when grown at non-permissive (high) Ca 2+ concentrations. The mutation mapped to chromosome 7B and sequencing of the 7B chromosomes in both wild type and Stumpy identified a candidate gene underlying the Stumpy mutation. As part of the process to determine whether the candidate gene was causative, we identified wheat lines in a Cadenza TILLING population with large rhizosheaths but accompanied with normal root length. This finding illustrates the potential of manipulating the gene to disconnect root length from root hair length as a means of developing wheat lines with improved efficiency of nutrient and water uptake. The Stumpy mutant will be valuable for understanding the mechanisms that regulate root morphology in wheat.</p

High-resolution synchrotron imaging shows that root hairs influence rhizosphere soil structure formation

In this paper, we provide direct evidence of the importance of root hairs on pore structure development at the root-soil interface during the early stage of crop establishment. This was achieved by use of high resolution (~5 μm) synchrotron radiation computed tomography (SRCT) to visualise both the structure of root hairs and the soil pore structure in plant-soil microcosms. Two contrasting genotypes of barley (Hordeum vulgare L.), with and without root hairs, were grown for 8 days in microcosms packed with sandy loam soil at 1.2 g cm-3 36 dry bulk density. Root hairs were visualised within air filled pore spaces, but not in the fine-textured soil regions. - We found that the genotype with root hairs significantly altered the porosity and connectivity of the detectable pore space (&gt; 5 μm) in the rhizosphere, as compared with the no-hair mutants. Both genotypes showed decreasing pore-space between 0.8 mm and 0.1 mm from the root surface. Interestingly the root-hair-bearing genotype had a significantly greater soil pore volume-fraction at the root-soil interface. - Effects of pore structure on diffusion and permeability were estimated to be functionally insignificant under saturated conditions when simulated using image based modelling

Fatigue in advanced cancer: a prospective controlled cross-sectional study

Uncontrolled studies have reported that fatigue is a common symptom among patients with advanced cancer. It is also a frequent complaint among the general population. Simply asking cancer patients whether or not they feel fatigued does not distinguish between the ‘background’ level of this symptom in the community and any ‘excess’ arising as a result of illness. The aim of this study was to determine the prevalence of fatigue among palliative care inpatients in comparison with a control group of age and sex-matched volunteers without cancer. In addition, the correlates of fatigue were investigated. The prevalence of ‘severe subjective fatigue’ (defined as fatigue greater than that experienced by 95% of the control group) was found to be 75%. Patients were malnourished, had diminished muscle function and were suffering from a number of physical and mental symptoms. The severity of fatigue was unrelated to age, sex, diagnosis, presence or site of metastases, anaemia, dose of opioid or steroid, any of the haematological or biochemical indices (except urea), nutritional status, voluntary muscle function, or mood. A multivariate analysis found that fatigue severity was significantly associated with pain and dypnoea scores in the patients, and with the symptoms of anxiety and depression in the controls. The authors conclude that subjective fatigue is both prevalent and severe among patients with advanced cancer. The causes of this symptom remain obscure. Further work is required in order to determine if the associations reported between fatigue and pain and between fatigue and dyspnoea are causal or coincidental. © 1999 Cancer Research Campaig

Signatures of the Tricritical Point in QCD

Several approaches to QCD with two massless quarks at finite temperature T and baryon chemical potential mu suggest the existence of a tricritical point on the boundary of the phase with spontaneously broken chiral symmetry. In QCD with massive quarks there is then a critical point at the end of a first order transition line. We discuss possible experimental signatures of this point, which provide information about its location and properties. We propose a combination of event-by-event observables, including suppressed fluctuations in T and mu and, simultaneously, enhanced fluctuations in the multiplicity of soft pions.Comment: 5 pages (published version

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure