527 research outputs found
Assessing the drought risk of oilseed rape to target future improvements to root systems
The yield of UK’s commercial oilseed rape (Brassica napus) crops has not increased over
the last three decades, while a significant increase in yield has been found in trials that
test new varieties before they enter the market. It has been suggested that oilseed rape is
susceptible to drought and that this may contribute to the poor yield of some
commercial crops. A thorough literature review revealed that there is little information
on the water relations of oilseed rape crops and in particular on root growth and
function and thus no strong evidence to support the above hypothesis. The aim of this
thesis was to investigate root function and water relations of oilseed rape to determine
whether it is more sensitive to drought than wheat, a crop species grown in rotation
with oilseed rape.
The water relations of wheat (Triticum aestivum L. cv. Tybalt) and oilseed rape
(Brassica napus L. cv. SW Landmark) were compared in a lysimeter experiment conducted
in an open sided glass house to test the hypothesis that oilseed rape was more sensitive
to drying soil than wheat. Plants were grown with or without irrigation at a population
density equivalent to that of commercial field crops. Irrigated oilseed rape crops
transpired more water than wheat crops and oilseed rape showed a greater reduction in
growth when water was withheld. The onset of drought also occurred slightly earlier in
oilseed rape. In a separate experiment the root hydraulic conductance of oilseed rape,
measured on a root surface area basis, was about twice that of wheat (113.1 ± 20.0
mlNm-2Nh-1NMPa-1 for oilseed rape and 53. 5 ± 10.6 for wheat). These results suggest that
oilseed rape needs a less dense root system for water extraction than wheat.
In the above experiment plants were grown in relatively loose soil repacked into
the lysimeters. It has been suggested that oilseed rape is particularly sensitive to soil
compaction, which may be a common occurrence in commercial fields. Therefore the
sensitivity of oilseed rape and wheat growth to compaction was compared in an
experiment under well-watered conditions. Plants were grown in a controlled
environment chamber in pots packed with soil at four different bulk densities. Although
the root length, shoot mass, leaf area and stomatal conductance of oilseed rape were all
reduced by soil compaction, oilseed rape was no more sensitive to soil compaction than
wheat under these well-watered conditions.
When soil dries it also hardens and high soil strength is known to impede root
growth and alter plant-water relations. The hypothesis that oilseed rape is more sensitive
to increasing soil strength than wheat was tested in an experiment in which soil bulk
density and soil water content were varied to create a range of soil strengths. At low soil
strength oilseed rape had a greater stomatal conductance than wheat, but as soil strength
increased, stomatal conductance decreased to a greater extent in oilseed rape, indicating
a more sensitive response. In dense or strong soil, plants often rely on pores created by
earthworms or roots of the previous crop to explore the soil volume. The ability of
oilseed rape and wheat to exploit soil pores to penetrate hard soil layers was compared
in a pot experiment. A hard layer, comparable to a hard–pan in a cultivated field, was
created at twelve centimetre depth of each pot by packing the soil to a bulk density of
1.5 g·cm-3 relatively loose soil at a bulk density of 1.1 g·cm-3 was present above and
below the layer. In one treatment seven pores were drilled through the hard layer;
controls had none. Presence of pores in the hard layer led to a significant increase in
number of roots in the deeper soil, of 29% for wheat and 54% for oilseed rape.
This project has shown that the physiological response to drought occurred
earlier in oilseed rape than in wheat and that stomatal conductance and biomass
production of oilseed rape reacted more sensitively to soil drying. However, water use
by oilseed rape does not seem to be limited by the ability of its roots to explore the soil
and transport water compared to wheat. The growth and distribution of roots under a
range of soil conditions was as good as, if not better than, that of wheat. The
implications of these findings for the commercial production of oilseed rape in the UK
are discussed
Prospective Comparison of FFR Derived From Coronary CT Angiography With SPECT Perfusion Imaging in Stable Coronary Artery Disease:The ReASSESS Study
Algorithmic corrections for localization microscopy with sCMOS cameras - characterisation of a computationally efficient localization approach
Modern sCMOS cameras are attractive for single molecule localization microscopy (SMLM) due to their high speed but suffer from pixel non-uniformities that can affect localization precision and accuracy. We present a simplified sCMOS non-uniform noise model that incorporates pixel specific read-noise, offset and sensitivity variation. Using this model we develop a new weighted least squared (WLS) fitting method designed to remove the effect of sCMOS pixel non-uniformities. Simulations with the sCMOS noise model, performed to test under which conditions sCMOS specific localization corrections are required, suggested that pixel specific offsets should always be removed. In many applications with thick biological samples photon fluxes are sufficiently high that corrections of read-noise and sensitivity correction may be neglected. When correction is required, e.g. during fast imaging in thin samples, our WLS fit procedure recovered the performance of an equivalent sensor with uniform pixel properties and the fit estimates also attained the Cramer-Rao lower bound. Experiments with sub-resolution beads and a DNA origami test sample confirmed the results of the simulations. The WLS localization procedure is fast to converge, compatible with 2D, 3D and multi-emitter localization and thus provides a computationally efficient sCMOS localization approach compatible with most SMLM modalities
Strain field analysis on Montserrat (W.I.) as tool for assessing permeable flow paths in the magmatic system of Soufrière Hills Volcano
Strain dilatometers have been operated on the volcanic island of Montserrat (West Indies) for more than a decade and have proven to be a powerful technique to approach short-term dynamics in the deformational field in response to pressure changes in the magmatic system of the andesitic dome-building Soufrière Hills Volcano (SHV). We here demonstrate that magmatic activity in each of the different segments of the SHV magmatic system (shallow dyke-conduit, upper and lower magma chambers) generates a characteristic strain pattern that allows the identification of operating sources in the plumbing system based on a simple scheme of amplitude ratios. We use this method to evaluate strain data from selected Vulcanian explosions and gas emission events that occurred at SHV between 2003 and 2012. Our results show that the events were initiated by a short phase of contraction of either one or both magma chambers and a simultaneous inflation of the shallow feeder system. The initial phase of the events usually lasted only tens to hundreds of seconds before the explosion/gas emission started and the system recovered. The short duration of this process points at rapid transport of fluids rather than magma ascent to generate the pressure changes. We suggest the propagation of tensile hydraulic fractures as viable mechanism to provide a pathway for fluid migration in the magmatic system at the observed time scale. Fluid mobilization was initiated by a sudden destabilization of large pockets of already segregated fluid in the magma chambers. Our study demonstrates that geodetic observables can provide unprecedented insights into complex dynamic processes within a magmatic system commonly assessed by theoretical modeling and petrologic observations. Key Points Strain data analysis from explosions/degassing events at Soufriere Hills Volcano Pressure release deep within the magmatic system sec-min prior to events Rapid gas rise from magma reservoir to surface via tensile hydraulic fractures © 2014. American Geophysical Union. All Rights Reserved
Cementless Total Hip Arthroplasty with Medial Wall Osteotomy for the Sequelae of Septic Arthritis of the Hip
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Changes in the arabinoxylan fraction of wheat grain during 1 alcohol production
Laboratory produced DDGS samples were compared with commercial samples from a distillery and a
biofuel plant. Changes in structure, solubility and content of arabinoxylan (AX) was determined. The
distillation process results in a relative increase of AX content compared to the starting material. The
heating and drying processes involved in the production of DDGS lead to an increased solubility and
viscosity of water-extractable AX. Production of DDGS results in structural changes to the AX. There
is a decrease in 2-and 3-linked arabinose oligosaccharides, that contributes to around a 50%
reduction in arabinosylation in DDGS compared with the starting grains. The current study shows
that laboratory-scale DDGS provide an accurate representation of the commercial scale and that the
AX composition of DDGS is consistently uniform irrespective of starting material. The uniformity of
DDGS and thin stillage makes them a good potential source of AX for production of prebiotics or
other novel products
4D Super-Resolution Microscopy with Conventional Fluorophores and Single Wavelength Excitation in Optically Thick Cells and Tissues
Optical super-resolution imaging of fluorescently stained biological samples is rapidly becoming an important tool to investigate protein distribution at the molecular scale. It is therefore important to develop practical super-resolution methods that allow capturing the full three-dimensional nature of biological systems and also can visualize multiple protein species in the same sample
A guide to super-resolution fluorescence microscopy
For centuries, cell biology has been based on light microscopy and at the same time been limited by its optical resolution. However, several new technologies have been developed recently that bypass this limit. These new super-resolution technologies are either based on tailored illumination, nonlinear fluorophore responses, or the precise localization of single molecules. Overall, these new approaches have created unprecedented new possibilities to investigate the structure and function of cells
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