ORCID Profile
0000-0001-8710-1063
Current Organisation
University of Southampton
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Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-8609
Abstract: & & Sufficient nitrogen fertilisation is essential for obtaining the crop yields required to feed the growing population. Moreover, nitrogen applied to fields is often lost to a number of processes including denitrification, surface run-off and leaching. These processes can damage the local ecology and contaminate water supplies. Additionally, nitrogen lost as ammonia gas and the large energy input required to synthesize ammonia are both large contributors to global greenhouse gas emissions. Choosing fertilisation strategies to optimise the proportion of nitrogen taken up by crops (nitrogen use efficiency) can reduce the production of ammonia and the pollution of water supplies.& & & & We developed a mathematical model that describes the movement of water and multiple nitrogen species in soil at the field scale over a growing season. The model was then used to assess the nitrogen use efficiency of varying fertilisation strategies. We consider the effects of a number of biological, chemical, and physical processes including: root growth, root uptake, the transformation of nitrogen between different nitrogen species, and the effect of soil water movement on nitrogen transport. The resulting model is comprised of a coupled system of partial and ordinary differential equations that describe the mathematical interplay between nitrogen transport, water movement, and root uptake, which were solved numerically using a finite element approach. Numerical experiments were conducted to determine how nitrogen uptake efficiency was affected by different fertilisation strategies. We examine numerous cases by varying the quantity of fertiliser applied to the soil and the fertiliser application times.& & & & The numerical experiments suggest that, under uniform rainfall rates, the optimal fertilisation times (within the bounds of typical times found in agriculture) can result in 25% more nitrogen uptake than the worst strategies. However, there were large time periods, 28 days for the first application and 10 days for the second, which resulted in close-to-optimal nitrogen use efficiency. The results of this study, in addition to crop health and past and predicted rainfall, could be taken into consideration by farmers while choosing fertilisation times to optimise nitrogen uptake efficiency.& &
Publisher: Springer Science and Business Media LLC
Date: 13-06-2015
Publisher: Springer Science and Business Media LLC
Date: 06-12-2019
DOI: 10.1007/S11104-019-04308-2
Abstract: Root hairs play a significant role in phosphorus (P) extraction at the pore scale. However, their importance at the field scale remains poorly understood. This study uses a continuum model to explore the impact of root hairs on the large-scale uptake of P, comparing root hair influence under different agricultural scenarios. High vs low and constant vs decaying P concentrations down the soil profile are considered, along with early vs late precipitation scenarios. Simulation results suggest root hairs accounted for 50% of total P uptake by plants. Furthermore, a delayed initiation time of precipitation potentially limits the P uptake rate by over 50% depending on the growth period. Despite the large differences in the uptake rate, changes in the soil P concentration in the domain due to root solute uptake remains marginal when considering a single growth season. However, over the duration of 6 years, simulation results showed that noticeable differences arise over time. Root hairs are critical to P capture, with uptake efficiency potentially enhanced by coordinating irrigation with P application during earlier growth stages of crops.
Publisher: Wiley
Date: 24-06-2014
DOI: 10.1111/PCE.12376
Abstract: The readily available global rock phosphate (P) reserves may run out within the next 50-130 years, causing soils to have a reduced P concentration which will affect plant P uptake. Using a combination of mathematical modelling and experimental data, we investigated potential plant-based options for optimizing crop P uptake in reduced soil P environments. By varying the P concentration within a well-mixed agricultural soil, for high and low P (35.5-12.5 mg L(-1) respectively using Olsen's P index), we investigated branching distributions within a wheat root system that maximize P uptake. Changing the root branching distribution from linear (evenly spaced branches) to strongly exponential (a greater number of branches at the top of the soil) improves P uptake by 142% for low-P soils when root mass is kept constant between simulations. This causes the roots to emerge earlier and mimics topsoil foraging. Manipulating root branching patterns, to maximize P uptake, is not enough on its own to overcome the drop in soil P from high to low P. Further mechanisms have to be considered to fully understand the impact of P reduction on plant development.
Publisher: Copernicus GmbH
Date: 28-04-2021
DOI: 10.5194/ISMC2021-11
Abstract: & & Half of the nitrogen applied to arable-fields is lost through several processes linked to soil moisture. Low soil moisture limits nitrogen mobility reducing nitrogen-uptake while wetter conditions can increase nitrogen leaching. Rainfall ultimately governs soil moisture and the fate of nitrogen in soil. However, the interaction between rainfall and nitrogen use efficiency (NUE) remains poorly understood.& & & & We developed a field-scale modelling platform that describes coupled water and nitrogen transport, root growth and uptake, rainfall, the nitrogen-cycle and leaching to assess the NUE of split fertilisations with realistic rainfall patterns. The model was solved for every possible split fertilisation timing in 200+ growing seasons to determine optimal timings. Two previous field trials regarding rainfall and NUE had contrasting results: wetter years have enhanced fertiliser loss and drier years reduced plant nitrogen uptake. By choosing appropriate fertilisation timings in the model we could recreate the two contrasting trends and maintain variability in the data. However, we found by choosing other fertilisation timings we could mitigate the leaching in wetter years. Optimised timings could increase plant nitrogen uptake by up to 35% compared to the mean in dry years. Plant uptake was greatest under drier conditions due to mitigated leaching, but less likely to occur due to low nitrogen mobility. Optimal fertilisation timings varied dramatically depending on the rainfall patterns. Historic and projected rainfall patterns from 1950-2069 were used in the model. We found optimal NUE has a decrease from 2022-2040 due to increased heavy rainfall events and optimal fertilisation timings are later in the season but varied largely on a season-to-season basis.& & & & The results are a step towards achieving improved nitrogen efficiency in agriculture by using the & #8216 at the right time& #8217 agronomic-strategy in the & #8216 Rs& #8217 of improved nitrogen fertilisation. Our results can help determine nitrogen fertilisation timings in changing climates.& &
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.NEDT.2014.12.021
Abstract: Previous research has indicated a disconnect between academic nursing programmes and workplace learning environments. Nurse supervisors and clinical practitioners have reported inadequate information and training on how to support students of nursing to learn in the clinical setting. This study aimed to investigate the level of confidence that clinical supervisors have in relation to specific components of supporting student learning in the work place. Survey of clinical nurse supervisors. Simulation-based clinical reasoning workshops. Sixty participants: fifty nine registered nurses, including nurse managers and clinical nurse educators, and one allied health professional. Survey using Likert scales and free-text questions. The findings indicated that clinicians were confident in sharing their knowledge and experience with students and making them feel welcome in the work place, they were less confident about what were the significant learnings in relation to students' academic programme. Registered nurses supervising students were experienced clinicians with many role responsibilities, which were perceived as barriers to the role of clinical supervisor. Participants reported that they would like tools to assist them with developing links to the academic programme. They considered that these tools would support student learning and remediation in the work place. This study found that the abilities of supervisors to support student learning is an identified gap impacting on work integrated learning. The results indicated the need for a professional development workshop, to enable clinical supervisors to move beyond promoting a supervision model, towards a theoretical framework for assisting and guiding students to learn. Addressing this deficit will improve growth and change in student learning in the work place.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-8648
Abstract: & & & & Soil microbial communities contribute many ecosystem services including soil structure maintenance, crop synergy, and carbon sequestration. However, it is not fully understood how the health of microbial communities is effected by fertilization at the pore scale. This study investigates the nature of nitrogen (N) transport and reactions at the soil pore scale in order to better understand the influence of soil structure and moisture content on microbial community health. Using X-ray Computed Tomography (XRCT) scans, we reconstructed a microscale description of a dry soil-pore geometry as a computational mesh. Solving two-phase water/air models produced pore-scale water distributions at 15, 30 and 70% water-filled pore volume. The model considers ammonium (NH& sub& & /sub& & sup& +& /sup& ), nitrate (NO& sub& & /sub& & sup& -& /sup& ) and dissolved organic N (DON), and includes N immobilization, ammonification and nitrification processes, as well as diffusion in soil-solution. We simulated the dissolution of a fertilizer pellet and a pore scale N cycle at the three different water saturation conditions. To aid interpretation of the model results, microbial activity at a range of N concentrations was quantified experimentally using labelled C to infer microbial activity based on CO& sub& & /sub& respiration measurements in bulk soil. The pore-scale model showed that the diffusion and concentration of N in water films is critically dependent upon soil moisture and N species. We predicted that the maximum NH& sub& & /sub& & sup& +& /sup& and NO& sub& & /sub& & sup& -& /sup& concentrations in soil solution around the pellet under low water saturation conditions (15%) are in the order of 1x10& sup& & /sup& and 1x10& sup& & /sup& mol m& sup& -3& /sup& respectively (1-10 M), and under higher water saturation conditions (70%) where on the order of 2x10& sup& & /sup& and 1x10& sup& & /sup& mol m& sup& -3& /sup& , respectively (0.1-1 M). Supporting experimental evidence regarding microbial respiration suggests that these concentrations at the pore-scale would be sufficient to reduce microbial activity in the zone immediately around the fertilizer pellet (ranging from 0.9 to 3.8 mm depending on soil moisture status), causing a major loss of soil biological activity by up to 90%. This model demonstrates the importance of pore-scale processes in regulating N movement in soil with special capability to predict the effects of fertilizers on rhizosphere-scale processes and the root microbiome.& & & / &
Publisher: Springer Science and Business Media LLC
Date: 02-02-2019
Publisher: The Royal Society
Date: 11-2017
Abstract: The parameters in Richards' equation are usually calculated from experimentally measured values of the soil–water characteristic curve and saturated hydraulic conductivity. The complex pore structures that often occur in porous media complicate such parametrization due to hysteresis between wetting and drying and the effects of tortuosity. Rather than estimate the parameters in Richards' equation from these indirect measurements, image-based modelling is used to investigate the relationship between the pore structure and the parameters. A three-dimensional, X-ray computed tomography image stack of a soil s le with voxel resolution of 6 μm has been used to create a computational mesh. The Cahn–Hilliard–Stokes equations for two-fluid flow, in this case water and air, were applied to this mesh and solved using the finite-element method in COMSOL Multiphysics. The upscaled parameters in Richards' equation are then obtained via homogenization. The effect on the soil–water retention curve due to three different contact angles, 0°, 20° and 60°, was also investigated. The results show that the pore structure affects the properties of the flow on the large scale, and different contact angles can change the parameters for Richards' equation.
Publisher: Wiley
Date: 22-04-2013
DOI: 10.1111/NPH.12294
Abstract: Root hairs are known to be highly important for uptake of sparingly soluble nutrients, particularly in nutrient deficient soils. Development of increasingly sophisticated mathematical models has allowed uptake characteristics to be quantified. However, modelling has been constrained by a lack of methods for imaging live root hairs growing in real soils. We developed a plant growth protocol and used Synchrotron Radiation X ‐ray T omographic M icroscopy ( SRXTM ) to uncover the three‐dimensional (3 D) interactions of root hairs in real soil. We developed a model of phosphate uptake by root hairs based directly on the geometry of hairs and associated soil pores as revealed by imaging. Previous modelling studies found that root hairs dominate phosphate uptake. By contrast, our study suggests that hairs and roots contribute equally. We show that uptake by hairs is more localized than by roots and strongly dependent on root hair and aggregate orientation. The ability to image hair–soil interactions enables a step change in modelling approaches, allowing a more realistic treatment of processes at the scale of in idual root hairs in soil pores.
Publisher: Frontiers Media SA
Date: 25-05-2018
Publisher: Springer Science and Business Media LLC
Date: 19-06-2007
Publisher: American Physiological Society
Date: 11-2016
Abstract: Mechanosensory neurons detect physical events in the local environments of the tissues that they innervate. Studies of mechanosensitivity of neurons or nerve endings in the gut have related their firing to strain, wall tension, or pressure. Digital image correlation (DIC) is a technique from materials engineering that can be adapted to measure the local physical environments of afferent neurons at high resolution. Flat-sheet preparations of guinea pig distal colon were set up with arrays of tissue markers in vitro. Firing of single viscerofugal neurons was identified in extracellular colonic nerve recordings. The locations of viscerofugal nerve cell bodies were inferred by mapping firing responses to focal application of the nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium iodide. Mechanosensory firing was recorded during load-evoked uniaxial or biaxial distensions. Distension caused movement of surface markers which was captured by video imaging. DIC tracked the markers, interpolating the mechanical state of the gut at the location of the viscerofugal nerve cell body. This technique revealed heterogeneous load-evoked strain within preparations. Local strains at viscerofugal nerve cell bodies were usually smaller than global strain measurements and correlated more closely with mechanosensitive firing. Both circumferential and longitudinal strain activated viscerofugal neurons. Simultaneous loading in circumferential and longitudinal axes caused the highest levels of viscerofugal neuron firing. Multiaxial strains, reflecting tissue shearing and changing area, linearly correlated with mechanosensory firing of viscerofugal neurons. Viscerofugal neurons were mechanically sensitive to both local circumferential and local longitudinal gut strain, and appear to lack directionality in their stretch sensitivity.
Publisher: Wiley
Date: 31-07-2017
DOI: 10.1111/NPH.14705
Abstract: 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 ( c . 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 ), with and without root hairs, were grown for 8 d in microcosms packed with sandy loam soil at 1.2 g cm −3 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 ( 5 μm) in the rhizosphere, as compared with the no‐hair mutants. Both genotypes showed decreasing pore space between 0.8 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.
Publisher: Springer Science and Business Media LLC
Date: 14-04-2016
Publisher: Wiley
Date: 27-10-2017
DOI: 10.1111/EJSS.12487
Publisher: Springer Science and Business Media LLC
Date: 13-03-2015
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.EJCA.2006.05.020
Abstract: The distribution of chemotherapeutics in solid tumours is poorly understood and the contribution it makes to treatment failure is unknown. Novel approaches are required to understand how the three-dimensional organisation of cancer cells in solid tumours affects drug availability. Since convective drug transport is limited by increased interstitial pressure in poorly vascularised cancers, the aim of this study was to measure the diffusive hindrance exerted by solid tumour tissue. Multicell layer tumour models comprising DLD1 colon cancer cells were characterised and fluxes were determined for [3H]-vinblastine and [14C]-sucrose. The mathematical models provided the diffusion coefficients for both compounds and predicted higher exposure of cells in the vicinity of vessels. The diffusion of vinblastine was three times slower than that of sucrose. Although slow diffusion delays vinblastine penetration into the avascular regions of tumours, the proliferating cells are generally in the marginal area of tumours. The mathematical model that we have developed enabled accurate quantification of drug pharmacokinetic behaviour, in particular, the diffusivity of vinblastine within solid tissue. This mathematical model may be adapted readily to incorporate the influence of factors mediating pharmacokinetic drug resistance.
Publisher: Springer Science and Business Media LLC
Date: 11-06-2022
DOI: 10.1007/S11104-022-05530-1
Abstract: Recent laboratory studies revealed that root hairs may alter soil physical behaviour, influencing soil porosity and water retention on the small scale. However, the results are not consistent, and it is not known if structural changes at the small-scale have impacts at larger scales. Therefore, we evaluated the potential effects of root hairs on soil hydro-mechanical properties in the field using rhizosphere-scale physical measurements. Changes in soil water retention properties as well as mechanical and hydraulic characteristics were monitored in both silt loam and sandy loam soils. Measurements were taken from plant establishment to harvesting in field trials, comparing three barley genotypes representing distinct phenotypic categories in relation to root hair length. Soil hardness and elasticity were measured using a 3-mm-diameter spherical indenter, while water sorptivity and repellency were measured using a miniaturized infiltrometer with a 0.4-mm tip radius. Over the growing season, plants induced changes in the soil water retention properties, with the plant available water increasing by 21%. Both soil hardness ( P = 0.031) and elasticity ( P = 0.048) decreased significantly in the presence of root hairs in silt loam soil, by 50% and 36%, respectively. Root hairs also led to significantly smaller water repellency ( P = 0.007) in sandy loam soil vegetated with the hairy genotype (-49%) compared to the hairless mutant. Breeding of cash crops for improved soil conditions could be achieved by selecting root phenotypes that ameliorate soil physical properties and therefore contribute to increased soil health.
Publisher: The Royal Society
Date: 09-2018
Abstract: Most water and nutrients essential for plant growth travel across a thin zone of soil at the interface between roots and soil, termed the rhizosphere. Chemicals exuded by plant roots can alter the fluid properties, such as viscosity, of the water phase, potentially with impacts on plant productivity and stress tolerance. In this paper, we study the effects of plant exudates on the macroscale properties of water movement in soil. Our starting point is a microscale description of two fluid flow and exudate diffusion in a periodic geometry composed from a regular repetition of a unit cell. Using multiscale homogenization theory, we derive a coupled set of equations that describe the movement of air and water, and the diffusion of plant exudates on the macroscale. These equations are parametrized by a set of cell problems that capture the flow behaviour. The mathematical steps are validated by comparing the resulting homogenized equations to the original pore scale equations, and we show that the difference between the two models is ≲7% for eight cells. The resulting equations provide a computationally efficient method to study plant–soil interactions. This will increase our ability to predict how contrasting root exudation patterns may influence crop uptake of water and nutrients.
Publisher: Springer Science and Business Media LLC
Date: 11-12-2015
Publisher: Wiley
Date: 05-2016
Publisher: Springer Science and Business Media LLC
Date: 21-02-2014
DOI: 10.1007/S11538-013-9932-4
Abstract: At a time of increasing global demand for food, dwindling land and resources, and escalating pressures from climate change, the farming industry is undergoing financial strain, with a need to improve efficiency and crop yields. In order to improve efficiencies in farming, and in fertiliser usage in particular, understanding must be gained of the fertiliser-to-crop-yield pathway. We model one aspect of this pathway the transport of nutrients within the vascular tissues of a crop plant from roots to leaves. We present a mathematical model of the transport of nutrients within the xylem vessels in response to the evapotranspiration of water. We determine seven different classes of flow, including positive unidirectional flow, which is optimal for nutrient transport from the roots to the leaves and root multidirectional flow, which is similar to the hydraulic lift process observed in plants. We also investigate the effect of diffusion on nutrient transport and find that diffusion can be significant at the vessel termini especially if there is an axial efflux of nutrient, and at night when transpiration is minimal. Models such as these can then be coupled to whole-plant models to be used for optimisation of nutrient delivery scenarios.
Publisher: Wiley
Date: 20-11-2018
DOI: 10.1111/NPH.15516
Abstract: 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 (<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.
Publisher: The Royal Society
Date: 10-10-2012
Abstract: We develop a model of the buckling (both planar and axial) of capillaries in cancer tumours, using nonlinear solid mechanics. The compressive stress in the tumour interstitium is modelled as a consequence of the rapid proliferation of the tumour cells, using a multiplicative decomposition of the deformation gradient. In turn, the tumour cell proliferation is determined by the oxygen concentration (which is governed by the diffusion equation) and the solid stress. We apply a linear stability analysis to determine the onset of mechanical instability, and the Liapunov–Schmidt reduction to determine the postbuckling behaviour. We find that planar modes usually go unstable before axial modes, so that our model can explain the buckling of capillaries, but not as easily their tortuosity. We also find that the inclusion of anisotropic growth in our model can substantially affect the onset of buckling. Anisotropic growth also results in a feedback effect that substantially affects the magnitude of the buckle.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Tiina Roose.