High resolution synchrotron imaging of wheat root hairs growing in soil and image based modelling of phosphate uptake

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 Tomographic Microscopy (SRXTM) to uncover the 3D 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 localised 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 individual root hairs in soil pores

Hormonal regulation of stem cell maintenance in root meristems of Arabidopsis thaliana

Continuing root growth is crucial for the ongoing survival of a plant and provides the structure basis for the acquisition of valuable resources such as water and nutrients required for growth and development. The root apical meristem, located at the root apex, contains a stem cell niche which is the source of root cell production and patterning. This project focuses on the influence of phytohormone signalling upon the maintenance of the root apical meristem (RAM) in Arabidopsis thaliana. Through a combination of physiological, genetic and molecular approaches, the project has uncovered evidence of the involvement of three plant hormones, auxin, abscisic acid (ABA) and ethylene, in regulating the differentiation of stem cells and their descendants in Arabidopsis root meristems. Key findings include: 1) exogenous application of auxin, ABA or 1-aminocyclopropane-1-carboxylic acid (ACC), which is an ethylene precursor, rescues the root meristem failure of a1f3-1 seedlings; 2) exogenous application of ABA promotes QC quiescence and suppresses stem cell differentiation in wild type Arabidopsis root meristems; 3) inhibition of ethylene biosynthesis and mutations that cause ethylene insensitivity induce differentiation of stem cells in root meristems and.i.on the other hand, exogenous application of ethylene precursor or mutations causes ethylene over-production suppress stem cell differentiation in Arabidopsis root meristems; 4) ABA and ethylene interact antagonistically with auxin in the regulation of both stem cell differentiation in Arabidopsis root meristem, and the expression of the CLE40 gene, which encodes a negative regulator of stem cell differentiation in root meristems; 5) ABA modulates the abundance of the LM6 arabinan cell wall epitope within at the root meristem; 6) ethylene suppresses the stem cell differentiation in Arabidopsis root meristems induced by nitrogen (N) and phosphorus (P) deficiencies. The results of the project demonstrate that stem cell regulation in Arabidopsis root meristems involves complex interactions of plant hormones and environmental signals.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Hormonal regulation of stem cell maintenance in root meristems of Arabidopsis thaliana

Continuing root growth is crucial for the ongoing survival of a plant and provides the structure basis for the acquisition of valuable resources such as water and nutrients required for growth and development. The root apical meristem, located at the root apex, contains a stem cell niche which is the source of root cell production and patterning. This project focuses on the influence of phytohormone signalling upon the maintenance of the root apical meristem (RAM) in Arabidopsis thaliana. Through a combination of physiological, genetic and molecular approaches, the project has uncovered evidence of the involvement of three plant hormones, auxin, abscisic acid (ABA) and ethylene, in regulating the differentiation of stem cells and their descendants in Arabidopsis root meristems. Key findings include: 1) exogenous application of auxin, ABA or 1-aminocyclopropane-1-carboxylic acid (ACC), which is an ethylene precursor, rescues the root meristem failure of a1f3-1 seedlings; 2) exogenous application of ABA promotes QC quiescence and suppresses stem cell differentiation in wild type Arabidopsis root meristems; 3) inhibition of ethylene biosynthesis and mutations that cause ethylene insensitivity induce differentiation of stem cells in root meristems and.i.on the other hand, exogenous application of ethylene precursor or mutations causes ethylene over-production suppress stem cell differentiation in Arabidopsis root meristems; 4) ABA and ethylene interact antagonistically with auxin in the regulation of both stem cell differentiation in Arabidopsis root meristem, and the expression of the CLE40 gene, which encodes a negative regulator of stem cell differentiation in root meristems; 5) ABA modulates the abundance of the LM6 arabinan cell wall epitope within at the root meristem; 6) ethylene suppresses the stem cell differentiation in Arabidopsis root meristems induced by nitrogen (N) and phosphorus (P) deficiencies. The results of the project demonstrate that stem cell regulation in Arabidopsis root meristems involves complex interactions of plant hormones and environmental signals.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Struvite: a slow-release fertiliser for sustainable phosphorus management

Background and Aim: Recycled sources of phosphorus (P), such as struvite extracted from wastewater, have potential to substitute for more soluble manufactured fertilizers and help reduce the long-term threat to food security from dwindling finite reserves of phosphate rock (PR). This study aimed to determine whether struvite could be a component of a sustainable P fertiliser management strategy for arable crops.Methods: A combination of laboratory experiments, pot trials and mathematical modelling of the root system examined the P release properties of commercial fertiliser-grade struvite and patterns of P uptake from a low-P sandy soil by two different crop types, in comparison to more soluble inorganic P fertilisers (di-ammonium phosphate (DAP) and triple super phosphate (TSP)). Results: Struvite had greatly enhanced solubility in the presence of organic acid anions; buckwheat, which exudes a high level of organic acids, was more effective at mobilising struvite P than the low level exuder, spring wheat. Struvite granules placed with the seed did not provide the same rate of P supply as placed DAP granules for early growth, but fertiliser mixes containing struvite and DAP applied to spring wheat demonstrated optimal early P-uptake and higher rates of P-fertiliser recovery.Conclusions: We conclude that the potential resource savings and efficiency benefits of utilising a recycled slow release fertiliser like struvite offers a more sustainable alternative to only using conventional, high solubility, PR-based fertilisers.?<br/

A mathematical model of water and nutrient transport in xylem vessels of a wheat plant

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 crop 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 7 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

Combining seed dressing and foliar applications of phosphorus fertiliser can give similar crop growth and yield benefits to soil applications together with greater recovery rates

Phosphorus (P) fertilisers have a dramatic effect on agricultural productivity, but conventional methods of application result in only limited recovery of the applied P. Given the increasing volatility in rock phosphate prices, more efficient strategies for P fertiliser use would be of economic and environmental benefit in the drive for sustainable intensification. This study used a combination of controlled-environment experiments and radioisotopic labelling to investigate the fertiliser use efficiency of a combination of seed (grain) dressing and foliar applications of P to spring wheat (Triticum aestivum L.). Radioisotopic labelling showed that the application of foliar P in the presence of photosynthetic light substantially increased both P-uptake into the leaf and P-mobilisation within the plant, especially when an adjuvant was used. When compared with soil application of inorganic P buried into the rooting zone, a combination of 3 μmol seed dressings and three 46.3 μmol plant-1 foliar applications were far more efficient at providing P fertilisation benefits in P-limiting conditions. We conclude that a combination of seed dressing and foliar applications of P is potentially a better alternative to conventional soil-based application, offering greater efficiency in use of applied P both in terms of P-uptake rate and grain yield. Further work is required to evaluate whether these results can be obtained under a range of field conditions

Myartspace: Design and evaluation of support for learning with multimedia phones between classrooms and museums

This paper presents a description and evaluation of Myartspace, a service on mobile phones for inquiry-led learning that allows students to gather information during a school field trip which is automatically sent to a website where they can view, share and present it, back in the classroom or at home. The evaluation focused on three levels: a micro level, concerned with issues of usability; a meso level, which examined educational effectiveness in terms of learning breakthroughs and breakdowns; and a macro level, which looked at the impact of the new technology on school museum visits practice. Issues of implementing mobile learning across school and museum settings are identified and cross-level influences are discussed. The study showed that the service was effective in enabling students to gather information in a museum and this provided resources for effective construction and reflection in the classroom. Minor usability problems did not detract from the learning, however there are significant issues concerning how to structure the visit and on the viability of Myartspace as a regular service