Dissertationen zum Thema „Nutrient“

High concentrations of dissolved nutrients in stormwater have been identified as contributing to eutrophication of receiving waterways near urban areas. To reduce dissolved nutrient concentrations in stormwater a range of devices such as wetlands and bioretention systems are used. Bioretention systems are increasingly employed for their supposedly high nutrient removal capacity, however very little is known about their treatment efficiency or the chemical and biological mechanisms controlling their function. This research aimed firstly to test and compare the efficiency of different bioretention system designs for the removal of dissolved nutrients from stormwater, and secondly to investigate the chemical and biological mechanisms responsible for the nutrient removal (sorption, microbial uptake, and plant uptake). Bioretention mesocosms were built in plastic containers (1 m x 0.5 m x 0.5 m). Three different media treatments were built, representing those most commonly used: gravel, fine sand and loamy-sand. To assess the nutrient removal capacity of plants, vegetated and unvegetated examples of each media type were made. The mesocosms were regularly irrigated with tap water for six months, and then regularly irrigated with synthetic stormwater for a further six months to ensure that the treatment performance assessed would represent fully established systems. The synthetic stormwater solution was based on field measurements of stormwater, and was made using a combination of inorganic chemicals and organic fertilisers. By incorporating organic carbon and major cations (Ca, Mg, Na, K), the measured treatment performance of the biofilters would be more realistic than previous studies that did not corporate these compounds. Some mesocosms were watered only with tap water so that the effect of frequent fertilisation (enrichment) could be compared. It was expected that vegetated media would enhance nutrient removal directly through plant uptake, and indirectly by stimulating microbial productivity and microbial uptake in the rhizosphere. Nutrient removal was evaluated by comparing the influent to the effluent. Detention times of 24 and 72 hours were compared to test if longer contact periods resulted in greater nutrient removal. The mesocosms were also flushed with tap water (no nutrients) to determine the proportion of entrained nutrients that might subsequently leach from the media. Vegetated bioretention mesocosms were much more efficient than unvegetated systems at removing total nitrogen (63 – 77 % removal compared to -12 – 25 %) and total phosphorus (85 – 94 % removal compared to 31 – 90 %). The vegetation effect did not improve dissolved organic carbon removal but there was a difference between soil types, with smaller particle size media removing more organic carbon. Enriched mesocosms removed similar quantities of nutrients to non-enriched mesocosms. Extending the detention time from 24 hours to 72 hours slightly increased the removal of total nitrogen from the vegetated mesocosms, but reduced total nitrogen removal from unvegetated mesocosms. When flushed with tap water, inorganic and organic forms of nitrogen and phosphorus leached from the unvegetated mesocosms, but were mostly retained within the vegetated mesocosms...
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Science, Environment, Engineering and Technology
Full Text

Nutrient sensing neurons are unique in coupling changes in the concentration of nutrients to changes in neuronal activity. These neurons typically exist in regions of the brain where the blood brain barrier is fenestrated, such as the arcuate nucleus of the hypothalamus. Glucose and leucine are nutrients known to be sensed by neurons in this brain region, but the mechanisms by which they are sensed, and cells that sense them require further study. Using calcium imaging of adult neuron cultures from the mouse mediobasal hypothalamus, I demonstrated that leucine bidirectionally regulates neuronal activity in a neurochemically heterogeneous population of neurons, including AgRP/NPY and POMC neurons. Using pharmacological tools, I demonstrated, unexpectedly, that this acute sensing is independent of mTOR and leucine metabolism, known pathways involved in leucine sensing in vivo. Leucine sensing is LAT1 independent. The response principally relies on calcium entry into the cell across the plasma membrane, but IP3 sensitive calcium stores play a role in neurons inhibited by leucine. Using phosphoTRAP and single cell RNA sequencing, I aimed to identify a molecular marker for leucine sensing cells to allow their manipulation in vivo. PhosphoTRAP, and subsequent pharmacological studies identified a T Type calcium channel may be a marker for leucine sensing cells. AgRP neurons are essential for feeding, and also play roles in controlling glucose homeostasis. Using chemogenetics to selectively activate these neurons, I demonstrated, in contrast to a similar, recently published study, that blood glucose concentrations did not rise upon activation of these neurons. A subpopulation of AgRP neurons express glucokinase, and some AgRP neurons are glucose inhibited, but the role of glucokinase in these neurons has not been characterised. Our lab generated an AgRP neuron specific glucokinase knock out mouse line. Preliminary results suggest 18 – 25 week old female AgRP glucokinase knock out mice may have altered glucose tolerance, but conclusions can only be drawn once further mice have been phenotyped, and the success of the glucokinase knock out from AgRP neurons has been confirmed.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
A cultura da batata tem grande importância para o Brasil e para o Estado de São Paulo. Porém, apesar de sua importância, falta maiores informações sobre a fisiologia e nutrição mineral desta cultura, limitando a obtenção de elevadas produtividades, com alta qualidade e baixo custo de produção, já que as peculiaridades de cada cultivar podem fazer grande diferença no manejo. Além disso, as doses de fertilizantes normalmente utilizadas na cultura da batata são elevadas, o que gera grande impacto no custo de produção e riscos ambientais. Assim, para obtenção da máxima eficiência produtiva, faz-se necessário o conhecimento do desenvolvimento da planta e da absorção e acumulação de nutrientes nas diferentes fases de desenvolvimento. O objetivo deste trabalho foi avaliar o crescimento, acúmulo de nutrientes durante o ciclo, produtividade de tubérculos e exportação de nutrientes em cinco cultivares de batata. O delineamento experimental utilizado foi o de blocos casualizados, em esquema de parcela subdividida, com quatro repetições. As parcelas foram constituídas pelas cultivares (Ágata, Asterix, Atlantic, Markies e Mondial) e as subparcelas por épocas de coletas de plantas, que foram realizadas a cada 7 dias após a emergência até a colheita final. Cada parcela foi constituída por 10 linhas de 10 m de comprimento. Todas as cultivares tiveram crescimento lento até o início da fase de enchimento de tubérculos. Desta época até o final do ciclo ocorreu o desenvolvimento dos tubérculos, com a máxima taxa de acúmulo de MS concentrando-se no início dessa fase. A cultivar Mondial foi mais tardia em acumular MS, apresentando as maiores taxas de crescimento na fase final do ciclo.As cultivares Ágata, Atlantic e Markies apresentam crescimento semelhante durante todo o ciclo, porém...
The potato crop has great economical importance for Brazil and São Paulo State. However, despite its importance, it lacks more information about physiology and mineral nutrition of this crop, limiting to obtain high yield, high quality and low production cost, since the peculiarities of each cultivar can make difference in management. Furthermore, the fertilizers rates commonly used in potato crop are high, which has a strong impact on production costs and environmental risks. To get the maximum production efficiency, it is necessary to understand the development of the plant, uptake and accumulation of nutrients in different stages of the plant development. The objective of this study was to evaluate growth, nutrient accumulation, tubers yield and the nutrient exportation in five potato cultivars. The experimental design was the completely randomized block in split-plot with four replications. The plots treatments consisted of potato cultivars (Ágata, Asterix, Atlantic, Markies and Mondial) and subplots were established by harvest time of plants, were carried out every 7 day after emergence to last harvest. Each plot consisted of 10 lines of 10 m in length. All cultivars showed slow growth until the beginning of the tubers bulking stage. Since this time until the end of the cycle, occurred the tubers development, with maximum dry matter accumulation rate focusing in this initial stage. Mondial cultivar took longer time to accumulate dry matter, presenting the highest growth rates in the final stage of the cycle. Ágata, Atlantic... (Complete abstract click electronic access below)

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The Atlantic rainforest is one of the richest biomasses of the planet in terms of biodiversity, but has been compromised by considerable anthropogenic action. The present study investigated a managed fragment of the Atlantic rainforest in the city of Goiana, PE, Brazil, on the Megaó farmland, with the aim of evaluating the distribution and exportation of mineral nutrients in Tapirira guianensis Aulb. (cupiúva), a perennial, pioneering halophyte species belonging to the family Anacardiaceae. Analysis of the mineral nutrients in the vegetal biomass and litter was carried out at the Mineral Nutrition of Plant Laboratory (Chemistry Department) and the Soil Chemistry Laboratory (Agronomy Department); soil analysis was carried out at the Soil Physics and Soil Fertility Laboratories (Agronomy Department) of the Rural Federal University of Pernambuco. Macronutrient (N, P, K, Ca, Mg, S) and micronutrient (Cu, Fe, Mn, Zn) determinations were performed on the leaves, branches, bark and trunk. Pre-dried samples were submitted to nitro-perchloric digestion, with the exception of N, for which sulfuric digestion was performed. Colorimetry was used for the analytic determination of P, whereas turbidimetry was used for S; K was assessed using the flame photometric technique, and the Ca, Mg, Cu, Fe, Mn and Zn contents were determined by the atomic absorption spectrophotometric method. N concentration was determined by the Kjeldahl method. Results were submitted to variance analysis and the averages were compared through the Tukey test at 5 % probability. The concentration of nutrients in the Tapirira guianensis Aulb. biomass obeyed the following order: leaves>bark>branches>trunk. The distribution of macronutrients in the leaves, bark and branch were distributed in N>Ca>Mg>K>S>P, and in the trunk in N>Ca>S>P>Mg>K. Micronutrients followed the distribution sequence for all arboreal components: Fe>Zn>Mn. The leaves presented a greater accumulation of nutrients, despite their biomass being smaller than the remaining components. Leaf maintenance is therefore important in the management area, thereby ensuring the cycling of nutrients through litter and the adequate maintenance of the management area. The total of exported nutrients was 71 % at the time of the cutting of the tree when the trunk, bark and branches are removed from the site, which could compromise the sustainability of the site.
A mata Atlântica é um dos biomas mais ricos em biodiversidade do planeta, diversidade esta que se encontra comprometida por causa da forte ação antrópica, que entre outros problemas, produz a degradação do solo. O presente trabalho teve como área de estudo um fragmento manejado de mata Atlântica no município de Goiana – PE, na fazenda Megaó. O objetivo foi avaliar a distribuição e exportação de nutrientes minerais em Tapirira guianensis Aulb. (cupiúva), espécie perenifólia, pioneira, e heliófita, pertencente à família Anacardiaceae. As análises dos nutrientes minerais na biomassa vegetal e na serrapilheira foram realizadas no Laboratório de Nutrição Mineral de Plantas (Departamento de Química) e no Laboratório de Química do Solo (Departamento de Agronomia), e as análises do solo foram realizadas nos Laboratórios de Física do solo e Fertilidade do Solo (Departamento de Agronomia), da Universidade Federal Rural de Pernambuco. As determinações dos macronutrientes (N, P, K, Ca, Mg, S) e micronutrientes (Cu, Fe, Mn, Zn), foram realizadas nas folhas, galhos, casca e fuste. As amostras pré-secas foram submetidas à digestão nitroperclórica, com exceção do N, onde foi feita a digestão sulfúrica. A determinação analítica de P se deu por colorimetria e S por turbidimetria; K, foi avaliado através da técnica de fotometria de chama e os teores de Ca, Mg, Cu, Fe, Mn e Zn foram determinados pelo método de espectrofotometria de absorção atômica. Os teores de N foram determinados pelo método de Kjeldahl. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey a 5 % de probabilidade. A concentração de nutrientes na biomassa da cupiúva obedeceu a seguinte ordem folhas>casca>galhos>fuste. A distribuição de macronutrientes nas folhas, casca e galho foi distribuídos em N>Ca>Mg>K>S>P e no fuste foi N>Ca>S>P>Mg>K. Os micronutrientes seguiram a seqüência de distribuição para todos os componentes arbóreos Fe>Zn>Mn. As folhas apresentaram maior concentração de nutrientes, apesar de sua biomassa ser menor que os outros componentes, sendo assim importante sua manutenção na área de manejo, garantindo a ciclagem de nutrientes via serrapilheira e a boa manutenção da área de manejo. O total de nutrientes exportados no momento do corte da árvore, em que são retirados o fuste, a casca e os galhos do sítio, é de 71 %, o que representa uma grande perda no total de nutrientes da área de manejo, e pode comprometer a sustentabilidade do sítio.

Thesis (M.S.)--Marshall University, 2002.
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Reindeer appear to have strong positive effects on plant productivity and nutrient cycling in strongly nutrient-limited ecosystems. While the direct effects of grazing on vegetation composition have been intensively studied, much less is known about the indirect effect of grazing on plant-soil interactions. This thesis investigated the indirect effects of ungulate grazing on arctic plant communities via soil nutrient availability and plant nutrient uptake. At high density, the deposition of dung alone increased plant productivity both in nutrient rich and nutrient poor tundra habitats without causing major changes in soil possesses. Plant community responses to dung addition was slow, with a delay of at least some years. By contrast, a 15N-urea tracer study revealed that nutrients from reindeer urine could be rapidly incorporated into arctic plant tissues. Soil and microbial N pools only sequestered small proportions of the tracer. This thesis therefore suggests a strong effect of dung and urine on plant productivity by directly providing nutrient-rich resources, rather than by stimulating soil microbial activities, N mineralization and ultimately increasing soil nutrient availability. Further, defoliation alone did not induce compensatory growth, but resulted in plants with higher nutrient contents. This grazing-induced increase in plant quality could drive the high N cycling in arctic secondary grasslands by providing litter of a better quality to the belowground system and thus increase organic matter decomposition and enhance soil nutrient availability. Finally, a 15N natural abundance study revealed that intense reindeer grazing influences how plants are taking up their nutrients and thus decreased plant N partitioning among coexisting plant species. Taken together these results demonstrate the central role of dung and urine and grazing-induced changes in plant quality for plant productivity. Soil nutrient concentrations alone do not reveal nutrient availability for plants since reindeer have a strong influence on how plants are taking up their nutrients. This thesis highlights that both direct and indirect effects of reindeer grazing are strong determinants of tundra ecosystem functioning. Therefore, their complex influence on the aboveground and belowground linkages should be integrated in future work on tundra ecosystem N dynamic.

The aim of this thesis is to investigate how a biological structure changes its shape and boundary under different cases of load if flow of nutrients is included, since nutrient flow has not been taken into account in previous studies. In order to simulate such a scenario we construct a model by using topology optimization (the SIMP model) and a balance law which is suitable for biological structures. Moreover, the model is derived by using an analogy with the dissipation inequality and Coleman-Noll’s procedure. The model can be interpreted as bone or some other biological structure, where the growth and remodeling partly occurs due to nutrient flow. The theory is first investigated by selecting an MBB beam with a special boundary condition for the nutrient concentration and inflow of nutrients, and then with a bone-like model. For the analysis with different loads we have observed that the structure becomes thicker were the load is applied. Parameters like beta (β) (reflecting the relation between nutrients and material) and nutrient concentration (c) seem to play an important role in nutrient transport and building of the structure. The result for larger values of β and nutrient concentration (c) gives a thicker structure in the entire domain. We also made an assumption of Fick’s law of diffusion. Fick’s law of diffusion describes the flux from high concentration to low concentration. This phenomenon is observed in analysis with different nutrient concentrations (c): we can see that the structure tends to be built up where the concentration is high and continues to be built in the direction from high to low concentration. In analyses with mu-value (μ), which represents cost of material, the result gives a thinner structure for larger values of μ.

Ectomycorrhizal (ECM) fungi form mutualistic symbioses with trees in boreal and north temperate forests and have key roles in regulating biogeochemical cycles. The extensive mycelium produced by many ECM fungi enables resources to be transported over large distances. Some ECM fungi are considered to be specialists and have a restricted range of host plant species whilst others are considered generalists and can form mycorrhizas with a number of species. Little is currently known about the reasons why specialist and generalist mutualists have evolved and so this project aims to investigate the basis for these different strategies. The resource stoichiometry between plant and fungal partners was predicted to be a key factor: specialist fungi may be more efficient in obtaining nutrients from litter and transporting these rapidly to host plants and in return may receive larger amounts of plant photosynthate. Here, stable and radioisotopes were used to trace and quantify transfer of carbon and phosphorus, and fine-scale spatial-temporal analysis of amino acid transportation between host plants and fungi. The photon-counting scintillation imaging (PCSI) was used to show the amino acid was transported long-distance by ECM fungi intact and that the transportation was highly directional but the speed of transfer varies between species of ECM. The transportation of amino acid and phosphorus from generalist fungus to the host plant was rapid compared to the specialist fungus.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
Rose is an economically important crop for the national and the international market and due to this fact generates income to the Ceara State. Rose is a demanding crop in relation to fertilizers, requiring knowledge of soil fertility, nutritional plant requirements and nutrients use efficiency to obtain adequate fertilization. Based on the nutritional balance through the use of mechanistic and empirical models, it is possible to develop a system to quantify the plant nutrients demands to achieve a given productivity. This paper aims to establish parameters of a fertilizer and lime recommendation system to rose crop, based on the plant nutritional balance. The experiment was conducted at the company Cearosa in SÃo Benedito - CE. Plants will be collected during five months and once a month, five rose plants from four varieties (Top Secret, Avalanche, Attache and Ambience) As contradictory Airlines plants Were grinded. Samples will be ground and nutrients content will be determined: N, P, K, Ca, Mg, S, B, Fe, Mn, e Zn. Every sampling plant time, were also soil samples collected at two depths (0-20 and 20-40 cm) In which they underwent fertility analysis. To estimate the fertilizer recommendation, the system was be subdivided into requirement subsystem (REQ), which includes the plant nutrients demands, considering the recovery efficiency of the nutrients to be applied and a rate to achieve the "sustainability" criteria and the supply subsystem (SUP) that comprises the soil nutrient supply. After determining the total REQ and SUP, held -if the nutritional balance, and if the result is positive (REQ> SUP), fertilizers application is recommended and if the result negative or zero (REQ ≤ SUP), fertilizers application is not recommended. The system estimated that there is excess nitrogen and phosphorus fertilization for all cultivars , however , there needs to be supplemental potassium fertilizer . The system estimated that the soil is able to meet the demand of plants for P and Fe for all cultivars , however , there must be supplementary nitrogen fertilizer , potassium . As for micronutrients , the system estimated that there is need for additional fertilizer for Zn in all rosebushes and Mn for the rosebushes "Top Secret " and " Avalnche " , however with very close recommendation the optimal dose , ie equal to zero
A roseira à uma cultura de grande valor no mercado interno e externo, devido a esse fato, as rosas geram benefÃcios para o estado do CearÃ. à uma cultura muito exigente em relaÃÃo à adubaÃÃo, sendo necessÃrios conhecimentos da fertilidade do solo, exigÃncias nutricionais da planta e eficiÃncia na utilizaÃÃo de nutrientes, para obtenÃÃo de uma adubaÃÃo adequada. Partindo a hipÃtese de que conhecendo-se o balanÃo nutricional da cultura, levando-se em consideraÃÃo a demanda de nutrientes pela cultura para alcanÃar uma dada produtividade e o suprimento de nutrientes pelo solo, à possÃvel determinar a quantidade de nutrientes a ser adicionada na fertilizaÃÃo do solo. O presente trabalho tem como objetivo determinar com base no balanÃo de nutrientes solo-planta a quantidade de nutrientes a ser adicionada no solo para cultura da roseira. O experimento foi conduzido na empresa Cearosa, em SÃo Benedito - CE, as plantas foram coletadas durante cinco meses, sendo uma vez por mÃs, amostrando cinco plantas aleatÃrias, de quatro cultivares de rosas: (Top Secret, Avalanche, Attache e Ambience). As partes aÃreas das plantas foram moÃdas e mineralizadas para determinaÃÃo dos teores dos nutrientes: N, P, K, Ca, Mg, S, B, Fe, Mn e Zn. Simultaneamente a coleta de plantas, tambÃm foram coletadas amostras de solo em duas profundidades, camada de 0 a 20 e de 20 a 40cm. Na qual foram submetidas à anÃlise de fertilidade. Para estimar a recomendaÃÃo de adubaÃÃo o sistema foi subdividido em: subsistema requerimento (REQ), que contempla a demanda de nutrientes pela planta, considerando a eficiÃncia de recuperaÃÃo dos nutrientes a serem aplicados, alÃm de uma dose que atende ao critÃrio de âsustentabilidadeâ e o subsistema suprimento (SUP), que corresponde à oferta de nutrientes pelo solo. ApÃs a determinaÃÃo do REQ total e SUP total, realizou -se o balanÃo nutricional, no qual se apresentar resultado positivo (REQ > SUP), recomenda-se a aplicaÃÃo de fertilizantes, e negativo ou nulo (REQ ≤ SUP), nÃo serà recomendado aplicar fertilizantes. O sistema estimou que o solo à capaz de suprir a demanda das plantas para P e Fe para todas as cultivares, no entanto, à necessÃrio que haja complementaÃÃo de adubaÃÃo nitrogenada, potÃssica. Assim como para os micronutrientes, o sistema estimou que hà necessidade de complementaÃÃo de adubaÃÃo, para Zn em todas as roseiras e Mn para as roseiras âTop secretâ e âAvalncheâ, no entanto com a recomendaÃÃo bem prÃximos a dose ideal, ou seja, igual a zero

It is estimated that 2.7 billion people worldwide are served by on-site sanitation facilities that require faecal sludge management. Anaerobic digestion is a treatment mechanism that can provide faecal sludge management, methane production and an effluent digestate rich in nutrients. However, there is a paucity of information regarding the composition of the input faecal sludge which hinders the advancement of anaerobic digestion treatment and downstream nutrient recovery together with a lack of knowledge as to how best to recover these output nutrients in a simple process. Following an initial review to collate composition data for fresh faeces and urine, practical studies examined the physical, biological and chemical composition and variation of four different types of faecal sludge from on-site sanitation facilities. Faecal sludge storage strongly influenced the biodegradability and methane production potential in subsequent anaerobic digestion. However, the high concentrations of ammonium observed in faecal sludge (520-1853 mg NH4-N L- 1 ) were highlighted as a key goal for nutrient recovery and the ability of biochar and clinoptilolite as natural adsorbents for ammonium recovery in a drying bed application were investigated through batch and dynamic studies using synthetic and real digestate. Batch tests observed ammonium uptake of 5 and 12.2 mg NH4-N/g for biochar and clinoptilolite respectively whilst under dynamic experimental conditions the most efficient operation for ammonium recovery was at the longest empty bed contact times (354 minutes), ensuring the maximum fertiliser value was obtained (60g NH4-N/kg clinoptilolite). Nevertheless, clogging occurred rapidly at the surface of the media bed (0.04 – 0.5 kg TS/m2 ), consequently a sacrificial sand layer (0.05 m) was included to increase the longevity of the nutrient recovery system (15 fold increase in TS application rates). It has been demonstrated that clinoptilolite can effectively be used as part of a sludge drying bed configuration to recover nutrients from digestate and the saturated media can be used directly as a fertiliser product or blended with the dried sludge to create a balanced nitrogen, phosphorus and potassium fertiliser product (5.9% NH4-N/ 4.2% P/ ≥6.0% K+ ).

A full understanding of nutrient cycling in lotic ecosystems is crucial given the increasing influence of human activities on the eutrophication of streams and rivers. However, existing knowledge about nutrient cycling in human-altered streams (i.e., receiving point and diffuse sources) is still limited. The general objective of this dissertation was to examine point source effects on stream functional attributes, such as nutrient retention, denitrification and metabolism rates. We also quantified how the studied biogeochemical processes contribute to remove dissolved inorganic nitrogen (DIN) from point and diffuse sources, and examined relationships between N uptake measured based on experimental nutrient additions and N demand estimated from metabolism measurements. We selected two reaches located upstream and downstream of a point source in two streams draining a forest- and an agriculturaldominated catchments. Hence, the point source represented the main human influence in the forested stream, whereas the agricultural stream also received diffuse sources. The point source increased concentrations of ammonium (NH4 +-N), nitrate (NO3--N), soluble reactive phosphorus (SRP) and dissolved organic carbon in the forested stream, while only increased SRP concentration in the agricultural stream. The point source effect on water chemistry was likely to be overwhelmed by diffuse sources in this latter stream. Accordingly, point source inputs decreased nutrient retention efficiency, and increased denitrification and metabolism rates in the forested stream, whereas these effects were less clear in the agricultural stream. Retention of NH4 +-N was similar to potential nitrification rates in the two reaches of the two study streams, suggesting the importance of this process in NH4 +-N removal from the water column. Retention of NO3--N was similar to potential denitrification rates in the forested stream, suggesting the importance of this process as a net sink of NO3 --N. In contrast, high NO3--N fluxes in the agricultural stream resulted in low efficiency of denitrifiers to remove N from the water column. Hence, in-stream processes controlled DIN export in the forested stream, despite point source inputs, whereas much of the NO3--N reaching the channel via diffuse sources was lost downstream in the agricultural stream. Finally, estimated N demand was not correlated with measured N demand in any of the study reaches. Nevertheless, decoupling between measured and estimated N demand was clearly lower for the upstream reach of the forested stream (i.e., site with lowest human influence) than for the downstream reach and the two reaches of the agricultural stream (i.e., sites receiving nutrient inputs from human activities). Hence, coupling between carbon metabolism and N uptake in stream ecosystems is likely to become weaker with increasing anthropogenic nutrient inputs.

Evidence from human and animal studies has highlighted the sensitivity of the developing fetus to environmental insults, such as maternal undernutrition, during gestation. These nutritional perturbations to the intrauterine milieu may engender a legacy of deleterious health consequences in adulthood. This thesis presents a series of studies which test the `mis-match‘ fetal programming theory; that is, whether a nutritionally poor diet prenatally interacts with a nutritionally excessive diet postnatally to overtly increase risk factors for adult disease. The effect of a maternal global energy restriction is contrasted against a maternal specific protein restriction, each fed during either early or late gestation. Adult offspring were subsequently exposed to an obesogenic environment (elevated feed with increased lipid content whilst restricting physical activity). Offspring metabolic flexibility and competence were assessed through routine blood samples throughout postnatal life and at 7, 18 and 24 months of age by glucose (GTT) and insulin (ITT) tolerance tests and body composition by dual energy x-ray absorptiometry. In general males appeared more susceptible to developmental programming than females at a number of timepoints. Furthermore, an increased first-phase or incremental area-under-the-insulin-response curve was observed in 1) offspring following maternal protein restriction in early gestation at 7 and 24 months of age, despite maternal protein restriction in late gestation significantly reducing birthweight and 2) in offspring exposed to maternal energy restriction during late gestation at 24 months of age in response to a GTT. Since, in both groups, the response of all offspring to an ITT (from a euglycemic baseline) was similar, infers that developmental programming in sheep followed by nutritional excess is first revealed as affecting either the pancreas (~insulin hypersecretion) or the liver (hepatic insulin resistance, reduced first-pass insulin metabolism). The studies illustrate the importance of habitual consumption of an `optimal’ balanced diet through gestation on postnatal health, especially in light of the current obesity epidemic.

1- ROLE OF SIRT1 IN THE REGULATION OF FATTY ACID OXIDATION AND KETOGENESIS UNDER DIFFERENT NUTRIONAL CHANGES. The homolog of the yeast silencing information regulator2 (SIRT1) has been implicated in several aspects of food limitation and caloric restriction in mammals. We have observed that there were no important changes, between wild type (WT) and SIRT1 liver-specific knockout (LKO) mice subjected to either CR or high fat diet (HFD), in the mRNA expression of Cpt1a, Cpt2 and Hmgcs2. SIRT1 had been shown to control hepatic glyconeogenic/glycolytic pathways in response to nutrients (Rodgers et al., 2005). So, we have hypothesized that SIRT1 could have a role in the metabolic adaptation to the changes of nutrient of weaning, when milk is replaced by the adult diet which contains less fat and more carbohydrate. Neither fatty acid oxidation (Cpt1a), ketogenesis (Hmgcs2), nor gluconeogenic (Pck1) liver pathways were significantly affected by the liver-specific knockdown of SIRT1, in both suckling and post-weaning conditions. If SIRT1 is involved in the response to aging, old LKO mice might be more susceptible to age-associated diseases as obesity, type 2 diabetes, hypertension, etc. To test this hypothesis we first weight and performed a glucose tolerance test in 7 months-old mice. There were no differences in weight neither in glucose tolerance between WT and LKO mice. Using a cell system, PPARα induced the expression of its known target genes CPT1A, HMGCS2, and FGF21 in HepG2 cells. SIRT1 overexpression by itself had almost no effect, although it increased PPARα induction of its target genes. We have interfered SIRT1 in these cells, and PPARα-induced expression of PEPCK and FGF21 was SIRT1-dependent. We have fasted WT and LKO mice for 15h and we found that the expression of Pck1 in liver was moderately but significantly induced in SIRT1-LKO mice after fasting, consistent with an increase in glucose levels. However, neither G6pase nor Pgc1α mRNA levels were affected. As expected, liver mRNA levels of Cpt1a, Hmgcs2, and Fgf21 were also induced upon fasting. However, Cpt1a and Hmgcs2 mRNA transcripts were comparable in fasted WT versus LKO mice, while Fgf21 expression was reduced around 40% in LKO mice liver. This result was consistent with the fact that fasting induction of FGF21 serum levels was also impaired in LKO mice. 2- ROLE OF SIRT1 IN THE HMGCS2 REGULATION OF FGF21 EXPRESSION. (Article 1: Human HMGCS2 regulates fatty acid oxidation and FGF21 expression in HepG2 cells. Vilà-Brau et al., 2011) Recently, our group has seen that HMGCS2 expression stimulates FGF21 expression and that these events are dependent on HMGCS2 activity. A catalytic dead mutant (C166A) failed to induce either fatty acid β-oxidation or FGF21 expression, whereas acetoacetate (an oxidized form of ketone bodies) could stimulate FGF21 mRNA expression in a dose-dependent manner. Because ketone bodies production implies the reduction of acetoacetate to β- hydroxybutyrate with the concomitant generation of NAD+ (Hegardt et al, 1999), and SIRT1 is a NAD+-dependent deacetylase enzyme, this specificity could explain why FGF21 fasting induction was affected in LKO-SIRT1 mice liver, while other PPARα target genes were not. We have treated HepG2 cells with the oxidizing (acetoacetate) partner of ketone bodies, and endogenous SIRT1 was knockdown by a specific siRNA. FGF21 induction was dependent on SIRT1 expression, since knocking down impaired acetoacetate response. 3- ACTIVATING TRANSCRIPTION FACTOR 4-DEPENDENT INDUCTION OF FGF21 DURING AMINO ACID DEPRIVTION (Article 2: De Sousa-Coelho et al., 2012) Considering the central role of PPARα in the regulation of metabolic homeostasis we sought to investigate how the turnover of PPARα affected the expression of its target genes. HepG2 cells were infected with PPARα and exposed to DMSO or to the 26S proteasome inhibitor MG132. As expected, MG132-treatment blocked the PPARα-dependent expression of HMGCS2, indicating that the transcriptional activity of PPARα is increased by protein degradation (Blanquart et al, 2004). Contrary to what we had predicted, the expression of FGF21 was strongly increased by the MG132 treatment. We hypothesized that proteasome inhibition in HepG2 could decrease the pool of free amino acids. We treated HepG2 cells with histidinol (HisOH) a potent and reversible inhibitor of protein synthesis, (Hansen et al, 1972). Amino acid deprivation produced a time-dependent induction of FGF21 mRNA. To test whether this induction was due to an increase in the FGF21 gene transcription, we measured the FGF21 primary transcript (hnRNA) levels; HisOH treatment clearly induced FGF21 hnRNA levels in a time-dependent manner. As expected, HisOH induced an increase in the ATF4 protein levels after 2h treatment. By analyzing the sequence of the 5’-flanking region of the human FGF21 gene, we found two putative ATF4 response elements (AARE) starting at positions -152 and -610 upstream of the transcription start site. HepG2 cells were transfected with pGL3b-hFGF21 promoter-luciferase constructs and an expression vector for human ATF4. The expression of ATF4 induced the WT reporter in a concentration dependent manner. This induction was totally obliterated either when the AARE1 was mutated or when both elements were deleted. Induction was diminished when AARE2 was mutated. To further analyze the functionality of this sequence we tested the binding of ATF4 by an EMSA, where ATF4 bound as a C/EBPβ heterodimer to both AARE sequence elements. We also confirmed the in vivo binding by ChIP experiments. The chromatin binding of ATF4 was greatly increased in both ATF4 responsive sequences in HisOH treated cells. To confirm if the induction of FGF21 produced by amino acid starvation was mediated by ATF4, we treated siCtl and siATF4 HepG2 cells with HisOH. FGF21 mRNA levels after HisOH treatment were significantly lower when ATF4 was depleted. To analyze the effect of amino acid deprivation on FGF21 expression in vivo, we fed mice with a leucine-deficient [(-)leu] diet or a control (Ctl, nutrionally complete) diet for 7 days. Fgf21 mRNA levels were greatly increased in liver from mice fed a (-)leu diet compared to control. The circulating FGF21 levels were also increased in the serum of leucine deprived animals, paralleling hepatic gene expression. 4- LEUCINE DEPRIVATION SIGNALING UNDER FASTING CONDITIONS. We were interested to know whether FGF21 induction by a (-)leu diet would affect, or be affected by, the adaptive fasting response. We have fed mice for 7 days within a Ctl or (-)leu diet. Weights and food intake were recorded daily. Then, mice were randomly separated in a total of 4 groups, where 2 groups (one from each diet) were fasted overnight. Leucine deprivation affected the levels of free fatty acids and ketone bodies in serum in the fed state, while it does not upon fasting. Although no changes between groups were observed in the fed state, after fasting the β-oxidation, ketogenesis and gluconeogenesis keygenes were further up-regulated in the (-)leu diet group compared to control. The highest induction was seen in the Pgc1α gene, a known coactivator on these processes. The fasting activation of FGF21 was impaired in mice fed with (-)leu diet, underlying a crosstalk between the fasting and amino acid deprivation signalling. 5- ROLE OF FGF21 IN THE LEUCINE DEPRIVATION PHENOTYPE IN MICE (Article 3: De Sousa-Coelho et al., in preparation). According with our previously reported results (De Sousa-Coelho et al., 2012) mice maintained on a leucine-deficient [(-)leu] diet show a dramatic increase in FGF21 circulating levels. To check its origin we analyzed the Fgf21 gene expression in liver, where Fgf21 mRNA levels paralleled those in serum; brown adipose tissue (BAT), where it were unchanged; and in epididymal white adipose tissue (eWAT), where unexpectedly it were significantly decreased in wild type mice maintained in (-)leu diet. Because upon (-)leu diet, mice undergo rapid weight loss (Cheng et al., 2010), we wanted to investigate whether this phenotype is FGF21-dependent. For this purpose, WT and FGF21-KO mice were fed a Ctl or (-)leu diet for 7 days. Weight loss was diminished in FGF21-KO, while food intake decrease by (-)leu was unchanged between genotypes. Histological analysis of WAT showed that leucine deprivation resulted in a reduction in adipocyte volume compared with mice fed a control diet, while it was only slightly reduced in (-)leu FGF21-KO mice. It has been previously described that leucine deprivation increases lipolysis in WAT (Cheng et al., 2010). Consistent with changes in body weight, lack of FGF21 significantly decreased levels of phosphorylated (P)-HSL in WAT, indicating an impaired lipolysis. Gene expression analysis revealed reduction in the mRNA levels of the lipogenic genes Fas, Srebp1c and Acc1 in the WAT of mice maintained in (-)leu diet. These changes were impaired in FGF21-KO. Consistent with previous results (Cheng et al., 2010), leucine deprivation increased levels of Ucp1 mRNA in WT mice BAT. This increase was not observed in the FGF21-KO mice. mRNA levels of Pgc1α, which regulates the expression of Ucp1 (Handschin and Spiegelman, 2006), were also increased, although did not differ between WT and FGF21-KO mice under either control or (-)leu diet conditions. It has been recently proposed a link between FGF21 and SREBP1c during lipogenesis in HepG2 cells (Zhang et al., 2011). We examined levels of Fas, Srebp1c and Acc1 mRNA in liver of WT and FGF21-KO. As expected (Guo and Cavener, 2007), lipogenic program was decreased upon (-)leu diet, but this reduction was blocked in FGF21-KO mice. However, the amino acid response program was correctly initiated in these mice as shown by the increased levels of ATF4 protein and the increase in mRNA levels of Asns, a prototypical ATF4 target gene. The liver staining showed a decreased lipid accumulation under (-)leu in WT animals that is not produced in the FGF21-KO mice. These results demonstrate an important role of FGF21 in the regulation of lipid metabolism during amino acid starvation. References: Blanquart C, Mansouri R, Fruchart JC, Staels B, & Glineur C (2004) Different ways to regulate the PPARalpha stability. Biochem Biophys Res Commun 319, 663-70. Cheng, Y., Meng, Q., Wang, C., Li, H., Huang, Z., Chen, S., Xiao, F., and Guo, F. (2010). Leucine deprivation decreases fat mass by stimulation of lipolysis in white adipose tissue and upregulation of uncoupling protein 1 (UCP1) in brown adipose tissue. Diabetes 59, 17-25. Guo, F., and Cavener, D.R. (2007). The GCN2 eIF2alpha kinase regulates fatty-acid homeostasis in the liver during deprivation of an essential amino acid. Cell Metab 5, 103-14. Handschin, C., and Spiegelman, B.M. (2006). Peroxisome proliferator-activated receptor gamma coactivator 1 coactivators, energy homeostasis, and metabolism. Endocr Rev 27, 728-735. Hansen BS, Vaughan MH, & Wang L (1972) Reversible inhibition by histidinol of protein synthesis in human cells at the activation of histidine. J Biol Chem 247, 3854-3857. Hegardt FG (1999) Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase: a control enzyme in ketogenesis. Biochem J. 338, 569-582. Hotta, Y., Nakamura, H., Konishi, M., Murata, Y., Takagi, H., Matsumura, S., Inoue, K., Fushiki, T., and Itoh, N. (2009). Fibroblast growth factor 21 regulates lipolysis in white adipose tissue but is not required for ketogenesis and triglyceride clearance in liver. Endocrinology 150, 4625-4633. Rodgers JT, Lerin C, Haas W, Gygi SP, Spiegelman BM, Puigserver P (2005) Nutrient control of glucose homeostasis through a complex of PGC-1alpha and SIRT1. Nature 434, 113-8 Zhang, Y., Lei, T., Huang, J.F., Wang, S.B., Zhou, L.L., Yang, Z.Q., and Chen, X.D. (2011). The link between fibroblast growth factor 21 and sterol regulatory element binding protein 1c during lipogenesis in hepatocytes. Mol Cell Endocrinol 342, 41-47.
Durante su vida un individuo se somete a diversos cambios nutricionales. La capacidad de detectar la disponibilidad de nutrientes y regular la homeostasis energética es un proceso fundamental. SIRT1 es un regulador clave en el metabolismo energético. SIRT1 puede modular la expresión génica en tejidos metabólicamente activos en respuesta a la restricción calórica o el ayuno. La dependencia de la actividad deacetilasa de SIRT1 en los niveles de NAD+ constituye un vínculo fundamental entre el estado metabólico celular y la regulación de genes. FGF21 es una hormona que se induce en el ayuno y que afecta al metabolismo de los carbohidratos y de los lípidos. Recientemente se han demostrado sus efectos benéficos en la protección de la obesidad inducida por la dieta y en la mejoría en la resistencia a la insulina. En este trabajo hemos demostrado que en células hepáticas en cultivo, SIRT1 desempeña un papel importante en la activación por PPARα de la expresión de FGF21, CPT1A, HMGCS2, y PEPCK. También, que la actividad de SIRT1 regula los niveles de glicemia y la expresión de PCK1 en hígado, en la respuesta al ayuno. Aún así, hemos visto que la actividad de SIRT1 no afecta la expresión de los genes de la oxidación de los ácidos grasos o la cetogénesis en el hígado, en respuesta a diferentes cambios nutricionales, como la restricción calórica, la transición de la lactancia/destete, y el ayuno. Adicionalmente, hemos demostrado que la activación de FGF21 por SIRT1 depende de la actividad HMGCS2. También hemos descrito que FGF21 se induce por la privación de aminoácidos, de manera dependiente de ATF4, y hemos identificado dos elementos de respuesta funcionales en la región promotora del gene humano, altamente conservados entre las especies. Además, hemos demostrado que FGF21 interviene en la regulación del metabolismo de los lípidos en el hígado y el tejido adiposo blanco, y de la termogénesis en el tejido adiposo marrón, durante la privación de aminoácidos. De todas formas, hemos visto que la privación de leucina afecta a los niveles de ácidos grasos libres y cuerpos cetónicos en suero en el estado de alimentación, mientras que no lo hace en el ayuno; y la activación de FGF21 en el ayuno está afectada en los ratones alimentados con esta dieta, desvelando un “crosstalk” entre la señalización del ayuno y la privación de aminoácidos.

A food web comprises exchanges of matter and energy that occur among species and between biotic and abiotic environment. Given that abiotic components form the basal resources, the approach of this work consists of evaluating the effects of nutrients input in strategic models that describe food web and chain dynamics. Its focus lies on the determination of the nature of equilibrium populations as well as on their dynamics for different functional responses. Strategic models that describe the behavior of interactive populations under nutrient inputs are an important basis for outlining general phenomena that occur in community dynamics.
Uma rede trófica reúne as trocas de matéria e energia que ocorrem entre as espécies e entre o meio biótico e abiótico. Visto que os componentes abióticos formam a fonte de recursos basais, a abordagem deste trabalho consiste na avaliação dos efeitos da entrada de nutrientes alóctones em modelos estratégicos que descrevem a dinâmica de redes e cadeias tróficas, concentrando-se na determinação das características das populações de equilíbrio e das dinâmicas das espécies com diferentes respostas funcionais. Modelos estratégicos que contêm informações acerca do comportamento de populações interativas frente à entrada de nutrientes são uma base importante no delineamento de fenômenos gerais que podem ocorrer dentro da dinâmica de comunidades.

The top-down effects of consumers and bottom-up effects of resource availability are important in determining community structure and ecological processes. I experimentally examined the roles of consumers — both detritivores and predators — and habitat context in affecting nutrient cycling using the detritus-based insect community in bromeliad leaf wells. I also investigated the role of multiple resources in limiting plant productivity using meta analyses. The insect community in bromeliads only increased nitrogen release from leaf detritus in the presence of a predator trophic level. When only detritivores were present, the flow of stable isotope-labeled nitrogen from detritus to bromeliads was statistically indistinguishable from that in bromeliads lacking insects. I suggest that emergence of adult detritivores constitutes a loss of nitrogen from bromeliad ecosystems, and that predation reduces the rate of this nutrient loss. Hence, insects facilitate nutrient uptake by the plant, but only if both predators and detritivores are present. Moreover, predators can affect nutrient cycling by influencing the spatial scale of prey turnover. This mechanism results in a pattern opposite to that predicted by classic trophic cascade theory. Increasing habitat complexity can have implications for nutrient cycling by decreasing the foraging efficiency of both predators and their prey, and by affecting the vulnerability of predators to intraguild predation. Along a natural gradient in bromeliad size, I found that, depending on the relationship between community composition and habitat size, habitat complexity interacts with the changing biotic community to either complement or counteract the impact of predators on nutrient uptake by bromeliads. In contrast to the existing emphasis on single-resource limitation of primary productivity, meta-analyses of a database of 653 studies revealed widespread limitation by multiple resources, and frequent interaction between these resources in restricting plant growth. A framework for analyzing fertilization studies is outlined, with explicit consideration of the possible role of multiple resources. I also review a range of mechanisms responsible for the various forms of resource limitation that are observed in fertilization experiments. These studies emphasize that a wider range of predator and nutrient impacts should be considered, beyond the paradigm of single resource limitation or classic trophic cascades.

Purified brush border membrane vesicles (BBMV) were isolated to characterize primary cellular transport mechanisms for white shrimp. The ultimate goal is to determine the effective components of a shrimp’s diet, thereby enhancing growth, as well as nutrient content. Juvenile shrimp are dependent on plant material as a food source. Potassium is a key component of plants, thus it may play a role in nutrient transport. In addition, divalent metals have been shown to act as co-transporters in several other organisms, thus they may serve as a transport mechanism for shrimp. Fresh, live, white or brown shrimp were obtained, and from them 15-30 hepatopancreases were dissected to prepare the BBMV. Methods for preparing BBMV were based on the Mg2+ precipitation technique developed by Kessler et al., (1978) and Biber et al. (1981) for mammalian eipithelia and applied to crustaceans. The results suggest that there is a sodium/potassium-dependent glucose transport system that resembles the SGLT1 system of vertebrates, except the shrimp transporter can accept both sodium and potassium as cofactors, while the vertebrate system is restricted to sodium stimulation. Potassium showed strong stimulation of L-histidine uptake by shrimp BBMV, suggesting that a crustacean isoform of the insect potassium-dependent carrier protein (KAAT1) might be present in shrimp, and contribute to amino acid uptake. Amino acids also appear to form bis-complexes with divalent metals, that are transported by an analog of the dipeptide transporter (PEPT1). The metals appear to be accommodated, with varying affinities. PEPT1 has been described as a very non-specific carrier process because it transports such a wide range of di- and tripeptide combinations.

Phytoplankton across the majority of the world’s oceans are thought to be limited by the availability of either nitrate or iron (Fe). However, the spatial resolution of experiments confirming this is low. Two thesis chapters present the results of bottle enrichment experiments at high spatial resolution across (i) the South Subtropical Convergence (SSTC) in the South Atlantic, and (ii) the Scotia Sea-Drake Passage sector of the Southern Ocean. These studies have added detail to the boundaries of limiting nutrients in these regions. Patterns of Fast Repetition Rate fluorometry (FRRf) derived parameters, physiological regulation of these parameters including influences of community structure, and the environmental controls driving them are analysed. Given its role as an essential micronutrient, there has been much effort in constraining potential sources of bioavailable Fe to the ocean, with one such source receiving recent interest: erupted ash from volcanoes. Bottle-scale ash-incubation experiments alongside conventional iron additions and laboratory ash-leaching experiments were conducted, the results of which suggest phytoplankton would respond strongly to ash deposition in the High Nitrate, Low Chlorophyll (HNLC) areas of the Southern Ocean. Particularly notable was the evidence these experiments provided for potential (co-)limitation of phytoplankton in these waters by the micronutrient manganese. The first three chapters of this thesis highlight a number of biogeochemical implications of trace metal stress, particularly that of Fe stress. Therefore, the ability to map the oceanographic extent of Fe-stressed regions using remote sensing would represent a particularly useful advance in marine biogeochemistry. Theoretically it could be possible to map Fe stress from space using satellite images of chlorophyll fluorescence, yet there are important uncertainties that need to be addressed before this can be carried out. In particular, a better understanding of the midday non-photochemical quenching driven reductions in chlorophyll fluorescence occurring at the time satellite images are captured is required. Analysis of over 200 non-photochemical quenching experiments collected over three research cruises, has allowed us to explore non-photochemical quenching and its relevance for using sunlight induced chlorophyll fluorescence to assess broad patterns of Fe stress. Our results have confirmed that satellite fluorescence quantum yields have the potential to reveal broad regions of Fe stress, however a dynamic non-photochemical quenching correction derived from our experiments and analysis was necessary to achieve this.

Title from PDF of title page (University of Missouri--Columbia, viewed on March 17, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Laura McCann. Vita. Includes bibliographical references.

Obwohl es sehr detaillierte Studien zur Nährstoffretention in einzelnen Auen und Feuchtgebieten gibt, ist die Bedeutung von Auen für die Nährstoffbilanz auf Landschaftsebene wenig untersucht. Dies liegt an dem geringen Wissensstand über die wichtigsten Parameter der Nährstoffretention, nämlich die überflutete Auenfläche sowie die in die Aue strömende Nährstofffracht. Zusätzlich gibt es bislang keinen Ansatz, demzufolge beide Parameter abhängig vom Abfluss, und damit variabel für verschiedene zeitliche Einheiten, berechnet werden können. Aus diesem Grund analysiert diese Arbeit die Überflutungshäufigkeiten der Auen von drei Flüssen, Elbe, Main und Rhein. Darauf aufbauend wird eine Abhängigkeit zwischen der überfluteten Fläche und dem Abfluss empirisch abgeleitet, die auf detaillierten Berechnungen der etablierten Software Flys basieren. Ausgehend auf diesen im Folgenden generalisierten Ergebnissen werden eine letztendlich Ereignis basierte mittlere überflutete Auenfläche sowie einströmende Nährstofffracht abhängig vom jeweiligen Abfluss berechnet. Diese und weitere Geoinformationsdaten wie auch Pegel und Gütedaten finden Eingang in jährliche und monatliche empirische Retentionsmodelle. Die berechnete Nährstoffretention in den Auen ist abhängig von der hydrologischen Konnektivität der Auen und dem tatsächlichen Abfluss. Deshalb wird letztendlich das weiterentwickelte Konzept der Ereignis bezogenen Nährstoffretention angewendet und als am realistischsten in Kombination mit hydro-exponentiellen Retentionsmodellen erachtet. Für die naturnahe Elbe werden in Monaten mit Hochwässern bis zu 9% bzw. 10% Retention der transportierten TP bzw. der NO3-N Fracht berechnet. Die Übertragbarkeit dieser Ergebnisse auf eine deutschlandweite Kulisse ist durch die generalisierten Methoden geschaffen. Die vorliegende Arbeit leistet damit einen Beitrag, die Bedeutung der Auen für die Nährstoffbilanz auf Landschaftsebene abhängig von hydrologischen Gegebenheiten zu quantifizieren.
Although there are detailed studies on nutrient retention in single wetlands and floodplains, the role of riparian floodplains for nutrient retention is not investigated very well on a landscape scale, since knowledge on the most important parameters for nutrient retention, inundated floodplains and incoming load, is insufficient. Additionally, a method for describing these parameters as discharge dependent variables is missing. Therefore, the present work analyzes the flooding frequencies on floodplains of three study rivers, Elbe, Main and Rhine. The relation of inundated floodplain extent and current discharge conditions based on detailed results of the established Software Flys is deduced empirically. Based on these subsequently generalized results, finally event related average inundated floodplain extent respectively, incoming nutrient loads are calculated by considering the effects of the hydrologic conditions of each river system. Therefore, available geodata as well as data on water quality and discharge is processed and serves as input data for yearly and monthly empirical retention models. The calculated nutrient retention in floodplains varies with hydrological connectivity of the floodplain to the surface waters as well as with the current hydrologic condition of the river system. For this reason the finally developed concept of event related nutrient retention is suggested as the most realistic in combination with hydro-exponential retention models. The Elbe floodplains are the most natural, and in years with high floods nutrient retention in the floodplains contributes up to 9% respectively 10% of the monthly transported load of TP and NO3-N, which is significant. The transfer of the results to a German-wide application is possible due the generalization of the methods carried out. With the presented results the hydrology dependent role of floodplains for nutrient balances in river systems can be quantified on a landscape scale.

Doctor of Philosophy
Department of Animal Sciences and Industry
R. Scott Beyer
Broiler chicken feed is processed. Cereal grains are ground to reduce particle size and the feed usually is pelleted. When pelleted, broiler diets are steam conditioned and forced through a die causing varying levels of starch gelatinization. Cereal grain particle size and starch gelatinization can be controlled during feed manufacturing. Earlier research has shown that starch gelatinization negatively affects growth performance of 0 to 21 d of age. An experiment was conducted to determine the effects of corn particle size and starch gelatinization on growth performance, dressing percentage, and gizzard size when fed to 22 to 42 d of age broilers. Increasing particle size from 470 to 1240 μm increased body weight gain, dressing percentage, and relative gizzard size. Starch gelatinization increased relative gizzard size. No interaction effects were detected. To expand on previous experiments, a trial was conducted to investigate the effect of starch gelatinization on broiler chick gastrointestinal pH, glucose absorption, and glucoregulation. Starch gelatinization level affected jejunum pH, with a higher pH reported at 20% starch gelatinization. Increases in starch gelatinization decreased blood glucose and increased glucagon level. Highest measured glucagon level was reported in broiler chicks fed the diet with 20% starch gelatinization level diet after 6 hours of starvation. A third experiment was conducted to determine the effect of starch gelatinization on metabolizable energy and amino acid digestibility. Increasing starch gelatinization from 0 to 100% increased true metabolizable energy and fecal output in roosters. No effect was found on apparent metabolizable energy or amino acid digestibility, with an increase in starch gelatinization from 0 to 20%. Increasing particle size from 470 to 1240 μm had a positive effect on 22 to 42 d growth performance. A starch gelatinization level of 20% or lower had no effect on metabolizable energy or amino acid digestion. Older broilers with larger gastrointestinal tracts are unaffected by 20% gelatinized starch; whereas, 20% gelatinized starch reduced blood glucose and increased glucagon levels of young broilers. Lower blood glucose and increased glucagon are indicative of lower glucose storage, and could cause reduced young broiler growth performance when fed diets with gelatinized starch.

The Lake Manassas Watershed is a 189 km2 basin located in the Northern Virginia suburbs of Washington, DC. Lake Manassas is a major waterbody in the watershed and serves as a drinking water source for the City of Manassas. Lake Manassas is experiencing eutrophication due to nutrient loads associated with agricultural activities and urban development in its drainage areas. Two watershed model applications using HSPF, and one receiving water quality model application using CE-QUAL-W2, were linked to simulate Lake Manassas as well as its drainage areas: the Upper Broad Run (126.21 km2) and Middle Broad Run (62.79 km2) subbasins. The calibration of the linked model was for the years 2002-05, with a validation period of 2006-07. The aspects of effective modeling of nutrient losses and nutrient management practices in the Lake Manassas watershed were investigated. The study was mainly conducted in the Upper Broad Run subbasin, which was simulated with an HSPF model. For nutrient simulation, HSPF provides two algorithms: PQUAL (simple, empirically based) and AGCHEM (detailed, process-based). This study evaluated and compared the modeling capabilities and performance of PQUAL and AGCHEM, and investigated significant inputs and parameters for their application. Integral to the study was to develop, calibrate and validate HSPF/PQUAL and HSPF/AGCHEM models in the Upper Broad Run subbasin. â One-variable-at-a-timeâ sensitivity analysis was conducted on the calibrated Upper Broad Run HSPF/PQUAL and HSPF/AGCHEM models to identify significant inputs and parameters for nutrient load generation. The sensitivity analysis results confirmed the importance of accurate meteorological inputs and flow simulation for effective nutrient modeling. OP (orthophosphate phosphorus) and NH4-N (ammonium nitrogen) loads were sensitive to PQUAL parameters describing pollutant buildup and washoff at land surface. The significant PQUAL parameter for Ox-N (oxidized nitrogen) load was groundwater nitrate concentration. For the HSPF/AGCHEM model, fertilizer application rate and time were very important for nutrient load generation. NH4-N and OP loads were sensitive to the AGCHEM parameters describing pollutant adsorption and desorption in the soil. On the other hand, plant uptake of nitrogen played an important role for Ox-N load generation. A side by side comparison was conducted on the Upper Broad Run HSPF/PQUAL and HSPF/AGCHEM models. Both PQUAL and AGCHEM provided good-to-reasonable nutrient simulation. The comparison results showed that AGCHEM performed better than PQUAL for OP simulation, but PQUAL captured temporal variations in the NH4-N and Ox-N loads better than AGCHEM. Compared to PQUAL, AGCHEM is less user-friendly, requires a lot more model input parameters and takes much more time in model development and calibration. On the other hand, use of AGCHEM affords more model capabilities, such as tracking nutrient balances and evaluating alternative nutrient management practices. This study also demonstrated the application of HSPF/AGCHEM within a linked watershed-reservoir model system in the Lake Manassas watershed. By using the outputs generated by the HSPF/AGCHEM models in the Upper Broad Run and Middle Broad Run subbasins, the Lake Manassas CE-QUAL-W2 model adequately captured water budget, temporal and spatial distribution of water quality constituents associated with summer stratification in the lake. The linked model was used to evaluate water quality benefits of implementing nutrient management plan in the watershed. The results confirmed that without the nutrient management plan OP loads would be much higher, which would lead to OP enrichment and enhanced algae growth in Lake Manassas.
Ph. D.

Consumer-driven nutrient cycling has been shown to be an important process in supplying inorganic nutrients to autotrophic and heterotrophic organisms in aquatic ecosystems. Theory indicates that consumer nutrient excretion is influenced primarily by an organismâ s nutrient composition; however, an organismâ s diet should also play an important role in nutrient excretion, especially if the consumer is nutrient limited. This study asks the question, how does diet influence nutrient excretion of consumers at different trophic levels? Macroinvertebrates and fish were collected from six streams and nitrogen (N) and phosphorus (P) excretion were quantified. Epilithon, leaf detritus, and seston (fine particulate organic matter in transport) were collected and analyzed for carbon (C), nitrogen (N), and phosphorus (P) content in an attempt to qualitatively assess the nutritional status of the diet of primary consumers. Macroinvertebrates were also analyzed for C, N, and P content to assess their nutritional composition in relation to their excretion and also to assess the nutritional composition of the diet of predatory insects and fish. Fish were also analyzed for C, N, and P.

Similar to theoretical predictions, fish and macroinvertebrate P excretion was negatively related to P content and the N:P excretion ratio was negatively related to the body N:P ratio. However, this relationship was driven primarily by two phosphorus rich species, mottled sculpin in the fish and crayfish in the macroinvertebrates. Some relationships did emerge between consumer excretion and diet. For example, hydropsychid caddisflies had the highest macroinvertebrate P excretion, possibly explained by the low N:P of seston. However, shredders, eating on a very low N and P diet of leaf detritus, had very low N and P excretion.

The relationship between consumers, their food, and nutrient excretion is a matter of mass balance. If the food N:P ratio is higher than that of the consumer, then the N:P excretion should be higher than the consumer N:P and the food N:P, especially if organisms are P-limited. However, N:P excretion by macroinvertebrates and fish were very similar despite large differences in diet. The majority of macroinvertebrates and fish had a lower N:P excretion ratio than the predicted N:P of their food, possibly indicating that 1) consumers were either selectively consuming more P-rich foods than the diets that I assigned them or 2) consumers are generally not N or P limited or influenced by the N or P in their diet. Mottled sculpin and crayfish were the only organisms with a higher N:P excretion than their resources and both had a higher %P than the other fish and macroinvertebrates, respectively. High N:P excretion along with high phosphorus content is indicative of P-limitation. Macroinvertebrates and fish, excluding mottled sculpin and crayfish, had a lower N:P excretion and the N:P ratio of the water column. If consumers do play a role in nutrient dynamics, then consumers could alter the relative abundance of nitrogen and phosphorus by supplying more phosphorus. However, the presence of a P-limited organism, such as mottled sclupin or crayfish, could alter the relative abundance of nitrogen and phosphorus by supplying less phosphorus.
Master of Science

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
O meloeiro à uma das cucurbitÃceas mais exigentes em relaÃÃo à adubaÃÃo, sendo necessÃrios conhecimentos de solo, exigÃncia nutricional e eficiÃncia na utilizaÃÃo de nutrientes, para uma adubaÃÃo adequada. Objetivou-se a parametrizaÃÃo de um sistema para recomendaÃÃo de corretivos e fertilizantes para a cultura do meloeiro (Ferticalc-MelÃo) com base no balanÃo nutricional. O sistema apresenta um mÃdulo para correÃÃo da acidez no solo utilizando dois mÃtodos de recomendaÃÃo de calagem. Para estimar a adubaÃÃo recomendada o sistema foi subdividido: subsistema requerimento (REQ), que contempla a demanda de nutrientes pela planta, considerando a eficiÃncia de recuperaÃÃo dos nutrientes aplicados, alÃm de uma dose que atende ao critÃrio de âsustentabilidadeâ apenas para o nutriente K, e o subsistema suprimento (SUP), que corresponde à oferta de nutrientes pelo solo e Ãgua de irrigaÃÃo. ApÃs a determinaÃÃo do REQtotal e SUPtotal, realizou-se o balanÃo nutricional, no qual em resultado positivo (REQ > SUP), recomenda-se a aplicaÃÃo de fertilizantes, e negativo ou nulo (REQ ≤ SUP), nÃo se recomenda aplicar. Foram feitas simulaÃÃes para quatro diferentes tipos de meloeiro: Amarelo, Cantaloupe, GÃlia e Pele-de-sapo, numa faixa de produtividade esperada total de 15.000 a 45.000 kg ha-1 considerando diferentes valores de P-rem. O sistema estimou que o GÃlia foi o menos exigente em P enquanto o Pele-de-sapo mostrou-se mais exigente. Dentre os tipos, o Cantaloupe foi menos exigente em N e Ca, enquanto o Amarelo exigiu menos K, Mg e S. Para os micronutrientes, o Amarelo foi o que menos exigiu Fe, Cu e Zn, enquanto Mn foi menos demandado pelo Cantaloupe. O suprimento dos nutrientes K, Ca e Mg pela Ãgua de irrigaÃÃo foram respectivamente, 23,40; 1.216,00 e 136,08 kg ha-1 para as condiÃÃes de solo (AS - I) e 6,24; 48,00 e 4,86 kg ha-1 para (AS-II). De maneira geral, o sistema recomendou adubaÃÃo com macronutrientes para (AS-II) com exceÃÃo para Mg e Ca, enquanto para (AS-I) foi recomendado apenas para N e P, em funÃÃo dos altos teores de K, Ca e Mg no solo e Ãgua de irrigaÃÃo. Comparando com outros mÃtodos o sistema mostrou-se mais dinÃmico e flexÃvel nas suas recomendaÃÃes. AtravÃs da anÃlise de sensibilidade do sistema, constatou que a variÃvel que mais influenciou as recomendaÃÃes foi a produtividade, seguida dos teores de nutriente no solo. O sistema apresentou resultados satisfatÃrios em relaÃÃo Ãs recomendaÃÃes, porÃm necessita ser avaliado sob condiÃÃes de campo para seu aperfeiÃoamento em futuras versÃes.
The melon is one of cucurbitaceae most demanding in relation to fertilization, being necessary knowledge of soil, nutritional requirements and nutrient use efficiency, for a proper fertilization. The objective was parameterization of a system for recommendation of fertilizers for the melon (Ferticalc-Melon) based on the nutrient balance. The system features a module for soil acidity correction using two methods of liming. To estimate the fertilizer recommended, the system was subdivided: requirement subsystem (REQ), which includes the demand for nutrients by the plant, whereas the efficiency of nutrient recovery, and a dose that meets the criterion of "sustainability" only for the nutrient K, and supply subsystem (SUP), which corresponds to the supply of nutrients from the soil and irrigation water. After determining the REQamount and SUPamount, held the nutritional balance, in which a positive result (REQ > SUP), it is recommended that the application of fertilizer, and negative or zero (REQ ≤ SUP), not recommended to apply. Simulations were made for four different types of melon: Amarelo, Cantaloupe, GÃlia e Pele-de-sapo, in the range of productivity expected total of 15,000 to 45,000 kg ha-1 considering different values of P-rem. The system estimated that the GÃlia was the least demanding in P while Pele-de-sapo was the most demanding. Among the types, Cantaloupe was the least demanding in N and Ca, while the Amarelo requires less K, Mg and S. For the micronutrients, Amarelo was the least demanded that Fe, Cu and Zn, whereas Mn was less demanded by Cantaloupe. The supply of nutrients K, Ca and Mg by irrigation water were respectively, 23.40; 1,216.00 e 136.08 kg ha-1 to soil conditions (AS - I) and 6.24; 48.00 and 4.86 kg ha-1 to (AS-II). In general, the system recommended fertilization with macronutrients for (AS-II) except for Mg and Ca, while for (AS-I) was recommended only N and P, due to high levels of K, Ca and Mg in the soil and irrigation water. Compared with other methods the system proved to be more dynamic and flexible in its recommendations. By analyzing the sensitivity of the system, found that the variable that most influenced the recommendations was the productivity, then the nutrient content in soil. The system showed good results in relation to the recommendations, but needs to be evaluated under field conditions for your improvement in future versions.

This study was conducted to investigate the efficacy of phytase for improving the nutrient utilization for pigs and poultry. Two experiments, one with broilers and one with pigs, were conducted to compare the efficiency of transgenic microbial (Natuphosà ) and plant (Phytaseedà ) phytase for enhancing the utilization of phytate P in corn-soybean diets fed to young broilers and pigs, and to evaluate the safety of Phytaseedà phytase. Three levels of the two sources of phytase (250, 500 and 2,500 U/kg of diet) were added to a corn-soybean meal basal diet containing 0.21 and 0.26% nonphytate P, respectively, for broilers and pigs. Forty birds and thirty pigs (8 broilers and 6 pigs, one per cage, from the diet without added phytase and the diets with 500 or 2,500 U/kg phytase from both sources) were randomly selected for gross necropsy and histologic evaluation of liver, kidney and bone tissues. Adding both sources of phytase to the basal diet resulted in similar increases of BW, BW gain, feed intake, gain:feed, apparent digestibilities (retention) of DM, P and Ca, and bone measurements. Phosphorus excretion decreased as phytase addition increased. No significant abnormalities were seen in any of the broilers and pigs necropsied. In a study with pigs (n=120 and 80, respectively for grower and finisher), the effects of supplemental microbial phytase on crude protein and amino acid utilization of low protein plant-based diets was investigated. During the grower period (32 to 67 kg), diets 1, 2 and 3 contained 14, 13 and 12% crude protein and no added phytase, respectively, and diets 4 and 5 contained 12% crude protein with either 250 or 500 U of phytase/kg of diet, respectively. During the finisher period (67 to 109 kg), diets 1, 2 and 3 contained 12, 11 and 10% crude protein with no added phytase, respectively, and diets 4 and 5 contained 10% crude protein with either 250 or 500 U of phytase/kg of diet, respectively. At the end of grower phase, two pigs (1 barrow and 1 gilt) were removed from each pen; 12 of the barrows that were removed from diets 1, 3 and 5 were put in metabolism cages for total collection, and the remaining four pigs in each pen continued on test for the finisher phase. At the end of finisher phase, 12 barrows from diet 1, 3, and 5 were put in metabolism cages for total collection. Ileal contents were taken (slaughter technique) from the remaining barrows and the barrows used in metabolism cages. Daily gain increased as protein and phytase levels was added to the lowest protein level. Fecal P and Ca digestibilities improved with added phytase. Phytase addition to basal diet linearly increased ash weight in the grower phase. With the exception of proline and glycine, the digestibilities of the other amino acids were linearly increased with phytase and CP level. Nitrogen excretion was estimated to be reduced by 4.6% when phytase was added to pig diets at a level of 500 U/kg. In a study with cecectomized roosters, the main effects and interaction of phytase and non-startch polysaccharide enzymes on the nutrient utilization of barley, canola meal, rice bran and soybean meal, and canola-barley (36:64) and soybean meal-barley (27.3:72.7) were evaluated. Phytase supplementation to basal diets increased the utilization of energy, N, total amino acid and most of amino acids in barley, canola meal, and canola-barley and numerically increased energy and N utilization in rice brain, soybean meal and soybean-barley. The magnitudes of improvements in the digestibilities of lysine, arginine, cysteine, serine, and threonine were higher compared with the other amino acids. The true utilization of energy and N, and the digestibilities of total amino acid and of glycine, isoleucine, and histidine in barley quadratically increased with Ronozyme™ B. Phytase addition increased Ca retention in barley, canola and soybean meal, and the soybean meal-barley blend, and increased P retention in barley and soybean meal-barley. Addition of Ronozyme™ B to barley linearly decreased Ca retention and quadratically increased P retention. In summary, the efficiency of phytase in Phytaseed is equal to that of Natuphos for enhancing the utilization of phytate P in corn-soybean diets, and microbial phytase is effective in improving the utilization of N and amino acid in pigs and N, amino acid, and energy in poultry.
Ph. D.

Many proposed and implemented packet classification algorithms trade off JT1emory against lookup-time. Matching algorithms implemented in software cannot keep up with ever-increasing data rates. On the other hand, devices implemented in hardware such as Content Addressable Memory (CAM) have deterministic high lookup rates, but they are expensive in terms of silicon cost and power dissipation. Therefore, a trade-off between hardware and software solutions Le. algorithmic-architectural solutions take advantage of the emerging technologies to provide the required high speed classification without sacrificing the deterministic performance of CAMs. I~ chapter 3 an algorithmic-architectural solution is provided that exploits the geometrical distribution of rules, Hypercuts packet classification algorithm, and CAMs. It works by multi-level cutting ofthe classification space into sub-spaces. It prOVides the deterministic performance of CAMs, support for dynamic updates, and fleXibility for the system designer to trade off the components of the architecture. In chapter 4 Adaptive Rules Cutting (ARC), a heuristic algorithm for packet classification, is proposed. This heuristic algorithm works by selecting the bit positions that divide the classification space into sub-spaces at l-Ievel in a way that reduces the redundancy of rules in cuts and maximizes the equal distribution of rules in cuts. An architecture for packet classification by l-Ievel cutting of the classification space is presented. In chapter 5, architecture for hardware acceleration of session-based IP packet classification is provided and implemented in FPGA. The architecture works by dividing the classification space into sub-spaces at l-Ievel using CRC16. Overall, the thesis provides three new solutions for packet classification based on cutting the classification space into smaller spaces. Supplied by The British Library - 'The world's knowledge'

Background: Metabolic syndrome is a complex disorder that increases the risk of cardiovascular diseases. Metabolic syndrome has an unknown aetiology, but shifting dietary patterns such as increased consumption of industry-processed refined sugars have been implicated in the pathogenesis of the syndrome. Distributed along the length of the alimentary tract are macronutrient sensing mechanisms that play a key role in regulating feeding behaviour and energy balance and control intestinal nutrient-transport capacity and the release of peptide hormones. Recent studies have suggested that the sweet-taste receptor, T1R2/3, senses small-intestinal glucose levels and co-ordinates transport capacity and GLP1 release; however, the precise role of T1R2/3 in intestinal sugar sensing remains controversial. Studies have also suggested that macronutrient sensing is attenuated in diet-related metabolic disease; however, the mechanisms by which this occurs are not known. Aims: We hypothesised that T1R2/3 expressed in enterocytes regulates intestinal sugar-transport capacity. We also hypothesised that macronutrient sensors demonstrate a diurnal rhythm that is controlled by clock genes and that in obesity/diabetes the gene-expression levels of such sensors are diminished. Methods: To test our hypotheses we studied the expression levels of intestinal sugar sensors in nocturnal feeding rodents, rodents chronically fed a high-sucrose diet and Caco-2 cells — an enterocyte model. Results: T1R2/3 gene expression was highest in the tongue, absent from the stomach and detected at low levels in the small intestine. SGLT3, a novel sugar sensor, was not expressed in the tongue but was expressed in the stomach and small intestine. A clear diurnal rhythm of clock genes CRY2 and BMAL1 was found in the tongue, stomach and small intestine. A diurnal rhythm for T1R2, T1R3 and the novel sugar sensor SGLT3 was detected in the stomach and small intestine, but not the tongue. SGLT3 expression, but not T1R2/3, was significantly decreased in mice fed a high-sucrose diet. SGLT3 and T1R3, but not T1R2, were detected in Caco-2 cells; however, we found no evidence of a functional sweet-taste receptor. Conclusion: Taken together, these data suggest a novel interaction between intestinal clock genes and sugar-sensor mechanisms. Disturbances in clock gene/nutrient sensing interactions may be important in the development of diet-related diseases. T1R2/3 regulation of sugar transport most likely occurs via an enteroendocrine cell/enterocyte interaction.

Background In April 2004 Hull City Council introduced free healthy school meals for all primary and special school pupils (approximately 20,500 children from 71 primary schools and 6 special schools) in an attempt to reduce health and education inequalities. The meals were prepared to meet the Caroline Walker Trust (CWT) nutritional guidelines for primary schools. This study was carried out to assess the nutritional content of the meals and children’s actual intake from school dinners in comparison to children’s nutritional intake from packed lunches. The study then aimed to assess how food intake at lunch time impacted upon food consumed for the remainder of the day. Methods Children were recruited onto the study from two schools in Hull. The schools were selected by the number of pupils on roll and the number of children eligible for free school meals. The first phase of research assessing lunch consumption was conducted with 147 children, aged 8 – 11 years. School meals and packed lunches were weighed and photographed before and after consumption to assess actual intakes. The second phase assessed total daily food and nutrient intakes in a small sample of 20 children. All assessments were carried out over five consecutive days. Results The food provided by the schools for lunch met the majority of the CWT nutritional guidelines, however children’s intake did not. Children who ate a hot school dinner consumed only the foods they liked from the school meals provided leading to a low energy and nutrient intake. Large differences, for example 367kcal in comparison to 760kcal, in nutritional intakes were found between those children who ate a hot school dinner and those who ate a packed lunch. Children who consumed a packed lunch consumed significantly (p less than 0.05) more energy, fat, saturated fat, non-milk extrinsic (NME) sugar and sodium than children who ate a hot school dinner, but with this consumed more micronutrients. However, neither of the groups of children met the CWT guidelines for lunch time micronutrient intakes. The food diary analysis revealed that those children who ate a hot school dinner went on to consume food high in energy, fat, saturated fat, NME sugar and sodium later in the day. The significant differences in nutrient intakes between the hot dinner and packed lunch groups at lunch time disappeared when total daily intakes were compared. Differences were found between the children’s nutritional intake from the two schools, which may be due to socio economic factors. Conclusion The free healthy school dinners were not having the desired effect of improving children’s nutritional intake, children chose to eat the foods they liked and left the rest. Children who ate a free healthy school dinner went on to consume foods high in energy, fat, NME sugar and sodium later in the day and overall did not have a lower intake of these macronutrients than those children who had a packed lunch.

In conditions of phosphate deprivation, the budding yeast, Saccharomyces cerevisiae activates the phosphate starvation response pathway (PHO pathway). Induction of the PHO pathway causes the transcription of genes involved with phosphate metabolism. Phosphate transport genes are activated during starvation, giving rise to the presence of Pho84, the high affinity transporter. In high phosphate conditions low affinity transporters reside at the plasma membrane. Here we show that Spl2, a suppressor of phospholipase-C, is involved in the down-regulation of the low affinity transport system. This phenomenon gives rise to complex population dynamics and bistability. Furthermore, we demonstrate how the phenotype of strains lacking Pho84 can be explained in context of unconstrained positive feedback through Spl2. We then turn our attention towards comparative studies of the PHO pathway, comparing the transcriptional response of S. cerevisiae to C. glabrata. Using expression microarrays and deep sequencing, we find that the transcriptional circuit in C. glabrata has been altered such that transcriptional cooperativity is lost, nucleosome positioning is altered, and transcriptional competition between the transcription factor Pho4 and centromere binding factor, Cbf1, is relatively conserved.

This thesis deals with the mathematical modelling of nutrient uptake by plant roots. It starts with the Nye-Tinker-Barber model for nutrient uptake by a single bare cylindrical root. The model is treated using matched asymptotic expansion and an analytic formula for the rate of nutrient uptake is derived for the first time. The basic model is then extended to include root hairs and mycorrhizae, which have been found experimentally to be very important for the uptake of immobile nutrients. Again, analytic expressions for nutrient uptake are derived. The simplicity and clarity of the analytical formulae for the solution of the single root models allows the extension of these models to more realistic branched roots. These models clearly show that the `volume averaging of branching structure' technique commonly used to extend the Nye-Tinker-Barber with experiments can lead to large errors. The same models also indicate that in the absence of large-scale water movement, due to rainfall, fertiliser fails to penetrate into the soil. This motivates us to build a model for water movement and uptake by branched root structures. This model considers the simultaneous flow of water in the soil, uptake by the roots, and flow within the root branching network to the stems of the plant. The water uptake model shows that the water saturation can develop pseudo-steady-state wet and dry zones in the rooting region of the soil. The dry zone is shown to stop the movement of nutrient from the top of the soil to the groundwater. Finally we present a model for the simultaneous movement and uptake of both nutrients and water. This is discussed as a new tool for interpreting available experimental results and designing future experiments. The parallels between evolution and mathematical optimisation are also discussed.

Background: Not only does IBD lead to nutritional deficiencies, but also nutrients influence its pathophysiology: exclusive enteral nutrition (EEN) is an effective primary treatment in Crohn's disease; and vitamin D (VitD) is involved in its pathogenesis and course. Aims: We hypothesised that nutrients impact on the course of IBD. We therefore studied the effect of EEN i) on long term clinical course in children; ii) on CD58, a costimulatory molecule at the intestinal epithelial cell (IEC) lines, iii) adults with Crohn's disease. We examined the possible effect of serum vitamin D levels on the course of IBD and also the possible role of ethnicity in our paediatric and adult populations that were treated with EEN but also in our general adult population. Results Chapter II: 56 paediatric patients with Crohn's disesase were followed up for 5 years. 57% of patients achieved remission after 6 weeks of EEN. Achievement of clinical remission within 6 weeks of EEN was significantly associated with a longer time to relapse and to treatment escalation. VitD deficiency was common; and those patients who were deficient were significantly more likely to require corticosteroids and also needed thiopurines sooner. Chapter III: CD58 was expressed in the IEC isolated from IBD patients and healthy controls. EN down-regulated the expression of CD58 on IEC lines. Chapter IV: 22 adult patients with Crohn's disease with a mean age of 30.8 years were given EEN and followed up for a mean time of 1.9 years. 22.7% of patients went into clinical remission and 77.3% experienced a clinical response. By the end of follow up 63.6% (14/22) of patients had clinically relapsed and 36.4% required surgery during their follow up. There was no difference between South Asian and Caucasian patients in the disease outcomes after administration of EEN. Chapter V: Bangladeshis were more often vitamin D deficient than white Caucasian patients; however vitamin D status was not associated with the course of IBD. Bangladeshis developed perianal disease and required thiopurines earlier in their disease course. Bangladeshi patients with UC had more extensive disease. Conclusions: EEN, when successful, improves the long term outcome of Crohn's disease in children, possibly in part, by down-regulating CD58 on the IEC. VitD deficiency may influence the clinical course of IBD; however our results were contradictory between children and adults and significantly limited by the assessment of the vitamin D level at a single time point.

Thesis (MScAgric)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: The macro-element uptake and distribution by higher density central leader ‘Donnarine’ nectarine trees was studied through the sequential excavation of trees. A large portion, 41.5%, of the nitrogen manifested in the new growth from dormancy up to pit-hardening, originated from nitrogen reserves in the permanent structure. The permanent structure was also an important source of phosphorous reserves. Of the phosphorous in the fruit, leaves and new shoots at pit-hardening, 35.0% came from reserves in the permanent structure. Potassium did not act as an important reserve in the nectarine trees and was taken up throughout the season. From pit hardening to harvest the fruit represented the most important sink for potassium. Calcium and magnesium, like potassium, did not play significant roles as reserves in the nectarine tree and must be available for uptake from the beginning of the season for new growth and development as well as fruit quality. The micro-element uptake and distribution was also studied through the sequential excavation of the same ‘Donnarine’ nectarine trees. Little scientific data is available on this topic. Manganese and iron was found to act as important reserves in the tree with 46.2% of manganese and 59.5% of the iron found in the new growth at pithardening coming from reserves translocated from the permanent structure. Zinc and boron reserves also play a role in nectarine trees, but to a lesser extent than manganese and iron. The seasonal mineral nutrient demand of the same ‘Donnarine’ nectarine trees was determined through the sequential excavation of trees and losses and fixation was calculated. Guidelines regarding nutritional requirements per ton of fruit produced per hectare by higher density nectarine orchards are respectively 3.82kg nitrogen, 0.35kg phosphorous, 4.43kg potassium, 1.53kg calcium, 0.52kg magnesium, 32.45g sodium, 9.44g manganese, 37.46g iron, 3.24g copper, 13.95g zinc and 10.52g boron. Sodium is not commonly considered to be essential to higher plants, but was included in the trial. Nutrient solutions with four different EC (electrical conductivity) levels were applied to ‘Donnarine’ nectarine trees under pulsating drip fertigation for three periods of different lengths, before harvest. Raising the nutrient solution EC to positively affect fruit quality is a technique widely utilised in the vegetable industry. This technique did, however, not have similar positive effects on nectarine fruit grown under a pulsating drip fertigation system. Good production practices such as accurate nutrition and irrigation as well as the correct horticultural inputs should be the primary focus of producers who wish to alter or improve the fruit quality of their crop.
AFRIKAANSE OPSOMMING: Voedingbestuur strategieë in nektarien boorde Die makro-element opname en verspreiding deur hoër digtheid sentrale leier ‘Donnarine’ nektarien bome is bestudeer d.m.v. opeenvolgende opgrawings van volledige bome en die ontleding van monsters. ‘n Groot hoeveelheid, 41.5%, van die stikstof wat tydens pitverharding in die nuwe groei teenwoordig was, is d.m.v. translokasie vanuit die permanente struktuur van die boom afkomstig. Die permanente struktuur was ook ‘n belangrike bron van fosfaat reserwes. Teen pitverharding was 35.0% van die fosfaat in die nuwe groei afkomstig vanuit die permanente struktuur. Bevindings het getoon dat kalium nie as ‘n reserwe in die nektarien bome opgetree het nie en dié element is deur die groeiseisoen opgeneem. Vanaf pitverharding tot en met oestyd was die vrugte die sterkste setel van aanvraag vir kalium. Kalsium en magnesium het, soos in die geval van kalium, nie ‘n belangrike rol as reserwe vertolk nie. Beskikbaarheid van hierdie elemente vir opname vanaf die begin van die groeiseisoen is dus baie belangrik vir nuwe groei en ontwikkeling asook vrugkwaliteit. Die mikro-element opname en distribusie van dieselfde ‘Donnarine’ nektarien bome is ook bestudeer d.m.v. opeenvolgende opgrawings en analise van volledige bome. Min wetenskaplike literatuur oor hierdie onderwerp is beskikbaar. Bevindings het getoon dat mangaan asook yster baie belangrike reserwes in die nektarien boom is. Tydens pitverharding was 46.2% van die mangaan en 59.5% van die yster wat in die nuwe groei teenwoordig was, afkomstig vanaf reserwes uit die permanente struktuur van die boom. Verder het sink en boor ook as reserwes opgetree, maar tot ‘n mindere mate as mangaan en yster. Die seisoenale behoeftes aan minerale voeding van dieselfde ‘Donnarine’ nektarien bome is bepaal d.m.v. opeenvolgende opgrawings en analise van volledige bome asook die bepaling van verwyderingsverliese en vaslegging. Voedingsriglyne is vasgestel i.t.v. die hoeveelheid voedingstof wat per hektaar benodig word om een ton nektariens te produseer. Die riglyne is as volg: 3.82kg stikstof, 0.35kg fosfaat, 4.43kg kalium, 1.53kg kalsium, 0.52kg magnesium, 32.45g natrium, 9.44g mangaan, 37.46g yster, 3.24g koper, 13.95g sink en 10.52g boor. Natrium word nie in die algemeen as ‘n essensiële plantvoedingselement beskou nie, maar is by die berekeninge ingesluit. Voedingsoplossing met vier verskillende vlakke van EG (elektriese geleiding) is vir drie periodes van verskillende lengtes aan ‘Donnarine’ nekarien bome toegedien. Die verhoging van die EG van voedingsoplossings ten einde kwaliteit te verbeter is ‘n tegniek wat met groot suskses in die groentbedryf toegepas word. Hierdie tegniek het egter nie soortgelyke positiewe effekte op die nektarien vrugkwaliteit gehad nie. Produsente wat hul vrugkwaliteit wil verbeter behoort primêr te fokus op goeie produksiepraktyke soos akkurate voeding en besproeiing asook die korrekte tuinboukundige insette.