The effects of seed size on sprout growth of potato seed pieces were investigated in controlled temperature conditions. The objectives were to quantify the effects of seed size, plant growth regulators (gibberellin and paclobutrasol) and calcium availability on sprout length, sprout and root dry mass, as well as the fraction of seed reserves utilised for sprout development. The interactive effect between seed size and temperature was also investigated Sprout length did not differ among seed pieces ranging from 1 to 8g in mass. For larger seed pieces sprout length, dry mass and dry mass per unit length, and the root dry mass increased with increasing seed size, reaching a maximum at a seed mass of 24g after 40 days. The smaller the initial seed piece the larger was the fraction of assimilates utilised for sprout growth. Sprout length and dry mass as well as assimilate mobilisation for growth, were promoted by dipping seed pieces in gibberellin solutions, with the greatest effect obtained with 30 ppm GA, the highest concentration used in the experiment. Paclobutrasol showed inhibiting effects on all growth parameters except for sprout thickness. The root dry mass did not differ among treatments. Sprout growth was enhanced by calcium availability, with the greatest effect obtained with exogenous supply of calcium at 10 mmol/I as CaS04. A similar effect was noticed when complete nutrient solution was supplied. CaC03 was less effective than CaS04. Calcium availability to sprout tips affected sprout growth only when the roots were deprived of nutrients. Sprout length of the two seed pieces (3 and 5g in mass) was similarly affected by temperature over time, with the sprouts at the low temperature initially shorter, but reaching the same lengths as those at the high temperature after 30 and 40 days. Sprout dry mass and thickness of 3 and 5g seed pieces were similarly affected by temperature, with higher dry mass and greater thickening at 16°C than at 26°C. Exposure to low temperature (16°C) was associated with the transfer of a large fraction of seed reserves to the sprouts. / Dissertation (MSc (Agric): Agronomy)--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

Eutrophication is defined as the ‘over enrichment’ of a water body from nutrients, resulting in uncontrolled growth of primary producers, leading to periods of oxygen depletion from decomposition of the algal organic matter. According to the 2010 Water Infrastructure Needs and Investment (a U.S. Congressional Report), 40% of U.S. water bodies are contaminated with pollutants, including nutrients. Non-point sources of nutrient pollution are a major cause of this reduction in water quality. One way to decrease eutrophication is to manage nutrients found in stormwater runoff, before they reach a receiving water body. Bioretention cells containing an internal water storage zone (IWSZ) have been shown to remove higher amounts of nitrogen than conventional cells (without an IWSZ). The IWSZ contains an organic carbon substrate, usually derived from wood chips submerged in water, which supports the biochemical process of denitrification. Characteristics of wood chips that affect nitrogen removal include carbon content (%), leaching of dissolved organic carbon (DOC), and wood chip size and type. However, there is limited information on how the intermittent hydraulic loading that is associated with these field systems impacts their performance. Accordingly, the overall goal of this research is to improve understanding of the effect that the antecedent dry conditions (ADC) have on the performance of a field scale bioretention cell modified to contain an IWSZ. The nine different types of wood chips used in laboratory and field studies identified in the literature were categorized as hardwood and softwood. Literature showed that total organic carbon (TOC) leached from softwood chips is almost double the TOC measured from the hardwood chips, 138.3 and 70.3 mg/L, respectively. The average observed nitrogen removal for softwood chips was found to be greater than the removal for the average of the hardwood chips (75.2% and 63.0%, respectively). Literature also suggests that larger wood chip size may limit the availability of the carbon for the denitrifying organisms and provides less surface area for the biofilm growth. A field study conducted for this research compared the performance of a modified bioretention system designed to enhance denitrification, addition of an IWSZ, with a conventional system that does not contain an IWSZ. Fourteen storm events were completed from January 2016 to July 2016 by replicating storm events previously completed in the laboratory using hydraulic loading rates (HLR) of 6.9 cm/h, 13.9 cm/h, and 4.1 cm/h. The goal was to have results from storm events with ADCs of two, four, and eight days, with the varying durations of hydraulic loading of two, four, and six hours. Synthetic stormwater, simulating nitrogen levels common in urban runoff, was used as the system’s influent to assist in running a controlled experiment. The resultant ADCs ranged from 0 to 33 days, with the average ADC being 9 days. The fourteen sets of influent samples were averaged to obtain mean influent concentrations for the synthetic stormwater. These values were used when calculating the percent nitrogen removal for the four measured nitrogen species (NOx – N, NH4+– N, organic N, and TN). The field storm events were separated into three groups based on HLR and duration to eliminate the affects of both variables on nitrogen removal for these results, since the focus is the ADC. For the low HLR (4.1 cm/hr), there were four storm events (ADCs of 4 to 33 days), as the ADC increased, greater percentages of ammonium – nitrogen, organic nitrogen, and total nitrogen were removed. For nitrate/nitrite – nitrogen, the percent removal was rather consistent for all four storm events, not significantly increasing or decreasing with changes in the ADC. There were five storm events (ADCs of 0 to 28 days) tested with the median HLR (6.9 cm/hr), nitrogen removal for all four species increased as the ADC increased. The increase was significant (p0.05) for nitrate/nitrite – nitrogen. The third group also contained five storm events (ADCs from 0 to 11 days) that were tested with the highest HLR (13.9 cm/hr). Ammonium – nitrogen, nitrate/nitrite – nitrogen, and total nitrogen all increased with the ADC, and organic nitrogen removal decreased with the increasing ADC. As a result, this research concluded that the difference in HLR affects the nitrogen removal efficiency, but overall increasing the ADC increased nitrogen removal for NOx – N, NH4+ - N, organic N, and TN.

The structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar.

Nutrient loading to aquatic and marine ecosystems is a topic of interest, especially as the human population continues to grow and land use changes. Here, I examined the seasonal variability and relative amounts of different forms of nitrogen (N) and phosphorous (P) from four sites at Röbäcksdalen (Umeå, Västerbotten), an area influenced by both agriculture and partial urbanization. In addition, I studied how nutrient concentration varied with discharge during snowmelt. Overall, the results show that the seasonality of nutrient concentration did not differ drastically from what is expected in more pristine boreal catchments. However, the concentrations of dissolved inorganic N (DIN) and phosphate (PO4) were elevated. Land use activities in Röbäcksdalen also appear to be influencing inorganic N inputs to streams to a greater degree than inputs of inorganic P. Comparisons with more pristine boreal streams also reveal a fundamental change in the composition of the stream N pool, with greater dominance of DIN within the catchment. This pattern is likely due to inputs of nutrients in excess of biotic demand. Lastly, the results of the concentration-discharge analysis from Röbäcksdalen indicate that hydrological forcing rather than soil processes control the supply of nutrients to these streams during snowmelt. With concentrations being high, this also indicates that a considerable increase in the flux of nutrients from the area is expected with increased discharge.

Land uses dominated by human activity can have a significant effect on ecological processes. In Florida, oxygen depletion is the most common impairment in lake, stream, and coastal water bodies. The continual growth and development in Florida, along with a conversion to more human intense land uses warrants study and discussion on impacts to dissolved oxygen regimes along a gradient of human disturbance. This research study is designed to identify observable trends in dissolved oxygen regimes along a gradient of increasing human intensity. Twenty-six stations in the Tampa Bay area were selected to represent lotic systems in west-central Florida. Data was collected quarterly, during four-day deployments, using a deployable data sonde. Grab samples for nutrients and chlorophyll-a provided antecedent data to explain observed trends. Physical components of streams, such as channelization were also taken into account. Biological integrity of streams was assessed to identify if altered dissolved oxygen regimes as a result of human land use significantly affect the health of the systems. Analysis included the use of Spearman rank order correlations to identify patterns. Dissolved oxygen regimes were correlated with the Landscape Development Intensity Index (LDI). Nutrients, primary productivity, and physical alteration to the streambed play a significant role in understanding how land use affects dissolved oxygen regimes. Results indicate the intensity of human land use has a significant effect on dissolved oxygen regimes and has significant policy implications for Florida's Total Maximum Daily Load (TMDL) program. Diel variation in oxygen measurements may be a more appropriate indicator of impairment and stream biological integrity.

L’azote est un des macronutriments essentiels pour les plantes. Dans les sols, l’azote est présent sous différentes formes organiques et inorganiques. Les plantes utilisent préférentiellement le nitrate, qui n’est pas toujours disponible en quantités suffisantes dans les sols. Récemment, une étude a permis de montrer que le facteur de transcription NLP7 est un régulateur majeur de la réponse primaire au nitrate. La localisation subcellulaire de cette protéine est régulée par le nitrate : en son absence, elle est localisée dans le cytoplasme alors qu’après ajout de nitrate, une rétention nucléaire est activée. Les mécanismes moléculaires de cette rétention restent encore à comprendre ainsi que la transmission du signal nitrate, de l’extérieur de la plante à la protéine NLP7. Le transporteur de nitrate NPF6.3 a été montré comme jouant un rôle dans la perception du nitrate, c’est donc un transcepteur. Notre hypothèse était que NPF6.3 est le récepteur de nitrate en amont de NLP7. Pour tester cette hypothèse, nous avons étudié par des approches génétiques les liens d’épistasie entre les deux gènes. L’étude de la biomasse et de l’expression des gènes sentinelles en réponse au nitrate chez les simples et double mutants a permis d’observer des phénotypes additifs. Nous avons pu montrer que le mécanisme de relocalisation rapide de la protéine NLP7 dans le noyau est toujours actif dans le fond mutant npf6.3. Ces résultats ont donc permis de montrer que NLP7 et NPF6.3 n’appartiennent pas à la même voie de signalisation mais que ces deux voies pourraient être dépendantes selon les conditions. D’autre part, peu de régulateurs de la réponse au nitrate sont connus. De manière intéressante, les gènes cibles de NLP7 sont enrichis en protéines régulatrices comme par exemple d’autres facteurs de transcription ou encore des protéines kinases, ce qui place NLP7 à un haut niveau hiérarchique de régulation dans la voie de signalisation en réponse au nitrate. En effet, ces cibles directes de NLP7 pourraient elles-mêmes être impliquées dans des voies de signalisation en aval de NLP7. Dans le but de disséquer la voie de signalisation en aval de NLP7, nous avons étudié deux cibles directes de NLP7, des Mitogen-Activated Protein Kinase Kinase Kinases (MAPKKKs), MAPKKK13 et MAPKKK14. Les MAPKs sont connues pour leur mode d’action en cascades de phosphorylations. Par des approches biochimiques en protoplastes, nous avons montré que MAPKKK13/14 sont capables d’activer des MAPKs du groupe C via MKK3. De plus, nous avons obtenu de premières indications montrant que certaines réponses développementales au nitrate ainsi que la réponse primaire au nitrate seraient partiellement modifiées dans les simples mutants mapkkk13 et mapkk14, et dans le double mutant mapkkk13/14. / Nitrogen is one of the most important macronutrients for plants. In the soils, nitrogen can be found under different organic and inorganic forms. Plants preferentially use nitrate, which is not always available for plant uptake and assimilation in soils. Recently, it was shown that the NLP7 transcription factor is a master regulator of the primary nitrate response. Its subcellular protein localization is regulated by nitrate: without nitrate, the protein is localised in the cytoplasm whereas after nitrate resupply, a nuclear retention is observed. Molecular mechanisms of this nuclear-cytosolic shuttling and of the nitrate signal transduction from the external medium to the NLP7 protein are still unknown. It has been shown that the NPF6.3 nitrate transporter plays a role in the nitrate signal sensing, which made this protein a transceptor. Our hypothesis was that NPF6.3 is the nitrate sensor upstream of NLP7. To test this hypothesis, we studied by genetic approaches the epistasis link between the two genes. By studying the simple and double mutant’s biomass and sentinel gene regulation in response to nitrate, we observed additive phenotypes. We showed that the nuclear relocation mechanism of NLP7 is still active in the npf6.3 mutant background. All together, these results showed that NLP7 and NPF6.3 are not in the same signalling pathway but there would be an interplay depending on the conditions. On the other hand, only a few regulators of the nitrate response are known. Interestingly the direct target genes of NLP7 are highly enriched for regulatory proteins such as other transcription factors or protein kinases, which places NLP7 at a high hierarchical place in the nitrate signalling pathway. Indeed these direct targets of NLP7 may themselves be involved in signalling cascades downstream of NLP7. In order to identify molecular events downstream of NLP7, we studies two NLP7 direct targets, Mitogen-Activated Protein Kinase Kinase Kinases (MAPKKKs), MAPKKK13 and MAPKKK14. MAPKs are known to act as phosphorylation cascades. Using biochemical approaches in protoplasts, we have shown that MAPKKKK13/14 are able to activate Group C MAPKs via MKK3. In addition we showed in planta that nitrate addition indeed triggered the activation of group C MAPKs and that this activation is dependent on NLP7 and MKK3. Furthermore we obtained first indications that nitrate-dependent developmental traits and the primary nitrate response are partially impaired in the single mutants mapkkk13 and mapkkk14, and the double mutant mpkkk13mpkkk14.

Coastal oceans play an important role in the carbon cycle and are hotspots of ocean primary production and ocean acidification. These coastal regions are strongly influenced by rives, especially in the Arctic. Despite the importance of the riverine delivery of carbon and nutrients, their effect on the Arctic Ocean is still poorly understood due to hostile conditions and the consequently low number of observations. This thesis aims at improving our understanding of the influence of Arctic riverine delivery of carbon and nutrients by using ocean biogeochemical models.The first part of the thesis evaluated the model skills of the ocean biogeochemical model NEMO-PISCES in the Arctic Ocean. By analyzing model results at different horizontal resolutions, the importance of lateral influx from the adjacent oceans for anthropogenic carbon cycle in the Arctic Ocean wasdemonstrated. These results were then used to adjust a previously published data-based estimate of anthropogenic carbon storage in the Arctic Ocean and the corresponding ocean acidification.In the second part, a pan-Arctic observation-based dataset of riverine carbon and nutrient fluxes was created. This dataset was then used to force the ocean biogeochemical model and the river fluxes were quantified. River fluxes have been shown to sustain up to 24% of Arctic Ocean primary production, to reduce the air-sea CO2 uptake by 20%, and to reduce surface ocean acidification seasonally. Eventually, idealized simulations were made to quantify the sensitivity of the Arctic Ocean biogeochemistry to future changes in riverine delivery of carbon and nutrients. Sensitivities are of small magnitude on a pan-Arctic scale, importance in the coastal areas, and the dominant factor close to river mouths. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The presented diploma thesis is focused on complex characterization of chosen superfoods and subsequent composition of supplement suitable for children´s nutrition. Different kinds of superfoods were chosen for analyses, such as: barley grass (Hordeum vulgare), wheat grass (Triticum aestivum), moringa (Moringa oleifera), matcha tea (Camellia sinensis), microalgae chlorella (Chlorella pyrenoidosa), spirulina (Arthrospira platensis), flax seeds (Linum usitatissimum) and sesame seeds (Sesamum indicum). The theoretical part is focused on children´s nutrition issue and the most common food allergies and intolerances. Also, children food products legislation and characterization of chosen samples are included in theoretical part. Main macronutrients, such as saccharides, lipids and proteins, were analysed in the very beginning of experimental part. Fibre, fructan and -glucan, which have a high impact on intestinal microbiome and whole process of digestion, were analysed as well. However, barley grass was the best evaluated sample by containing 205,5 mg/g of insoluble fibre; 152,57 mg/g of fructans and 18,76 mg/g of -glucans. Finally, for complex nutritional profile, also samples pigments were analysed. Spectrophotometry, HPLC chromatography, gas chromatography and other analytical techniques were performed for experiments.

The annual advance and retreat of sea ice in the Southern Ocean is recognised as one of the largest seasonal events on Earth. Such considerable physical changes have profound effects on the vertical structure of the water column, and hence controls the availability of both light and nutrients to phytoplankton. This means that in the region seasonally covered by sea ice (the SSIZ), the timing of the growth and decline (phenology) of phytoplankton is determined to a large degree by the dynamic interactions between ice, ocean and atmosphere. However, this region is simultaneously one of the most poorly observed in the global ocean, and one of the most complex. This has led to significant gaps in our understanding of how sea ice modulates the exchanges of heat and momentum between atmosphere and ocean, as well as the implications this has for phytoplankton phenology in the SSIZ. This study seeks to address these gaps by combining both model and observationallybased methods. The lack of observational data are directly tackled through an analysis of BGC-Argo float data sampling under ice. Such data reveal high growth rates in the presence of near full ice cover and deep mixed layers, conditions previously thought to prevent growth. These results suggest a revision of our current understanding of the drivers of under ice phytoplankton phenology, which should take into account the unique character of Antarctic sea ice and its effect on the under ice light environment. In addition, results obtained from several numerical process studies indicates that phytoplankton may have a higher affinity for low light conditions than previously thought. From a modelling perspective, an analysis and intercomparison of 11 Earth System Models (ESMs) and their representation of vertical mixing and phenology is presented. This revealed that misrepresentations in phenology where driven by model biases in sea ice cover and vertical mixing. That is, only models with either too much or too little ice cover were able to simulate phenology close to observations. Furthermore, a strong correlation between the location of the ice edge and the extent of vertical mixing suggested that ESMs overly dampen ocean-atmosphere fluxes as mediated by sea ice. This led to the development of a regional ocean-sea ice model of the Atlantic sector of the Southern Ocean, from which experiments enhancing both heat and momentum fluxes could be conducted. It was found that the model responded more uniformly to enhanced heat flux, generally deepening the mixed layer closer to observations in winter. On the other hand, the effects of enhanced momentum flux (implemented by increased air-ice drag) where more complex and spatially heterogeneous, with contrasting responses depending on the initial vertical density structure of the water column. Overall, the argument is made that the unique features of Antarctic sea ice should be included in models if we are to improve the representation of the SSIZ mixed layer, and hence phenology

MESHWR / Department of Ecology and Resources Management / The presence of harmful algal blooms (HABs) and cyanobacteria toxins in drinking water sources are known to pose a great threat to humans. The main aim of this study was to use molecular technique to determine the origins of the cyanobacteria species at Musina raw water abstraction point by identifying and comparing the non-toxic and toxic cyanobacteria species in the Limpopo River and some of its tributaries based on the phylogenetic analyses of 16S rRNA gene. The Musina water treatment plant is located downstream of a weir and the Beit bridge on the Limpopo River and the raw water supply is abstracted from 22 boreholes of which 14 are along the Limpopo River and 8 boreholes are inside the Limpopo River channel. The bottom sediments samples were collected from these rivers: Limpopo, Crocodile, Mokolo, Mogalakwena, Nzhelele, Lephalale, Sand rivers (South Africa); Notwane (Botswana), Shashe River and Mzingwane River (Zimbabwe). The physical-chemical analysis of the bottom sediments showed the availability of nutrients, nitrates and phosphates, in excess of 0.5 mg/l for most the of rivers, alkaline pH and salinity in excess of 500 mg/l. Total genomic DNA were extracted from cyanobacteria species on the bottom sediments and Polymerase Chain Reaction (PCR) method was used to detect the genetic profile of the cyanobacteria species. Molecular identification of cyanobacteria was based on PCR amplification and sequencing of the 16S rRNA gene. The 16S rRNA gene was absent from sediments of the Mogalakwena and Lephalale rivers but present in all other selected rivers. The cyanotoxins detection was also based on PCR by amplification of microcystin/nodularin and cylindrospermopsin polyketide synthetase genes. Most of the samples showed no amplification of the toxin genes. While two samples showed the amplification of cylindrospermopsin polyketide synthetase gene (Sand River and Nzhelele River Next to Tshipise) and two samples showed amplification for microcystin/nodularin synthetase gene, Crocodile River and Mzingwane River. The first was the confirmation of similarity of samples from Crocodile River downstream of hartbeespoort Dam and Shashe River to Leptolyngbya boryana with 99% bootstrap confidence. The similarity of sample from Musina borehole to Sand River upstream to Alkalinema pantanalense with 98% bootstrap. Thus, the presence of toxic genes may imply the presence of toxic cyanobacteria species in the river sediments and may be hazardous to humans because rural communities and commercial farmers abstract water from Limpopo River catchment for human consumption, livestock and irrigation. The waters of the Limpopo River basin also provide drinking water to wildlife and a habitant for aquatic organisms/animals.