Flocculation is not only an important part of sediment dynamics within coastal marine waters, but is also a factor of sediment transport within small freshwater streams in Blacksburg, Virginia. The goal of this project was to develop a relationship between floc sizes and stream characteristics (temperature, salinity, chlorophyll-a, organic content, TSS, pH) and to compare how that relationship varies seasonally and spatially across two streams in the same watershed with a similar drainage area but different land uses within these areas. Microscopic images of flocs and water samples were taken within two local streams every two to four weeks throughout the span of one year. The images were analyzed to obtain the floc sizes and the water samples were tested in a lab for various stream properties. The compiled data from the entire year were analyzed to determine if there was a seasonal relationship between floc sizes and the various properties of the water. The process was also repeated at multiple locations along the entire length of both of the streams once in the summer and once in the winter to see if there was a spatial relationship within a single stream. Our study found that significant rainfall events tend to have the greatest effect on floc size in the small headwater streams. However, many of the individual variables alone do not correlate strongly with floc size and a combination of variables may be the best way to analyze the floc size. / Master of Science / Flocculation is the process of single particles coming together to form larger aggregated particles called "flocs". This project focuses on flocculation of sediment within local streams and how the sizes of these flocs may vary throughout the year. The rate of flocculation and the size of these flocs can have a large effect on the movement of sediment within freshwater streams. Images of flocs and water properties such as water temperature, salinity, and pH, were analyzed every two to four weeks throughout the span of a year to determine if there was a relationship between floc size and any of the measured water properties. While a relationship between rainfall and floc size was noticed, it is apparent that multiple variables should be factored into the analysis to get the most accurate results.

The primary goal of this research was to evaluate the effects of light on soymilk, including the oil component. Soybean oil with added chlorophyll a (0, 1, and 2μg/ml), a photosensitizer, was exposed to light (no light [control], broad-spectrum light) and narrow-band wavelengths (430nm, 450nm, and 660nm] for 4h. Chlorophyll completely degraded under broad-spectrum light and 430nm treatments; 64% degradation occurred at 660nm. Oil with chlorophyll addition resulted in significantly higher peroxide values and malondialdehyde concentrations with light exposure to broad spectrum and 430nm wavelengths. Light at 430 and 660 nm degraded chlorophyll and increased risk of oxidation in soybean oil. Soymilk contains low concentrations of chlorophyll, the photosensitizer riboflavin, as well as highly susceptible oxidizable substrates from the soy oil. Soymilk (1% fat from soybean oil) was packaged under a positive flow hood into 5 high density polyethylene (HDPE) packages and stored for 36 days at 4°C under fluorescent lighting (1122 lux ± 439 lux). Control packaging had no light protective additive (LPA; positive (foil-wrapped) and negative control) and the experimental packaging treatments had three levels of LPA (low, medium, high). Chemical and sensory analyses to measure oxidation changes were completed on the product at days, 1, 4, 8, 15, 22, 29, and 36. HDPE packages with high LPA protected the sensory quality of the product as well as the positive control (foil-wrapped) packages for a minimum of 15 days. High-LPA HDPE protected soymilk for 29 days from degradation of riboflavin and limited development of aldehyde end-products associated with photooxidation. Soymilk was treated with food grade TiO2 at levels of 0, 0.5, and 1.0% by weight. TiO2 significantly whitened the product as demonstrated by L* values. TiO2-treated soymilks resulted in significantly improved hedonic scores for appearance, smell, taste, mouthfeel, and aftertaste compared to control soymilk. However, in a second experiment, overall acceptability of TiO2-treated soymilk, at additions of 0.1%, 0.3%, and 0.5% TiO2, was not higher than control soy milk. / Ph. D.

Made available in DSpace on 2014-06-11T19:22:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-18Bitstream added on 2014-06-13T19:07:35Z : No. of bitstreams: 1 maia_scm_me_botfca.pdf: 3637798 bytes, checksum: 42c60ca08ea3f3717b8ba3a464ed6462 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Técnicas de manejo que possibilitem a maximização de absorção de N pelo feijoeiro são de extrema importância, em razão do alto custo dos fertilizantes nitrogenados e das perdas de N, que podem representar prejuízos aos produtores e riscos ao ambiente. Nesse sentido, a estimativa da necessidade de N pelo feijoeiro mediante a leitura indireta de clorofila, pelo clorofilômetro portátil, pode ser uma alternativa viável. Contudo, ainda existe a necessidade de estabelecimento de critérios para a utilização desse aparelho na cultura do feijão. Os objetivos do presente trabalho foram: a) verificar a correlação entre o índice relativo de clorofila (IRC), obtido mediante leituras do clorofilômetro portátil (SPAD- 502), e o teor de N da folha de dois cultivares de feijão (IAC Alvorada e Pérola) em diversos estádios de desenvolvimento; b) verificar o comportamento do IRC e do índice de suficiência de N (ISN) em função dos manejos de N aplicado em cobertura; c) avaliar o ISN calculado com base nas medidas IRC nas folhas como indicador do momento de aplicação de N em cobertura na cultura do feijão e, d) verificar qual valor do ISN (90% e 95%) em relação ao tratamento referência é o mais adequado para indicar o momento da adubação nitrogenada em cada cultivar utilizado. O trabalho foi constituído de um experimento conduzido durantes as safras “das águas” e “da seca” do ano agrícola 2009/2010, na Fazenda Experimental Lageado da FCA/UNESP - Botucatu-SP. O delineamento experimental foi em blocos ao acaso, em esquema de parcela subdividias, com quatro repetições. As parcelas foram constituídas por dois cultivares de feijão (Pérola e IAC Alvorada) e as subparcelas por seis manejos do N M1: 40 kg ha-1 de N na semeadura + 80 kg ha-1 de N aos 15 dias após a emergência (DAE) + 80 kg ha-1 de N aos 30 DAE; M2: 20 kg ha-1 de N na semeadura... (Complete abstract click electronic access below) / Management techniques that allow the maximization of N uptake by bean crop are extremely important, because of high cost of nitrogen fertilizers and N losing, which may represent losses to producers and risks to the environment. In this sense, the estimation of N needs of common bean crop by indirect reading of chlorophyll can be a viable alternative. However, there is remains the need to establish criteria for using this device in the bean. The aims of this study were: a) determine the correlation between relative chlorophyll index (RCI), obtained by reading of chlorophyll (SPAD 502) and leaf N content of two bean cultivars (IAC Alvorada and Pérola) in various stages of development; b) verify the behavior of the RCI and N sufficiency index (NSI) for different sidedressing N management practices; c) evaluated the NSI calculated based on the measures RCI leaves as an indicator of time of N application in sidedressing on bean crop and d) verify that value of NSI (90% and 95%) compared to the reference treatment is most appropriate to indicate the moment of fertilization in each cultivar. The work was composed of an experiment conducted in rainy and dry season of agricultural year 2009/2010 at the Experimental Lageado Farm FCA/UNESP - Botucatu-SP. A randomized block in split plot scheme, with four replications was used. Plots consisted of two bean cultivars (IAC Alvorada and Pérola) and subplots of six N managements M1: 40 kg ha-1 N at sowing + 80 kg ha-1 at 15 days after emergence (DAE) + 80 kg ha-1 N at 30 DAE; M2: 20 kg ha-1 N at sowing + 40 kg ha-1 N at 15 DAE + 40 kg ha-1 N at 30 DAE; M3: 10 kg ha-1 N at sowing + 20 kg ha-1 N at 15 DAE + 20 kg ha-1 N at 30 DAE; M4: 20 kg ha-1 N at sowing + 30 kg ha-1 N when chlorophyll meter readings indicated NSI <95%; M5: 20 kg ha-1 N at sowing + 30 kg N ha-1 N when chlorophyll meter readings indicated NSI <90% and, M6: control (without nitrogen)... (Complete abstract click electronic access below)

Air pollutant exposure poses a health risk to humans and impacts negatively on agriculture. High levels of air pollution resulted in extensive crop damage and yield reduction in Europe and USA. The Highveld region in South Africa, a very important area for maize and soya production, has already been declared an air pollution hot spot, with SO2 being the most concerning air pollutant. Most of the SO2 over the Highveld originates from the burning of coal for power generation. Developing countries, such as South Africa, are highly dependent on agriculture for food security and high levels of air pollution pose serious risks to the agricultural industry. Currently very little information is available on the effects of air pollution on crop production in South Africa. This study aimed to establish exposure-response relationship for SO2 on soybean and the quantification thereof on the morphological, physiological and biochemical characteristics. Two soybean cultivars were used, namely: LS 6164 and PAN 1666. The plants were fumigated for 7 hours, 7 days a week with 0 (carbon filtered control; CF), 25, 75 and 150 ppb SO2. The effect of SO2 was investigated on the growth, photosynthetic capabilities, photosynthetic gas exchange, peroxidase activity and lipoxygenase activity of the cultivars. Foliar injuries and interveinal chlorosis were visible with increasing levels of SO2 as well as a decrease in biomass accumulation, especially in root biomass; a more prominent feature of LS 6164. The number of nodules of both cultivars decreased insignificantly as the levels of SO2 increased. The number of pods per plant and the average weight of 30 seeds indicated a downward trend with an increase in SO2 concentration. The chlorophyll content of PAN 1666 was lower compared to LS 6164. PAN 1666 had the largest reduction in stomatal conductance at 150 ppb SO2 fumigation. The photosynthetic vitality index indicated that LS 6164 was more sensitive to SO2 inhibition from 25 ppb SO2 and higher, whereas PAN 1666 mostly became sensitive to SO2 from 75 ppb SO2. A decrease in the ability to absorb light energy, the trapping of excitation energy to transfer electrons beyond QA-, and the reduction of end electron acceptors all contributed to the decline in the vitality index. Sulphur content increased significantly in the 75 ppb and 150 ppb treatments of both cultivars. Induced peroxidase and lipoxygenase activity was seen in both cultivars, especially at higher concentrations of SO2 treatments. PAN 1666 had a higher rate of peroxidase and lipoxygenase activity compared to LS 6164. The implication for SO2 on crop production in the highly industrial Highveld area was demonstrated to be potentially of great concern. The dose-response relationships plotted for OJIP parameters emphasized that SO2 is an inhibitor of photosynthesis and phytotoxic of nature. Both cultivars experienced limitations from 75 ppb, especially at the 150 ppb SO2 concentration. From these results it appears that PAN 1666 is more adapted to SO2 compared to LS 6164 and levels of 75 ppb SO2 and higher become toxic to these plants. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Air pollutant exposure poses a health risk to humans and impacts negatively on agriculture. High levels of air pollution resulted in extensive crop damage and yield reduction in Europe and USA. The Highveld region in South Africa, a very important area for maize and soya production, has already been declared an air pollution hot spot, with SO2 being the most concerning air pollutant. Most of the SO2 over the Highveld originates from the burning of coal for power generation. Developing countries, such as South Africa, are highly dependent on agriculture for food security and high levels of air pollution pose serious risks to the agricultural industry. Currently very little information is available on the effects of air pollution on crop production in South Africa. This study aimed to establish exposure-response relationship for SO2 on soybean and the quantification thereof on the morphological, physiological and biochemical characteristics. Two soybean cultivars were used, namely: LS 6164 and PAN 1666. The plants were fumigated for 7 hours, 7 days a week with 0 (carbon filtered control; CF), 25, 75 and 150 ppb SO2. The effect of SO2 was investigated on the growth, photosynthetic capabilities, photosynthetic gas exchange, peroxidase activity and lipoxygenase activity of the cultivars. Foliar injuries and interveinal chlorosis were visible with increasing levels of SO2 as well as a decrease in biomass accumulation, especially in root biomass; a more prominent feature of LS 6164. The number of nodules of both cultivars decreased insignificantly as the levels of SO2 increased. The number of pods per plant and the average weight of 30 seeds indicated a downward trend with an increase in SO2 concentration. The chlorophyll content of PAN 1666 was lower compared to LS 6164. PAN 1666 had the largest reduction in stomatal conductance at 150 ppb SO2 fumigation. The photosynthetic vitality index indicated that LS 6164 was more sensitive to SO2 inhibition from 25 ppb SO2 and higher, whereas PAN 1666 mostly became sensitive to SO2 from 75 ppb SO2. A decrease in the ability to absorb light energy, the trapping of excitation energy to transfer electrons beyond QA-, and the reduction of end electron acceptors all contributed to the decline in the vitality index. Sulphur content increased significantly in the 75 ppb and 150 ppb treatments of both cultivars. Induced peroxidase and lipoxygenase activity was seen in both cultivars, especially at higher concentrations of SO2 treatments. PAN 1666 had a higher rate of peroxidase and lipoxygenase activity compared to LS 6164. The implication for SO2 on crop production in the highly industrial Highveld area was demonstrated to be potentially of great concern. The dose-response relationships plotted for OJIP parameters emphasized that SO2 is an inhibitor of photosynthesis and phytotoxic of nature. Both cultivars experienced limitations from 75 ppb, especially at the 150 ppb SO2 concentration. From these results it appears that PAN 1666 is more adapted to SO2 compared to LS 6164 and levels of 75 ppb SO2 and higher become toxic to these plants. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

The thesis focuses on regulation of the chlorophyll biosynthetic pathway and its coordination with synthesis of chlorophyll-binding proteins in the cyanobacterium Synechocystis sp. PCC 6803. One of the aims was to analyze correlation between syntheses of photosystems and chlorophyll in Synechocystis cells using radioactive labeling of proteins and chlorophyll by 35S and 14C, respectively. I also investigated the role of enzymes catalyzing protochlorophyllide reduction step in the chlorophyll biosynthesis by analyzing the synthesis and accumulation of photosynthetic proteins in Synechocystis mutants lacking one of the enzymes. Further, roles of Ycf54 and Psb27 proteins in stability and assembly of oxidative cyclase and CP43, respectively, are also described.

Les diatomées constituent le principal groupe du phytoplancton dans les océans, contribuant à près de 20% de la production primaire globale. Dans leur environnement très variable, les diatomées sont particulièrement efficaces dans leur capacité à ajuster leur activité photosynthétique en dissipant sous forme de chaleur l’énergie lumineuse absorbée en excès, par un processus appelé le « Non-Photochemical Quenching of chlorophyll fluorescence », (NPQ). Chez la diatomée modèle, Phaeodactylum tricornutum, il a été montré que LHCX1, une protéine proche des antennes photosynthétiques, est impliquée dans le NPQ. Par des approches intrégrées de génétique, biologie moléculaire, biochimie, imagerie des cinétiques de fluorescence et spectroscopie ultrarapide, j’ai étudié le rôle de la famille des LHCX chez P. tricornutum. J’ai tout d’abord pu corréler une expression différentielle des 4 gènes LHCX de P. tricornutum avec différentes dynamiques de NPQ et activités photosynthétiques, dans différentes conditions de lumiére et nutriments. En localisant les LHCX dans les differents complexes photosynthétiques et les différents sites de dissipation d’énergie, j’ai pu proposer un modèle de régulation dynamique du NPQ impliquant à court terme principalement LHCX1 au niveau des centres réactionnels, et une autre isoforme, possiblement LHCX3, au niveau des antennes lors d’un stress lumineux prolongé. Enfin, par le criblage d’une série de mutants potentiellement dérégulés dans leur contenu en LHCXs, j’ai pu identifier des lignées avec un NPQ altéré qui pourront constituer des nouveaux outils de recherche. Dans l’ensemble ce travail de thèse a permis de mettre en évidence la diversification fonctionnelle et l’importance de la famille des LHCX dans la fine modulation des capacités de collecte de lumière et de photoprotection, expliquant sans doute en partie le succès des diatomées dans leur environnement très fluctuant. / Diatoms dominate phytoplanktonic communities in contemporary oceans, contributing to 20% of global primary productivity. In their extremely variable environment, diatoms are especially efficient in adjusting their photosynthetic activity by dissipating as heat the light energy absorbed in excess, through a process called “Non-Photochemical Quenching of chlorophyll fluorescence”, (NPQ). In the model diatom Phaeodactylum tricornutum, it has been shown that LHCX1, a photosynthetic antenna-related gene, is involved in the NPQ process. Through integrated approaches of genetics, molecular biology, biochemistry, study of the kinetics of chlorophyll fluorescence yields and ultrafast spectroscopy, I studied the role of the LHCX family in the photoprotection activity of P. tricornutum. I first correlated a differential regulation of the 4 P. tricornutum LHCX genes with different dynamics of NPQ and photosynthetic activity, in different light and nutrient conditions. By localizing the LHCXs in fractioned photosynthetic complexes and the different sites of energy dissipation, I was able to propose a model of dynamic regulation of NPQ capacity involving mainly the LHCX1 in the reaction centers, during short-term high light responses. During prolonged high light stress, the quenching occurs mainly in the antennas, potentially mediated by the LHCX3 isoform. Finally, using photosynthetic parameters, I screened a series of transgenic lines putatively deregulated in their LHCX amount, and I identified lines with altered NPQ, which could represent novel investigation tools. Altogether, this work highlighted the functional diversification and the importance of the LHCX protein family in the fine-tuning of light harvesting and photoprotection capacity, possibly contributing to explain diatoms success in their highly fluctuating environment.

Baby spinach is a relatively new crop in South Africa with both commercial significance and reputed health benefits. It is known to assist in combating degenerative conditions associated with ageing, such as heart disease, cardiovascular disease, Alzheimer’s disease, cataracts and several forms of cancer. Three parallel NPK trials were conducted to investigate the effects of nitrogen (N), phosphorus (P) and potassium (K) on the growth and development of baby spinach. N and P treatments were arranged as (0, 45, 75, 105, 120 kg.ha -1 N and P), and K treatments were arranged as (0, 63, 85, 127, 148 kg.ha -1) in a randomised complete block designed with four replicates. Results showed that yield, dry matter, chlorophyll content and Leaf Area Index (LAI) were significantly increased by increasing the N application, while K had a significant effect on the LAI but not on yield, dry matter, chlorophyll content or stomatal conductance. Nitrogen treatments quadrupled fresh yield, dry matter and chlorophyll content, reaching maximum impact at 75 kg.ha-1 N. Phosphorus application showed significantly increased yields, dry matter and chlorophyll content, reaching maximum impact at 75 kg.ha-1 P. Therefore, to achieve optimum growth with N and P, 75 kg.ha-1 is recommended. The optimum rates of N, P and K were then used to formulate a NPK combined trial which was arranged as 0, 30:30:40, 45:45:60, 60:60:70, 75:75:90 kg.ha-1 in a randomised complete block design with three replicates. The results showed that maximum impact on yield, chlorophyll content, fresh and dry matter was achieved when combined NPK was applied at 45:45:60 / Agriculture and  Animal Health / M. Sc. (Agriculture)

The purpose of this study was to examine the suitability of the YSI model 6600 Environmental Monitoring System (multiprobe) for long term deployment at a site in Lewisville Lake, Texas. Specifically, agreement between a laboratory extraction procedure and the multiprobe chlorophyll/fluorescence readings was examined. Preliminary studies involved determining the best method for disrupting algal cells prior to analysis and examining the precision and linearity of the acetone extraction procedure. Cell disruption by mortar and pestle grinding was preferable to bath sonication. Comparison of the chlorophyll/fluorescence readings from the multiprobe and the extraction procedure indicated that they were significantly correlated but temperature dependent.

Das Anliegen dieser Arbeit besteht darin, die Kinetik von elektronischen Singulett- und Triplett-Anregungen innerhalb des solubilisierten Lichtsammelkomplexes des Photosystem II (LHCII) zu untersuchen. Die Untersuchungen gliedern sich in drei Teilkomplexe: Klärung der Frage, in welchem Maße die gegenseitige Wechselwirkung zwischen angeregten Singulett-Zuständen (Singuletts)zu deren Vernichtung führt. Um dies zu analysieren, wurden Messungen zur nichtlinearen Fluoreszenz von LHCII in einem großen Bereich der Anregungsimpuls-Intensität durchgeführt. Dazu war es notwendig, eine Methode zu entwickeln, die es erlaubt, die von der Probe ausgesandte Fluoreszenz räumlich zu selektieren. Die so gemessene Fluoreszenzausbeute von solubilisiertem LHCII verringert sich um bis zu 4 Größenordnungen bei maximaler Intensität und entspricht einem sättigenden Verhalten der Fluoreszenz. Aus diesen Untersuchungen ergibt sich, daß der Transfer der Anregungsenergie innerhalb eines gesamten solubilisierten LHCII-Trimers extrem schnell vonstatten geht. Untersuchung zur Kinetik der Karotinoid-Triplett-Bildung im LHCII. Dazu wurde ein Meßaufbau für Pump-Test-Messungen der nichtlinearen Transmission mit optischer Zeitverzögerung zwischen Pump- und Test-Impuls realisiert. Besonderes Augenmerk wurde auf die Vermeidung von Meß-Artefakten gelegt. Die zeitliche Änderung der Absorption bei 507 nm spiegelt die Kinetik der Karotinoid-Triplett-Bildung in solubilisiertem LHCII wider. Bei der Modellierung der gemessenen Daten wurde die Rate für den Triplett-Transfer von 3Chl nach Car variiert. Die beste Anpassung ergibt den Grenzfall . Als untere Grenze kann im Rahmen der Meßgenauigkeit ein Wert von (0.5 ns)-1 angegeben werden. Dieser Wert ist mehr als eine Größenordnung größer, als der noch vor kurzer Zeit akzeptierte Wert von Kramer und Mathis (1980). Dieses Ergebnis zeigt, daß die Wechselwirkung zwischen Chlorophyllen und Karotinoiden in LHCII wesentlich stärker ist, als bisher angenommen wurde. Untersuchung der Wechselwirkung von Singuletts mit langlebigen Tripletts anhand der Fluoreszenz, die durch einen elektronisch verzögerten Test-Laser-Impuls hervorgerufen wird. Diese "Test-Fluoreszenz" nimmt mit Erhöhung der Pump-Intensität drastisch ab und erreicht bei hohen Pump-Intensitäten wenige Prozent des Ausgangswertes. Das Zurückkehren zum Ausgangswert wurde als Funktion der Verzögerungszeit bei verschiedenen Pump-Intensitäten gemessen. Mit Hilfe der Stern-Volmer Gleichung lassen sich daraus die quenchenden Populationen berechnen. Dies ergibt, daß das Quenching bei vergleichsweise geringen Pump-Intensitäten eindeutig den Karotinoid-Tripletts zugeordnet werden kann. Bei hohen Pump-Impuls-Intensitäten wurde eine zusätzliche, extrem stark quenchende Spezies identifiziert, bei der es sich möglicherweise um Chlorophyll-Tripletts oder -Ionen handelt. / In this study the kinetics of electronically excited singlet and triplet states within solubilized light harvesting complexes of photosystem II (LHCII) is investigated. It is subdivided into three parts: The mutual interaction between excited singlet states and their annihilation was analyzed. For that purpose nonlinear fluorescence measurements were performed in a huge range of excitation pulse intensity. A method was developed that allows a spatial selection of the fluorescence. The fluorescence yield determined in this way shows a drastic decrease of up to 4 orders of magnitude at the highest intensity used and corresponds to a saturation like behavior of the fluorescence. As a result of the theoretical investigation of this result, the excitation energy transfer within the overall LHCII-trimer is extremely fast. The kinetics of carotenoid triplet formation in LHCII was analyzed by pump-probe measurements of nonlinear transmission using an optically generated delay between pump- and probe-pulses. Special care was taken to prevent artifacts in this kind of measurement. The temporal change of the absorbance at 507 nm reflects the kinetic of carotenoid triplet formation in solubilized LHCII. The fit of the experimental data by a kinetic model provides that the rate for the triplet transfer from 3Chl to Car is (0.5 ns)-1. This value is more than one order of magnitude higher than the results obtained so far (Kramer and Mathis, 1980). This shows that the interaction between chlorophylls and carotenoids is much higher than previously assumed. The interaction between singlets and (long living) triplets was investigated by measurements of the fluorescence originating from a delayed probe pulse in the presence of a pump pulse. This "probe-fluorescence" decreases drastically with increasing pump pulse intensity up to a level of a few percent at the highest intensity. The recovery to the initial value (pump pulse off) was studied as a function of the electronically generated time delay and at different pump intensities. The population of quenching species was calculated by means of the Stern-Volmer Equation. As a result of this analysis the quenching at low pump intensities can clearly be attributed to carotenoid triplets. At high pump pulse intensities an extremely strong quenching species is formed which can be probably identified by chlorophyll-triplets or -ions.