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1
Hodges, M. "Chlorophyll fluorescence and thylakoid membrane organisation." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37728.
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Pniewski, Filip Franciszek. "Capacité photosynthétique du microphytobenthos des vasières intertidales de la Baie de l'Aiguillon (Côte atlantique, France) et des lagunes non-tidales de faible profondeur de la Baie de Puck (Mer Baltique, Pologne)." Thesis, La Rochelle, 2010. http://www.theses.fr/2010LAROS300.
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Dans les écosystèmes littoraux, les communautés microphytobenthiques sont soumises à des conditions environnementales qui peuvent être extrêmes en particulier en ce qui concerne l'intensité lumineuse. Les mécanismes de protection mis en place dépendent étroitement du type d'habitat où se développent ces communautés et cette thèse a pour objectifs d'analyser les caractéristiques de l'activité photosynthétique et les mécanismes de protection développés par des assemblages microphytobenthiques dans deux écosystèmes littoraux très différents : les vasières intertidales atlantiques de la Baie de L'Aiguillon (France) et la lagune côtière non tidale de Puck Bay dans la Mer Baltique (Władysławowo, Pologne). Pour réaliser ces objectifs, trois études ont été réalisées : (1) la description des communautés microphytobenthiques, (2) la caractérisation de leur activité photosynthétique et (3) l'analyse des mécanismes de photoinhibition et de photoprotection.La structure taxonomique du microphytobenthos a été décrite en se basant sur des observations en microscopie optique et sur la mesure des caractéristiques des pigments photosynthétiques par chromatographie liquide à haute performance (HPLC). L'activité photosynthétique a été étudiée par des méthodes de microrespirométrie volumétrique et de spectrofluorométrie de la chlorophylle a. Les mécanismes de photoinhibition et de photoprotection ont été étudiés par fluorométrie en modulation d'amplitude pulsée (PAM).Les résultats obtenus nous ont permis de montrer que :1) Les communautés atlantiques sont fortement dominées par des diatomées épipéliques, alors que le microphytobenthos de la Mer Baltique est plus diversifié et comporte, outre des diatomées, une large part de cyanobactéries,2) Les microphytobenthos atlantique est bien acclimaté à des valeurs d'intensités lumineuses plutôt faibles, alors que les communautés de la Mer Baltique ont encore une bonne activité photosynthétique à de fortes irradiances,3) Les diatomées atlantiques présentent une plus forte photoinhibition que les microalgues de la Baltique,4) L'activité photosynthétique des communautés microphytobenthiques non perturbées montre un des rythmes circadien et tidal, qui semblent être contrôlés par des facteurs endogènes, qui mettent en jeu des adaptations comportementales comme la migration verticale pour les diatomées atlantiques,5) En ce qui concerne le microphytobenthos de la Mer Baltique, qui n'a pas de capacité migratoire, la photoprotection est assurée en premier lieu par la mise en jeu de processus physiologiques. Nous avons pu montrer la très grande flexibilité du photsystème PSII qui est capable de suivre très rapidement les changements à court terme de lumière ambianteThe scope of this thesis includes the characteristics and comparison of photosynthetic activity and photoprotection mechanisms of microphytobenthos assemblages inhabiting the Atlantic intertidal mudflats of Aiguillon Bay (Esnandes, France) and the littoral zone of the Baltic Sea in non-tidal Puck Bay (Władysławowo, Poland). In order to accomplish the main aims of the work the following tasks were carried out: (1) characterization of microphytobenthic assemblages; (2) characterization of their photosynthetic activity and (3) description of photoinhibition and photoprotective mechanisms. The structure of microphytobenthos was described based on observation of the material in light microscope (LM) and through the characteristics of photosynthetic pigments using high performance liquid chromatography (HPLC). Photosynthetic activity was described using various methods including classical (volumetric micro-respirometer) and modern (chlorophyll a fluorescence) ones. In addition, the measurements of variable fluorescence were also used to study photoinhibition and photoprotective mechanisms. Based on the obtained results it was stated that:1.) the Atlantic assemblages were strongly dominated by epipelic diatoms, while the Baltic microphytobenthos was more diverse and cyanobacteria, next to diatoms, were also very important component,2.) it was shown that the Atlantic microphytobenthos was well acclimated to rather low light intensities, while the Baltic assemblages showed good utilization of higher irradiance,3.) the Atlantic diatoms were more susceptible to photoinhibition than the Baltic microalgae,4.) the photosynthetic activity described for the undisturbed microphytobenthos communities revealed circadian and circatidal rhythms, which seemed to be controlled by endogenous factors, supporting diatoms’ behavioural adaptations i.e., vertical migration,5.) in case of the Baltic microphytobenthos, the lack of the ability to move caused their physiological processes the first line of defence against excess irradiances. The analysis revealed extreme flexibility of PSII which was able to follow rapidly the short-term changes in ambient light
3
Force, Lesleigh Eileen. "Applications of the JIP-test of chlorophyll fluorescence /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16307.pdf.
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Cendrero, Mateo Maria del Pilar. "Chlorophyll Fluorescence Response to Water and Nitrogen Deficit." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/312504.
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The increasing food demand as well as the need to predict the impact of warming climate on vegetation makes it critical to find the best tools to assess crop production and carbon dioxide (CO₂) exchange between the land and atmosphere. Photosynthesis is a good indicator of crop production and CO₂ exchange. Chlorophyll fluorescence (ChF) is directly related to photosynthesis. ChF can be measured at leaf-scale using active techniques and at field-scales using passive techniques. The measurement principles of both techniques are different. In this study, three overarching questions about ChF were addressed: Q1) How water, nutrient and ambient light conditions determine the relationships between photosynthesis and ChF? Which is the optimum irradiance level for detecting water and nutrient deficit conditions with ChF?; Q2) which are the limits within which active and passive techniques are comparable?; and Q3) What is the seasonal relationship between photosynthesis and ChF when nitrogen is the limiting factor? To address these questions, two main experiments were conducted: Exp1) Concurrent photosynthesis and ChF light-response curves were measured in camelina and wheat plants growing under (i) intermediate-light and (ii) high-light conditions respectively. Plant stress was induced by (i) withdrawing water, and (ii) applying different nitrogen levels; and Exp2) coincident active and passive ChF measurements were made in a wheat field under different nitrogen treatments. The results indicated ChF has a direct relationship with photosynthesis when water or nitrogen drives the relationship. This study demonstrates that the light level at which plants were grown was optimum for detecting water and nutrient deficit with ChF. Also, the results showed that for leaf-average-values, active measurements can be used to better understand the daily and seasonal behavior of passive ChF. Further, the seasonal relation between photosynthesis and ChF with nitrogen stress was not a simple linear function. Our study showed that at times in the season when nitrogen was sufficient and photosynthesis was highest, ChF decreased because these two processes compete for available energy. These results demonstrated that ChF is a reliable indicator of crop stress and has great potential for better understand the CO₂ exchange between the land and atmosphere.
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MATOS, ANA GABRIELA BARBOSA. "CHLOROPHYLL A DETERMINATION IN MARINE WATER BY FLUORESCENCE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2198@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA clorofila a é um composto-chave no processo de absorção e aproveitamento da energia luminosa na fotossíntese. Monitorar a fluorescência da clorofila a para obter informações do aparato fotossintético de produção de energia é uma abordagem atraente porque a fluorescência á percebida externamente às células, podendo ser detectada sem destruir sua fonte. Estudos anteriores realizados pelo Laboratório de Hidrobiologia (UFRJ) e pelo Laboratório de Monitoramento Ambiental Remoto (LabMAR) (PUC-Rio) em águas marinhas indicaram a existência de uma relação linear entre os valores absolutos obtidos pelo Laboratório de Hidrobiologia para a concentração da clorofila a e os valores relativos obtidos pelo LabMAR para a sua fluorescência. Este resultado motivou os dois laboratórios a obter valores absolutos para a concentração da clorofila a em águas marinhas, a partir da medida de sua fluorescência, com a maior confiabilidade possível para, então, relacioná-los aos valores relativos fornecidos pelo LIDAR-PUC. Neste sentido, a implantação de um programa de controle de qualidade no Laboratório de Hidrobiologia indicou que este laboratório encontra-se em condições de obter valores confiáveis para a concentração da clorofila a em amostras de águas marinhas através da fluorimetria. No entanto, uma avaliação rigorosa da relação entre a intensidade da fluorescência da clorofila a (normalizada pela intensidade da emissão do espalhamento Raman da água) e o respectivo valor confiável para a concentração da clorofila a se faz necessária.
Chlorophyll a is a key-compound in the process of light absorption in the photosynthesis. Monitor the chlorophyll a fluorescence to obtain information about the photosynthetic apparatus of energy production is attractive because the chlorophyll a fluorescence could be detected without destruction of the source. Studies performed by the Laboratório de Hidrobiologia (UFRJ) and by the Laboratório de Monitoramento Ambiental Remoto (LabMAR) (PUC-Rio) in marine water samples indicated a linear relation between the absolute values obtained by the former for the chlorophyll a concentration and the relative values obtained by the latter for the chlorophyll a fluorescence. This result motivated both laboratories to obtain absolute values for the chlorophyll a concentration, in marine water samples, as confident as possible and, then, relate these values to the relative values generated by the LIDAR-PUC. In this way, the introduction of a quality control program in the Laboratório de Hidrobiologia indicated that this laboratory is able to analyse marine water samples and to obtain confident values for the chlorophyll a concentration by fluorimetry. However, a more rigorous evaluation of the relation between the chlorophyll a fluorescence and the respective confident value for the chlorophyll a concentration is still necessary.
6
Wentworth, Mark. "Quenching of chlorophyll fluorescence in plant light-harvesting complexes." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340168.
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Ryan-Keogh, Thomas J. "Understanding the role of chlorophyll fluorescence in nutrient stress." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/362003/.
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Phytoplankton exert a dominant influence on the biogeochemical cycling of the oceans, but iron limitation in this dynamic environment can exert a control on photosynthesis. Phytoplankton evolved coping mechanisms to overcome and alleviate the effects of iron limitation. One mechanism is the alteration of the thylakoid membrane and the expression of chlorophyll-binding proteins, which can alter the variable chlorophyll fluorescence signal. Firstly, a study of the chlorophyll-binding iron-stress induced protein, IsiA, in Synechocystis PCC 6803 revealed a 60% increase under iron limitation, in agreement with the theoretical increase. On progressive iron-stress IsiA continued to accumulate without a concomitant increase in _PSI, while Fv/Fm, a measure of photochemical efficiency, continued to decrease. Secondly an oceanographic study to the high latitude North Atlantic in which chlorophyll fluorescence kinetics were used to measure the response to iron addition of in situ phytoplankton populations. The difference in the Fv/Fm between nutrient amended and control treatments (_(Fv/Fm)) was used as a measure of the relative degree of iron stress. The combined observations of both longterm (> 24 h) and short-term (24 h) indicated variability in the seasonal cycle of iron stress, with phytoplankton iron stress developing during the transition from prebloom to peak bloom conditions. Thirdly, similar physiological characteristics were also observed in an oceanographic study in the Ross Sea. The results further confirmed the highly variable response across temporal and spatial scales, but also within different phytoplankton groups. Consistent across all three studies is the reduction in Fv/Fm as the result of an elevated Fo signal, representing potentially unbound chlorophyll-binding proteins. These unbound chorophyll-binding proteins can dominate the total cellular chlorophyll, at least in culture, and reflect a large resource investment. These proteins may provide a rapid source of chlorophyll upon iron resupply. Irrespective of the underlying causes of unbound chlorophyll-binding proteins, the potential large scale expression of such complexes provides a powerful diagnostic tool with which to investigate iron stress in situ.
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Toomey, Heidi M. "Chlorophyll Fluorescence and Thermal Stress in Archaias angulatus (Class Foraminifera)." Thesis, University of South Florida, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1549223.
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Benthic foraminifers that host algal symbionts are similar to corals in that they rely on their algal endosymbionts for their energy needs, calcify prolifically, and are sensitive to changes in environmental conditions. They are abundant in the benthos of coastal coral-reef areas and are found throughout the tropical and subtropical regions. Pulse Amplitude Modulated (PAM) chlorophyll fluorometry and chlorophyll a extraction techniques were used to quantify and compare the photosynthetic responses of the benthic foraminifera, Archaias angulatus and their isolated endosymbionts, Chlamydomonas hedleyi, to short-term changes in temperature. Maximum quantum efficiency (Fv/Fm) and rapid light curves (RLCs), from which relative electron transport rates (rETR) of photosystem II (PSII) were derived, were investigated over a thermal range from 4.4° to 33.9 °C in three experiments that were 7 to 31 days in duration. Typical mean yields (Fv/Fm) for healthy holobionts (symbionts in hospite) were 0.6 - 0.7, and for isolated symbionts 0.5 - 0.6. Chronic photoinhibition, indicated by significant decreases in Fv/Fm, occurred at temperatures above 31.0°C; there was minimal reduction in efficiency in cooler treatments. The trends between holobiont and symbionts were very similar in all of the photophysiological parameters measured [yield, photoefficiency (á), ETRmax and minimum saturating irradiance (Ek)] and supported the temperature range findings in terms of the tolerance of the specimens in the low temperatures up to 31.0 °C. For all photochemical measurements assessed, the holobiont values tended to be somewhat higher than those for the symbionts, with the exception of Ek, possibly indicating a tight coupling in the host-symbiont response during photosynthesis. Chlorophyll a (ìg/foram) was negatively correlated with temperature (r = -0.37, p < 0.001) in Experiments 1 and 2. However, in all 3 experiments, chlorophyll a was variable, suggesting a high degree of individual variability in A. angulatus and the ability to acclimate. Some differences observed among treatments may be related to differences in seasons when the specimens were collected and in length of time in culture prior to experiments. Holobiont median rETR light curve trends and photophysiological derived parameters recorded median Ek ranges of ~100-150 ìmol photons m-2 s-1, observed ETRmax light intensities of ~200 ìmol photons m-2 s-1 and photoinhibition, induced by increasing irradiance intensities, which occurred > 500 ìmol photons m-2 s-1. These light curve trends and derived parameters generally supported previous photosynthesis O2 and CO2 gas production studies of A. angulatus. The differences in responses associated with acclimation should be considered in design of future experimental studies. This was the first known physiological study of the viable temperature range and photobiology of A. angulatus using chlorophyll fluorometry methods. Though commonly found in Caribbean and Atlantic waters ranging from 14.0 – 31.0 °C, these results indicate a wider thermal-tolerance range for A. angulatus than was previously known.
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au, jcos@iinet net, and Jeffrey John Cosgrove. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20071129.122222.
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Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary
production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density (çPSII) rather than use of an assumed value as changes in çPSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
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Cosgrove, Jeffrey John. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Cosgrove, Jeffrey John (2007) Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/503/.
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Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density ([eta]PSII) rather than use of an assumed value as changes in [eta]PSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
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Ali, Elham Mahmoud. "Processes and conditions influencing phytoplankton growth and bloom iniation in a macrotidal estuary, Southampton Water." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274569.
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Köhler, Philipp [Verfasser]. "Global retrievals of terrestrial chlorophyll fluorescence from spaceborne spectrometers / Philipp Köhler." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1110884621/34.
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Pinto, Jamie L. "Treatment Effects of Copper Sulfate and Carbaryl on Algal Chlorophyll Fluorescence Chemistry." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/PintoJL2008.pdf.
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Binnie, Nancy Elaine Carleton University Dissertation Chemistry. "Electronic origins of monomeric and dimeric chlorophyll a as determined from wavelength selective fluorescence and raman excitation profiles." Ottawa, 1988.
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Phillip, Denise Mary. "Xanthophylls in light-harvesting complexes of higher plants." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242313.
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Larroque, Claire. "Qualité et productivité du mai͏̈s fourrage : lignification et facteurs physiologiques du rendement." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT004A.
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(. . . ) l'etude des huit lignees et de neuf hybrides issus de celles-ci a montre l'existence d'une variabilite suffisamment importante pour etre exploitee. Les correlations etablies ont revele que les taux de lignine des tiges depend plus de la lignification des vaisseaux conducteurs que de leur nombre et le port erige apparait comme une caracteristique systematique des genotypes hyperlignifies. Les consequences sur la productivite de la culture sont envisagees (. . . )
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Marwood, Christopher A. "Chlorophyll fluorescence as a mechanistic bioindicator of photosynthetic inhibition in aquatic plants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/NQ43266.pdf.
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Schofield, Rex Andrew. "Evaluation of postharvest quality of iceberg lettuce by chlorophyll fluorescence and firmness." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/MQ43217.pdf.
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Toomey, Heidi M. "Chlorophyll Fluorescence and Thermal Stress in Archaias angulatus (Class Foraminifera)." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4955.
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ABSTRACT
Benthic foraminifers that host algal symbionts are similar to corals in that they rely on their algal endosymbionts for their energy needs, calcify prolifically, and are sensitive to changes in environmental conditions. They are abundant in the benthos of coastal coral-reef areas and are found throughout the tropical and subtropical regions. Pulse Amplitude Modulated (PAM) chlorophyll fluorometry and chlorophyll a extraction techniques were used to quantify and compare the photosynthetic responses of the benthic foraminiferal, Archaias angulatus and their isolated endosymbionts, Chlamydomonas hedleyi, to short-term changes in temperature. Maximum quantum efficiency (Fv/Fm) and rapid light curves (RLCs), from which relative electron transport rates (rETR) of photosystem II (PSII) were derived, were investigated over a thermal range from 4.4° to 33.9 °C in three experiments that were 7 to 31 days in duration. Typical mean yields (Fv/Fm for healthy holobionts (symbionts in hospite) were 0.6 - 0.7, and for isolated symbionts 0.5 - 0.6. Chronic photoinhibition, indicated by significant decreases in Fv/Fm, occurred at temperatures above 31.0°C; there was minimal reduction in efficiency in cooler treatments. The trends between holobiont and symbionts were very similar in all of the photophysiological parameters measured [yield, photoefficiency (<α>), ETRmax and minimum saturating irradiance (Ek)] and supported the temperature range findings in terms of the tolerance of the specimens in the low temperatures up to 31.0 °C. For all photochemical measurements assessed, the holobiont values tended to be somewhat higher than those for the symbionts, with the exception of Ek, possibly indicating a tight coupling in the host-symbiont response during photosynthesis. Chlorophyll a (<μ>g/foram) was negatively correlated with temperature (r = -0.37, p < 0.001) in Experiments 1 and 2. However, in all 3 experiments, chlorophyll a was variable, suggesting a high degree of individual variability in A. angulatus and the ability to acclimate. Some differences observed among treatments may be related to differences in seasons when the specimens were collected and in length of time in culture prior to experiments. Holobiont median rETR light curve trends and photophysiological derived parameters recorded median Ek ranges of ~100-150 <μ>mol photons m-2 s-1, observed ETRmax light intensities of ~200 <μ>mol photons m-2 s-1 and photoinhibition, induced by increasing irradiance intensities, which occurred > 500 <μ>mol photons m-2 s-1. These light curve trends and derived parameters generally supported previous photosynthesis O2 and CO2 gas production studies of A. angulatus. The differences in responses associated with acclimation should be considered in design of future experimental studies.
This was the first known physiological study of the viable temperature range and photobiology of A. angulatus using chlorophyll fluorometry methods. Though commonly found in Caribbean and Atlantic waters ranging from 14.0 - 31.0 °C, these results indicate a wider thermal-tolerance range for A. angulatus than was previously known.
Keywords: Foraminifera, Chlamydomonas sp., PAM fluorometry, photosynthesis, algal symbiosis
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Blowers, M. H. "Applications of chlorophyll fluorescence to study the penetration of herbicides into leaves." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235581.
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Sosik, Heidi Maria. "Analysis of chlorophyll fluorescence in marine phytoplankton : interpretation of flow cytometric signals." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14604.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1988.Includes bibliographical references.
Work supported in part by the NSF. OCE 8421041 OCE 8508032 OCE 8614332 Work supported in part by the ONR. N00014-83-0661 84-C-0278 87-K-0007
by Heidi Maria Sosik.
M.S.
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Truter, Johannes Petrus. "Using low cost components to determine chlorophyll concentration by measuring fluorescence intensity." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/24296.
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This dissertation describes the development of a low cost fluorometer with the aim of using it as an algae and phytoplankton concentration sensor. As it forms the core of this fluorometer's functionality, chlorophyll's fluorescence characteristics and origins are discussed. Special attention is given to the variability of chlorophyll fluorescence as it has a big influence on measurements. Experimental procedures and data are provided to show why each component was finally selected for use in the fluorometer. An analogue front end device with programmable gain on each 24-bit ADC channel forms the interface between the high sensitivity TSL257 light-to-voltage light sensors and the 32-bit ARM microcontroller that controls the system. The microcontroller software controls the 470 nm LED current to create a 75 ms light pulse that has a 63 Hz sine wave modulated on it. The low cost light sensors proved to be sensitive enough to detect the low light intensities of chlorophyll fluorescence. The challenges of measuring the low level voltages from these light sensors are discussed. The amount of noise on the light sensor voltages at low chlorophyll concentrations make it difficult to accurately measure the fluorescence signal. Different light modulation and digital signal processing techniques were investigated to compare the effective recovery of the fluorescence signal. Sine wave modulation along with sample averaging provided good results. The results of laboratory experiments with pure chlorophyll α and extracted chlorophyll are discussed to give an overview of the capabilities and limitations of the developed fluorometer that is able to measure the fluorescent light from extracted chlorophyll concentrations as low as 0.01 μg/1.
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Evain, Sébastien. "Télédétection passive de la fluorescence des couverts végétaux." Paris 11, 2002. http://www.theses.fr/2002PA112294.
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RDans des conditions naturelles, la faible quantité de fluorescence émise par la végétation est difficile à quantifier car elle est noyée dans la lumière réfléchie. Cependant, dans les raies du spectre solaire où le rayonnement incident est absorbé par les constituants des atmosphères solaire et terrestre, la part de la fluorescence par rapport à la lumière réfléchie n'est plus négligeable et peut-être alors quantifiée. Cette technique, appelée " Principe des raies de Fraunhofer " consiste à comparer la profondeur de la raie au niveau de l'éclairement et de la luminance de la cible. Au cours de cette thèse, nous avons développé plusieurs instruments appliquant ce principe aux bandes d'absorption de l'oxygène situées à 760 et 687 nm. Grâce à ces capteurs, nous avons pu suivre, pour des distances allant jusqu'à 15 m, les variations de fluorescence induites par des variations lumineuses à différentes échelles spatiales et temporelles et déterminer l'importance des mécanismes de régulation de l'excès d'énergie absorbée par les plantes. De plus, nous avons pu mettre en évidence des modifications physiologiques induites par un herbicide ou en présence d'un stress hydrique. Dans une perspective d'accroître la distance de mesure, nous avons développé un nouveau modèle, OBADE, basé sur l'absorption de l'oxygène moléculaire, qui calcule la profondeur des bandes de l'O2 mesurée par nos instruments en fonction de la configuration de l'expérience. Comparé aux mesures de terrain, OBADE a montré une excellente capacité à simuler les variations diurnes de la profondeur de la bande de l'O2 à 760 nm. En complément de ces travaux, nous avons montré que les variations de l'indice de réflectance PRI (physiological reflectance index) étaient liées aux mécanismes de dissipation thermique de l'excès d'énergie absorbée par la végétation et pouvaient être appliquées à la détection du stress hydrique chez la vigneUnder natural conditions of light, the weak amount of fluorescence emitted by a plant is difficult to measure because of the reflected light which blurred the signal. However, in the absorption bands of the solar spectrum where the incident light is attenuated by the components of the solar and terrestrial atmospheres, the Chl F can be quantified. This technique, called "Fraunhofer lines principle" compares the depth of an absorption band in the solar irradiance to the depth of the absorption band in the radiance of the target. During this thesis, we developed several instruments applying this principle to atmospheric oxygen A and B bands respectively centered at 760 and 687 nm. Thanks to these sensors, we followed, for distances going up to 15 m, the variations of fluorescence induced by light variations on various space and temporal scales and determined the importance of the mechanisms of regulation of the excess of energy absorbed by the plants. Moreover, we detected physiological modifications induced by an herbicide or in the presence of a water stress. To increase the measurement distance, we have developed a new model, OBADE, based on the absorption of the molecular oxygen, which calculates the depth of the oxygen bands measured by our instruments according to the configuration of the experiment. Compared with measurements on the ground, OBADE showed an excellent capacity to simulate the diurnal variations depth of the oxygen band at 760 nm. In complement of these works, we showed that the variations of the index of reflectance PRI (physiological reflectance index) were related to the mechanisms of thermal dissipation of the excess of energy absorbed by the vegetation and could be applied to the detection of the water stress in gravepine
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Galloway, Amanda Ann. "The use of chlorophyll fluorescence to select for quality in broadleaved nursery trees." Thesis, University of Strathclyde, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269892.
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Gull, Christopher Johannes. "A novel low- cost chlorophyll fluorescence Sensor for early detection of environmental pollution." Universidade Federal de Viçosa, 2017. http://www.locus.ufv.br/handle/123456789/18061.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A poluição afeta seriamente todos os organismos vivos, assim como economias que dependem, diretamente ou indiretamente, de recursos naturais. O monitoramento ambiental de estresses das plantas, causadas pelos poluentes, é necessário para antecipar e evitar os efeitos negativos antes que se manifestem como danos visíveis. A ausência de monitoramento constante das plantas resulta em diminuição do crescimento das culturas, danos aos ecossistemas, problemas de saúde, e, no fim das contas, perdas econômicas. Especialmente ao redor das áreas afetadas, como, por exemplo, depósitos de resíduos, mineradoras e indústrias, mas também dentro e ao redor das áreas urbanas, é importante reconhecer os problemas potenciais do meio ambiente que possam surgir por causa das atividades humanas. Entre as consequências estão chuva ácida, contaminação de metais pesados, ozônio superficial, modificações de temperatura, e seca, causando alterações na fisiologia vegetal, especificamente na eficiência fotossintética e conteúdo de clorofila. A medição da eficiência fotossintética das plantas, i.e. vitalidade, usando fluorômetros comerciais tais como aparelhos PAM (modulação de amplitude de pulso), torna-se um desafio, uma vez que custo, complexidade e os métodos de medição tornam difíceis o monitoramento em tempo real. Apesar dos aparelhos possuírem alta precisão, podem meramente fornecer uma medição “instantânea” de áreas pequenas. Assim, torna-se difícil o entendimento da vitalidade e eficiência das plantas em grandes áreas e períodos longos, resultando, muitas vezes, que ações sejam tomadas apenas após mudanças significativas nas plantas e na produtividade. Uma solução para o produtor em áreas impactadas por poluentes poderia ser a obtenção de vários desses aparelhos e empregar trabalhadores dedicados exclusivamente para o monitoramento de saúde das plantas, mas isto é caro e ineficiente. Outra solução seria simplificar os equipamentos de medição, e usar vários deles. De fato, neste trabalho nós nos concentramos na resolução deste problema, reduzindo o custo e a complexidade, e eliminando a necessidade de intervenção humana no processo de medição. Propõe-se um sistema de sensores de fluorescência de clorofila de baixo custo que pode monitorar, simultaneamente e sem fios, várias plantas individuais. Estes sensores foram desenvolvidos, prototipados e construídos do zero para dar precisão razoável, com a capacidade de diferenciar entre plantas submetidas à estresse e sem estresse. Nos casos em que o sistema, o Sensor CFY (rendimento fluorescência da clorofila), não possua alta precisão, o sistema compensa em várias medições simultâneas de uma rede de sensores. Isto é, o protótipo do sensor é, inerentemente, desenvolvido para ser usado em redes sem fio (WSN). Usando duas espécies de plantas, Clusia hilariana e Paspalum densum, foi construído, testado e verificado as nossas metodologias e o nosso protótipo através de uma série de experimentos. Baseado nisso, foram observado resultados significativos quando utilizamos o sensor em uma rede de sensores emulado, usando um sensor único em várias plantas durante um longo período de tempo. Foi possível a discriminação entre plantas nos grupos de estresse e as do controle, assim como a descoberta rápida bem antes de danos se manifestarem nas folhas. Concluímos que é, de fato, possível a detecção da estresse nas plantas utilizando métodos de baixo custo, assim como fazê-lo automaticamente e em tempo real, permitindo a detecção precoce de poluição e fornecendo, por exemplo, tempo suficiente para um produtor resolver os problemas antes de eles se tornarem irreversíveis e dispendiosos.
Pollution seriously affects all living organisms as well as economies directly or indirectly relying on natural growth resources. Monitoring the environment for stresses in plants, caused by pollutants, is necessary in order to anticipate and counteract the adverse effects before they manifest as visible damage. Failure to constantly monitor plants results in decreased crop growth, damage to ecosystems, health-related issues, and, ultimately, economic losses. Especially around affected areas, such as waste deposits, mining activities and factories, but also in and around urban areas, it is important to acknowledge the potential environmental issues that may arise from human activities. Among the consequences we find acid rain, heavy metal contamination, surface ozone, changes in temperature, and drought, contributing to alterations in plant physiology, specifically chlorophyll content and photosynthetic efficiency. Measuring plant efficiency, thus health, using commercial fluorometers, such as PAM (pulse-amplitude modulation) devices, presents a challenge, since cost, complexity and the measurement methods make real-time monitoring a difficult proposition. Although such devices are high-precision instruments, they are merely able to provide ‘snapshots’ of small areas. This makes it difficult to understand the health of plants over large areas and over extended periods of time, frequently resulting in actions taken only after significant changes to plants and productivity. One solution would be for a farmer in an area impacted by pollution to acquire multiple of these devices and to employ a workforce dedicated solely to monitoring plant health, but this is costly and inefficient. Another solution would be to simplify the devices with which to measure, and use a multitude of these. Indeed, in this work, we focus on solving this problem, by reducing costs and complexity, and eliminating the need for human input in the measurement process. We propose a system of low-cost chlorophyll fluorescence sensors able to monitor a large number of individual plants at the same time and wirelessly. These sensors have been designed, prototyped and built from the ground up to provide reasonable accuracy, and capacity for discriminating between plants subjected to stress from non-stressed plants. Where our sensor system, the CFY (chlorophyll fluorescence yield) Sensor, lacks in accuracy, it compensates with a multitude of potential simultaneous measurements from an array of sensors within a network. For this reason, the sensor prototype is inherently designed for wireless sensor networks (WSN). Using two species of plants, Clusia hilariana and Paspalum densum, we have built, tested and verified our methodologies and prototype sensors through a series of experiments. Through these, we observed significant results when employed in an emulated sensor network using one sensor on a large number of plants over extended periods of time. Differentiating the stressed group from the control group was possible, in addition to rapid and well before any visible damage had manifested on leaves. We conclude that it is indeed possible to not only detect plant stress using low-cost methods, but also to do so automatically and in real-time, allowing for early-detection of pollution and providing e.g. a farmer enough time to resolve problems before they become irreversible and costly.
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MacBean, Natasha, Fabienne Maignan, Cédric Bacour, Philip Lewis, Philippe Peylin, Luis Guanter, Philipp Köhler, Jose Gómez-Dans, and Mathias Disney. "Strong constraint on modelled global carbon uptake using solar-induced chlorophyll fluorescence data." NATURE PUBLISHING GROUP, 2018. http://hdl.handle.net/10150/627071.
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Accurate terrestrial biosphere model (TBM) simulations of gross carbon uptake (gross primary productivity - GPP) are essential for reliable future terrestrial carbon sink projections. However, uncertainties in TBM GPP estimates remain. Newly-available satellite-derived sun-induced chlorophyll fluorescence (SIF) data offer a promising direction for addressing this issue by constraining regional-to-global scale modelled GPP. Here, we use monthly 0.5 degrees GOME-2 SIF data from 2007 to 2011 to optimise GPP parameters of the ORCHIDEE TBM. The optimisation reduces GPP magnitude across all vegetation types except C4 plants. Global mean annual GPP therefore decreases from 194 +/- 57 PgCyr(-1) to 166 +/- 10 PgCyr(-1), bringing the model more in line with an up-scaled flux tower estimate of 133 PgCyr(-1). Strongest reductions in GPP are seen in boreal forests: the result is a shift in global GPP distribution, with a similar to 50% increase in the tropical to boreal productivity ratio. The optimisation resulted in a greater reduction in GPP than similar ORCHIDEE parameter optimisation studies using satellite-derived NDVI from MODIS and eddy covariance measurements of net CO2 fluxes from the FLUXNET network. Our study shows that SIF data will be instrumental in constraining TBM GPP estimates, with a consequent improvement in global carbon cycle projections.
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Proctor, Christopher. "Characterizing the Calibration and Sources of Variability in a New Sensor Package: Using Fluorescene to Estimate Phytoplankton Concentration and Composition." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/ProctorC2008.pdf.
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Roberts, Andrew. "Crassulacean acid metabolism and photosynthetic plasticity in the genus Clusia : an ecophysiological study." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360879.
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Crudace, Amanda Jayne. "The investigation of the in vivo behaviour of a maize herbicide : Isoxaflutole." Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327075.
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Sauzède, Raphaëlle. "Etude et paramétrisation de la distribution verticale de la biomasse phytoplanctonique dans l'ocean global." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066625/document.
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Les travaux présentés dans cette thèse concernent la paramétrisation de la distribution verticale de la biomasse et de la structure des communautés phytoplanctoniques dans l’océan global. Nous avons d’abord développé une méthode neuronale de calibration de la fluorescence en concentration en chlorophylle a ([Chl]) associée à la biomasse phytoplanctonique totale et à trois classes de taille de phytoplancton. Cette méthode, FLAVOR, a été entrainée et validée à l’aide une base de données de ~900 profils de fluorescence et de pigments mesurés pat HPLC. Une base de données globale de ~49000 profils de fluorescence a ensuite été assemblée et calibrée en termes de biomasse chlorophyllienne et composition du phytoplancton. Ce travail représente une première étape vers une vision tridimensionnelle de la biomasse phytoplanctonique. Nous avons ensuite développé deux réseaux de neurones (SOCA) pour estimer la distribution verticale de deux paramètres bio-optiques, [Chl] et le coefficient de rétrodiffusion. Ces réseaux de neurones requièrent comme données d’entrée des données satellites de couleur de l’eau co-localisées avec un profil hydrologique collecté par un flotteur Argo. Ils ont été entrainés et validés avec une base de données globale composée de ~5 000 profils de propriétés bio-optiques et hydrologiques acquises par des flotteurs Bio-Argo. Les bases de données utilisées pour développer les méthodes FLAVOR et SOCA proviennent de régions océaniques représentatives de l’océan global, permettant ainsi l’application de ces méthodes à la majorité des eaux océaniques. Finalement, nous avons mené une étude focalisée sur l’Atlantique Nord qui exploite les outils développés. Les champs tridimensionnels de biomasse obtenus, couplés à un modèle bio-optique de production primaire, permettent d’étudier les cycles saisonniers de la distribution verticale de la biomasse phytoplanctonique et de la production primaire dans différentes bio-régions de l’Atlantique NordThis PhD work focuses on the parameterization of the vertical distribution of phytoplankton biomass and community structure in the global open ocean. First we have developed a neural network-based method for the calibration of the fluorescence in chlorophyll a concentration [Chl] associated with the total phytoplankton biomass and with three phytoplankton size classes. This method, (FLAVOR for Fluorescence to Algal communities Vertical distribution in the Oceanic Realm), was trained and validated using a database of ~900 concomitant fluorescence and HPLC-determined pigment profiles. A global database comprising ~49 000 fluorescence profiles was assembled and calibrated with FLAVOR. The resulting database represents a first step towards a global three-dimensional view of phytoplankton biomass and community composition. Second, two neural networks (SOCA for Satellite Ocean Color and Argo data to infer vertical distribution of bio-optical properties) were developed to infer the vertical distribution of two bio-optical proxies of the phytoplankton biomass, [Chl] and the particulate backscattering coefficient, using as input satellite-derived products matched up with a hydrological Argo profile. The SOCA methods were trained and validated using a global database of ~5 000 profiles of bio-optical and hydrological properties collected from Bio-Argo floats with concomitant satellite products. The database used to develop FLAVOR and SOCA originates from various oceanic regions largely representative of the global ocean, making the methods applicable to most oceanic waters. Finally, we proposed a study dedicated to the North Atlantic where the tools developed in this thesis are used in conjunction with a bio-optical primary production model. This allows us to characterize the seasonal cycle of the vertical distribution of the phytoplankton biomass and primary production in various bio-regions of the North Atlantic
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Zarco-Tejada, Pablo J. "Hyperspectral remote sensing of closed forest canopies, estimation of chlorophyll fluorescence and pigment content." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ59161.pdf.
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Louis, Juliette. "Télédétection et modélisation des signaux de fluorescence et de réflectance (PRI) des couverts végétaux." Paris 7, 2004. http://www.theses.fr/2004PA077194.
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Matthews, Alison Mary. "High resolution spectral remote sensing of phytoplankton in the coastal zone." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241275.
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Dias, Carla da Silva. "Leaf gas exchange and chlorophyll a fluorescence imaging of soybean leaves Infected with Colletotrichum truncatum." Universidade Federal de Viçosa, 2015. http://www.locus.ufv.br/handle/123456789/7555.
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Fundação de Amparo à Pesquisa do Estado de Minas Gerais
A Anthracnose, causada pelo fungo Colletotrichum truncatum, é uma das doenças de soja mais importantes no mundo, mas não há estudos avaliando as alterações fisiológicas neste patossistema. Portanto, uma abordagem para avaliar os eventos que ocorrem no local da infecção e perto da área infectada na folha, ao longo do tempo, contribuirá para uma melhor compreensão da interação planta-hospedeiro e atividade fotossintética. Assim, o presente estudo buscou investigar parâmetros de fluorescência da clorofila a (Chl a) na área da lesão e uma área adjacente, associando os ás trocas gasosas e avaliação de pigmentos fotossintéticos em plantas de soja inoculadas ou não inoculadas com C. truncatum. O parâmetros de trocas gasosas não foram alterados em plantas inoculadas. No entanto, ocorreu redução da concentração de Chl a, Ch b e da Chl total (a + b) nas plantas inoculadas as 72 e 144 horas após a inoculação (hai), com redução máxima à 144 hai de 24% para Chl a, que demonstrou ser mais sensível que a Chl b, ocasionando, portanto, a redução da razão Chl a/ Chl b. Também foi encontrado queda em valores de fluorescência da clorofila a como, Fluorescência inicial (Fo), Fluorescência máxima (Fm), Eficiencia quântica máxima do fotossistema II (Fv/Fm), Rendimento quântico de dissipação de energia regulada Y(NPQ) e coeficiente não- fotoquímico (qN), e um acréscimo no Rendimento quântico efetivo do PSII Y(II), Rendimento quântico de dissipação de energia não regulada (NO) e coeficiente fotoquímico (qP) nas área sintomática de plantas inoculadas. Entretanto esses parâmetros sofreram pequenas alterações nas áreas adjacentes das plantas inoculadas, diferindo apenas em alguns tempos. Demonstrando, dessa forma, um menor efeito do patógeno nas áreas adjacentes.
Anthracnose, caused by Colletotrichum truncatum, is one of the most important soybean diseases worldwide. However, there are no studies evaluating the physiological changes affecting this pathossystem. Therefore, one approach to evaluating events that occur at the site of infection and near the infected area on the leaf, over time, will contribute to a better understanding of the host-plant interaction and photosynthetic activity. The present study aimed to investigate chlorophyll a fluorescence parameters at injured and adjacent areas and the related changes in gas exchange and evaluation of photosynthetic pigments in soybean plants inoculated or non-inoculated with C. truncatum. There were no significant differences regarding gas exchange parameters for inoculated plants. However, there was a reduction in the concentration of Chl a, Chl b e Chl total (a + b) of inoculated plants in the 72 and 144 hours after inoculation (hai). Reduction in chlorophyll a fluorescence parameters to as initial fluorescence (Fo), maximal fluorescence (Fm), maximal photosystem II quantum yield (Fv/ Fm), quantum yield of regulated energy dissipation Y (NPQ) and coefficient non-photochemical (qN), and an increase in the Effective PSII quantum yield Y (II), quantum yield of non- regulated energy dissipation (NO) and photochemical coefficient (qP) in the symptomatic area plants inoculated. However, these parameters have undergone minor adjacent areas of inoculated plants, differing only in a few days. Demonstrating a smaller effect of the pathogen in adjacent.
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Bone, Emma Lewis. "A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean." Doctoral thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31089.
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The apparent fluorescence quantum yield of chlorophyll-a (ΦF ), i.e. the ratio of photons emitted as chlorophyll-a fluorescence to those absorbed by phytoplankton, serves as a first order measure of photosynthetic efficiency and a photophysiological indicator of the resident phytoplankton community. Drivers of ΦF variability, including taxonomy, nutrient availability, and light history, differ in magnitude of influence across various biogeographic provinces and seasons. A Multi-Exciter Fluorometer (MFL, JFE Advantech Co., Ltd.) was selected for use in in situ ΦF derivation and underwent an extensive radiometric calibration for this purpose. Wavelength-specific ΦF was determined for 66 in situ field stations, sampled in the Atlantic Southern Ocean during the austral winter of 2012 and summer of 2013/ 2014. Phytoplankton pigments, macronutrient concentrations, and light levels were simultaneously measured to investigate their influence on ΦF . While no relationship was observed between macronutrient levels and ΦF , an inverse relationship between light and ΦF was apparent. This was likely due to the influence of speciesspecific fluorescence quenching mechanisms employed by local populations. ΦF derived from ocean colour products (Φsat) from the Moderate Resolution Imaging Spectroradiometer (MODIS) were compared to in situ ΦF to assess the performance of three existing Φsat algorithms. Results indicate that accounting for chlorophyll-a fluorescence reabsorption, the inherent optical properties of the surrounding water column, and the sensor angle of observation, is crucial to reducing Φsat uncertainty. A hybrid combination of two of the algorithms performed best, and was used to derive Φsat for stations co-located to in situ iron measurements in the Atlantic Southern Ocean. A significant negative relationship was observed, indicative of the effects of iron availability on quantum yield and its potential as a proxy for iron limitation. However, separating the individual contributions of light, taxonomy, and iron limitation to Φsat variability remains a challenge. A time series analysis of Φsat was also undertaken, which revealed a prominent Φsat seasonal cycle. Ultimately, increased in situ sampling would expedite the development of improved Φsat algorithms; the routine retrieval of Φsat would offer insight into phytoplankton dynamics in undersampled regions such as the climate relevant Southern Ocean.
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Pompodakis, Nektarios E. "Postharvest investigations into chlorophyll fluorescence and low temperature injury in cut roses (Rosa hybrida L.)." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/3503.
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This is one of the first studies on the relationship between pre-harvest environmental conditions found in the Mediterranean and postharvest characteristics of cut roses (Rosa hybrida L. ). Effects of storage temperature on vase life parameters were also studied for roses grown all year round. The postharvest storage of roses at low temperature is a useful practice, in terms of market flow regulation. However, a reduction in vase life and loss of flower quality has been recorded after storage due to Low Temperature Injury (LTI). LTI of roses is difficult to assess by visual observation. Relative chlorophyll fluorescence (F'IFR, ), which is a non-invasive technique that provides an index of stress effects on photosystem II (PS II) activity, was used to investigate LTI in roses. The plant growth regulator abscisic acid (ABA) can cause physiological responses that protect plants against CI or LTI. The overall objectives of this study were firstly to evaluate the pre-harvest environmental conditions affecting vase life and secondly to evaluate novel potential ABA treatments to protect cut roses against LTI. Vase life durations and Fv. /Fm ratios measured after low temperature storage for 'First Red' and 'Akito' roses were seasonally dependant. Vase lives of roses grown during winter were significantly (P _< 0.001) shorter compared to roses grown during the rest of the year. In autumn and winter experiments F.. IF.. ratios were generally reduced following storage at 1°C, suggesting LTI of roses. Thus, the fall of F,. /Fm was due to an interaction of growing season and storage at I. T. However, in second year experiments, growing temperature and PFD were relatively higher and, as a result, Fý/Fm did not decline for 'Akito' roses after low temperature storage, indicating a strong influence of environmental conditions. Higher PFD and temperature glasshouse during the year were positively and significantly correlated with maintenance of post-storage Fv. /Fm ratios and longer vase life. It is suggested that shorter vase lives and lower post-storage FV/Fm values after storage at 1°C are consequences of reduced photosynthesis and smaller carbohydrate pools in winter- harvested roses. Because of the lack of correlation between Fv. /Fm and post-storage vase life, it is concluded that the CF parameter F,. /Fm is not a practical index for assessing LTI in cold-stored roses. Growing roses in autumn and winter months increased flower blueing in red petals of 'First Red' roses and prevented flower opening for both cultivars. ABA applied as pulse treatment before storage or as vase solution during vase life generally improved vase life parameters. Pulsing 'Akito' roses with 10-1 M ABA before storage increased vase life and inhibited bent neck incidence. Also, the presence of ABA in vase solution increased vase life after storage at 1°C, reducing vase solution usage during vase life. Similarly, the synthetic ABA analogue PBI-365, as vase solution ingredient, was effective in extending vase life and reducing transpiration rates in roses after low temperature storage. Increased ABA levels were detected in leaves and petals using HPLC when roses were treated with exogenous ABA before storage and during vase life. Thus, it was assumed that ABA or PBI-365 acted on guard cells by causing stomatal closure. Electrolyte leakage and lipid peroxidation, measured after storage at 1°C, were markedly reduced by application of ABA. Both pulse ABA treatment and vase solutions containing ABA helped to recover F,, /Fm during vase life. Moreover, addition of PBI-365 in vase solution reduced the degree of lipid peroxidation in leaves and petals after storage at 1°C. These observations indicated a protection role of ABA against LTI for roses, which has also been observed in other crops. Further research at the cellular and/or molecular level may help in better understanding the physiological responses of roses to seasonal variation during the year and LTI. In addition, work is also required to look at the ABA and PBI-365 mode of action in roses. Additional research using a wide range of ABA concentrations and assays using exogenous radio-labelled ABA may help to better understand the nature of ABA efficacy.
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Longenberger, Polly Suzanne. "Evaluation of chlorophyll fluorescence as a tool for the identification of drought tolerance in upland cotton." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2815.
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Tardy, Florence. "Localisation et fonctions du cycle des xanthophylles dans les chloroplastes des plantes supérieures." Lyon 1, 1997. http://www.theses.fr/1997LYO10281.
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Le cycle des xanthophylles, i. E. La deepoxydation enzymatique de la violaxanthine (vio) en antheraxanthine et zeaxanthine (zea) mise en place sous forte lumiere et reversible a l'obscurite, constitue un systeme photoprotecteur dont le mode d'action est controverse. Nous proposons que l'interconversion vio->zea participe a la photoprotection non seulement au niveau des photosystemes mais egalement au niveau de la matrice lipidique des membranes thylacoidiennes. Des lhc du photosysteme ii (lhcii) purifies a partir de plantes soumises a un bref stress luminieux contiennent une quantite de zea inferieure a la fraction de vio effectivement deepoxydee. De plus, la conversion vio->zea s'accompagne d'une modification transitoire des proprietes physiques des membranes thylacoidiennes (fluidite et permeabilite ionique). Ces resultats suggerent que, suite a la deepoxydation de la vio, une part importante de la zea est liberee dans la phase lipidique des membranes photosynthetiques ou elle exerce un role photoprotecteur (limitation des peroxydations lipidiques) et stabilisateur (thermoresistance accrue des membranes). L'importance de ce mecanisme pour la fonctionnalite des membranes photosynthetiques et leur adaptation aux fortes lumieres et aux temperatures elevees est discutee. Par ailleurs, sous forte lumiere, un decouplage energetique carotenoides/chlorophylles independant de la conversion vio->zea se met en place au niveau des photosystemes. Il pourrait refleter des modifications de conformation des lhc de l'etat collecteur d'energie a l'etat de dissipation d'energie. Dans ce contexte, nous avons montre que le cycle des xanthophylles ne participe que tres indirectement (comme catalyseur cinetique) a la dissipation thermique de l'exces d'energie et que l'accumulation constitutive de zeaxanthine dans les lhcii chez le mutant aba-l d'arabidopsis thaliana n'assure pas a elle seule une meilleure photoprotection des photosystemes. La conversion dynamique vio->zea possede donc un double role de consolidation des structures membranaires et de modification de la reponse des antennes chlorophylliennes a la lumiere suite a un changement de leur composition en xanthophylles. La compatibilite eventuelle de notre modele avec d'autres hypotheses proposees dans la litterature est examinee.
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Allum, Stephen. "Evaluation of the use of chlorophyll fluorescence in the detection of metal-induced stress in plants." Thesis, Staffordshire University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341404.
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Lambert, Patricia. "Evaluation of the Chlorophyll/Fluorescence Sensor of the YSI Multiprobe: Comparison to an Acetone Extraction Procedure." Thesis, University of North Texas, 2001. https://digital.library.unt.edu/ark:/67531/metadc2794/.
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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.
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Corrêa, Maria José Pinheiro [UNESP]. "Eficácia e seletividade de herbicidas aplicados em pós-emergência em soja convencional e transgênica." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/105305.
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correa_mjp_dr_jabo.pdf: 913272 bytes, checksum: 5000bc011ba683f81e165123412cb4d8 (MD5)Uema-Universidade Estadual do Maranhao
O presente estudo teve por objetivo avaliar a eficácia e seletividade de herbicidas aplicados em pós-emergência, isolados e em misturas, para o controle de plantas daninhas e os efeitos sobre o crescimento e o desenvolvimento da soja convencional (M-SOY 8001) e transgênica (M-SOY 7908 RR). Também foram estudados os efeitos dos produtos sobre a atividade fotossintética e nas características morfológicas externas e internas das plantas. Foram conduzidos dois experimentos, no ano agrícola 2006/2007 e repetido em 2007/2008, em condições de campo, na Fazenda de Ensino, Pesquisa e Produção da UNESP, Câmpus de Jaboticabal, SP. O delineamento experimental utilizado foi em blocos ao acaso com quatro repetições. Os tratamentos constaram da aplicação de herbicidas isolados e em misturas: lactofen (168 g ha- 1), glyphosate (1080 g ha-1), lactofen + chlorimuron-ethyl (96 + 10 g ha-1), chlorimuron-ethyl + imazethapyr (10 + 70 g ha-1), chlorimuron-ethyl + bentazon (10 + 600 g ha-1), glyphosate + imazethapyr (900 + 70 g ha-1), lactofen + chlorimuronethyl + imazethapyr (96 + 10 + 70 g ha-1) e lactofen + chlorimuron-ethyl + imazethapyr/haloxyfop-methyl (96 + 10 + 70 / 60 g ha-1). Além disso, foram mantidas duas testemunhas sem aplicação de herbicida (capinada e mantida infestada). Concluiu-se que os herbicidas utilizados foram seletivos para a soja; exceção dos tratamentos com glyphosate na soja M-SOY 8001. Na condição de baixa infestação de plantas daninhas, os herbicidas aplicados foram eficazes no controle destas. Na área com maior infestação de plantas daninhas, a aplicação de glyphosate isolado ou em mistura com imazethapyr proporcionou melhor controle das plantas infestantes. Quanto a eficiência fotossintética máxima, apenas o cultivar convencional foi suscetível à aplicação dos herbicidas, principalmente às misturas contendo lactofen + chlorimuron-ethyl...
This research was carried out to evaluate the efficiency and selectivity postemergence herbicides applied alone and in mixtures to the weed control and the effects on the growth and the development transgenic (M-SOY 7908 RR) and conventional (M-SOY 8001) soybean. The effects of the products on the photosynthetic activity and the external and internal morphologic characteristics of the plants, also it studied. Two experiments were carried out from 2006/2007 and 2007/2008 under field conditions on Education, Research and Production Farm of UNESP in Jaboticabal, SP, Brazil. A randomized complete block experimental design with four replications was used. Herbicide treatments consisted lactofen (168 g ha-1), glyphosate (1080 g ha-1), lactofen + chlorimuronethyl (96 + 10 g ha-1), chlorimuron-ethyl + imazethapyr (10 + 70 g ha-1), chlorimuron-ethyl + bentazon (10 + 600 g ha-1), glyphosate + imazethapyr (900 g + 70 g ha-1), lactofen + chlorimuron-ethyl + imazethapyr (96 + 10 + 70 g ha-1) and lactofen + chlorimuron-ethyl + imazethapyr/haloxyfop-methyl (96 + 10 + 70 + 60 g ha-1). The tests included two nontreated (no hand weeded and hand weeded). The herbicides were selective for the soybean; exception of the treatments glyphosate applied in the M-SOY 8001 soybean. Under low weed condition, the herbicides applied were effective in the weed control. In the area with larger weed condition, glyphosate applied alone and glyphosate plus imazethapyr caused better control the weeds compared other herbicides. With respect to maximum photosynthetic efficiency response, just conventional soybean was susceptible the herbicides applied, mainly the mixtures containing lactofen + chlorimuron-ethyl and lactofen + chlorimuron-ethyl + imazethapyr / haloxifop-methyl. For total chlorophyll response, the varieties presented susceptibility to the lactofen alone and in mixture with chlorimuron-ethyl, imazethapyr... (Complete abstract click electronic access below)
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Ni, Zhuoya. "Méthode pour l'estimation de la fluorescence de la chlorophylle et son application pour la détection précoce du stress hydrique." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD022/document.
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La fluorescence chlorophyllienne induite par le soleil est une nouvelle façon de suivre l'évolution de la végétation et le cycle global du carbone. Grâce au modèle simulé et aux expériences sur le terrain et aéroportée, la recherche multi-échelles de méthode de détection de la fluorescence de la chlorophylle induite par le soleil est développé dans cette thèse. Les principales conclusions et innovations sont les suivantes : 1. Les expériences de contrôle en eau du maïs montrent que la fluorescence passive peut être utilisée pour détecter le stress hydrique des culture. L'analyse de la réponse de la fluorescence et de la température montre que la fluorescence est très sensible au stress hydrique précoce. 2. Après avoir analysé les effets de la température, de l'angle zénithal solaire et du rendement quantique de la fluorescence sur la détermination de la fluorescence, nous proposons une méthode d’obtention de la fluorescence qualitative basée sur l'indice de réflectance. 3. L’analyse des effets de la détermination de la fluorescence aéroportée nous a permis de montrer que l'angle zénithal solaire et la hauteur du capteur aéroporté sont les facteurs importants qui influent sur la détermination de la fluorescence induite par le soleilSun-induced chlorophyll fluorescence is a new way to monitor the vegetation change and global carbon cycle. Through the model simulated analysis, the pot experiment and the airborne flying experiment, the research on detecting the multi-scale sun-induced chlorophyll fluorescence is developed in this dissertation. The main conclusions and innovations are as follows: 1. The maize water control experiments demonstrate that the passive fluorescence can be used to detect the crop water stress, and the analysis of the different responses of the fluorescence and temperature illustrates that the fluorescence is much sensitive to the early water stress. 2. Analyze the effects of temperature, sun zenith angle and fluorescence quantum efficiency on the qualitative fluorescence retrieval, and propose a qualitative fluorescence retrieval method based on the reflectance index. 3. Analyze the effects of airborne fluorescence retrieval, and obtain that sun zenith angle and airborne sensor height are the important factors to affect the sun-induced fluorescence retrieval from the simulated analysis and airborne flying experiment
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Hanlon, A. R. M. "The effect of simazine on chlorophyll a fluorescence in axenic diatom monocultures and in estuarine microphytobenthic biofilms." Thesis, University of Essex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390991.
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Culver, Mary Evans. "Applications of chlorophyll a fluorescence in bio-optical models of phytoplankton biomass and productivity / by Mary Evans Culver." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10966.
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Foroozanfar, Maryam. "Genetic control of tolerance to salinity in Medicago truncatula." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0035/document.
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Parmi les contraintes abiotiques la salinité est considérée comme un problème majeur, qui affecte le fonctionnement des plantes, en particulier leur croissance et leur rendement. Afin d’étudier le contrôle génétique de la tolérance à la salinité chez Medicago truncatula, plante modèle de la famille des légumineuses, deux expérimentations ont été réalisées. La première expérimentation visait à étudier l’effet de la contrainte saline sur différents paramètres morpho-physiologiques pour un panel de génotypes de M. truncatula afin de déterminer les traits de phénotypage pour la tolérance à la salinité. Les génotypes A17, TN1.11, DZA315.16, A20, TN1.12 et F83005.5 ont été sélectionnés parmi des lignées originaires de différents pays méditerranéens, qui ont été déjà séquencées (http://www1.montpellierinra.fr/BRC-MTR/mauguio/mauguio.php). Les génotypes ont été étudiés sous 6 traitements salins (0, 30, 60, 90,120 et 150 mM NaCl) dans un essai factoriel sous forme de blocs complets aléatoires en trois répétitions. L’analyse de la variance montre des différences significatives entre les niveaux de salinité et une interaction entre les génotypes et les traitements salins concernant la plupart des caractères étudiés. Le génotype « DZA315.16 » présente les valeurs les plus importantes concernant les effets principaux pour les caractères morphologiques alors que « TN1.11 » présente les valeurs les plus faibles. La projection verticale de la surface foliaire de la plante (Leaf Area=LA), significativement corrélée à la biomasse des plantes, apparaît comme un trait d’intérêt pour le phénotypage de la tolérance à la salinité. La concentration saline la mieux adaptée pour démontrer les différences parmi les lignes étudiées se situe entre 90 et 120 mM NaCl. Le génotype « TN1.11 » contrairement à « DZA315.16 » et à « Jemalong-A17 » présente un maintien de la surface foliaire de la plante en réponse à la salinité. Pour la deuxième expérimentation, une population de cent lignées recombinantes (Recombinant Inbred Lines=RILs) produite par le croisement entre « TN1.11 » et « Jemalong-A17 » a été retenue pour l’analyse du contrôle génétique de la tolérance à la salinité. Les RILs ont été développés par la méthode de descendant mono graines (Single Seed descent= SSD) jusqu’ à la génération F6 à l’INP-ENSAT, France. Le plan d’experimentation est « Spli plots » , sous forme de blocs randomisés avec trois répétitions et deux conditions : traitement salin (100 mM NaCl) et témoin (eau). L’expérience a été menée pour déterminer la variabilité génétique et pour identifier les QTLs contrôlant les caractères morphologiques et physiologiques chez la population des lignées recombinantes (RILs). L’analyse de la variance a montré une large variation génétique et une ségrégation transgressive pour les caractères étudiés. La différence entre la moyenne des RILs et la moyenne de leurs parents n’est pas significative concernant tous les caractères étudiés dans les deux conditions, ce qui montre que les RILs utilisées dans notre expérimentation sont représentatives de toutes les lignées recombinantes possibles du croisement « TN1.11 x Jemalong-A17 ». 21 QTLs ont été détectés dans la condition témoin et 19 QTLs ont été identifiés sous contrainte saline (100 mM NaCl). Le pourcentage de la variance phénotypique expliqué par les QTLs varie entre 4.60% et 23.01%. Certains de ces QTLs sont spécifiques à la condition saline, ce qui démontre l’existence du contrôle génétique de la tolérance à la salinité chez M. truncatula ; tandis que les autres ne sont pas spécifiques et contrôlent un même caractère dans les deux conditions. Des QTLs superposés concernant différents caractères ont été aussi observés. Les résultats fournissent des informations importantes en vue de futures analyses fonctionnelles de la tolérance à la salinité chez M.truncatula et pour d’autres espèces voisinesAmong abiotic stresses salinity is considered as a serious problem affecting plant functions especially growth and yield. In order to study the genetic control of salt stress in the model legume Medicago truncatula, two experiments were performed. The first experiment was conducted to study the effect of salt stress on some morpho-physiological parameters in M. truncatula genotypes and to determine the eventual use of some traits as tolerance criteria. Genotypes including A17, TN1.11, DZA315.16, A20, TN1.12 and F83005.5 are selected through a sequenced lines collection (http://www1.montpellierinra.fr/BRC-MTR/mauguio/mauguio.php) which are originated from different Mediterranean countries. Genotypes were studied under 6 salinity treatments (0, 30, 60, 90,120 and 150 mM NaCl) in a factorial design based on randomized complete blocks with three replications. Analysis of variance show significant differences among genotypes, salinity levels and interaction between genotypes and salt treatments for most of studied traits. “DZA315.16” genotype presents the highest main effect values for morphological traits whereas”TN1.11” has low values. Vertically projected leaf area (LA); show the highest variability through all studied salt concentrations. The best concentration to find differences between parental lines is 90 to 120 mM Nacl. A segregating population of recombinant inbred lines (100 RILs) of M.truncatula derived from a cross between TN1.11 and Jemalong-A17 was used for the second experiment. RILs were developed by single-seed descent until F6 generation at the INP-ENSAT, France. The experiment was undertaken to determine the genetic variability and to identify QTLs controlling several traits related to plant growth and physiology, in the population of recombinant inbred lines (RILs). Analyses of variance showed a large genetic variation and transgressive segregation for the traits studied. The difference between the mean of RILs and the mean of their parents was not significant for all of the traits in both conditions, showing that the RILs used in our experiment are representative of the possible recombinant lines from the cross TN1.11 x A17. A total of 21 QTLs were detected under control and 19 QTLs were identified under 100mM salt stress conditions. The percentage of total phenotypic variance explained by the QTLs ranged from 4.60% to 23.01%. Some of the QTLs were specific for one condition, demonstrating that the genetic control of a traits differed under control and salt stress conditions. Some others are non-specific and control a trait in both conditions. Overlapping QTLs for different traits were also observed. The results provide important information for further functional analysis of salt tolerance in M. truncatula
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Bonnanfant, Marlène. "Étude des mécanismes de conversion photosynthétique de l'énergie lumineuse par Chlorella vulgaris en photobioréacteur solaire." Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1015.
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La production à grande échelle de micro-algues est principalement réalisée en cultures solaires. Dans ces conditions, les cellules subissent de nombreuses variations de lumière à cause des cycles jour/nuit, de la météo, de leur déplacement entre la surface éclairée et le fond sombre de la culture ou de leur passage régulier dans des parties non éclairées du photobioréacteur (PBR). En réponse à ces variations, les micro-algues ont développé des mécanismes leur permettant de se protéger à court terme contre de trop fortes intensités lumineuses, par exemple en dissipant l’énergie excédentaire sous forme de chaleur, et à long terme d’utiliser l’énergie lumineuse avec la meilleure efficacité en modifiant leur teneur en pigments. Cette étude porte sur la compréhension et l’optimisation de la conversion photosynthétique de l’énergie lumineuse par Chlorella vulgaris en PBR solaire. Pour cela des expériences en conditions contrôlées ont été réalisées à l’échelle du laboratoire. Au niveau de la cellule, des comportements transitoires ont pu être observés notamment en présence de lumière sursaturante. La photoacclimatation impacte les mécanismes de photoprotection et de photoinhibition des cellules. A l’échelle du PBR, les temps caractéristiques des réponses photosynthétiques de la culture ont été explorés lors de transitions lumineuses ascendantes ou descendantes. Par la suite, une sonde de mesure de la fluorescence de la chlorophylle a a été implémentée en ligne sur un PBR et son utilité a été étudiée pour le suivi de cultures solaires notamment pour le maintien de conditions favorables et l’estimation de la productivité. De plus, cette sonde a également permis de mesurer l’impact des boucles sombres sur la réponse photosynthétique de C. vulgaris grâce à des mesures complémentaires de flux de gazLarge-scale production of microalgae is mainly carried out in solar cultures. Under these conditions, cells experience various light fluctuation dynamics that is mostly due to day/night cycles, weather conditions, cell displacement between the light surface and the near-dark bottom of the culture, or regular passage through the design dark fractions of the photobioreactor (PBR). In response to these light variations, microalgae developed response mechanisms. In the short term, they protect themselves from supersaturating light intensity for example by dissipating excess energy as heat. In the long term they change their pigment content to use light energy with the greatest efficiency. This study aims at understanding and optimizing the photosynthetic conversion of light energy by Chlorella vulgaris in solar PBR. For this purpose, experiments under controlled conditions were carried out at the laboratory scale. At the cell level, transient behaviours were observed, particularly in the presence of supersaturating light. Photoacclimation impacted photoprotection and photoinhibition mechanisms of the cells. At the reactor scale, characteristic times of photosynthetic responses were explored during increasing or decreasing light step transitions. Subsequently, an in vivo chlorophyll a fluorescence measurement sensor was implemented online on a PBR and its usefulness was studied for monitoring solar cultures, particularly for maintaining good culture conditions and estimating productivity. In addition, this probe supplemented by gas flux measurements also made it possible to measure the impact of PBR dark fractions on the photosynthetic response of C. vulgaris
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Taddei, Lucilla. "The role of the LHCX light-harvesting complex protein family in diatom photoprotection." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066219/document.
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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 fluctuantDiatoms 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
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Wang, Pei [Verfasser], and Roland [Akademischer Betreuer] Gerhards. "From greenhouse to field practice : herbicide resistance detection using chlorophyll-fluorescence-imaging technology / Pei Wang ; Betreuer: Roland Gerhards." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2017. http://d-nb.info/1128211181/34.
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Smith, W. K., J. A. Biederman, R. L. Scott, D. J. P. Moore, M. He, J. S. Kimball, D. Yan, et al. "Chlorophyll Fluorescence Better Captures Seasonal and Interannual Gross Primary Productivity Dynamics Across Dryland Ecosystems of Southwestern North America." AMER GEOPHYSICAL UNION, 2018. http://hdl.handle.net/10150/627119.
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Satellite remote sensing provides unmatched spatiotemporal information on vegetation gross primary productivity (GPP). Yet understanding of the relationship between GPP and remote sensing observations and how it changes with factors such as scale, biophysical constraint, and vegetation type remains limited. This knowledge gap is especially apparent for dryland ecosystems, which have characteristic high spatiotemporal variability and are under-represented by long-term field measurements. Here we utilize an eddy covariance (EC) data synthesis for southwestern North America in an assessment of how accurately satellite-derived vegetation proxies capture seasonal to interannual GPP dynamics across dryland gradients. We evaluate the enhanced vegetation index, solar-induced fluorescence (SIF), and the photochemical reflectivity index. We find evidence that SIF is more accurately capturing seasonal GPP dynamics particularly for evergreen-dominated EC sites and more accurately estimating the full magnitude of interannual GPP dynamics for all dryland EC sites. These results suggest that incorporation of SIF could significantly improve satellite-based GPP estimates.
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Husby, Chad Eric. "Ecophysiology and Biomechanics of Equisetum Giganteum in South America." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/200.
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Equisetum giganteum L., a giant horsetail, is one of the largest living members of an ancient group of non-flowering plants with a history extending back 377 million years. Its hollow upright stems grow to over 5 m in height. Equisetum giganteum occupies a wide range of habitats in southern South America. Colonies of this horsetail occupy large areas of the Atacama river valleys, including those with sufficiently high groundwater salinity to significantly reduce floristic diversity. The purpose of this research was to study the ecophysiological and biomechanical properties that allow E. giganteum to successfully colonize a range of habitats, varying in salinity and exposure. Stem ecophysiological behavior was measured via steady state porometry (stomatal conductance), thermocouple psychrometry (water potential), chlorophyll fluorescence, and ion specific electrodes (xylem fluid solutes). Stem biomechanical properties were measured via a 3-point bending apparatus and cross sectional imaging. Equisetum giganteum stems exhibit mechanical characteristics of semi-self-supporting plants, requiring mutual support or support of other vegetation when they grow tall. The mean elastic moduli (4.3 Chile, 4.0 Argentina) of E. giganteum in South America is by far the largest measured in any living horsetail. Stomatal behavior of E. giganteum is consistent with that of typical C3 vascular plants, although absolute values of maximum late morning stomatal conductance are very low in comparison to typical plants from mesic habitats. The internode stomata exhibit strong light response. However, the environmental sensitivity of stomatal conductance appeared less in young developing stems, possibly due to higher cuticular conductance. Exclusion of sodium (Na) and preferential accumulation of potassium (K) at the root level appears to be the key mechanism of salinity tolerance in E. giganteum. Overall stomatal conductance and chlorophyll fluorescence were little affected by salinity, ranging from very low levels up to half strength seawater. This suggests a high degree of salinity stress tolerance. The capacity of E. giganteum to adapt to a wide variety of environments in southern South America has allowed it to thrive despite tremendous environmental changes during their long tenure on Earth.