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1
Sheard, J. P. "Glucose uptake by pea mesophyll protoplasts." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235210.
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Lee, Joonsang. "Influence of the mesophyll on stomatal opening." Thesis, University of Aberdeen, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314415.
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This study shows that stomata in the isolated epidermis do not behave like those in the intact leaf and that the mesophyll plays an important role in the mechanism of stomatal opening over short periods. The results suggested that the opening of stomata in isolated epidermis was inferior to that in the intact leaf and was influenced by the concentration of KCl in the medium rather than by light. Stomatal opening in isolated epidermis of Commelina was not only insensitive to light but also unaffected by CO2 in the medium containing 100 mol m-3 KCl. The absence of an effect of light and CO2 on the stomata in isolated epidermis and the evidence that they possessed the potential of those in the intact leaf to open wide, suggested that the mesophyll could be important in influencing stomatal opening in the intact leaf. The solution in which the mesophyll cells were incubated was separated by centrifugation. The medium from cells previously incubated in the light caused the stomata in the isolated epidermis to open but that from cells kept in the dark had no effect. Thus the stimulatory influence of the mesophyll cells in bringing about stomatal opening could be separated from the cells into solution. For ease of description it is tentatively suggested that the putative factor which promotes stomatal opening indicated by the results be called stomatin. Stomatin will be produced when the chloroplasts in the mesophyll are exposed to white light.
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Newell, Jane Marie. "Vacuole development in evacuolated oat mesophyll protoplasts." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295919.
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Hörtensteiner, Stefan. "Re-formation of vacuoles in evacuolated tobacco mesophyll protoplasts /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10426.
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Stoll, Marion. "Aktivierende T-DNA-Mutagenese in Nicotiana-tabacum-Mesophyll-Protoplasten." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96491638X.
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Shrestha, Arjina. "Variability in mesophyll conductance to CO2 in grain legumes." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17559.
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Mesophyll conductance (gm) limits the diffusion of CO2 from sub-stomatal cavities to the carboxylation site and is a significant limitation to photosynthesis. However, there is a lack of complete understanding of gm variability and its regulation under different environmental conditions, and relevant studies in grain legumes are scarce. My research projects aimed to characterize genetic variability in gm, to quantify the response of gm to short- and long-term environmental changes and to assess the relationship of gm with leaf water-use efficiency (WUE) in grain legumes. gm and leaf hydraulic conductance (Kleaf) were examined simultaneously under growth conditions to see if they show coordinated response. gm varied significantly among genotypes for most of the legumes studied, but the genotypes did not vary in cell wall and plasma membrane conductance (measured from the oxygen isotope method). gm responded to growth or measurement environments, increasing rapidly with increasing light intensity but decreasing under blue light. However, genotypes differed in their interactive response to water stress, light intensity and light quality. Rapid response of gm to changes in light intensity was affected by N source (N2-fixing or inorganic-N fed). Short-term temperature response of gm varied between species. Chloroplast membrane conductance varied among species and genotypes and with growth environment. Environmentally driven leaf anatomical traits were not the major factors determining gm, but genotypes differed in the degree to which leaf anatomy influenced gm. Our results did not show coordination between gm and Kleaf. gm was strongly associated with photosynthetic rate but not with stomatal conductance. The results of this project provide useful information for crop genetic improvement through gm in legumes under climate change scenarios. Increasing gm in legumes will increase photosynthetic rate and possibly WUE, when there is no increase in stomatal conductance.
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Vosloh, Daniel. "Subcellular compartmentation of primary carbon metabolism in mesophyll cells of Arabidopsis thaliana." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5553/.
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Metabolismus in Pflanzenzellen ist stark kompartimentiert. Viele Stoffwechselwege haben Reaktionen in mehr als einem Kompartiment. Zum Beispiel wird während der Photosynthese in pflanzlichen Mesophyllzellen Kohlenstoff in Form von Stärke in den Chloroplasten synthetisiert, während es im Zytosol in Form von Sacharose gebildet und in der Vakuole gespeichert wird. Diese Reaktionen sind strikt reguliert um ein Gleichgewicht der Kohlenstoffpools der verschiedenen Kompartimente aufrecht zu erhalten und die Energieversorgung aller Teile der Zelle für anabolische Reaktionen sicher zu stellen. Ich wende eine Methode an, bei der die Zellen unter nicht-wässrigen Bedingungen fraktioniert werden und daher der metabolische Status der während der Ernte herrschte über den ganzen Zeitraum der Auftrennung beibehalten wird.
Durch die Kombination von nichtwässriger Fraktionierung und verschiedener Massenspektrometrietechniken (Flüssigchromotagraphie- und Gaschromotagraphie basierende Massenspekrometrie) ist es möglich die intrazelluläre Verteilung der meisten Intermediate des photosynthetischen Kohlenstoffstoffwechsels und der Produkte der nachgelagerten metabolischen Reaktionen zu bestimmen. Das Wissen über die in vivo Konzentrationen dieser Metabolite wurde genutzt um die Änderung der freien Gibbs Energie in vivo zu bestimmen. Mit Hilfe dessen kann bestimmt werden, welche Reaktion sich in einem Gleichgewichtszustand befinden und welche davon entfernt sind. Die Konzentration der Enzyme und der Km Werte wurden mit den Konzentrationen der Metabolite in vivo verglichen, um festzustellen, welche Enzyme substratlimitiert sind und somit sensitiv gegenüber Änderungen der Substratkonzentration sind.
Verschiedene Intermediate des Calvin-Benson Zyklus sind gleichzeitig Substrate für andere Stoffwechselwege, als da wären Dihyroxyaceton-phosphat (DHAP, Saccharosesynthese), Fructose 6-phosphat (Fru6P, Stärkesynthese), Erythrose 4-phosphat (E4P, Shikimat Stoffwechselweg) und Ribose 5-phosphat (R5P, Nukleotidbiosynthese). Die Enzyme, die diese Intermediate verstoffwechseln, liegen an den Abzweigungspunkten zu diesen Stoffwechselwegen. Diese sind Trisose phosphat isomerase (DHAP), Transketolase (E4P), Sedoheptulose-1,7 biphosphat aldolase (E4P) und Ribose-5-phosphat isomerase (R5P), welche nicht mit ihren Substraten gesättigt sind, da die jeweilige Substratkonzentration geringer als der zugehörige Km Wert ist. Für metabolische Kontrolle bedeutet dies, dass diese Schritte am sensitivsten gegenüber Änderungen der Substratkonzentrationen sind. Im Gegensatz dazu sind die regulierten irreversiblen Schritte von Fructose-1,6.biphosphatase und Sedoheptulose-1,7-biphosphatase relativ insensitiv gegenüber Änderungen der Substratkonzentration.
Für den Stoffwechselweg der Saccharosesynthese konnte gezeigt werden, dass die zytosolische Aldolase eine geringer Bindeseitenkonzentration als Substratkonzentration (DHAP) aufweist, und dass die Konzentration von Saccharose-6-phosphat geringer als der Km Wert des synthetisierenden Enzyms Saccharose-phosphatase ist. Sowohl die Saccharose-phosphat-synthase, also auch die Saccharose-phosphatase sind in vivo weit von einem Gleichgewichtszustand entfernt.
In Wildtyp Arabidopsis thaliana Columbia-0 Blättern wurde der gesamte Pool von ADPGlc im Chloroplasten gefunden. Das Enzyme ADPGlc pyrophosphorylase ist im Chloroplasten lokalisiert und synthetisiert ADPGlc aus ATP und Glc1P. Dieses Verteilungsmuster spricht eindeutig gegen die Hypothese von Pozueta-Romero und Kollegen, dass ADPGlc im Zytosol durch ADP vermittelte Spaltung von Saccharose durch die Saccharose Synthase erzeugt wird. Basierend auf dieser Beobachtung und anderen veröffentlichten Ergebnissen wurde geschlußfolgert, dass der generell akzeptierte Stoffwechselweg der Stärkesynthese durch ADPGlc Produktion via ADPGlc pyrophosphorylase in den Chloroplasten korrekt ist, und die Hypothese des alternativen Stoffwechselweges unhaltbar ist. Innerhalb des Stoffwechselweges der Saccharosesynthsese wurde festgestellt, dass die Konzentration von ADPGlc geringer als der Km Wert des Stärkesynthase ist, was darauf hindeutet, dass das Enzym substratlimitiert ist.
Eine generelle Beobachtung ist, dass viele Enzmye des Calvin-Benson Zyklus ähnliche Bindeseitenkonzentrationen wie Metabolitkonzentrationen aufweisen, wohingegen in den Synthesewegen von Saccharose und Stärke die Bindeseitenkonzentrationen der Enzyme viel geringer als die Metabolitkonzentrationen sind.Metabolism in plant cells is highly compartmented, with many pathways involving reactions in more than one compartment. For example, during photosynthesis in leaf mesophyll cells, primary carbon fixation and starch synthesis take place in the chloroplast, whereas sucrose is synthesized in the cytosol and stored in the vacuole. These reactions are tightly regulated to keep a fine balance between the carbon pools of the different compartments and to fulfil the energy needs of the organelles. I applied a technique which fractionates the cells under non-aqueous conditions, whereby the metabolic state is frozen at the time of harvest and held in stasis throughout the fractionation procedure. With the combination of non-aqueous fractionation and mass spectrometry based metabolite measurements (LC-MS/MS, GC-MS) it was possible to investigate the intracellular distributions of the intermediates of photosynthetic carbon metabolism and its products in subsequent metabolic reactions. With the knowledge about the in vivo concentrations of these metabolites under steady state photosynthesis conditions it was possible to calculate the mass action ratio and change in Gibbs free energy in vivo for each reaction in the pathway, to determine which reactions are near equilibrium and which are far removed from equilibrium. The Km value and concentration of each enzyme were compared with the concentrations of its substrates in vivo to assess which reactions are substrate limited and so sensitive to changes in substrate concentration. Several intermediates of the Calvin-Benson cycle are substrates for other pathways, including dihydroxyacetone-phosphate (DHAP,sucrose synthesis), fructose 6-phosphate (Fru6P, starch synthesis), erythrose 4-phosphate (E4P,shikimate pathway) and ribose 5-phosphate (R5P, nucleotide synthesis). Several of the enzymes that metabolise these intermediates, and so lie at branch points in the pathway, are triose-phosphate isomerase (DHAP), transketolase (E4P, Fru6P), sedoheptulose-1,7-bisphosphate aldolase (E4P) and ribose-5-phosphate isomerase (R5P) are not saturated with their respective substrate as the metabolite concentration is lower than the respective Km value. In terms of metabolic control these are the steps that are most sensitive to changes in substrate availability, while the regulated irreversible reactions of fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase are relatively insensitive to changes in the concentrations of their substrates. In the pathway of sucrose synthesis it was shown that the concentration of the catalytic binding site of the cytosolic aldolase is lower than the substrate concentration of DHAP, and that the concentration of Suc6P is lower than the Km of sucrose-phosphatase for this substrate. Both the sucrose-phosphate synthase and sucrose-phosphatase reactions are far removed from equilibrium in vivo. In wild type A. thaliana Columbia-0 leaves, all of the ADPGlc was found to be localised in the chloroplasts. ADPglucose pyrophosphorylase is localised to the chloroplast and synthesises ADPGlc from ATP and Glc1P. This distribution argues strongly against the hypothesis proposed by Pozueta-Romero and colleagues that ADPGlc for starch synthesis is produced in the cytosol via ADP-mediated cleavage of sucrose by sucrose synthase. Based on this observation and other published data it was concluded that the generally accepted pathway of starch synthesis from ADPGlc produced by ADPglucose pyrophosphorylase in the chloroplasts is correct, and that the alternative pathway is untenable. Within the pathway of starch synthesis the concentration of ADPGlc was found to be well below the Km value of starch synthase for ADPGlc, indicating that the enzyme is substrate limited. A general finding in the comparison of the Calvin-Benson cycle with the synthesis pathways of sucrose and starch is that many enzymes in the Calvin Benson cycle have active binding site concentrations that are close to the metabolite concentrations, while for nearly all enzymes in the synthesis pathways the active binding site concentrations are much lower than the metabolite concentrations.
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Freiesleben, Konstanze. "Biosynthese der Luteolin-Glucuronide im Roggenprimärblatt-Mesophyll: Charakterisierung der Glucuronosyltransferasen." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971655162.
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Lin, Quan. "Differentiation of tracheary elements from mesophyll cells of Zinnia elegens L." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358693.
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Gillham, Malcolm C. "Biosysmetric studies on some mesophyll-feeding leafhoppers associated with trees and shrubs." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375963.
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Karley, Alison Jane. "Differential ion accumulation and ion fluxes in the mesophyll and epidermis of barley." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298388.
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Santos, Ana Cristina Rocha de Figueiredo. "Morfoanatomia foliar de onze cultivares de videira (Vitis vinifera L.subsp. vinifera)." Master's thesis, ISA/UL, 2014. http://hdl.handle.net/10400.5/8287.
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Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaThis work describes the leaf morphoanatomy of 11 grapevine cultivars, grown at Tapada Ajuda, Lisbon. The white cultivars studied were ‘Alvarinho’, ‘Arinto’, ‘Encruzado’, ‘Macabeu’, ‘Moscatel Galego’, ‘Moscatel de Setúbal’ and ‘Viosinho’. The red ones were ‘Cabernet Sauvignon’, ‘Syrah’, ‘Touriga Nacional’ and ‘Trindadeira’. The leaf area was determined by scanning and under Light Microscopy the thickness of the cuticule, epidermis, total mesophyll as well as palisade and spongy parenchyma. Under Scanning Electron Microscopy, stomata type, their length and width and density were observed, as the existence of indumentum. Significant differences were observed among the white and red cultivars for all the parameters studied. In general, leaves with lower specific weight showed ticker spongy parenchyma. In all cultivars, three types of stomata were observed – at the same level, raised above and sunken regarding the other epidermal cells, showing differences among their relative proportions. ‘Moscatel de Setúbal’ and ‘Moscatel Galego’ showed the highest stomata density value, for the white cultivars. Among the red ones, differences in the sunken and raised above stomata were observed, but not for the same level stomata. ‘Trincadeira’ presented the highest value for the leaf area, the greater stomata density and the highest sunken stomata percentage, with 38.1%.
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Sawers, Ruairidh J. H. "Functional analysis of bundle sheath defective2." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342541.
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Momayyezi, Mina. "Physiological basis of variation in mesophyll conductance of black cottonwood (Populus trichocarpa Torr. & Gray)." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61268.
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There is dramatic provenance level variation in tree species with geographically wide ranges. For example, in Populus trichocarpa Torr. & Gray, net photosynthesis (An) and stomatal conductance (gs) both increase with latitude of origin. This thesis reports a parallel cline in mesophyll conductance (gm) and explores its physiological basis. In addition to anatomical constraints, variation in gm should depend on chloroplast positioning, transmembrane CO₂ diffusion through aquaporins (AQPs), and biochemical facilitation of the CO₂↔HCO₃− equilibrium by carbonic anhydrase (CA), but evidence for the former has been lacking. I found that gm increases with latitude across 12 genotypes, as measured by chlorophyll fluorescence, and confirmed this pattern by the isotope discrimination method in six representative genotypes. Northern genotypes had greater CA activity. An inhibitor of CA, acetazolamide, reduced CA activity, gm, gs, chloroplast CO₂ concentration and An at normal CO₂ (400 µmol mol-¹), the latter being reversible at saturating CO₂. The relationship between CA activity and gm was similar whether the variation was inherent or inhibitor-induced. I then explored the role of chloroplast positioning in relation to gm, driven by the ratio of blue (BL) to red light supplied to leaves. Repositioning was manifested by a reversible decrease in chlorophyll content index (CCI), while actual chlorophyll content remained unchanged. Although gm was found to decrease as BL increased, and more so in northern genotypes, cytochalasin D, an inhibitor of chloroplast motility, blocked the effect of BL on CCI but not gm, suggesting that BL can mediate gm independently of repositioning. High BL reduced CA activity, consistent with a possible reduction in protein-facilitated diffusion, which might also involve AQPs. I found that the AQP inhibitor mercuric chloride reduces gm more in northern genotypes than in southern genotypes, both absolutely and proportionally, but also reduces CA activity. Although greater gm in high-latitude genotypes likely reflects contributions from several components of the liquid-phase diffusion pathway, this thesis draws particular attention to a major role for CA. Because gm is an equal or greater limitation on photosynthesis than gs, these findings may help direct crop improvement efforts to promote resource use efficiencies and yield.Forestry, Faculty of
Graduate
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Batta, Kucheli. "The role of guard cell chloroplasts in stomatal function and coordinating stomatal and mesophyll responses." Thesis, University of Essex, 2018. http://repository.essex.ac.uk/23447/.
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Guard cells controls the stomata through which exchange of gas takes place by balancing between CO2 uptake for photosynthesis and water loss through transpiration leading to ultimate plant water use efficiency (WUE). Climate change is predicted to lead to greater temperatures and reduced water availability resulting in adverse effect on plant productivity. Sustainable agriculture will therefore require a major reduction in plant water use hence stomata have become potential target for manipulation. Understanding the signal mechanisms of stomata in response to these changing environmental conditions is therefore critically important. In order to facilitate an understanding of stomatal regulation and how it is influenced by the surrounding mesophyll cells, we have used two approaches to find a possible coordination that links mesophyll and guard cell metabolism through the use of stomatal physiology and genetic engineering. The first approach used a novel epidermal mesophyll transfer experiment to monitor stomatal responses to dynamic environmental changes with and without the mesophyll present. The second approach used new molecular tools and techniques to manipulate chloroplast metabolism specifically in the guard cells to elucidate mesophyll-derived signals that coordinate mesophyll CO2 demands with stomatal behaviour towards crop improvement. The results presented have shown guard cells plays a role in stomatal function even though the degree of responsiveness is slower than when the mesophyll is present. Furthermore, the molecular approach demonstrated using Arabidopsis plants overexpressing Rieske and SBPase resulted in substantial and significant impacts on plant development coupled with increases in photosynthetic efficiency of photosystem II in the early stages of seedling development. The result obtained proves more opportunities await the exploitation of guard cells metabolism towards the improvement of plants.
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Tipping, Claudia, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty, and School of Horticulture. "Morphological and structural investigations into C3 C4 and C3/C4 members of the genus Panicum grown under elevated CO2 concentrations." THESIS_FSTA_HOR_Tipping_C.xml, 1996. http://handle.uws.edu.au:8081/1959.7/329.
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Three perennial tropical Panicum species were grown under ambient and elevated (900 ppm) carbon dioxide concentrations in especially designed microclimate chambers. The study aimed to investigate the influence of high carbon dioxide concentrations on morphology/anatomy with physiological change among three closely related species possessing distinctly different photosynthetic pathways. The anatomy of the leaf was investigated using light microscopy (LM), transmission electron microscopy (TEM), and graphics image analysis. A suitable schedule for fixation, dehydration and embedding of leaf specimens for both forms of microscopy was developed. The anatomy of the species investigated did not change qualitatively, but there were detectable changes in leaf thickness and tissue proportions of the epidermis, mesophyll and thickened tissues (sclerenchyma, bundle sheath, vascular elements) that differed with species. This study is also relevant to the investigation of the evolution of C4, although species, and the progression involved in plants with characteristics intermediate between those of C3 and C4 species. These intermediate species have been mainly characterized by CO2 exchange and biochemical analysis, but they also display anatomical characteristics in between those of C3 and C4 plants. The evolutionary progression of the C3 to C4 species remains unsolved, although current studies indicate that the evolutionary step was from the C3 plant to the C4. Thus the intermediate C3/C4 plants may not be intermediate in an evolutionary sense and they could be seen as a simple hybridization between a C3 plant and C4 plant. In most of the parameters measured the C3/C4 P. decipiens resembled either the C3 P. tricanthum or the C4 P. antidotale. It may therefore be likened to a physiological chimera rather than to a true intermediate formDoctor of Philosophy (PhD)
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Rautenkranz, Andreas A. F. "Transport of ascorbic and dehydroascorbic acids across membranes of barley (Hordeum vulgare L., cv Gerbel) mesophyll cells /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10804.
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Vosloh, Daniel [Verfasser], and Mark [Akademischer Betreuer] Stitt. "Subcellular compartmentation of primary carbon metabolism in mesophyll cells of Arabidopsis thaliana / Daniel Vosloh. Betreuer: Mark Stitt." Potsdam : Universitätsbibliothek der Universität Potsdam, 2011. http://d-nb.info/101740769X/34.
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Vosloh, Daniel Verfasser], and Mark [Akademischer Betreuer] [Stitt. "Subcellular compartmentation of primary carbon metabolism in mesophyll cells of Arabidopsis thaliana / Daniel Vosloh. Betreuer: Mark Stitt." Potsdam : Universitätsbibliothek der Universität Potsdam, 2011. http://d-nb.info/101740769X/34.
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Gessese, Mesfin Kebede. "Characterization of wheat landraces for resistance to biotic and abiotic stresses." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17198.
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This study covered genetic and molecular analyses of stripe rust and leaf rust resistance in common wheat landraces and investigation of response of drought and short term leaf temperature changes among a set of 20 durum wheat genotypes. Three all stage resistance genes (YrAW5 in Aus27430 and YrAW6 and YrAW7 in Aus27492) were identified. YrAW5 and YrAW7 were located on chromosomes 6AS and 5AL, respectively. The location of YrAW6 was inconclusive. While Aus27430 was concluded to carry Yr18, Aus27492 appears to carry an uncharacterized adult plant resistance gene. Four QTL for stripe rust resistance (QYr.sun-1BL, QYr.sun-2AL, QYr.sun-5AL and QYr.sun-3BS) were detected in Aus28166/AvS RIL population. QYr.sun-1BL and QYr.sun-5AL also conferred resistance to leaf rust in Aus28166. QYr.sun-1BL and QLr.sun-1BL corresponded to the pleiotropic locus Lr46/Yr29/Sr58/Pm39/Ltn. The co-located loci QYr.sun-5AL and QLr.sun-5AL appear to represent a new pleiotropic resistance locus. Durum wheat genotypes showed significant variation for mesophyll conductance in response to water stress and short-term variation of leaf temperature highlighting the potential for improving durum wheat for drought and heat stress.
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Milla-Moreno, Estefania. "Structural properties related to mesophyll conductance and underlying variation in leaf mass area of balsam poplar (Populus balsamifera L.)." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52158.
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In leaves, the ease with which CO₂ may diffuse from substomatal cavities to the sites of carboxylation (mesophyll conductance, gm) is inversely proportional to the pathway length in the gas phase and the structural resistances encountered in the liquid phase. Increased length of any pathway component should decrease gm, whereas increased area for diffusion should increase gm. There is evidence that within native balsam poplar (Populus balsamifera L.) populations, gm may increase with latitude of origin, as do leaf mass (LMA) and nitrogen per unit area. To investigate the internal structural characteristics that might limit maximum gm in leaves, a balsam poplar family (K4×C) known to have high variation in LMA was chosen. Several whole tissue properties (LMA, carbon-nitrogen ratio, chlorophyll concentration index), microanatomy traits (leaf thickness, intercellular air space, cell wall surface area, chloroplast counts), and ultrastructural attributes (cell wall thickness, thylakoid grana thickness, and cell wall area adjacent to chloroplasts) were measured.
There were significant genotypic differences in chlorophyll concentration index, numbers of chloroplasts per mesophyll cell, leaf thickness (tleaf), and thicknesses and cross-sectional areas of the palisade and spongy mesophyll layers. There were also differences in the fraction of intercellular air space (fias), as well as total and exposed cell wall surface areas of the mesophyll and its component tissues. Although genotypic differences in LMA were not significant, LMA varied as a function of tleaf (r=0.515, p<0.05) and fias (r=-0.510, p<0.05), which together explained considerable variation in this trait. The single best correlate of LMA was the cell wall area of the palisade (r=0.813, p<0.001), which accounted for well over half of the total cell wall area of the mesophyll. The areas of mesophyll cell walls and chloroplasts exposed to intercellular air space, both of which should contribute to gm, also increased with LMA. Along the same lines, but not correlated with LMA, there was a decrease in nitrogen density per unit exposed mesophyll surface area associated with thicker leaves (r=-0.481, p<0.05).Forestry, Faculty of
Graduate
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Gupta, Shipan Das [Verfasser]. "Characterization of mesophyll-specific promoters for C4 engineering of rice and mutational analysis of leaf anatomy in Arabidopsis thaliana / Shipan Das Gupta." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2019. http://d-nb.info/1175202703/34.
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Woffenden, Bonnie Jean. "The Role of the Ubiquitin-Proteasome Pathway During Xylem Differentiation in Zinnia elegans Mesophyll Cells and Arabidopsis thaliana." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/29220.
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A biochemical characterization of ubiquitin (Ub)-proteasome pathway activity was conducted in Zinnia mesophyll cell cultures to examine potential differences between differentiating cells of tracheary element (TE) cultures and non-differentiating cells of control cultures. The pathway is highly active throughout development of differentiating TEs, a programmed cell death (PCD) process during which the majority of cellular proteins and biochemical processes are expected to be down-regulated in activity and/or expression. Addition of the proteasome inhibitors clasto-lactacystin Beta-lactone (LAC) and carbobenzoxy-leucinyl-leucinyl-leucinal (LLL) at culture initiation prevented TE differentiation in this system. Proteasome inhibition at 48h did not alter the final percentage of TEs compared to controls. However, proteasome inhibition at 48 h delayed the differentiation program by approximately 24 h, as indicated by examination of morphological markers and the expression of putative autolytic cysteine proteases.These results suggest that proteasome activity is required both for induction of TE differentiation and for progression of the TE program in committed cells. Treatment at 48 h with LLL resulted in partial uncoupling of autolysis from differentiation. Results of protease activity gel analysis suggest that incomplete autolysis was due to the ability of LLL to inhibit TE cysteine proteases.
A characterization of phytohormone-stimulated growth of non-differentiating cultured Zinnia cells is also presented. Differential effects on radial cell expansion versus cell elongation were observed for the four plant growth regulators examined. Auxin (naphthaleneacetic acid, NAA) and a brassinosteroid (2,4-epibrassinolide, BI) stimulate only cell elongation. Cytokinin (N-6-benzyladenine, BA) has a greater effect on growth in cell girth rather than length. Gibberellic acid (GA₃) has equivalent effects on expansion in both dimensions. These results demonstrate that radial cell expansion and cell elongation can be uncoupled, and therefore, may be controlled by different mechanisms. Additionally, this study establishes the utility of Zinnia suspension cultures as a valuable model for studies of cell expansion.
Finally, we modified Arabidopsis plant growth conditions to promote proliferation of secondary tissues, permitting the separation of secondary xylem from bark (phloem plus nonvascular) tissues using hypocotyl-root segments. Dissected tissues were used for semi-quantitative and quantitative RT-PCR and for the construction of bark and xylem cDNA libraries for PCR-based screening of several Ub pathway components, including Ub-conjugating enzymes (UBCs), deubiquitinating enzymes (DUBs), and an Alpha (PAF1) and Beta (PAF1) subunit of the proteasome. All targeted UBC families, candidate UBCs and DUBs, and proteasome subunits are expressed in secondary xylem and bark in this system.Ph. D.
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Souza, Naiara Célida dos Santos de. "A difusão e assimilação de CO2 em folhas C4 (Saccharum spp. e Sorghum bicolor) e suas relações com o nitrogênio foliar e o deficit hídrico." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-25042017-173033/.
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O aumento para demanda na produção de alimentos associado a possíveis alterações climáticas globais tem promovido um interesse renovado em pesquisas envolvendo o metabolismo fotossintético. Acredita-se que com o melhoramento fotossintético a produtividade das culturas aumente. Para se alcançar este objetivo, além do uso de práticas biotecnológicas, ainda são necessários estudos abordando as limitações intrisecas do processo fotossintético que possam contribuir com a identificação de alvos para a engenharia genética. Neste contexto, esta tese aborda perguntas especificas sobre a regulação da fotossíntese C4 pela nutrição nitrogenada, o deficit hídrico e a interação destes dois fatores. No primeiro capítulo experimental foi desenvolvido um estudo envolvendo os efeitos da nutrição nitrogenada na difusão interna de CO2. Foi observado que o conteúdo de nitrogênio (N) foliar é determinante para a condutância interna de CO2 (? 18O-gm). Um menor conteúdo de N induz reduções iniciais em ? 18O-gm devido menor atividade das enzimas carboxilativas. Conforme o conteúdo de N reduz em folhas mais velhas alterações na antomia passaram a contribuir com a regulação de ? 18O-gm. No segundo capítulo, foi explorada a variação genotipica de cana-de-açúcar quanto a parâmetros relacionados a fotossíntese e o nitrogênio foliar, envolvendo a eficiência de uso de nitrogênio fotossintética (PNUE) e índices de herdabilidade. A variabilidade dos materiais genéticos foi explicada principalmente pelos parâmetros de trocas gasosas que contribuíram com o agrupamento dos materiais em três grupos. A partir deste agrupamento é possível verificar as diferenças entre os materiais em reposta a nutrição nitrogenada. Além disto, parâmetros de trocas gasosas como a taxa de assimilação de CO2 e condutância estomática junto com PNUE apresentaram altos índices de herdabilidade no sentido restrito. Por fim, o terceiro capítulo investigou a regulação do metabolismo de assimilação de CO2 em resposta ao deficit hídrico em folhas de cana-de-açúcar e como o metabolismo de nitrogênio está envolvido neste processo. Diferentes fatores envolvidos na regulação negativa da fotossíntese foram identicados. Interesantemente, alterações nos componentes nitrogenados só contribuíram com a inibição metabólica na fase de estresse severo. Adicionalmente foi observado que a superação da inibição metabólica durante a reidratação é mais rápida quando a cultivar apresenta decréscimos mais lentos no metabolismo de N no período de seca, associado a menores danos na capacidade fotossintética.Increased demand for food production and the possibility of global climate change has promoted renewed interest in photosynthesis research. It is expected that with the photosynthetic improving the crop productivity increase. For this, besides of the use of biotechnological practices, further studies are needed about intrinsic limitations of the photosynthetic process that can contribute to the identification of targets for genetic engineering. In this context, this thesis discusses specific questions about photosynthesis regulation C4 by nitrogen nutrition, water deficit and the interaction of these two factors. In the chapter I, it was developed a study of the effects of nitrogen nutrition in the internal diffusion of CO2. It was observed that the leaf nitrogen (N) is essential for the internal CO2 conductance (Δ 18O-gm). A lower leaf N induces initial reductions in Δ18O-gm by lower activity of the carboxylation enzymes. With N leaf reduction in older leaves anatomy changes began to contribute to the regulation of Δ18 O-gm. In the chapter II, the genotypic variation of sugarcane to photosynthetic parameters and leaf nitrogen was explored, involving the photosynthetic nitrogen use efficiency (PNUE) and heritability analysis. The variability of the genetic material is explained mainly by gas exchange parameters that contributed to the grouping of materials into three groups. From this, it is possible examine the differences between the materials in response to nitrogen nutrition. Furthermore, gas exchange parameters such as CO2 assimilation rate and stomatal conductance along with PNUE showed high heritability in the narrow sense. Finally, the chapter III investigated the regulation of CO2 assimilation metabolism in response to water deficit sugarcane leaves and how nitrogen metabolism is involved in this process. Different factors involved in the negative regulation of photosynthesis were identified. Interestingly, changes in nitrogen components only contributed to metabolic inhibition in severe stress. Additionally it noted that overcoming metabolic inhibition during rehydration is faster when the cultivar presents slower decreases in N metabolism during water deficit, associated with less damage to the photosynthetic capacity.
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Sakoda, Kazuma. "Physiological and Genetic Factors for High Leaf Photosynthetic Capacity in Soybean (Glycine max (L.) Merr.)." Kyoto University, 2019. http://hdl.handle.net/2433/242682.
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Tomeo, Nicholas J. "Genetic Variation in Photosynthesis as a Tool for Finding Principal Routes to Enhancing Photosynthetic Efficiency." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1492185865465393.
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Douthe, Cyril. "Relations entre échanges gazeux foliaires et discrimination isotopique du carbone-13 pendant la photosynthèse : estimations et variations rapides de la conductance mésophyllienne au CO2." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10125/document.
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Les travaux de cette thèse se sont situés autour de la relation entre discrimination isotopique du carbone 13 et échanges gazeux foliaires. Le modèle établi par Farquhar et al. (1982) permet de prédire la discrimination contre le 13C pendant la photosynthèse (delta13C) en tenant compte des processus de diffusion, de carboxylation et décarboxylation engagés pendant la photosynthèse. Cette relation permet d'utiliser delta13C comme indicateur de l'efficience d'utilisation de l'eau (WUE, quantité de carbone fixé en fonction de l'eau consommée), un paramètre particulièrement important dans un contexte de changement climatique, d'agriculture et de sylviculture. Le modèle de delta13C a également été utilisé pour estimer la conductance mésophyllienne au CO2 (gm), un paramètre qui limite fortement la photosynthèse via la disponibilité en carbone dans le chloroplaste. Au cours de nos travaux, nous avons analysé le modèle delta13C pour identifier les paramètres les plus influents dans le modèle, et mis en évidence que l'utilisation du "modèle simple" de delta13C (ignorant gm et les processus de décarboxylation) peut induire un biais important dans l'estimation de WUE. Dans un second temps nous nous sommes concentrés sur les possibles variations à court-terme de gm, un domaine encore sujet a débat. Nous avons confirmé que gm était sensible aux variations de CO2 et d'irradiance sur toutes les espèces d'arbres mesurées dans cette étude. Nous avons aussi montré que ces variations rapides ne peuvent pas être dues a des variations des autres paramètres du modèle, à l'exception possible du paramètre b (discrimination pendant la carboxylation). Nous suggérons que les prochaines études dans ce domaine portent sur (i) la possible variabilité environnementale et génétique du paramètre b et (ii) les mécanismes à l'origine des variations rapides de gm (aquaporines et anhydrases carboniques)This work was focused on the relationship between isotopic discrimination of 13C during photosynthesis (delta13C) and leaf gas exchange. The model of Farquhar and colleagues (Farquhar et al. 1982) predicts delta13C by accounting for diffusion, carboxylation and decarboxylation processes during the photosynthesis. This relationship is widely used and delta13C is frequently considered as a proxy water use efficiency (WUE, the amount of water required to fix a amount of carbon), an interesting parameter in the context of climate change, crop production and sylviculture. The delta13C model is also used to assess mesophyll conductance to CO2 (gm), that strongly limits photosynthesis via the availability of carbon in the chloroplast. Along this work we analyzed the delta13C model and identified the most important parameters, and highlighted that using the "simple form" of the model (which ignores gm and the decarboxylations) could lead to misestimating WUE. We also focused on the possible rapid variations of gm, a subject still under debate. We confirmed that gm was sensitive to rapid variations of CO2 and irradiance in all species tested in this study. We also showed that apparent rapid variations of gm could not be induced by variations of other parameters in the model, with the exception of parameter b (discrimination during carboxylation). We propose that future studies should focus on (i) the possible environmental and genetic variability of parameter b, and (ii) the physiological processes able to change gm at short time scales (aquaporins and carbonic anhydrase)
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Monteiro, Octave William Ademola. "Quantitative Analyse der Beteiligung genetisch verschiedener internaler Sprossscheitelschichten (L2, L3) an der Bildung des Blattmesophylls." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2002. http://dx.doi.org/10.18452/14765.
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Die vorliegende Arbeit liefert neue Kenntnisse über das Konkurrenzverhalten der Sprossscheitelschichten bei der Blattmesophyllbildung und trägt dadurch zum Verständnis der Entwicklungsgeschichte höherer Pflanzen bei. Weißbunte Pflanzen von Peperomia serpens SW. LOUD, Sedum rubrotinctum R. T. CLAUSEN, Pedilanthus tithymaloides (L.) POIT. und Plectranthus coleoides BENTH wurden verwendet, um den Bau des Sprossscheitels und die chimärische Natur des Laubblattes zu analysieren. Durch die Untersuchungen zum Bau des Sprossscheitels und zur Blattanatomie wurden die Anzahl initialer Sprossscheitelschichten und die periklinalchimärische Natur der untersuchten Pflanzen bestätigt. Mit Hilfe von Mittelwertvergleichen der Mächtigkeit L2- und L3-bürtiger Mesophyllgewebe wurde die Beteiligung genetisch verschiedener internaler Sprossscheitelschichten an der Bildung des Blattmesophylls bei Sedum rubrotinctum, Pedilanthus tithymaloides und Peperomia serpens erfasst. Die Existenz histogenetisch grüner L2- oder L3-bürtiger Gewebe verursacht eine Zunahme der Blattquerschnittfläche (Sedum rubrotinctum) und eine Vergrößerung der Blattmesophyllhöhe (Peperomia serpens und Pedilanthus tithymaloides). Es wurden Regenerationsversuche an Blattstecklingen der Periklinalchimäre von Peperomia serpens und Sedum rubrotinctum durchgeführt. Durch In-vivo-Provozierung von Adventivsprossen an Blattstücken und achselknospenfreien Sprossen gelang es, die zwei untersuchten heterohistischen Musterpflanzen von Peperomia serpens ('GGW' und 'GWG') in grüne und weiße Nachkommen zu zerlegen. An Blattstecklingen bildeten sich in der Mehrzahl L3-bürtige Regenerate (ca. 75 %). Eine Beteiligung der L2-bürtigen Gewebe bei der Regeneration war an den Blattrandexplantaten zu beobachten. Das L1-bürtige Hypoderm konnte nur in der In-vitro-Blattregeneration deutlich seine Fähigkeit zur Adventivsprossbildung zeigen. Die Blattregenerationsergebnisse bei Peperomia serpens demonstrieren deutlich, dass sich alle drei Sprossscheitelschichten (L1, L2, L3) an der Blattmesophyllbildung beteiligen können. An Blattstecklingen von Periklinalchimären bei Sedum rubrotinctum bildeten sich grüne, weiße und neue chimärische Adventivsprosse. Aus den Regenerationsergebnissen lässt sich die entscheidende Rolle der L2-bürtigen Gewebe bei der Adventivsprossbildung ablesen. Die Regenerationsergebnisse sprechen dafür, dass die Bildung der Adventivsprosse durch die Beteiligung der L2- und L3-bürtigen Gewebe hervorgerufen wurde und die L1-bürtigen Gewebe an der Adventivsprossbildung nicht beteiligt sein konnten. Demzufolge sind tiefer liegende Gewebe (L2- und L3-bürtige) des Laubblattes beider Arten bei der Bildung der Adventivsprosse entscheidender als die L1-bürtige Epidermis. Das Ausmaß der Beteiligung an der Adventivsprossbildung bei Peperomia serpens und Sedum rubrotinctum wird nicht von der genetischen Herkunft (weiß oder grün) des L2- bzw. L3-bürtigen Gewebes gesteuert, sondern durch die Lage und damit durch die Abstammung der Gewebe aus der entsprechenden Sprossscheitelschicht bestimmt. Die abschließenden Untersuchungen an Plectranthus coleoides, dessen Chlorophyll- und Ploidiechimären quantitativ analysiert wurden, verdeutlichen die Erkenntnisse über die Beteiligung der Sprossscheitelschichten an der Bildung des Blattmesophylls. Es wurde deutlich, dass die Gewebekonkurrenz im Beisein einer doppelten Markierung nicht lagebedingt sein kann, sondern aufgrund verschiedener Ploidiestufen stattfindet.The studies presented in this thesis provide new insights into the competitive reaction of the shoot apical layers during the foliar mesophyll formation and thus contribute to understanding of plant development. The variegated plants of Peperomia serpens SW. LOUD, Sedum rubrotinctum R. T. CLAUSEN, Pedilanthus tithymaloides (L.) POIT. and Plectranhus coleoides BENTH were used to analyse the cellular organisation of shoot apex and the histogenetic constitution of the leaf. Shoot apex and leaves structural analyses confirm the number of initial shoot apical layers and the periclinal chimeric nature of investigated plants. Quantitative analysis of foliar mesophyll of Sedum rubrotinctum, Peperomia serpens and Pedilanthus tithymaloides have been used to deduce patterns of meristem layers intercellular interaction during mesophyll formation. The expression of the histogenetic green meristem layer (L2 or L3) causes a increase of "mesophyll area" (Sedum rubrotinctum) and a enlargement of "mesophyll height" (Peperomia serpens and Pedilanthus tithymaloides) in leaves. Four periclinal chimeric forms of Peperomia serpens ('GGW' and 'GWG') and of Sedum rubrotinctum ('GGW' and 'GWG'), each of which possesses normal green cell layers but a genetically different chlorophyll-deficient cell layer, were utilized to study the effect of genotype on the ability of the cell layers of in vivo and in vitro leaf cutting to regenerate adventitious shoots and to analyse the competition between apical layers and their derivatives in the plant ontogeny. Among the in vivo adventitious shoots of the leaf cuttings and leaf of Peperomia serpens, shoots were green, white and variegated. The L3-derived cell layer is alone responsible for the formation of ca. 75 % of adventitious shoots. The relative significant contribution of L2-derived cell layers to mesophyll formation increases in margin of leaf. The L1-derived hypoderm in foliar mesophyll of Peperomia serpens were apparently incapable of shoot regeneration of in vivo leaf cutting, yet in both periclinal forms clearly produced green shoots in vitro. Results demonstrate that all initial apical meristem layers in Peperomia serpens can contribute with different ability to foliar mesophyll formation. Adventitious shoots were in vivo induced on leaf of periclinal chimeric plants of Sedum rubrotinctum. Plants derived from leaf culture were three types: green, white and variegated. Among the adventitious shoots of green- and white-margined leaf of Sedum rubrotinctum, most adventitious shoots (ca. 90 %) were L2-derived, a few were L3-derived. Results demonstrate that the L1 derivatives can not contribute to foliar mesophyll formation. According to these results the internal tissues (L2- and L3-derived cell layers) of leaf are more competitive than the epidermis. The lineage of adventitious shoot is not controlled by the genetic origin of L2- and L3-derived tissues, but by the position of these derived tissues according to the shoot apical meristem layer. The last experiments on Plectranthus coleoides which have combined quantitative analysis of variegated- leaf chimeras with quantitative analysis of cytochimeras have begun to shed more light on the contribution of apical meristem layers to foliar mesophyll formation. It has revealed how the ploidy degree of apical layers derivatives in a cytochimera control leaf cell fate more than their position in the meristem.
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He, Lin. "Studies on xylan depolymerisation by the mesophile Streptomyces A451." Thesis, Open University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303667.
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CRIQUI, MARIE-CLAIRE. "Evenements moleculaires precoces dans les protoplastes issus de cellules de mesophylle de nicotiana sylvestris." Université Louis Pasteur (Strasbourg) (1971-2008), 1992. http://www.theses.fr/1992STR13015.
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Les protoplastes issus du mesophylle de nicotiana sylvestris sont capables de reinitier le cycle cellulaire, a savoir, regenerer une nouvelle paroi et se diviser. L'etude des evenements moleculaires precoces par l'intermediaire d'une banque d'adn complementaire a permis de montrer que tres rapidement le protoplaste n'exprime plus les messagers caracteristiques d'une cellule de mesophylle principalement impliquee dans la photosynthese, mais par contre il exprime une nouvelle gamme de genes principalement impliques dans la reponse aux nombreux stress subis lors de son isolement comme les genes codant pour une gluthathion peroxydase, une hmg-coa-reductase, une peroxydase anionique, l'ubiquitine, une extensine (messager de 1,2 kb), un inhibiteur de serine protease de type i de structure particuliere et d'autres genes encore qui pour l'instant restent inconnus mais qui presentent de caracteristiques structurales interessantes. La majorite de ces genes sont sous la double regulation environnement/developpement puisqu'ils sont egalement exprimes dans un ou plusieurs organes de la plante. Parallelement, on commence a detecter les genes impliques dans le developpement du protoplaste comme celui codant pour une extensine (messager de 1,4 kb) et celui codant pour une proteine de fusion ubiquitine-cep. Ces observations montrent que la reponse au stress et la reinitiation du cycle cellulaire semblent etre deux evenements indissociables. L'expression de la totipotence doit largement dependre de la capacite du protoplaste a surmonter le stress impose par la methode d'isolement
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Tomás, Mir Magdalena. "Physiological mechanisms involved in water use efficiency in grapevines." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/84126.
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La sequera és una de les majors limitacions per a l’agricultura en general, factor que pot incrementar d’acord amb les prediccions del canvi climàtic. Per això, reduir l’ús de l’aigua en el reg i augmentar l’eficiència en l’ús de l’aigua (EUA) constitueix una de les majors prioritats per aconseguir una agricultura sostenible.
L’EUA és un balanç entre guanys de biomassa i les despeses d’aigua. Aquesta Tesi s’ha centrat en l’estudi de 3 dels processos fisiològics que afecten a l’ús de l’aigua i a la producció de la planta en el cas de la vinya, i que per tant poden ser considerats factors potencials per millorar l’EUA: (1) conductància del mesòfil, (2) transpiració nocturna (3) respiració.
Els resultats d’aquesta Tesi revelen que la conductància del mesòfil i la respiració són els principals components per millorar l’EUA permetent millorar l’assimilació de carboni o minimitzant les pèrdues del carboni fixat per la fotosíntesis
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Farias, Julyana da Nóbrega. "Aspectos taxonômicos de Lithothamnion superpositum e Mesophyllum engelhartii (Corallinales; Rhodophyta) do Brasil." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/92809.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Biologia Vegetal, Florianópolis, 2009Made available in DSpace on 2012-10-24T12:35:34Z (GMT). No. of bitstreams: 1 269446.pdf: 4870259 bytes, checksum: 66a7f7c1a006806399372012726d6b00 (MD5)
Apesar da enorme importância das algas calcária não-geniculadas, elas são pouco conhecidas no Brasil, onde se acredita que se localizem os maiores bancos naturais. Em nossa tentativa de identificar este grupo na costa do Brasil, coletamos alguns espécimes que concordam com o conceito de Lithothamnion Heydrich. Dentro deste gênero, os espécimes foram identificados como L. heteromorphum (Foslie) Foslie, espécie originalmente descrita para o Brasil. No entanto, foram feitas análises detalhadas do material tipo e da literatura de L. superpositum Foslie descrito para a África do Sul e Austrália, os resultados indicam que se trata do mesmo táxon. Portanto, este trabalho estende a distribuição de L. superpositum para costa oeste do Atlântico e propõe que L. heteromorphum (Foslie) Foslie seja considerado seu sinônimo heterotípico. Além disso, o presente trabalho também reporta Mesophyllum engelhartii (Foslie) Adey pela primeira vez na costa oeste do Atlântico. As amostras foram coletadas no Espírito Santo e Santa Catarina e incluíam crostas tetraspóricas ou não férteis. Alguns espécimes não férteis foram mantidos em cultura e desenvolveram conceptáculos masculinos. O material foi analisado utilizando microscopia eletrônica de varredura e de luz. Questões relativas ao conceito de Mesophyllum também são discutidas.
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Jannaud, Dorothée. "Les transferts d'H2O et de CO2 dans le mésophylle : étude fonctionnelle par des approches non-invasives de traçage isotopique." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22097.
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Le travail présenté dans ce manuscrit décrit quelques-uns des mécanismes qui régissent les échanges de CO2 et d’eau dans le mésophylle. Nous présentons dans une première partie une méthode originale qui utilise une technique de traçage isotopique et une modélisation deséchanges gazeux pour décrire le transfert du CO2 et la concentration de CO2 aux sites catalytiques des anhydrases carboniques. Dans une deuxième partie, cette approche nous permet de caractériser la diffusion de CO2 intra-mésophylienne et d’aborder l’étude du rôle des anhydrases carboniques et des aquaporines dans la facilitation du transport de CO2. Cette étude est basée sur une analyse fonctionnelle de mutants d’insertions d’Arabidopsis affectésdans l’expression des anhydrases carboniques (ACs) ou des aquaporines. La contribution fonctionnelle d’une AC, bCA4 localisée à la membrane plasmique et récemment identifiée estanalysée plus spécifiquement. Dans une troisième partie, nous montrons par un travail de modélisation que l’approche de traçage isotopique précédemment introduite pour étudier le transfert de CO2 peut être utilisée pour étudier la compartimentation de l’eau mésophyllienne et les flux associés. Cette approche nous permet de démontrer l’existence d’une compartimentation fonctionnelle de l’eau foliaire. La signification de cette compartimentation est discutée, et une nouvelle méthode de suivi quantitatif des flux d’eau entre l’apoplasme etle symplasme est proposée. Enfin, dans une dernière partie nous abordons expérimentalement les effets de l’acide abscissique sur la transpiration foliaire et la régulation stomatiqueN this study, mechanisms that govern CO2 and water fluxes in the mesophyll are investigated. In a first part, an original approach based on isotopic tracing and modeling of gas exchange is presented to describe the CO2 transfer towards sites of carbonic anhydrases catalysis that are used to probe the intracellular CO2 concentration. In a second part, this approach allows to characterize the intracellular diffusion of CO2 and to address the implication of carbonicanhydrases and aquaporins in the facilitation of the CO2 transfer. The functional analysis is based on the characterization of Arabidopsis mutants in which the expression of some carbonic anhydrases (CAs) or aquaporins is impaired. The implication of a recently identified CA, bCA4 located at the plasma membrane, is studied in detail. In a third part a modeling approach is used to show that the method of isotopic tracing introduced to probe the CO2 fluxes can also be used to study the compartmentation of the mesophyll water and the associated fluxes. The basis of this functional compartmentation is analyzed and a newmethod is proposed to quantitatively monitor the water fluxes between the apoplasm and the symplasm. In a last part, the effects of abscissic acid on the leaf transpiration and on the stomatal aperture regulation are addressed
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Arendse, Garron Mark. "Selection and metabolic characterization of mesophylic starter cultures for optimizing the sensory attributes of fruit flavoured Maas." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51906.
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Thesis (MSc Food Sc)--Stellenbosch University, 2000.ENGLISH ABSTRACT: Maas is a traditional fermented milk drink of the indigenous people of Southern Africa and can thus be used to uplift the nutritional status of the South African population, especially for the lower income groups. Furthermore, the problem of lactose intolerance among the Black population can also be addressed by the consumption of Maas. The objective of this study was to screen mesophylic lactic acid bacterial strains (25 in total) from the University of Stellenbosch Food Science Culture Collection for suitable metabolite production and then to produce traditional Maas with a starter culture combination that produces a distinctive acid and traditional flavour. The representative 25 single lactic acid starter strains were identified as Lactococcus lactis subsp. leetis biovar diacetylactis (12 strains), L. leetis subsp. leetis (four strains) and L. leetis subsp. cremoris (nine strains). These strains were inoculated into pasteurised full cream milk and activated for 8 h at 22°C. Pasteurised full cream milk was then inoculated with each of the activated starter strains, incubated at 22°C for 16 h and assessed for acid production abilities (pH = 4.6) under controlled time-temperature conditions. The results of this study showed that nine of the single strains, L. lactis subsp. leetis biovar diacetylactis (S1, S2, S3 and S5), L. teetis subsp. lactis (S13, S15 and S16) and two L. leetis subsp. cremoris strains (S17 and S22), produced sufficient acid, rendering them suitable for the use as starters in the production of traditional Maas. A pH range of 4.3 - 5.1 was reached by the nine single strains after 16 h at 22°C. Two-strain starter combinations were then formed by combining the most suitable single L. leetis subsp. leetis biovar diacetylactis, L. lactis subsp. lactis and L. lactis subsp. cremoris strains, respectively. From the data, it was concluded that acceptable Maas could be produced with four two-strain combinations (S3S 17, S3S22, S5S17 and S5S22). This selection was again based on suitable acid and metabolite production, as well as on sensory evaluation of the final product. These four two-strain combinations produced sufficient acid to reach a pH in the 4.6 - 4.8 range, and showed a high metabolite concentration for the most suitable compounds and formed a thick, smooth and creamy body texture after 16 h at 22°C. Three-strain combinations formed between the two-strain starter combinations and L. leetis subsp. teetis strains (813, 815 and 816), were also evaluated. With these combinations a lack of a pronounced Maas flavour was found. Thus, it was decided to add aroma producing strains of the species Leuconostoc mesenteroides subsp. dextranicum (strain L1) and L. mesenteroides subsp. citrovorum (strain L2) to the three-strain combinations. Four culture combinations (A, B, C and D) were then formed by combining the selected Leuconostoc strains (L1 and L2) with the most suitable Lactococcus strains (83,817,813 and 822). These combinations produced sufficient acid to reach the pH 4.5 - 4.6 range after 14 h at 22°C. Acetaldehyde was the major flavour metabolite formed in the Maas made with these four combinations, with concentrations ranging between 26.6 - 89.3 mg.l ̄ ¹, while other flavour metabolites (ethanol, acetone, diacetyl and 2-butanone) were present at lower concentrations. It was found that three of the four culture combinations (A, C and D) were characterised by a superior, but delicate flavour and a typical characteristic Maas body texture. Fruit flavoured Maas was subsequently prepared with the three most suitable culture combinations (A, C and D) using 11 flavours and a sensory evaluation performed. The statistically evaluated data showed that the appearance, smoothness, flavour intensity, sweetness and overall acceptability were influenced by the type of fruit flavour and the culture combination. Fruit flavour 4 (banana) was the most preferred flavour. The sensory panellists also indicated that the culture combination C gave the best overall acceptability over a three week study period. Data on the shelf-life study of natural unflavoured Maas, prepared with the three culture combinations (A, C and D), showed that the Maas still had an acceptable appearance, taste and good microbiological quality after 15 d at refrigerated temperatures.
AFRIKAANSE OPSOMMING: Maas is 'n tradisionele gefermenteerde melkdrankie onder die inheemse bevolking van Suid-Afrika en kan gebruik word om die voedingstatus van die Suid-Afrikaanse bevolking te verhoog, veral vir die laer inkomste groepe. Bowendien, kan die probleem van laktose intoleransie onder die Swart gemeenskap ook aangespreek word deur die verbruik van Maas. Die doel van hierdie studie was om enkelstam mesofiliese melksuur bakterieë (25 in totaal) van die Universiteit van Stellenbosch Voedselwetenskap Kultuur Versameling te ondersoek vir geskikte metaboliet produksie en tradisionele Maas met 'n kenmerkende suurheid en tradisionele geur met 'n geskikte kultuur kombinasie te produseer. Die toonaangewende 25 enkelstamme is Lactococcus lactis subsp. leetis biovar diacetylactis (12 stamme), L. lactis subsp. lactis (vier stamme) en L. lactis subsp. cremoris (nege stamme). Hierdie stamme was in gepasteuriseerde volroom melk geïnokuleer en geaktiveer vir 8 h teen 22°C. 'n Inokulum van die onderskeie geaktiveerde stamme is hierna in gepasteuriseerde volroom melk geplaas, vir 16 h teen 22°C geïnkubeer en hul vermoë om suur te produseer (pH = 4.6) onder beheerde tyd-temperatuur kondisies is bepaal. Die resultaat van die studie het aangedui dat nege enkelstamme, naamlik L. leetis subsp. lactis biovar diacetylactis (S1, S2, S3 en S5), L. lactis subsp. leetis (S13, S15 en S16) en twee L. leetis subsp. cremoris (S 17 en S22), geskikte suurheidsvlakke vir die produksie van Maas bereik het. 'n pH vlak van 4.3 - 5.1 is na 16 h teen 22°C deur hierdie nege enkelstamme bereik. Twee-stam kombinasies is onderskeidelik gevorm tussen die geskikte enkel L. lactis subsp lactis biovar diacetylactis, L. lactis subsp. lactis en L. lactis subsp. cremoris stamme. Die gevolgtrekking gemaak uit die data, is dat aanvaarbare Maas voorberei kan word met vier van die twee-stam kombinasies (S3S17, S3S22, S5S17 en S5S22) op grond van suurvorming, metaboliet produksie en sensoriese evaluasie. Hierdie vier kombinasies het genoegsame suur geproduseer om 'n pH vlak van 4.6 - 4.8 bereik, hoë metaboliet konsentrasies geproduseer en 'n dik, gladde en romerige tekstuur aangeneem na 16 h teen 22°C. Drie-stam kombinasies is gevorm tussen die onderskeie twee-stam kombinasies en L. lactis subsp. lactis stamme (813,815 en 816) en ook geëvalueer. Die tekort aan 'n skerp Maas geur in die drie-stam kombinasies het daartoe gelei dat Leuconostoc mesenteroides subsp. dextranicum (stam L1) en L. mesenteroides subsp. citrovorum (stam L2) bygevoeg is. Vier kultuur kombinasies (A, B, C en D) is gevorm deur die geselekteerde Leuconostoc stamme (L1 en L2) te kombineer met die mees gepaste Lactococcus stamme (83, 817, 813 en 822). Hierdie kombinasies het genoegsame suur geproduseer wat 'n pH vlak van 4.5 - 4.6 na 14 h teen 22°C bereik het. In die Maas wat met bovermelde kombinasies gemaak is, was die asetaldehied die mees geproduseerde geur metaboliet teen konsentrasies van 26.6 - 89.3 mg.l ̄ ¹. Ander geur metaboliete (etanol, asetoon, diasetiel, 2-butanoon) is in laer konsentrasies geproduseer. Daar is gevind dat drie uit die vier kultuur kombinasies (A, C en D) 'n superieur, delikate geur wat 'n tipies karakteristiek van die Maas gehad het. Vrugte gegeurde Maas geproduseer met die drie kultuur kombinasies (A, C en D) deur 11 geursels te gebruik, is sensories geëvalueer. Die statistiese geëvalueerde data het getoon dat die voorkoms, gladheid, geur intensiteit, soetheid en die algehele aanvaarbaarheid beïnvloed is deur die tipe vrugte geursels en die kultuur kombinasies. Die vrugte geursel 4 (piesang) het voorkeur geniet. Die sensoriese paneellede het ook aangedui dat kultuur kombinasie C die algehele mees aanvaarbare Maas geproduseer het oor die studie periode van drie weke. Data van die rakleeftyd van die natuurlike ongegeurde Maas wat geproduseer is met die drie kultuur kombinasies (A, C en D) het aangedui dat die Maas na 15 d by yskas temperatuur steeds 'n aanvaarbare voorkoms, smaak en goeie mikrobiologiese kwaliteit gehad het.
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MOURA, Ana Cristine Sandes. "Caracterização da qualidade do leite cru refrigerado produzido em Municípios do Estado de Alagoas, Brasil." Universidade Federal Rural de Pernambuco, 2008. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5120.
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The state of Alagoas is an important producer of milk's derived of the country, but there are few researches about milk's quality, covering their several aspects, targeting the new legislation's requirements. The objective of this study was to assess the chilled raw milk quality in municipalities of this State, in view of, the standards established for the Normative Instruction nº. 51 (IN 51), published in September 18 of 2002 of the Ministry of Agriculture, Livestock and Supplying. In the first stage of the research, held between the months of september and december of 2006, 32 samples of chilled raw milk from eight dairy located in different municipalities of the state of Alagoas were analyzed for counting of somatic cells and determination of fat levels, protein, lactose and total solids and also was verified the existing correlation between them. In the second phase, held between the months of april and august of 2007, 55 samples of chilled raw milk from eleven dairy located in different municipalities of the State previously cited were analyzed for counting of aerobic mesophiles and psychrotrophic and also the determination of the density, cryoscopy and titratable acidity. Among the dairy analyzed, seven (87.5%) presented samples with counting of somatic cells, fat concentration, protein and total solids within the limits required for the legislation. However, one of the dairy analyzed (14.3%) was note that the medium value of somatic cells was finding outside of the default permitted by legislation. Was found a positive correlation (p<0.05) between counting of somatic cells and the fat concentration, while that for protein and total solids such correlation wasn't observed. Of the 55 samples, 35 (63.64%) were outside of the default permitted by legislation for the counting of aerobic mesophiles, seven (12.73%) for the counting of microorganisms psychrotrophic, 14 (25.45%) for the cryoscopy, 11 (20%) for the acidity and five (9.09%) for the density. As to the temperature of collection, there was not influence of it in the microorganisms counting. The analyze of the results found permit say that the majority of the dairy studied meet main requirements on the somatic cells counting, the components and the physicochemical properties of the milk. Meanwhile, about the milk's microbiological aspects, it is accepted that the changes found have their origin associated to the faults in the health management of the herds and the milk's manipulation, including the milking, refrigeration and its transport from farms to the dairy. The effective deployment of the requirements established for IN 51, with the participation of all members of the productive chain of milk, will promote, certainly, the improvement of milk's quality and their derivatives in the Alagoas state, contributing with the good health of the population and increasing the competitiveness of the milk products from this state in other marketplaces.
O estado de Alagoas é um importante produtor de lácteos do País, porém, há poucos estudos sobre a qualidade do leite, abrangendo seus vários aspectos, visando às novas exigências da legislação. Objetivou-se avaliar a qualidade do leite cru refrigerado produzido em municípios deste Estado, tendo em vista os padrões estabelecidos pela Instrução Normativa n 51 (IN 51), publicada em 18 de setembro de 2002 pelo Ministério da Agricultura, Pecuária e Abastecimento. Na primeira etapa da pesquisa, realizada entre os meses de setembro a dezembro de 2006, 32 amostras de leite cru refrigerado, provenientes de oito laticínios localizados em diferentes municípios do estado de Alagoas, foram analisadas para contagem de células somáticas e determinação dos teores de gordura, proteína, lactose e sólidos totais, bem como foi verificada a possibilidade de correlação entre eles. Na segunda etapa da pesquisa, realizada entre os meses de abril a agosto de 2007, 55 amostras de leite cru refrigerado, provenientes de 11 laticínios localizados em diferentes municípios do referido Estado, foram analisadas para a contagem de aeróbios mesófilos e de psicrotróficos, além da determinação da densidade, crioscopia e acidez titulável. Dentre os laticínios analisados, sete (87,5%) apresentaram amostras com contagem de células somáticas, concentração de gordura, proteína e sólidos totais dentro dos limites exigidos pela legislação. Contudo, em um dos laticínios analisados (14,3%), observou-se que o valor médio das células somáticas encontrava-se fora dos padrões permitidos pela legislação. Houve uma correlação positiva (p< 0,05) entre a contagem de células somáticas e a concentração de gordura, enquanto que para proteína e sólidos totais tal correlação não foi observada. Das 55 amostras analisadas, 35 (63,64%) encontravam-se fora dos padrões exigidos pela legislação para contagem de aeróbios mesófilos, sete (12,73%) para contagem de microsganismos psicrotróficos, 14 (25,45%) para a crioscopia, 11 (20%) para a acidez e cinco (9,09%) para a densidade. No que se refere à temperatura de coleta, não houve influência da mesma na contagem de microorganismos. A análise dos resultados obtidos permite afirmar que a maioria dos laticínios estudados atende as principais exigências quanto à contagem de células somáticas, os componentes e as propriedades físico-químicas do leite. Entretanto, no que se refere aos aspectos microbiológicos do leite, admite-se que as alterações observadas tenham sua origem associada à falhas voltadas ao manejo sanitário dos rebanhos e à manipulação do leite, incluindo a ordenha, a refrigeração e o seu transporte das propriedades rurais aos laticínios. A efetiva implantação das exigências estabelecidas pela IN 51, com a participação de todos os integrantes da cadeia produtiva dos lácteos, promoverá, certamente, a melhoria da qualidade do leite e derivados do estado de Alagoas, contribuindo com a boa saúde da população e aumentando a competitividade dos produtos lácteos deste Estado em novos mercados.
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MBARGA, BINDZI MARIE-ALAIN. "Processus de reconstitution de la foret dense mesophile guineenne : cas du secteur forestier de la region de yaounde (cameroun)." Paris 11, 1992. http://www.theses.fr/1992PA112346.
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Cette etude concerne l'evolution de la composition floristique et de la structure des communautes vegetales apres la deprise agricole dans le secteur de la foret mesophile du cameroun. En outre, elle tente d'apprecier les modalites qui accompagnent la reconstitution du couvert forestier et de retracer les differentes etapes de la remontee biologique dans ce secteur. Apres un rappel des caracteres generaux du territoire et de la zone d'etude qui est prise en sandwich entre deux entites phytogeographiques distinctes (secteur de la foret dense ombrophile et secteur des savanes periforestieres), l'etude de la reconstitution du couvert forestier est realisee par approche synchronique. La discrimination des communautes vegetales par la methode phytosociologique faisant appel aux techniques numeriques (afc, cah, etc) a permis la mise en evidence de dix-sept groupements, apparentes a sept types de vegetation ayant valeur d'alliance, dont le determinisme est essentiellement edaphique et chronologique. L'aspect structural des communautes discriminees est etudie sous l'angle de la repartition des individus et des types biophysionomiques dans le plan vertical. Les rythmes de changement des parametres structurels et fonctionnels sont egalement abordes et un schema syndynamique de la vegetation postculturale est propose. Les resultats obtenus montrent un emboitement des stades floristiques le long de la chronosequence, en raison de la presence d'un lot impressionnant d'especes compagnes. La composition floristique montre des variations importantes liees a la fois aux facteurs introduits ou preexistants dans le milieu et a l'age d'abandon des parcelles. En general, la richesse et la diversite specifiques sont plus elevees aux stades intermediaires et preclimaciques, stades correspondant a la presence simultanee de plusieurs strates. La syndynamique de cette vegetation demeure essentiellement sous l'influence des activites humaines, cependant elle montre des potentialites d'un retour rapide vers le stade climacique
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Humphry, David Robert. "Taxonomy of the psychrophile Flavobacterium frigidarium and the mesophile Cellvibrio japonicus, and comparative analyses of their xylanolytic and laminarinolytic activities." Thesis, University of Sunderland, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269167.
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Guivarc'h, Nathalie. "Mecanisme de photoregulation post-traductionnelle par phosphorylation de la phosphoenolpyruvate carboxylase de plantes c#4 : etude de la chaine de transduction dans les cellules de mesophylle de sorghum vulgare et digitaria sanguinalis." Paris 11, 1995. http://www.theses.fr/1995PA112450.
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Chez les plantes a metabolisme photosynthetique de type c#4, la phosphoenolpyruvate carboxylase (ec 4. 1. 1. 31, pepc) est l'enzyme cle de la fixation du co#2 atmospherique. Son activite est soumise a deux niveaux de controle: metabolique, par son substrat (phosphoenolpyruvate), des effecteurs positifs (glucose 6-p) ou negatifs (l-malate), et par phosphorylation d'un residu serine du domaine n-terminal, a la lumiere. Cette modification provoque une augmentation de l'activite catalytique et de l'ic#5#0 pour le l-malate de l'enzyme. L'etude de la chaine de transduction du signal photonique a ete faite sur des protoplastes de cellules de mesophylle de digitaria sanguinalis. Une approche pharmacologique, associee a la microscopie confocale et a la cytometrie en flux, a permis d'impliquer dans le processus d'activation de la pepc-kinase 1) l'alcalinisation du ph cytosolique ; provoquee in situ par une base faible, et in planta par l'internalisation de l'acide 3-phosphoglycerique sous forme protonee dans les chloroplastes de mesophylle, 2) l'activite d'une phospholipase c, 3) le ca#2#+: il serait mobilise par ouverture de canaux situes sur le tonoplaste et specifiquement actives par l'inositol trisphosphate. Le calcium et la calmoduline sont des elements intermediaires de la chaine ; ces deux composes auraient pour cible une proteine kinase dependante du ca#2#+, differente de la pepc-kinase, et 4) une etape de synthese proteique, de la pepc-kinase elle-meme ou d'un facteur d'activation, stimulee par la proteine kinase sensible au calcium et a la calmoduline. Dans le contexte de la photosynthese c#4, la phosphorylation de la pepc permet de proteger l'enzyme contre le l-malate et de coordonner l'activite des cycles c#4 et de calvin-benson en fonction des conditions environnementales
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Sundberg, Cecilia. "Improving compost process efficiency by controlling aeration, temperature and pH /." Uppsala : Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005103.pdf.
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Drca, Milan. "Seuchenhygienisch-mikrobiologische Untersuchungen an einer mesophil betriebenen Biogasanlage zur Verwertung von Speiseresten in Verbindung mit methodischen Untersuchungen zum Nachweis von Salmonellen und Escherichia coli aus biologischem Material." Doctoral thesis, Universitätsbibliothek Leipzig, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:15-20071108-144306-2.
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ZUSAMMENFASSUNG Milan Drča Seuchenhygienisch-mikrobiologische Untersuchungen an einer mesophil betriebenen Biogasanlage zur Verwertung von Speiseresten in Verbindung mit methodischen Untersuchungen zum Nachweis von Salmonellen und Escherichia coli aus biologischem Material Institut für Tierhygiene und Öffentliches Veterinärwesen der Veterinärmedizinischen Fakultät der Universität Leipzig und Institut für Umwelt- und Tierhygiene sowie Tiermedizin mit Tierklinik der Universität Hohenheim 156 Seiten, 17 Tabellen, 35 Abbildungen, 307 Literaturstellen, 1 Anhang Seuchenhygienisch-mikrobiologische Untersuchungen Es wurden folgende Versuchsvarianten an der Biogasanlage berücksichtigt: Keimträgerversuche während der Hygienisierung, Keimträgerversuche im mesophilen Reaktor und hygienisch-bakteriologische Untersuchungen des Substrates vor und nach der anaeroben Vergärung. Das Ziel der Tenazitätsversuche mit den Keimträgern Typ 1 und Typ 2 während der Pasteurisierung und im mesophilen Reaktor lag darin, nachzuweisen, ob eine sichere Inaktivierung seuchenhygienisch relevanter Bakterien und Viren zu erreichen ist. Es wurden folgende Bakterien und Viren verwendet: Listeria monocytogenes, Yersinia enterocolitica, Salmonella Senftenberg W775 H2S negativ, Escherichia coli, Campylobacter jejuni, Enterococcus faecalis, Felines Calicivirus, ECBO-Virus und Bovines Parvovirus. Zusätzlich zu den Keimträgerversuchen wurde das Substrat vor und nach der anaeroben Behandlung („Input- und Outputkontrolle“) auf seinen Gehalt an Salmonellen, Enterokokken und Gesamtcoliforme sowie Fäkalcoliforme untersucht. Das Ziel der durchgeführten Untersuchungen lag darin, die Effektivität der in der Biogasanlage ablaufenden Prozesse zu überprüfen. Die Ergebnisse der Versuche zur Tenazität der eingebrachten Bakterien während der Hygienisierung zeigten bei allen untersuchten Bakterien eine Inaktivierung bzw. Keimzahlreduktion um mehr als sieben Zehnerpotenzen. Die Ergebnisse der Versuche zur Tenazität der eingebrachten Viren während der Hygienisierung zeigten eine vollständige Inaktivierung von ECBO- und Felinen Caliciviren. Dagegen konnte das Bovine Parvovirus während des gesamten Hygienisierungsprozesses nicht inaktiviert werden. Am Ende der Hygienisierung betrug die Konzentration noch 102,0 (KID50/ml) bei einem Ausgangstiter von 104,50 (KID50/ml). Im mesophilen Reaktor wurden die ermittelten Konzentrationen von Salmonella Senftenberg W775 H2S negativ und Escherichia coli in einer Zeitspanne von 7 d um mehr als acht Zehnerpotenzen reduziert. Enterococcus faecalis erwies sich als wesentlich thermostabileres Testbakterium. Nach 14 d Aufenthaltszeit wurde die ermittelte Ausgangskonzentration von 108 KBE/ml um sechs Zehnerpotenzen reduziert. Die Ergebnisse der hygienisch-bakteriologischen Untersuchungen der Substrate nach der Hygienisierung bzw. die ermittelten Konzentrationen von Gesamtcoliforme, Fäkalcoliforme und Enterokokken zeigten eine Inaktivierung von 5 log 10. In keiner der untersuchten Input- und Outputproben konnten Salmonellen nachgewiesen werden. Untersuchungen zum Nachweis von Salmonellen aus biologischem Material Ziel der vorliegenden Untersuchungen war es, die entsprechenden vier CEN-Nachweismethoden für Salmonellen mit den Substraten Klärschlamm-, Gülle und Erde zu erproben, um deren Eignung für die Praxis beurteilen zu können. Es wurden artifiziell kontaminierte Proben untersucht. Als Testbakterien diente Salmonella Senftenberg. Alle drei verwendeten Salmonella-Konzentrationen (101, 102 und 103 KBE/ml) konnten durch die Methode 2 (MPN-Verfahren) und Methode 3 (Filtrationsmethode) bei allen drei beimpften Substraten wiedergewonnen werden. Der qualitative Nachweis von Salmonella Senftenberg (Methode 4) konnte ebenfalls bei allen untersuchten Proben erbracht werden. Ein Vergleich der beiden Methoden 1 und 2, die jeweils der Ermittlung der wahrscheinlichsten Keimzahl dienen, zeigte die Ungenauigkeit der Methode 1. Das angewandte MPN-Verfahren der Methode 1 lieferte bei allen untersuchten Substraten, die mit einer Konzentration von 102 und 103 KBE/ml beimpft waren, einen ungenauen Wert von >2,4 x 102 KBE/ml. Aufgrund der angewandten Nachweisverfahren sowie der gewonnenen Ergebnisse (mit Ausnahme der Methode 1) konnte festgestellt werden, dass die vorgeschlagenen Entwürfe zum Nachweis von Salmonellen für alle drei untersuchten Substrate geeignet sind. Untersuchungen zum Nachweis von Escherichia coli aus biologischem Material 120 natürlich kontaminierte Gülle-, Klärschlamm-, Speiserest- und Bioabfallproben wurden mittels zweier quantitativen MPN- Nachweismethoden (Makro- und Mikromethode) untersucht. Die gewonnenen Maximal- und Medianwerte der Makromethode lagen bei allen untersuchten Substraten durchschnittlich zwischen einer halben und einer Zehnerpotenz höher als bei der Mikromethode. Eine Ausnahme stellten allerdings die Medianwerte der untersuchten Gülleproben und die Maximalwerte der untersuchten Speiseabfallproben dar. Hierbei zeigten die beiden Methoden vergleichbare Werte. Aufgrund der Ergebnisse und der Tatsache, dass die Makromethode drei biochemische Eigenschaften von Escherichia coli umfasst, und damit eine sicherere Identifizierung von Escherichia coli gewährleistet, empfiehlt sich daher, bei Untersuchungen von biologischem Material die Makromethode anzuwenden.
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Petitjean, Celine. "Phylogénie et évolution des Archaea, une approche phylogénomique." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01070633.
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En 1977, Carl Woese sépare les procaryotes en deux grands groupes en proposant une nouvelle classification basée sur des critères phylogénétiques. Les Archaea deviennent ainsi un domaine à part entière aux cotés des Bacteria et des Eucarya. Depuis, la compréhension de ce nouveau groupe et de ses relations avec les deux autres domaines, essentielles pour comprendre l'évolution ancienne du vivant, est largement passée par l'étude de leur phylogénie. Presque 40 ans de recherche sur les archées ont permis de faire évoluer leur image : de bactéries vivant dans des milieux spécialisés, souvent extrêmes, on est passé à un domaine indépendant, très diversifié aussi bien génétiquement, métaboliquement ou encore écologiquement. Ces dernières années la barre symbolique de cent génomes complets d'archées séquencés a été franchie et, parallèlement, les projets génomiques et métagénomiques sur des groupes peu caractérisés ou de nouvelles lignées de haut rang taxonomique (e.g. Nanohaloarchaea, Thaumarchaeota, ARMAN, Aigarchaeota, groupe MGC, groupe II des Euryarchaeota, etc.) se sont multipliés. Tout ceci apporte un matériel sans précédent pour l'étude de l'histoire évolutive et de la diversité des Archaea. Les protéines ribosomiques ont été utilisées de façon courante pour inférer la position phylogénétique des nouvelles lignées d'Archaea. Néanmoins, les phylogénies résultantes ne sont pas complètement résolues, laissant des interrogations concernant d'importantes relations de parenté. La recherche de nouveaux marqueurs est donc cruciale et c'est dans ce contexte que mon projet de thèse s'inscrit. À partir de l'analyse des génomes de deux Thaumarchaeota et d'une Aigarchaeota, nous avons identifié 200 protéines conservées et bien représentées dans les différents phyla d'archées. Ces protéines sont impliquées dans de nombreux processus cellulaires, ce qui peut apporter un signal phylogénétique complémentaire à celui des marqueurs de type informationnel utilisés par le passé. En plus de confirmer la plupart des relations phylogénétiques inférées à partir de ces derniers (i.e., protéines ribosomiques et sous unités de l'ARN polymérase), l'analyse phylogénétique de ces nouveaux marqueurs apporte un signal permettant une meilleure résolution de la phylogénie des archées et la clarification de certaines relations jusqu'ici confuses. Un certain nombre de ces nouveaux marqueurs sont aussi présents chez les bactéries. Les relations entre les grands phyla d'archées restant encore non résolues, nous avons utilisé ces protéines pour essayer de placer la racine de l'arbre des Archaea en utilisant comme groupe extérieur les bactéries. Nous avons ainsi pu identifier 38 protéines, parmi les 200 sélectionnées précédemment, ayant un signal phylogénétique suffisamment fiable pour cette étude, auxquelles nous avons ajouté 32 protéines ribosomiques universelles. L'utilisation conjointe de ces données nous a permis de placer la racine entre les Euryarchaeota, d'une part, et un groupe rassemblant les Thaumarchaeota, les Aigarchaeota, les Korarchaeota et les Crenarchaeota, d'autre part. Ce nouvel éclairage sur l'évolution ancienne des archées nous a amené à proposer une révision de leur taxonomie avec, principalement, la création du nouveau phylum "Proteoarchaeota" contenant les quatre phyla actuels que nous proposons de rétrograder en classes : Thaumarchaea, Aigarchaea, Korarchaea et Crenarchaea.Finalement, l'analyse des protéines codées dans les trois génomes qui ont servi de point de départ de ma thèse nous a permis de générer une masse considérable de données qui ont révélé des traits particuliers ou encore des histoires évolutives inattendues. Un exemple est l'histoire du complexe formé par la chaperonne DnaK et de ses co-chaperonnes GrpE, DnaJ, et DnaJ-Fer chez les Thaumarchaeota, impliquant plusieurs transferts horizontaux entre les trois domaines du vivant.
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VRÁBL, Daniel. "Carbon dioxide transport within the leaf mesophyll: physico-chemical and biological aspects." Doctoral thesis, 2013. http://www.nusl.cz/ntk/nusl-161509.
Full textAbstract:
Stomatal conductance and mesophyll conductance for CO2 transport are two key components of diffusive limitations of photosynthesis, since they restrict CO2 flux from the leaf surface to the sub-stomatal cavity and from there to the sites of carboxylation. This thesis summarizes our findings in the field of nature of mesophyll conductance to CO2 transport and its regulation per se and in respect to stomatal conductance.
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Sun, Ying active 2013. "Role of mesophyll CO₂ diffusion and large-scale disturbances in the interactions between climate and carbon cycles." 2013. http://hdl.handle.net/2152/21525.
Full textAbstract:
Reliable prediction of climate change and its impact on and feedbacks from terrestrial carbon cycles requires realistic representation of physiological and ecological processes in coupled climate-carbon models. This is hampered by various deficiencies in model structures and parameters. The goal of my study is to improve model realism by incorporating latest advances of fundamental eco-physiological processes and further to use such improved models to investigate climate-carbon interactions at regional to global scales. I focus on the CO₂ diffusion within leaves (a key plant physiological process) and large-scale disturbances (a fundamental ecological process) as extremely important but not yet in current models. The CO₂ diffusion within plant leaves is characterized by mesophyll conductance (g[subscript m]), which strongly influences photosynthesis. I developed a g[subscript m] model by synthesizing new advances in plant-physiological studies and incorporated this model into the Community Land Model (CLM), a state-of-art climate-carbon model. I updated associated photosynthetic parameters based on a large dataset of leaf gas exchange measurements. Major findings are: (1) omission of g[subscript m] underestimates the maximum carboxylation rate and distorts its relationships with other parameters, leading to an incomplete understanding of leaf-level photosynthesis machinery; (2) proper representation of g[subscript m] is necessary for climate-carbon models to realistically predict carbon fluxes and their responsiveness to CO₂ fertilization; (3) fine tuning of parameters may compensate for model structural errors in contemporary simulations but introduce large biases in future predictions. Further, I have corrected a numerical deficiency of CLM in its calculation of carbon/water fluxes, which otherwise can bias model simulations. Large-scale disturbances of terrestrial ecosystems strongly affect their carbon sink strength. To provide insights for modeling these processes, I used satellite products to examine the temporal-spatial patterns of greenness after a massive ice storm. I found that the greenness of impacted vegetation recovered rapidly, especially in lightly and severely impacted regions. The slowest rebound occurred over moderately impacted areas. This nonlinear pattern was caused by an integrated effect of natural regrowth and human interventions. My results demonstrate mechanisms by which terrestrial carbon sinks could be significantly affected and help determine how these sinks will behave and so affect future climate.text
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Stoll, Marion [Verfasser]. "Aktivierende T-DNA-Mutagenese in Nicotiana-tabacum-Mesophyll-Protoplasten / vorgelegt von Marion Stoll." 2002. http://d-nb.info/96491638X/34.
Full text
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Hsu, Jen-Chieh, and 許仁傑. "Comparison of grana stacking of mesophyll cell and bundle sheath cell of maize." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/09055266851157377838.
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HISEM, Daniel. "Effect of abscisic acid on mesophyll conductance at different CO\dindex{2} concentrations." Master's thesis, 2011. http://www.nusl.cz/ntk/nusl-47076.
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Freiesleben, Konstanze [Verfasser]. "Biosynthese der Luteolin-Glucuronide im Roggenprimärblatt-Mesophyll: Charakterisierung der Glucuronosyltransferasen / vorgelegt von Konstanze Freiesleben." 2004. http://d-nb.info/971655162/34.
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Percey, WJ. "Linking detrimental effects of salinity on leaf photosynthesis with ion transport in leaf mesophyll." Thesis, 2014. https://eprints.utas.edu.au/22609/1/Percey%2C%20William%20whole%20thesis.pdf.
Full textAbstract:
Soil salinity is defined as a situation when the electrical conductivity of the saturated
paste extract from the upper layers of the soil is in excess of 4 dSm-1 (which equates to
~40 mM NaCl). Soil salinisation is an ever-growing problem, resulting in vast losses
of agricultural land and costing industry in excess of $12 billion in the lost production
globally. The only practical way of dealing with increasing land salinisation is to
develop ways of growing plants in these saline environments, either through breeding/
engineering of salinity tolerant plants or through the application of chemicals that
have ameliorative effect on plant performance under saline conditions. Both of these
approaches have been tried in the past, but with a rather limited success. To increase
the efficiency of breeding/ engineering and the development of chemical applications,
the processes by which salinity affects key intracellular structures and processes, and
physiological mechanisms behind salinity tolerance, should be understood.
Salinity causes osmotic and ionic limitations to growth. While osmotic effects causing
reduced growth within minutes, ionic limitations take longer but are predominate long
lasting effects. Less tolerant plants (glycophytes) tend to be Na+ excluders while
naturally more tolerant plants (halophytes) tend to include Na+. Na+ has long been
believed to be toxic in the cytosols of cells, however, its uptake into the shoot is
necessary to provide low carbon-cost osmotic adjustment, which is essential for plants
to maintain tissue turgor and expansion growth under saline conditions. The exact
biochemical/ physiological targets of Na+ stress in the cytosol are not well understood,
despite many years of research. It has long been suggested that the maintenance of
high K+/Na+ ratios in the cytosol is more important than the Na+ concentration itself.
Despite being a long-standing paradigm in salinity tolerance, this notion has not been
well tested either in vitro or in vivo.
The major aim of this work was to investigate mechanisms of non-stomatal limitation
to photosynthesis caused by salinity stress and link them with ionic relations and ion
transport across mesophyll cell plasma and chloroplast membranes. By doing this the
following objectives were addressed:
• To understand effects of salinity on ionic homeostasis and light-induced
changes in ion transport in leaf mesophyll, in the context of leaf
photosynthetic and growth responses.
• To elucidate effects of altered ionic homeostasis and cytosolic osmolality on
photosynthetic performance in chloroplasts.
• To reveal differences between chloroplast responses to salinity from species
contrasting in salinity tolerance, e.g. halophytes and glycophytes.
• To the link ion transport in the chloroplast and their resilience to perturbed
ionic homeostasis.
• To investigate effects of ameliorative chemicals (polyamines, compatible
solutes and antioxidants) on salinity-induced disturbance to leaf
photosynthetic machinery, at the chloroplast level.
• To understand the differences in mesophyll ion transport between species with
contrasting salinity tolerance and link them with primary photosynthetic
processes in green leaf tissues.
For plants to be truly salinity tolerant they need to be able to handle elevated Na+
concentrations in leaves. The ability to handle Na+ in leaves is called tissue tolerance.
Using non-invasive microelectrode ion flux measuring (the MIFE) technique it was
found that an increase in salinity within the apoplast of bean leaves results in a large
K+ efflux from mesophyll tissue. This efflux was mediated predominately by K+
outward rectifying channels (84%), with the remainder of the efflux being through
non-selective cation channels. The reduction in K+ concentration associated with this
efflux was linked to a decline in the photochemical efficiency of photosystem II
(chlorophyll fluorescence FV/FM values). In addition to K+ efflux, Na+ has also
induced a vanadate sensitive H+ efflux presumably mediated by the plasma membrane
H+-ATPase. This H+ efflux is essential for the maintenance of membrane potential
and ion homeostasis in the cytoplasm of bean mesophyll. Salinity also caused
reductions in the ability of bean mesophyll tissue to respond to light with both K+ and
H+ fluxes. This decline in response was both time- and NaCl concentrationdependant.
The effects of salinity-induced altered ionic conditions in the cytoplasm of mesophyll
cells on photosynthesis were assessed.
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Demir, Fatih. "Lipid rafts in Arabidopsis thaliana leaves." Doctoral thesis, 2010. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-53223.
Full textAbstract:
Arabidopsis thaliana (A.th.) mesophyll cells play a pivotal role in the regulation of the drought stress response. The signaling & transport components involved in drought stress regulation within lipid rafts of the plasma membrane were investigated by DRM isolation from highly purified plasma membranes. Detergent treatment with Brij-98 and Triton X-100 resulted in a total of 246 DRM proteins which were identified by nano HPLC-MS/MS. The majority of these proteins could be isolated by Triton X-100 treatment (78.5 %) which remains the ”golden” standard for the isolation of DRMs. Comparing in-gel and in-solution digestion approaches disclosed additional protein identifications for each method but the in-gel approach clearly delivered the majority of the identified proteins (81.8 %). Functionally, a clear bias on signaling proteins was visible – almost 1/3 of the detected DRM proteins belonged to the group of kinases, phosphatases and other signaling proteins. Especially leucine-rich repeat receptor-like protein kinases and calcium-dependent protein kinases were present in Brij-98 & Triton X-100 DRMs, for instance the calcium-dependent protein kinase CPK21. Another prominent member of DRMs was the protein phosphatase 2C 56, ABI1, which is a key regulator of the ABA-mediated drought stress response in A.th. The lipid raft localization of the identified DRM proteins was confirmed by sterol-depletion with the chemical drug MCD. Proteins which depend upon a sterol-rich environment are depleted from DRMs by MCD application. Especially signaling proteins exhibited a strong sterol-dependency. They represented the vast majority (41.5 %) among the Triton X-100 DRM proteins which were no longer detected following MCD treatment. AtRem 1.2 & 1.3 could be shown to be sterol-dependent in mesophyll cells as well as two CPKs (CPK10 & CPK21) and the protein phosphatase ABI1. AtRem 1.2 & 1.3 could be proven to represent ideal plant lipid raft marker proteins due to their strong presence in Triton X-100 DRMs and dependency upon a sterol-rich environment. When fluorescence labeled AtRem 1.2 & 1.3 were transiently expressed in A.th. leaves, they localized to small, patchy structures at the plasma membrane. CPK21 was an intrinsic member of Triton X-100 DRMs and displayed extreme susceptibility to sterol-depletion by MCD in immunological and proteomic assays. Calcium-dependent protein kinases (CPKs) have already been studied to be involved in drought stress regulation, for instance at the regulation of S-type anion channels in guard cells. Hence, further transient expression studies with the anion channel SLAH3, protein kinase CPK21 and its counterpart, protein phosphatase ABI1 were performed in Nicotiana benthamiana. Transient co-expression of CPK21 and the anion channel SLAH3, a highly mesophyll- specific homologue of the guard cell anion channel SLAC1, resulted in a combined, sterol-dependent localization of both proteins in DRMs. Supplementary co-expression of the counterpart protein phosphatase ABI1 induced dislocation of SLAH3 from DRMs, probably by inactivation of the protein kinase CPK21. CPK21 is known to regulate the anion channel SLAH3 by phosphorylation. ABI1 dephosphorylates CPK21 thus leading to deactivation and dislocation of SLAH3 from DRMs. All this regulative events are taking place in DRMs of A.th. mesophyll cells. This study presents the first evidence for a lipid raft-resident protein complex combining signaling and transport functions in A.th. Future perspectives for lipid raft research might target investigations on the lipid raft localization of candidate DRM proteins under presence of abiotic and biotic stress factors. For instance, which alterations in the DRM protein composition are detectable upon exogenous application of the plant hormone ABA? Quantitative proteomics approaches will surely increase our knowledge of the post-transcriptional regulation of gene activity under drought stress conditionsMesophyllzellen spielen eine sehr wichtige Rolle bei der Regulierung der Trockenstress-Antwort in der Pflanze Arabidopsis thaliana (A.th.). Um die an der Trockenstress-Antwort beteiligten Signaltransduktions- und Transportproteine zu identifizieren, die sich in Lipid Rafts der pflanzlichen Plasmamembran befinden, wurden Detergent-Resistant Membranes (DRMs) aus hochreinen Arabidopsis Plasmamembran-Präparationen isoliert. Behandlung dieser hochreinen Plasmamembran mit den Detergentien Brij-98 und Triton X-100 führte zur Identifikation von 246 DRM Proteinen, die mittels der nano HPLC-MS/MS Technologie detektiert wurden. Hierbei war festzustellen, dass das Detergens Triton X-100 eindeutig den Standard für die Isolierung von DRMs darstellt. Die große Mehrheit (78,5 %) der identifizierten DRM Proteine konnte nämlich mit Triton X-100 aufgereinigt werden. Vergleichende Anwendung verschiedener Verdaumethoden (In-Gel & In-Lösung Verdau) zeigte auf, dass jede Methode einen unterschiedlichen Pool an Proteinen identifiziert. Das Gros der analysierten Proteine (81,8 %) konnte jedoch auch alleine durch In-Gel Verdau ermittelt werden. Unter den identifizierten DRM Proteinen stellten Proteine, die an der Signaltransduktion beteiligt sind, fast 1/3 dar. Diese Proteingruppe wurde hauptsächlich durch Kinasen und Phosphatasen vertreten. Insbesondere Leucin-reiche rezeptor-artige and Calcium-abhängige Proteinkinasen waren in Brij-98 & Triton X-100 DRMs zu beobachten, z.B. die Calcium-abhängige Proteinkinase CPK21. Ebenso in Triton X-100 DRMs wurde die Proteinphosphatase 2C 56 (ABI1) lokalisiert, die eine zentrale Rolle bei der ABA-vermittelten Antwort auf Trockenstress in A.th. inne hat. Zur Bestätigung der Lipid Raft Lokalisation der identifizierten DRM Proteine wurden Sterole aus der Plasmamembran mittels der Chemikalie Methyl-ß-D-cyclodextrin entfernt. Besonders Proteine, die an der Signalweiterleitung beteiligt sind, zeigten eine starke Abhängigkeit von der Präsenz der Sterole. Sie waren besonders betroffen: 41,5 % der Proteine, die nach MCD Behandlung nicht mehr in DRMs identifiziert wurden, gehörten zur Gruppe der Signaltransduktionsproteine. Beispiele waren sowohl die Calcium-abhängigen Proteinkinasen CPK10 & CPK21, als auch die Proteinphosphatase ABI1. Die A.th. Remorine AtRem 1.2 & 1.3 stellen ideale Kandidaten für pflanzliche Lipid Raft Markerproteine dar, da beide sowohl ziemlich stark in Triton X-100 DRMs vertreten, als auch im besonderen Maße auf die Präsenz von Sterolen in DRMs angewiesen sind. Fluoreszenzmarkierte AtRem 1.2 & 1.3 Fusionskonstrukte lokalisierten bei transienter Expression in A.th. Blättern in kleinen, punktförmigen Strukturen an der Plasmamembran. Diese Strukturen zeigten frappierende Ähnlichkeit zu bereits bekannten Mustern von Lipid Raft Proteinen in Hefen und Säugetieren. CPK21 stellte ein besonderes Mitglied der Triton X-100 DRMs dar, welches ebenfalls stark auf die Präsenz von Sterolen in DRMs angewiesen war. Dies konnte durch immunologische and massenspektrometrische Experimente nachgewiesen werden. Calcium-abhängige Proteinkinasen (CPKs) sind an der Regulierung der Trockenstress-Antwort in Pflanzen beteiligt, z.B. bei der Aktivierung von S-typ Anionenkanälen in Schließzellen von A.th. Aufgrund dieser Beteiligung an der Trockenstress-Antwort, wurden transiente Co-Expressionsstudien des Anionenkanals SLAH3, der Proteinkinase CPK21 und ihrem Gegenspieler, der Proteinphosphatase ABI1 in Nicotiana benthamiana Blättern durchgeführt. Transiente Co-Expression von CPK21 und SLAH3, einem zum schließzell-spezifischen Anionenkanal SLAC1 homologen Protein in Mesophyllzellen, resultierte in einer sterol-abhängigen Co-Lokalisation beider Proteine in DRMs. Zusätzliche Gabe vom Gegenspieler ABI1 führte zum Verschwinden von SLAH3 aus DRMs, was möglicherweise auf die Inaktivierung der Proteinkinase CPK21 durch ABI1 zurückzuführen ist. Für CPK21 konnte schon aufgezeigt werden, dass es den Anionenkanal SLAH3 durch Phosphorylierung aktiviert. ABI1 hingegen dephosphoryliert die Proteinkinase CPK21 und führt zur Deaktivierung vom Anionenkanal SLAH3, welcher dann auch nicht mehr in DRMs lokalisierbar ist. Diese streng regulierten Prozesse im Rahmen der Trockenstress-Antwort spielen sich in DRMs von A.th. Mesophyllzellen ab. Die vorliegende Arbeit ist der erste Bericht eines Lipid Raft-lokalisierten Proteinkomplexes, der Signalweiterleitung und Transportprozesse in Arabidopsis Lipid Rafts vereint. Zukünftige Lipid Raft Studien könnten sich mit der Lokalisation von putativen DRM Proteinen nach Anwendung von abiotischen und biotischen Stressfaktoren befassen. So könnte man sich die Frage stellen, inwiefern sich die Proteinzusammensetzung in DRMs von der Zugabe des pflanzlichen Hormons Abscisinsäure (ABA) beeinflussen läßt. Insbesondere quantitative Proteomstudien werden in Zukunft mit Sicherheit unser Wissen über die posttranskriptionelle Regulation der Genaktivität bei Trockenstress erweitern
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Abdul, Bahar Nur Hazwani. "Photosynthetic characterisation of tropical and temperate rainforest species." Phd thesis, 2016. http://hdl.handle.net/1885/117236.
Full textAbstract:
Rubisco catalyses a rate-limiting step in photosynthesis and is
the largest nitrogen sink in leaves. The maximum rate of
carboxylation of Rubisco, Vcmax, is routinely estimated from gas
exchange using the Farquhar, von Caemmerer & Berry 1980 model of
photosynthesis. As Vcmax allows mechanistic representation of
photosynthesis, it has been incorporated into terrestrial
biosphere models to estimate global primary productivity.
However, doubts remain about previous estimates of Vcmax for
globally important biomes, such as moist forests, both in
tropical and temperate regions.
In my thesis, I present a survey of Vcmax values – calculated
assuming infinite mesophyll conductance - along a 3,300-meter
elevation gradient from lowland western Amazon to the Andean tree
line in Peru; this region is home to the largest moist forest on
Earth. Large variations in Vcmax were found within and across the
18 field sites. As hypothesised, when estimated at a common
measuring temperature (25°C), average Vcmax values of lowland
Amazon trees were significantly lower than that of Andean trees.
When data for the lowland Amazon and upland Andean trees were
combined, the resultant mean tropical Vcmax value was lower than
that of temperate trees reported in past studies. My analysis
points to low Vcmax of Peruvian tropical trees being linked to
limitations in phosphorus supply, and to a high proportion of
Rubisco being inactive.
The second part of my thesis investigated how mesophyll
conductance influences the estimation of Vcmax for several
Australian tropical (i.e. warm-adapted) and temperate (i.e.
cool-adapted) moist-forest trees. Consistent with previous
glasshouse studies, the selected tropical tree species exhibited
significantly lower Vcmax values than their temperate
counterparts. Importantly, I showed, for the first time, that the
Vcmax estimated on the basis of intercellular CO2 partial
pressure was equivalent to that on the basis of chloroplastic CO2
partial pressure, when using appropriate Michaelis-Menten
constants for CO2 and O2. Thus, low mesophyll conductance in
tropical moist forest is unlikely to account for the low
estimates of Vcmax found in the Peruvian field work study.
Finally, mechanisms underpinning development of photosynthesis in
tropical moist forest trees, which include ontogenetic changes in
leaf anatomy, and mesophyll and stomatal conductances, were
examined. Key components of photosynthesis such as Vcmax, maximum
electron transport rate and chlorophyll content increased
synchronously during expansion, accompanied by development of
leaf internal structures such as intercellular air spaces and
mesophyll cells. The balance between photosynthetic carbon uptake
and respiratory release changed dramatically during leaf
development, reflecting a two-fold decline in area-based rates of
respiration in expanding leaves as photosynthesis became fully
functional.
The dataset presented in my PhD thesis adds to the growing number
of empirical estimates highly needed by the photosynthetic
modelling communities, and validates the accuracy of Vcmax
estimation using biochemical approaches. Collectively, my study
is expected to contribute towards better understanding and
representation of Vcmax in tropical forests.