Made available in DSpace on 2016-06-02T19:31:38Z (GMT). No. of bitstreams: 1 1456.pdf: 806888 bytes, checksum: c1a017c0d739e9db5205b7784a9e4a47 (MD5) Previous issue date: 2007-06-06 / Universidade Federal de Sao Carlos / Young plants of Coffea arabica grafted over C. canephora were submitted to six watering cycles (WC) during 35 days. Each WC was accomplished until net photosynthesis (PN) close to zero or leaf water potential (&#936;) close to -2.0 MPa in Acauã (AC), Mundo- Novo (MN), and Obatã (OB) cultivars. After 2 WC (about 10 days) gs dropped from 0.15 to 0.01 mol m-2 s-1 in all cultivars changing the pattern of leaf gas exchange in subsequent WC. From 3 to 6 WC the cultivars showed high oscillations of water use efficiency or substomatal CO2 concentration (Ci) besides negative PN at the end of WC. After 3 WC, gs increased faster than PN after watering and Ci increased indicating some damage in photosynthetic machinery. It happened strongly in OB, which showed progressive reduction of PN after 3 WC and the lowest values of &#936; (-2.0 MPa) at the end of 6 WC. The survivorships for cultivars were 80% till 3 WC and 70% after 6 WC. The gas exchange pattern alteration could indicate the potential hardening of AC, MN and OB cultivars. After field plantation of hardened and control (without perivous hardening) Mundo-Novo and Obatã cultivars, with 180-days-old, it was observed significant (p<0.05) greater accumulation of leaf, stem and root biomass in hardened in control plants. Stem diameter, height and the number of leaf and branch were also higher (p<0.05) in previous hardened individuals. Greater differences in crown structure and biomass between control and hardened plants were observed mainly after the first period of low water availability (210 days under field conditions). The higher leaf number and leaf area in more branched crowns could carbon assimilation and grain production. For practical proposes, 3 WC before growing under field conditions are sufficient for changing consistently the leaf gas exchange pattern in 3 cultivars studied, keeping photosynthetic machinery free of damage and high survivorship. Previous hardening proportioned less interrupted vegetative development after transplantation under field conditions in both cultivars. / Plantas jovens de Coffea arabica enxertadas sobre C. canephora foram submetidas a 6 ciclos de suspensão de rega (CR) durante 35 dias. Cada CR foi acompanhado até que a fotossíntese líquida (PN) fosse próxima de zero ou até que o potencial hídrico foliar (&#936;) fosse próximo de -2.0 MPa nos cultivares Acauã (AC), Mundo-Novo (MN) e Obatã (OB). Após 2 CR (cerca de 10 dias) os valores médios de condutância estomática (gs) diminuíram de 0,15 para 0,01 mol m-2 s-1 em todos os cultivares, mudando o padrão de trocas gasosas nos subseqüentes CR. De 3 a 6 CR os cultivares apresentaram maiores oscilações da eficiência do uso da água e da concentração substomática de CO2, além de valores negativos de PN ao final dos CR. Após 3 CR ocorreu um aumento proporcionalmente maior em gs do que em PN após rega, com um aumento correspondente de Ci, indicando possíveis danos no aparato fotossintético. Este evento ocorreu de forma mais clara em OB, o qual demonstrou redução progressiva de PN após 3 CR e os menores valores de &#936; (-2,0 MPa) ao final de 6 CR. A sobrevivência dos cultivares foi de 80% em 3 CR e 70% em 6 CR. As alterações dos padrões de trocas gasosas nos cultivares AC, MN e OB podem indicar que os exemplares foram potencialmente rustificados. Após o plantio de MN e OB rustificados e controle (sem prévia rustificação) em campo, com 180 dias de idade, foi observado no tratamento rustificado valores significativamente (p<0,05) maiores do acúmulo de biomassa e do número de componentes estruturais da copa. A rustificação prévia proporcionou maior acumulo de biomassa de folhas, de caule e de raízes que nas plantas controle em ambos os cultivares. O diâmetro do caule, a altura, o número de folhas e o número de ramos também foram significativamente maiores (p<0,05) nos indivíduos previamente rustificados. As maiores diferenças da estrutura da copa e da biomassa acumulada entre plantas controle e rustificadas foram encontradas principalmente após o primeiro período de rezudida disponibilidade hídrica (210 dias em condições de campo). O maior número de folhas e a maior área foliar em copas mais ramificadas podem proporcionar um aumento da assimilação de carbono por planta e maior produção de grãos nas plantas rustificadas. Em termos práticos, 3 CR antes do crescimento em campo são suficientes para mudar consistentemente o padrão de trocas gasosas foliares nos 3 cultivares estudados, mantendo o aparato fotossintético livre de danos e proporcionando maior sobrevivência. A prática de rustificação prévia antes do plantio deve ser adotada nos cultivares estudados, pois o custo é reduzido e o desenvolvimento vegetativo inicial é fortemente favorecido após o transplante sob condições de campo.

Made available in DSpace on 2015-03-26T13:36:45Z (GMT). No. of bitstreams: 1 texto completo.pdf: 381629 bytes, checksum: ba2d77de1fafa6029bbd57e8ee35252d (MD5) Previous issue date: 2013-03-25 / Blast, caused by the fungus Pyricularia oryzae, has become an economically important disease in wheat. The objective of this study was to determine the effect of silicon (Si) on the photosynthetic gas exchange parameters (net CO 2 assimilation rate (A), stomatal conductance to water vapor (g s ), internal CO 2 concentration (C i ), and transpiration rate (E)) and chlorophyll fluorescence parameters (maximum quantum quenching (F v /F m and F v '/F m '), photochemical (q P ) and nonphotochemical (NPQ) quenching coefficients and electron transport rate (ETR)) in wheat plants grown in a nutrient solution containing 0 (-Si) or 2 mM Si (+Si) and inoculated with P. oryzae. The leaf Si concentration significantly increased for the +Si plants compared to the - Si plants and contributed to a decrease in the severity of blast symptoms. For the inoculated +Si plants, A was significantly higher at 72 (14%), 96 (12%) and 120 (58%) hours after inoculation (hai) when compared with their inoculated -Si counterparts. The g s and E were significantly higher by 60 and 42% at 120 hai for the inoculated +Si plants compared with the inoculated -Si plants, respectively. Significant differences between non-inoculated and inoculated plants were observed from 48 to 120 hai for A, g s and E and from 48 to 96 hai for C i . For the inoculated +Si plants, significant differences of F v /F m between the -Si and +Si treatments occurred at 48, 96 and 120 hai and at 72, 96 and 120 hai of F v '/F m '. The values of F v /F m significantly decreased by 1, 3 and 5% at 48, 96 and 120 hai, respectively, in the -Si plants compared with the +Si plants. Significant decreases of 10, 11 and 22% at 72, 96 and 120 hai, respectively, were observed for F v '/F m ' in the -Si plants when compared with the +Si plants. Significant differences between the non-inoculated and inoculated plants occurred from 48 to 120 hai for F v /F m and F v '/F m ', respectively. For the inoculated plants, significant differences between the -Si and +Si treatments occurred at 96 hai for both q P and NPQ and 72 and 120 hai for ETR. Significant differences between the non-inoculated and inoculated plants occurred at 120 hai for q P and at 96 and 120 hai for ETR. The total chlorophyll content (a + b) and the chlorophyll a/b ratio significantly decreased for the -Si plants compared with the +Si plants. The results of this study clearly demonstrate that the severity of blast symptoms decreased in wheat plants supplied with Si. These plants also exhibited improved gas exchange performance and less dysfunctions at the photochemical level. / A brusone, causada pelo fungo Pyricularia oryzae, tornou-se uma doença economicamente importante no trigo. Este estudo teve como objetivo determinar o efeito do silício (Si) sobre os parâmetros das trocas gasosas (taxa de assimilação líquida de CO 2 (A), condutância estomática ao vapor de água (g s ), a concentração interna de CO 2 (C i ) e taxa de transpiração (E)) e parâmetros de fluorescência da clorofila (eficiencia quântica máxima do fotosistema II (F v /F m e F v '/F m '), fotoquímica (q P ) e coeficiente de extinção não-fotoquimico (NPQ) e a taxa de transporte de eletrons (TTE)) em plantas de trigo crescendas em recipiente com solução nutritiva contendo 0 ou 2 mM de silício (Si) e inoculadas com P. oryzae. A concentração foliar de Si incrementou-se significativamente para plantas, contribuindo à dismunição da severidade da brusone. Para plantas inoculadas com +Si, A foi significativamente maior a 72 (14%), 96 (12%) e 120 (58%) hai do que em suas contrapartes inoculadas. A g s e E foram significativamente maiores em 60 e 42%, respectivamente, às 120 hai para as plantas inoculadas +Si em comparação com as plantas inoculadas -Si. Diferenças significativas entre as plantas inoculadas e não inoculadas ocorreu entre as 48 a 120 hai para A, g s e E e entre as 48 a 96 hai para C i . Para as plantas inoculadas +Si, diferenças significativas para F v /F m entre os tratamentos Si e +Si foram encontradas às 48, 96 e 120 dai e às 72, 96 e 120 hai para F v '/ F m '. Os valores de F v /F m diminuiram significativamente em 1, 3 e 5%, respectivamente, aos 48, 96 e 120 hai para plantas -Si, em comparação com as plantas de +Si. Reduções significativas de 10, 11 e 22%, respectivamente, às 72, 96 e 120 hai para F v '/F m ' ocorreu para as plantas -Si, em comparação com as plantas +Si. Diferenças significativas entre as plantas inoculadas e não inoculadas ocorreu às 48 a 120 hai para F v /F m e F v '/F m '. Para as plantas inoculadas, diferenças significativas entre os tratamentos -Si e +Si ocorreu apenas às 96 hai para ambos q P e NPQ e às 72 e 120 hai para TTE. Diferenças significativas entre as plantas inoculadas e não inoculadas só ocorreu em 120 hai para q P e às 96 e 120 hai para TTE. A concentração de clorofila total (a + b), e a razão de clorofil a/b diminuiu significativamente para as plantas -Si, em comparação com as plantas de +Si. Os resultados deste estudo demonstraram claramente que a severidade da brusone diminuiu em plantas de trigo supridas com Si em paralelo a um melhor desempenho das trocas gasosas e menores perdas disfuncionais ao nível fotoquímico.

Acompanha: Manual de instruções do jogo de tabuleiro ludo da fotossíntese / Os mecanismos bioquímicos da Fotossíntese estão entre os conteúdos indicados tanto por professores quanto por estudantes de ensino médio como um tema que traz dificuldades no seu ensino-aprendizagem. O presente trabalho procura auxiliar neste processo, sendo uma alternativa para o ensino da Fotossíntese, de maneira lúdica, sem deixar de lado a relevância dos conceitos científicos. A produção de um jogo didático intitulado Ludo da Fotossíntese busca ser uma ferramenta que auxilie na compreensão dos mecanismos bioquímicos da Fotossíntese. O jogo foi elaborado com base na literatura referente a jogos didáticos e ao conteúdo de Biologia, considerando-se também os materiais didáticos já existentes disponíveis sobre o tema. Os jogos didáticos proporcionam modos diferenciados de aprendizagem de conceitos. Devido a seu aspecto lúdico, constituem uma motivação adicional para que os estudantes busquem o conhecimento. Proporcionam, ainda, a socialização, melhorando as condições de ensino-aprendizagem e momentos de afetividade e cooperação. Sob o aspecto pedagógico foi utilizado durante o planejamento do jogo e no processo de validação, como eixo norteador, o conceito de Alfabetização Científica. Como resultados podem se elencar que os estudantes demonstraram interesse pelos estudos científicos, entusiasmo ao jogar, empatia com os demais colegas durante o jogo, espírito esportivo diante das dificuldades e interesse em repetir a atividade. Os resultados da aplicação do jogo no contexto da sala de aula indicam sua real possibilidade de utilização. / These biochemical mechanisms lie behind common issues associated with difficulties in teaching and learning certain fundamental processes in biology classes at secondary level. This work seeks to present an alternative approach to the teaching of photosynthesis, in a playful manner, without ignoring the relevance of key scientific concepts. This work aims at the production of an educational game entitled Photosynthesis Ludo. It refers to a board game as a pedagogical tool in teaching of biochemical mechanisms related to photosynthesis. The game is based on the literature regarding educational games and biology contents, and takes into account other available teaching materials on the subject. Educational games constitute different and powerful ways in science concepts learning for they provide an additional motivation for students. They also stimulate socialization and cooperation, together with improving teaching and learning conditions. The concept of Scientific Literacy was taken as a guideline for both game planning and validation. Our results indicate the feasibility applying the game in the context of biology classes in Brazilian public schools. The results can be to list the students showed an interest in science education, enthusiasm to play, empathy with other colleagues during the game, sportsmanship face of difficulties and interest in repeating the activity. The results of the application of the game in the context of the classroom indicate a real possibility of use.

Os efeitos da aplicação foliar de fósforo (Pi) na condutância estomática (gs) e na fotossíntese (A), foram avaliados em genótipos de feijoeiro, A320, Carioca e Ouro Negro, cultivados em potes numa casa de vegetação. Este estudo foi feito durante o dia após a aplicação foliar de 10 g de Pi L-1, em plantas hidratadas, e durante um período de deficiência hídrica iniciada dois ou cinco dias após a aplicação. Durante o dia após a aplicação de Pi, não foi observado nenhuma diferença, entre os tratamentos com e sem Pi, nas trocas gasosas de ambas as cultivares. Durante a desidratação, a aplicação de Pi não causou aumento de gs, mas causou aumento de A, nas medições às 0900, 1200 e 1500 horas, nas cultivares (Carioca e Ouro Negro), mas com um efeito maior na cultivar Ouro Negro, principalmente às 1200 horas. A eficiência intrínseca do uso da água (EIUA) também foi superior nas plantas com suprimento foliar de Pi. Quanto aos componentes da produção, a aplicação de Pi causou aumento do número de vagens das plantas da cultivar Ouro Negro, sob desidratação. Portanto, a aplicação de Pi foliar pode reduzir o efeito de uma desidratação quando aplicado dois dias antes da suspensão da irrigação. Além disso, o potencial fotossintético (Ac) de Ouro Negro com Pi foi superior ao de A320, com e sem Pi, na seca máxima, e ao A320 sem Pi, na reidratação. A dissipação térmica, não fotoquímica (NPQ), do genótipo A320 sem Pi foi maior que com Pi e que a do Ouro Negro, com e sem Pi, na reidratação, provavelmente devido aos menores valores de A neste tratamento sem Pi. O uso de fosfato de amônio substituindo a uréia ou o sulfato de amônio, que são aplicados aos 25 DAE, é recomendável. / The effects of foliar Pi supplying (Pi) on stomatal conductance (gs) and photosynthesis (A) were measured in genotypes, A320, Carioca and Ouro Negro, grown under greenhouse condition. Measurements of gs and A were taken one day after Pi application (10 g L-1) on well-irrigated plants, and during drought stress period beginning two or five days after Pi supplying. During the day after Pi application, it was not observed any difference on gas exchange of genotypes (Carioca and Ouro Negro) due to the treatments with and without Pi. During water stress, the Pi supplying did not cause increase of gs, however, caused increase of A at 0900, 1200 and 1500 h in both genotypes. This effect was higher when considered Ouro Negro at 1200 h. The intrinsic water use efficiency (IWUE) was also increased in Pi-supplied plants. The Pi supplying caused increase on pod number of Ouro Negro plants under water deficit. These results suggest that the foliar Pi application may reduce the effect of water deficit on photosynthesis when supplied two days before the water withholding. In addition, the O2 evolution (Ac) on Ouro negro with extra Pi was higher than for A320, with or without Pi, at the last day of the mild water deficit, and it was higher than A 320 with extra Pi at rehydration. The non-photosynthetic quenching (NPQ), was higher for A320 without Pi at recovery, probably due to the smaller values of A at this treatment. The use of ammonium phosphate, instead of urea or ammonium sulphate to be applied as usual 25 DAS, is recommended.

Photosynthesis involves the absorption of photons by light-harvesting pigments and the subsequent transfer of excitation from the absorption centre to the reaction centre. This highly efficient phenomenon of excitation transfer has traditionally been explained by the Forster mechanism of incoherent hopping of excitation from one chromophore to another. Recently 2D electronic spectroscopic evidences were gathered by Fleming and coworkers on the photosynthetic Fenna-Matthews-Olson (FMO) complex in green sulfur bacteria [1]. Subsequent simulation studies by the same group [2] led to the proposition of a quantum-mechanical, coherent, wave-like transfer of excitation among the chromophores. However, Fleming's conclusions regarding retention of coherence appeared surprising because, the complex would interact with the numerous degrees of freedom of the protein scaffold surrounding it, leading to decoherence, which is expected to be rapid. Thus, we were interested in proposing an analytical treatment to rationalize the excitation transfer. Traditional approaches employed for studying excitation energy transfer involve the master equation techniques where the system-bath coupling is perturbative and is truncated after a few orders. It is important to note that the system-bath coupling causes both decoherence and population relaxation. Such a perturbative approximation is difficult to justify for the photosystem, as the system-bath coupling and the interchromophoric electronic coupling have comparable values. Also, these treatments are largely numerical studies and demand involved calculations. Thus, exact calculations for such a system (7-level) are very difficult. Consequently, we were interested in developing an analytical approach where the coupling is treated as non-perturbative. We devised a novel analytical treatment which employs a unitary transformation analogous to the one used for the theory of nonadiabatic effects in chemical reactions [3]. Our treatment rests on an adiabatic basis which are eigenstates calculated at each nuclear position (i.e. at each configuration of the bath) bearing a parametric dependence in Qi, where Qi denotes the shift of the exciton at site `i' due to the environment. The treatment is justified because in the case of coherent transfer, the excitation would travel mostly amongst the adiabatic states and the effects of non-adiabaticity are small. We observed that the system-bath coupling, after the unitary transformation, could be decoupled at the lowest order into two parts: a) an adiabatic contribution, which accounts solely for decoherence (this is evaluated almost exactly in our approach) and b) a non-adiabatic contribution which accounts for population relaxation from one adiabatic state to another (treated by a Markovian master equation). When we applied our technique to the FMO complex, our prediction for population evolution at the chromophores showed excellent correspondence with those obtained by Nalbach and coworkers using path-integral calculations [4], which are exact. These were calculations where the environment was modelled using a Drude spectral density. Our method allowed the calculations to be readily performed for different temperatures as well. It should be specifically emphasized that, unlike the involved and cumbersome path-integral calculations by Nalbach and coworkers [4] or the hierarchical equation calculations by Ishizaki et al. [2], our method is simple, easy to apply and computationally expedient. Further it became evident that the ultra-efficiency of energy transfer in photosynthetic complexes is not completely captured by coherence alone but is the result of an interplay of coherence and the dissipative influence of the environment (also known as ENAQT or Environment Assisted Quantum Transport [5]). An added advantage of our analytical treatment was the flexibility it offered. Thus, we could use our formalism to perform expedient analyses on the behavior of the system under various conditions. For example, we may wish to evaluate the consequences of introducing correlations among the bath degrees of freedom on the efficiency of transfer to the reaction centre. To this end, we applied our formalism by introducing correlations among the bath degrees of freedom and then by introducing anticorrelations among the bath degrees of freedom. The conclusions were interesting, for they suggested that the efficiency of transfer to the reaction centre was enhanced by the presence of anti-correlations, when compared with an uncorrelated bath. Uncorrelated baths, in turn, had a higher efficiency of energy transfer than correlated baths [6]. Thus, the population evolution is fastest for the anti-correlated bath, followed by the uncorrelated bath and is slowest for the correlated bath. Similar conclusions have been reached at by Tiwari et al. [7]. We could also extend the formalism for studying the system under different spectral densities for the environment, apart from just the Drude spectral density which is popularly used in literature associated with FMO calculations. For instance, the FMO system could be analyzed for the Adolphs-Renger spectral density [3, 8]. Once again our results showed excellent agreement with those reported by Nalbach. We also analyzed the FMO system under the spectral density proposed by Kleinekathofer and coworkers [9]. It was found that these latter spectral densities had more profound participation from the environment, therefore coherences were destroyed more effectively and population relaxation was faster. The excitation transfer to the final site (site closest to the reaction centre in the FMO complex) was found to be faster for the Adolphs and Renger spectral density and the spectral density proposed by Kleinekathofer and coworkers, when compared to the Drude spectral density. Also, the excitation transfer was fastest when we modelled the environment using the Kleinekathofer spectral density. This reinforced the previous conclusions that the dissipative effects of the environment promote a faster energy transport. Being an almost analytical approach, our technique could be applied to systems with larger number of levels as well. A good example of such a case is the MEH-PPV polymer. 2D electronic-spectroscopic experiments performed on this polymer in solution speculate that the excitation energy transfer might be coherent even at physiological temperatures [10]. A prototype for studying this system might be a conjugated polymer with around 80-100 chromophores. Linewidths and Lineshapes in the vicinity of Graphene It has been reported that a vibrating dipole may de-excite by transferring energy non-radiatively to a neighboring metal surface [11]. It is also understood that due to its delocalized pi-cloud, graphene has a continuum of energy states and can behave like a metal sheet and accept energies. Thus, we proposed that if a vibrationally excited dipole de-excites in the vicinity of a graphene sheet, graphene may get electronically excited and thus serve as an effective quencher for such vibrational excitations. Depending on the distance of the dipole from the graphene sheet, the transfer might be intense enough to be spectroscopically probed. We have investigated the rate of such an energy transfer. We use the Dirac cone approximation for graphene, as this enables us to obtain analyt-ical results. The Fermi Golden rule was used to evaluate the rate of energy transfer from the excited dipole to the graphene sheet [12]. The calculations were performed for both the instances: a) energy transfer from a dipole to undoped graphene and, b) energy trans-fer from a dipole to doped graphene. For undoped graphene, the carrier (electron) charge density in the conduction band is zero and we would only have transitions from the valence band to the conduction band. As a consequence of absence of carrier charge density in CB (conduction band), the screening of Coulombic interactions in the graphene plane is ineffective. Thus, one could use the non-interacting polarizability for undoped graphene in the rate expression [13]. However, when we consider the case of doped graphene where EF is shifted upwards into CB, the conduction band electrons will contribute to screening. In this case, we have two sets of transitions: a) from ki in VB (valence band) to kf in CB and b) ki in CB to kf in CB, where ki and kf are the wavevectors which correspond to the initial and final electronic states in graphene. So we have used the polarizability propagator in the random phase approximation [14] to calculate the rate following the approach of [13]. It is also known that the imaginary part of the frequency domain dipole-dipole corre-lation function is a measure of the lineshape [15]. We were, thus, interested in evaluating the lineshape for these transitions. For evaluating the correlation function, we used the partitioning technique developed by L•owdin [16] and subsequently extracted the lineshape from its imaginary part. Using this method, we calculated lineshape for the vibrational excitation of CO molecule in the vicinity of an undoped graphene lattice. The linewidth for this system also was obtained. It could be seen that the vibrational linewidth for 1 CO in the vicinity (5 A) of undoped graphene (EF = 0:00eV ) is small (0:012 cm ) but could be observed experimentally. The lineshape calculations were also extended to cases where it is possible to have atomic transitions by placing an electronically excited atom in the vicinity of the graphene sheet. We considered the following two cases: a) 3p ! 2s transition in hydrogen atom, at a distance of 12 A from the graphene sheet and, b) 4p ! 3s transition in hydrogen atom, at a distance of 20 A from the graphene sheet. The linewidths for atomic transitions could be easily probed in these cases ( 55 cm 1 for 3p ! 2s and 56 cm 1 for 4p ! 3s). In the preceding calculations, the transi-tion dipoles were considered perpendicular to the graphene surface. It is worthwhile to note that if the transition dipoles are considered parallel to the graphene surface, the respective linewidths would be half of those obtained for the case where the transition dipoles are perpendicular. Another interesting possibility would be to consider a lanthanide metal complex placed within a few nanometers from graphene. Lanthanides are known to have sharp f-f transitions [17] and consequently, one could easily observe the effects of broadening due to energy transfer to the electronic system of graphene. Energy Eigenmodes for arrays of Metal Nanoparticles In the final part of the thesis we consider organized assemblies of metal nanoparti-cles, specifically helical and cylindrical assemblies and investigate the plasmonic excitation transfer across these assemblies. These were motivated by recent studies which reported growth of chiral asymmetric assemblies of nanoparticles on D and L- isomers of dipheny-lalanine peptide nanotubes [18]. The plasmons in the helical/cylindrical assemblies are expected to couple with each other via electromagnetic interactions. We construct the Hamiltonian for such systems and evaluate the eigenmodes and energies pertaining to these modes in the wave vector space. We also perform calculations for the group velocity for each eigenmode as this gives us an idea of which eigenmode transports excitation the fastest.

Biogeochemical processes of reefs have been studied for over fifty years, however, information is still lacking on several fundamental reef processes. This lack of information has been limited essentially by techniques that cannot repeatedly sample large spatial areas. These limitations can be reduced with the use of an optical model to estimate biogeochemical processes. This project applied Monteith's light-use efficiency model to coral reef communities for determining photosynthetic and calcification efficiency of light. Gross primary production and net calcification were pooled from the peer-reviewed literature to calculate efficiency. Process efficiency was then compared across functional types of reef communities (i.e., coral, algae/seagrasses, mixed, and sand), and by year, location, season, and depth. Photosynthetic efficiency was calculated from 19 studies, showing an average of 0.039 mol O2 mol-1 photons. Photosynthetic efficiency differed significantly for mixed communities between studies, and for algae/seagrass communities among depths. Calcification efficiency averaged at 0.007 mol CaCO3 mol-1 photons. Significant differences were found in calcification efficiency of algae/seagrasses and mixed reef communities among studies and localities. Additionally, calcification efficiency of algae/seagrasses varied significantly in accordance with depth. Future use of the light-use efficiency model will require determining the efficiency of each functional type to estimate gross production and calcification. Additionally, further investigation of the light-use efficiency model will require long-term measurements of APAR, which is the fraction of incident light absorbed, and the incorporation of environmental parameters that reduce efficiency.

De fortes illuminations peuvent être dommageables voire même létales pour les organismes photosynthétiques. Une des stratégies utilisées pour se protéger de tels effets délétères consiste à augmenter la dissipation thermique de l’énergie absorbée en excès au niveau des antennes. Chez les cyanobactéries une protéine photo-active, l’Orange Carotenoid Protein (OCP), contrôle ce processus. Une fois photo-activée l’OCP interagit avec le coeur des phycobilisomes (PBs, les antennes collectrices majoritaires chez les cyanobactéries) et déclenche le mécanisme, entrainant à la fois une baisse de l’énergie parvenant aux photosystèmes et une diminution de la fluorescence des PBs. L’énergie absorbée en excès est dissipée sous forme de chaleur. Pour que les PBs regagnent leur pleine capacité de transfert, une autre protéine nommée Fluorescence Recovery Protein (FRP) est requise. La FRP accélère la désactivation de l’OCP. Dans ce manuscrit, je vais présenter ma contribution à la compréhension du mécanisme de photo-protection lié à l’OCP.J’ai continué la caractérisation de la FRP chez Synechocystis PCC 6803, organisme modèle utilisé dans nos études. J’ai montré que la FRP de Synechocystis est plus courte que ce qui est indiqué dans Cyanobase, commençant en fait à la méthionine 26. Mes résultats ont aussi révélé que la photo-protection n’a lieu que lorsque le ratio OCP/FRP est élevé.Le plus grand aboutissement de ma thèse a été la reconstitution in vitro du mécanisme de photo-protection lié à l’OCP en utilisant de l’OCP, de la FRP et des PBs isolés. J’ai montré que la lumière est requise uniquement pour la photo-activation de l’OCP et que l’attachement de l’OCP au PB ne demande aucune illumination. Ce n’est qu’une fois photo-activée que l’OCP peut interagir avec le PB et entrainer la diminution de fluorescence (quenching). En se basant sur les résultats obtenus in vitro nous avons proposé un modèle moléculaire pour le mécanisme de photo-protection lié à l’OCP. Le système de reconstitution in vitro a été utilisé pour évaluer l’importance d’un pont salin conservé (Arg155-Glu244) entre les deux domaines de l’OCP et a révélé que celui-ci stabilise la forme inactive de l’OCP. La photo-activation entraine rupture du pont salin, l’Arg155 étant ensuite impliquée dans l’interaction entre OCP et PB. Le site d’attachement de l’OCP au coeur du PB a aussi été étudié en utilisant le système in vitro. Nos résultats ont montré que les émetteurs terminaux du PB ne sont pas requis et que le site primaire de quenching est un trimère d’allophycocyanine émettant à 660nm. Enfin nous avons étudié les propriétés des états excités du caroténoïde dans l’OCP photo-activée, montrant qu’un de ces états a un caractère de transfert de charge très prononcé et peut avoir un rôle principal dans la dissipation de l’énergie. Nos résultats suggèrent fortement que non seulement l’OCP induit dissipation de l’énergie absorbée sous forme de chaleur mais aussi que l’OCP agit directement comme dissipateur d’énergie. / Strong light can cause damage and be lethal for photosynthetic organisms. An increase of thermal dissipation of excess absorbed energy at the level of photosynthetic antenna is one of the processes protecting against deleterious effects of light. In cyanobacteria, a soluble photoactive carotenoid binding protein, Orange Carotenoid Protein (OCP) mediates this process. The photoactivated OCP by interacting with the core of phycobilisome (PB; the major photosynthetic antenna of cyanobacteria) triggers the photoprotective mechanism, which decreases the energy arriving at the reaction centres and PSII fluorescence. The excess energy is dissipated as harmless heat. To regain full PB capacity in low light intensities, theFluorescence Recovery Protein (FRP) is required. FRP accelerates the deactivation of OCP.In this work, I present my input in the understanding of the mechanism underlying the OCPrelated photoprotection. I further characterized the FRP of Synechocystis PCC6803, the model organism in our studies. I established that the Synechocystis FRP is shorter than what it was proposed in Cyanobase and it begins at Met26. Our results also revealed the great importance of a high OCP to FRP ratio for existence of photoprotection. The most remarkable achievement of this thesis is the in vitro reconstitution of the OCPrelated mechanism using isolated OCP, PB and FRP. I demonstrated that light is only needed for OCP photoactivation but OCP binding to PB is light independent. Only the photoactivated OCP is able to bind the PB and quench all its fluorescence. Based on our in vitro experiments we proposed a molecular model of OCP-related photoprotection. The in vitro reconstituted system was applied to examine the importance of a conserved salt bridge (Arg155-Glu244) between the two domains of OCP and showed that this salt bridge stabilises the inactive form of OCP. During photoactivation this salt bridge is broken and Arg155 is involved in the interaction between the OCP and the PB. The site of OCP binding in the core of a PB wasalso investigated with the in vitro reconstituted system. Our results demonstrated that the terminal energy emitters of the PB are not needed and that the first site of fluorescence quenching is an APC trimer emitting at 660 nm. Finally, we characterised the properties of excited states of the carotenoid in the photoactivated OCP showing that one of these states presents a very pronounced charge transfer character that likely has a principal role in energy dissipation. Our results strongly suggested that the OCP not only induces thermal energy dissipation but also acts as the energy dissipator.

L’objectif de ce travail était de caractériser la variabilité saisonnière des échanges gazeux des arbres de la canopée en forêt tropicale humide guyanaise confrontés à des saisons sèches.L’étude s’est orientée sur la mesure des flux de carbone et d’eau au cours des saisons sèches dans deux habitats contrastés du point de vue hydrique, afin de préciser leur sensibilité et réponse à la sècheresse. Nos résultats montrent qu’une proportion non négligeable d’arbres ne subit pas de sécheresse marquée en saison sèche, malgré la forte diminution de la teneur en eau du sol en surface. Nous faisons l’hypothèse que ces arbres possèdent alors des racines en profondeur qui leur permettent d’accéder aux horizons qui restent humides malgré la faible pluviométrie. Durant les longues saisons sèches, nous observons une diminution de l’assimilation nette de CO2 foliaire, de l’efflux de CO2 des troncs ou de la densité de flux de sève, et dans une moindre mesure de la respiration foliaire. Cette diminution concerne un nombre plus important d’arbres, quand l’intensité de la sécheresse est plus forte (2008 par rapport à 2007). Néanmoins, de grandes différences de réponse à la sècheresse du sol ont été observées, suggérant des sensibilités et des mécanismes de réponse différents entre ces arbres. En habitat de bas-fond, nous montrons une plus faible diminution des flux carbonés et hydriques en saison sèche, suggérant un accès pour ces arbres aux horizons humides, proches de la nappe phréatique. Par ailleurs, nos résultats suggèrent pour certains arbres un effet négatif des conditions d’anoxie sur ces flux en saison des pluies.Si l’accentuation de l’intensité des saisons sèches en forêt tropicale humide Amazonienne se confirme, comme suggérée par les modèles climatiques, ce travail suggère des modifications rapides de la composition spécifique des forêts, au profit des espèces plus résistantes aux contraintes hydriques / The aim of this work was to characterize the seasonal variations in leaf and trunk gas exchange of tropical rainforest canopy trees exposed to dry seasons. This study focused on measuring gas exchange (CO2 and H2O) at the leaf and trunk level during dry seasons in a Terra firme forest and in a seasonally flooded forest in order to specify their sensitivity and response to drought.Our results showed that part of the studied trees do not encounter a large reduction in soil water content during dry seasons, suggesting that they display deep rooting systems.During long dry periods, we recorded a decrease in leaf photosynthesis, trunk CO2 efflux or sap flow density, and foliar respiration to a lesser extent, for a majority of the trees. Nevertheless, large differences among trees in their response to these conditions were observed, suggesting distinct sensitivities and response to soil drought among trees. Furthermore, these variations were greatest when soil drought was highest (2008 as compared to 2007).In seasonally flooded forest, the decrease in gas exchange was less, suggesting that these trees do have access to wet layers during the dry season, close to the groundwater. However, during wet seasons, we observed a negative effect of anoxia for some trees, whereas others did not display any response, suggesting large differences in tolerance to anoxia among trees abundant in these seasonally flooded forests.We conclude that would seasonal soil droughts increase over the next decades, large vegetation changes might occur because of the large differences among trees in their functional response to soil drought conditions

Integrate the NGSS and CCSS ELA by using a cycle of science and ELA activities to help students learn about the flow of energy between photosynthesis and cellular respiration.

Plant invertases are a class of proteins that have enzymatic function in cleaving sucrose to fructose and glucose. Cell wall invertase, located on the exterior of the cell wall of plant cells, plays a key role in the unloading of sucrose from the apoplast to the sink tissues. Cell wall invertase interacts with an inhibitor, cell wall invertase inhibitor, post-transcriptionally to regulate its activity. The inhibitor is constitutively expressed in pollen development, early developing seeds, and senescing leaves: indicative of sucrose allocation being a limiting factor at these stages of development. We introduced algal bicarbonate transporters LCIA/CCP1 to Camelina sativa for the purpose of increasing photosynthetic capacity. The bicarbonate transporters concentrate CO2 at RuBisCO by pumping CO2 in the form of bicarbonate through the membrane, then converting it back to CO2 at RuBisCO, increasing CO2 concentration. Results from these plants have shown an increase in seed number, but not seed mass, along with a faster rate of maturity and senescence. This is indicative of acclimation to high CO2 conditions, resulting from insertion of the bicarbonate transporters. RNA sequencing was performed and a putative invertase inhibitor was recognized as being expressed in the transgenic C. sativa but not in the wild type. Our strategy is to knock out two invertase inhibitors using induced RNA silencing, dramatically altering sucrose allocation into developing seeds and resulting in an increase in seed biomass. It is the aim of this research to increase the biomass of C. sativa seeds in order to increase its effectiveness as an agent to create sustainable biofuels.