Submitted by DENISE APARECIDA CHICONATO (denise.ac@hotmail.com) on 2016-02-04T14:10:02Z No. of bitstreams: 1 Tese_Denise_Aparecida_Chiconato.pdf: 1322746 bytes, checksum: 5a673f4bca29c82501e188fb0ce8d28d (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-02-05T12:07:51Z (GMT) No. of bitstreams: 1 chiconato_da_dr_jabo.pdf: 1322746 bytes, checksum: 5a673f4bca29c82501e188fb0ce8d28d (MD5) / Made available in DSpace on 2016-02-05T12:07:51Z (GMT). No. of bitstreams: 1 chiconato_da_dr_jabo.pdf: 1322746 bytes, checksum: 5a673f4bca29c82501e188fb0ce8d28d (MD5) Previous issue date: 2016-01-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A cana-de-açúcar é uma cultura mundialmente importante. O Brasil é o maior produtor mundial de cana-de-açúcar e se destaca na comercialização e exportação de açúcar e etanol originados a partir desta cultura. Os diferentes estresses abióticos alteram negativamente o desenvolvimento das plantas e, entre os estresses, a salinidade de solos se apresenta pela grave redução de produtividade, sendo o principal fator estressante em regiões de clima árido e semiárido. Este trabalho objetivou verificar os efeitos do NaCl sobre o desenvolvimento de plantas jovens de cana-de-açúcar, cultivares SP 81-3250 e IAC 87-3396, mediante o estudo de variáveis fisiológicas-bioquímicas: (I) os osmoprotetores prolina, glicina betaína e sacarose, (II) a ocorrência de alterações nutricionais pela relação Na+/K+, (III) a peroxidação lipídica (IV) a influência do NaCl na atividade da enzima redutase do nitrato; (V) o efeito do estresse salino nas trocas gasosas; (VI) o crescimento de parte aérea e raízes das diferentes cultivares de cana-de-açúcar sob estresse salino. Para tanto, foram utilizadas quatro concentrações de NaCl (0, 40, 80 e 160 mM) e realizadas as seguintes avaliações: teores de Na+ e K+ nas folhas e raízes, os osmólitos compatíveis prolina, glicina betaína e sacarose, potencial hídrico, a peroxidação lipídica, atividade da enzima redutase do nitrato, trocas gasosas, clorofilas totais, rendimento quântico do FSII e crescimento de parte aérea e raiz aos 15 e 30 dias de desenvolvimento após aplicação do estresse. A partir dos resultados, observou-se maior suscetibilidade das plantas da cv. IAC 87-3396 pelo maior acúmulo de Na+ e relação Na+/K+, maior peroxidação lipídica pelo acúmulo de MDA e maior efeito negativo sobre as trocas gasosas. Ambas as cultivares apresentaram acúmulo de prolina sob estresse, porém, plantas da cv. SP 81-3250 apresentaram, além de mais rápido acúmulo deste aminoácido, menor peroxidação lipídica e crescimento superior. Sob estresse salino severo a cv. IAC 87-3396 apresenta maior suscetibilidade. / Sugarcane is a globally important crop. Brazil is the largest producer of sugarcane and stands out in the marketing and exportation of sugar and ethanol derived from this culture. The various abiotic stresses adversely change plant growth and between the stresses, soil salinity is presented by the severe reduction in productivity, it is the main stressor in arid and semi-arid climates. This study aimed to verify the effects of NaCl on the development of sugarcane young plants, SP 81- 3250 and IAC 87-3396 cultivars, through the study of physiological-biochemical variables: (I) the osmoprotectors proline, glycine betaine and sucrose, (II) the occurrence of nutritional changes the ratio Na+/K+ (III) lipid peroxidation (IV) effect of NaCl in the activity of nitrate reductase enzyme; (V) the effect of salt stress on gas exchange; (VI) the growth of shoots and roots of the sugarcane cultivars under salt stress. Thus, it was used four concentrations of NaCl (0, 40, 80 and 160 mM) and made the following assessments: Na+ and K+ accumulation in the leaves and roots, compatible osmolytes: proline, glycine betaine and sucrose, water potential, peroxidation lipid, activity of nitrate reductase enzyme, gas exchange, total chlorophyll, quantum yield of PSII and shoot and root growth at 15 and 30 days of development after stress application. The results showed higher susceptibility of the cv. IAC 87-3396 by higher accumulation of Na+ and Na+/K+ ratio, increase in lipid peroxidation by MDA accumulation and greater negative effect on gas exchange. Both cultivars showed proline accumulation under stress, however, the cv. SP 81- 3250 showed in addition faster accumulation of this amino acid, reduced lipid peroxidation and higher growth. Under severe salt stress cv. IAC 87-3396 is more susceptible.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis quantifies the net change of CO2 (NEE) in an irrigated rice crop cultivation in RS (Brazil). The research is part of the project CT-HIDRO, which presents as main purpose the description of surface conditions for different ecosystems in the country. Data were gathered during the cultivation period, from October 2003 to March 2004. During this time, the average air temperature and the incident radiation were suitable for the development of the culture in such an area. The turbulent flows, calculated by the eddy covariance method, overestimated the NEE value, probably due to the low estimate of breathing tax, because, during some night-times, sensor registered little turbulence. Moreover, other factor could have interfered in the result of the flows, for instance, the time in which the flows are calculated. The Webb correction was applied in the curve of NEE, and a value smaller than 1% was found. Such result didn't modify the previous result significantly. The behavior of CO2 flow during the whole analyzed period showed a maximum of -0,47mgCO2 m−2 s −1 in January 2004, what demonstrates the largest absorption of CO2 from the atmosphere by the plant during the day and a smaller liberation at night, due to the development phase in which the plant is. In this case, the Webb correction was also little emphasized, not interfering in the obtained result. The curves that demonstrate the three phases of development of the rice presented a larger absorption of CO 2 during the reproductive phase. The behavior of the flow of CO 2 showed a negative flow during the day, when the plant absorbs CO2 from the atmosphere, and a positive flow during the night, when the inverse process occurs, what was waited for. The latent heat flow presented larger diary average values from January to February, always with positive values, consequence of the rice crop irrigation. Two days with high values of flow of latent heat were obtained, what motivated the analysis of the energy balance. The closing of the energy balance was not reached in both days. A possible reason for that could be the low estimate of flows when the eddy covariance method was applied. / Este trabalho quantifica a troca líquida de CO2 (NEE) em uma área de cultivo de arroz irrigado no RS, como parte do projeto CT-HIDRO, projeto este que tem como finalidade descrever condições de superfície para diferentes ecossistemas do país. Os dados utilizados foram coletados durante o período de cultivo, entre outubro de 2003 e março de 2004. Neste período a temperatura média do ar e a radiação incidente são adequadas para o desenvolvimento da cultura nesta região. Os fluxos turbulentos, calculados pelo método de covariância de vórtices (eddy covariance), superestimaram o valor da NEE, provavelmente devido, a subestimativa da taxa de respiração, pois em alguns períodos noturnos os sensores registraram pouca turbulência. Além disso, outro fator que pode interferir no resultado dos fluxos, como por exemplo, o intervalo em que os fluxos são calculados. Foi aplicada a correção de Webb na curva de NEE e encontrou-se um valor menor que 1%, fato este que não modificou significativamente o resultado encontrado. O comportamento do fluxo de CO 2 durante todo o período analisado, mostrou um pico de -0,47mgCO2 m−2 s −1 , em janeiro de 2004, o que demonstra a maior captura de CO2 da atmosfera pela planta durante o dia e uma menor liberação à noite, devido a fase de desenvolvimento em que a planta se encontra. Neste caso, a correção de Webb também foi pouco acentuada, não interferindo no resultado obtido. As curvas que demonstram as três fases de desenvolvimento do arroz mostraram claramente uma maior absorção de CO 2 durante a fase reprodutiva. O comportamento do fluxo de CO 2 mostra um fluxo negativo durante à dia, quando a planta absorve CO2 da atmosfera e um fluxo positivo durante à noite quando ocorre o processo inverso, o que era esperado. O fluxo de calor latente apresentou maiores valores médios diários entre os meses de janeiro e fevereiro, apresentando sempre valores positivos, conseqüência da irrigação do campo de arroz. Obtivemos dois dias com valores elevados de fluxo de calor latente, o que fez com que analisássemos o balanço de energia. O fechamento do balanço de energia não foi alcançado em ambos os dias. Uma possível razão para isto pode ser o devido à subestimativa dos fluxos quando aplicado o método de covariância de vórtices.

Made available in DSpace on 2014-06-11T19:32:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-19Bitstream added on 2014-06-13T20:23:45Z : No. of bitstreams: 1 david_efs_dr_botfca.pdf: 686866 bytes, checksum: add99507812561505444aeadcdf4bfbf (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo do trabalho foi avaliar o desenvolvimento, as trocas gasosas, o rendimento e a composição do óleo essencial de Mentha piperita L. cultivada em solução nutritiva no2 Hoagland & Arnon (1950) com variação dos níveis de N, P, K e Mg. Assim, os tratamentos com 50% de N, P, K e 25% de Mg continha 94,0/15,5/107,5/12,15, com 50% de N, P, K e Mg continha 94,0/15,5/107,5/24,3, com 65% de N, 50% de P, 25% de K e 100% de Mg, continha 124,0/15,5/53,6/48,6 e com solução completa continha 189,0/31,0/214,5/48,6 mg L-1 de N/P/K/Mg. As variáveis avaliadas foram comprimento de parte aérea, massas secas dos diferentes órgãos, área foliar, razão de área foliar (RAF), área foliar específica (AFE), taxa assimilatória líquida (TAL), taxa de crescimento relativo (TCR), razão de massa foliar (RMF), distribuição de massa seca para os diferentes órgãos, assimilação de CO2 (A), transpiração (E), concentração intercelular de CO2 (Ci), condutância estomática (gs), resistência estomática (S%), ponto de compensação (PtCe), eficiência de carboxilação da rubisco, rendimento e composição do óleo essencial e teores de macro e micronutrientes em lâminas foliares e caules e pecíolos. Os resultados obtidos foram avaliados estatisticamente por análise de variância do fatorial e análise de regressão polinomial, utilizando-se o programa computacional SAS, com o nível de 5% de significância. As variáveis, comprimento, área foliar, massa seca dos diversos órgãos e total apresentaram variância heterogênea entre tratamentos, o que levou a utilização de análise de regressão ponderada e transformação logarítmica dos resultados para a análise de variância. Os resultados dos 18 índices fisiológicos, foram estimados pelo programa ANACRES. As plantas cultivadas com a solução nutritiva completa apresentaram maior TAL até 35 dias após transplante... / The aim of this stundy was to evaluate the development, gas exchange, yield and composition of essential oil of Mentha piperita L. cultivated in no 2 Hoagland & Arnon nutritive solution with varying levels of nitrogen, phosphorus, potassion and magnesium. Treatment of 50% nitrogen, phosphorus, potassion and 25% of magnesium content 94,0/15,5/107,5/12,15, Treatment of 50% nitrogen, phosphorus, potassion and magnesium content 94,0/15,5/107,5/24,3, Treatment of 65% de nitrogen, 50% phosphorus, 25% potassion and 100% magnesium, content 124,0/15,5/53,6/48,6 and Treatment of 100% nitrogen, phosphorus, potassion and magnesium content 189,0/31,0/214,5/48,6 mg L-1. The parameters evaluate were Shoot length, leaf area, and dry matter of leaf blades, stems plus petioles, roots and total,relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and specific leaf area (SLA), leaf mass ratio (LMR), dry matter distribution in several organs (DMD), CO2 assimilation (A), transpiration (E), Intracelular CO2 concentration, stomatal conductance (gs), stomatal resistence (S%), CO2 compensation point (PtCe), Rubisco carboxlation efficiency, yield and composition oil. The results were evaluated by factorial ANOVA and polynomial regression analisys, usen SAS softwear with 5% significance. The parameters, Shoot length, leaf area, and dry matter of leaf blades, stems plus petioles, roots and total showed heterocedastcity making necessary the use of ponderated regression analisys and logarithmic transformation. The physiological indexes were stimated using ANACRES softwear. Plants grown whit complete nutritive solution presented higher TAL until 35 days after transplantation (DAT) and deacreased AFE at the begining of the cicle. TCR evolution was similar in different levels. Plants grown 50% N, P, K and Mg showed higher RAF and lower TAL, what ...(Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:32:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-03Bitstream added on 2014-06-13T18:43:51Z : No. of bitstreams: 1 merlin_tpa_dr_botfca.pdf: 564602 bytes, checksum: 0d5aeeb10e9efed41f754174a7c6205d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho objetivou avaliar a aplicação de reguladores vegetais (tratamento de semente e via foliar) em limoeiro ´Cravo´ (Citrus limonia Osbeck) visando o encurtamento do tempo de produção do porta-enxerto. O experimento foi dividido em duas etapas, sendo a primeira realizada no laboratório de Análise de Sementes, Departamento de Produção Vegetal - Agricultura da Faculdade de Ciências Agronômicas - Botucatu, SP, determinando-se a taxa de embebição das sementes. Após este procedimento, realizou-se o teste de germinação das sementes após tratamento com os produtos (testemunha, ácido giberélico GA3 10 mg 0,2 L-1, ácido giberélico GA3 20 mg 0,2 L-1, cinetina 10 mL 0,2 L-1, piraclostrobina + metil tiofanato 0,03 mL L-1, cinetina + ácido giberélico + ácido indolilbutírico 30 mL 0,2 L-1, ácido giberélico GA4+7 + 6-benziladenina 1 mL 0,2 L-1, ácido giberélico GA4+7 + 6-benziladenina 2,12 mL 0,2 L-1, cloreto de chlormequat 0,2 mL 0,2 L-1 e cloreto de chlormequat 0,2 mL 0,2 L- 1 + ácido giberélico GA3 20 mg 0,2 L-1. A segunda etapa do experimento foi realizada no viveiro ELPA Mudas Cítricas, localizado na cidade de Botucatu, SP. Após resultado da taxa de embebição as sementes foram mantidas em contato com os tratamentos e semeadas em tubetes com substrato de fibra de coco. Foram empregados dez tratamentos aplicados via foliar, mensalmente: testemunha, ácido giberélico GA3 50 mg L-1, ácido giberélico GA3 100 mg L-1, cinetina 50 mL L-1, piraclostrobina + metil tiofanato 0,18 mL L-1, cinetina + ácido giberélico + ácido indolilbutírico 150 mL L-1, ácido giberélico GA4+7 + 6-benziladenina 5 mL L-1, ácido giberélico GA4+7 + 6-benziladenina 10 mL L-1, cloreto de chlormequat... / The aim of this project was to evaluate the plant growth regulator application (seed and leaves) in rangpur lime (Citrus limonia Osbeck) on rootstock production in a shorter period of time. The experiment was divided into two steps; the first one was carried in the Seed Analysis Laboratory, Crop Science Department - College of Agricultural Sciences - Botucatu, SP, in order to analyze the inhibition. Afterwards, the germination test was done after the contact of the seeds with the treatments (control, gibberellic acid GA3 (10 mg L-1) 10 mg 0,2 L-1, gibberellic acid GA3 (10 mg L-1) 20 mg 0,2 L-1, kinetin (0,4 mg L-1) 10 mL 0,2 L-1, pyraclostrobin + thiophanate methyl (50 g L-1 + 450 g L-1) 0,03 mL L-1, kinetin (90 mg L-1) + gibberellic acid (50 mg L-1) + indolebutyric acid (50 mg L-1) 30 mL 0,2 L-1, gibberellic acid GA4+7 (19 mg L-1) + 6-benzyladenine (19 mg L-1) 1 mL 0,2 L-1, gibberellic acid GA4+7 (19 mg L-1) + 6-benzyladenine (19 mg L-1%) 2,12 mL 0,2 L-1, chlormequat chloride (100 g L-1) 0,2 mL 0,2 L-1 and chlormequat chloride (100 g L-1) 0,2 mL 0,2 L-1 + gibberellic acid GA3 (10 mg L-1) 20 mg 0,2 L-1. The second part of the experiment was carried out in ELPA Citric Seedlings’ Nursery, in Botucatu, SP. After the inhibition test, the seeds were kept in contact with the treatments and sowed in the coconut fiber substrate. Ten treatments were provided monthly by foliar application: control, gibberellic acid GA3... (Complete abstract click electronic access below)

Made available in DSpace on 2015-06-17T19:34:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-12-15. Added 1 bitstream(s) on 2015-06-18T12:46:51Z : No. of bitstreams: 1 000826599.pdf: 355264 bytes, checksum: 4558703c058aacd9e557c795384ef368 (MD5) / Objetivou-se avaliar os efeitos de doses de potássio no crescimento de plantas jovens de mogno-africano (Khaya senegalensis) submetidas a duas condições hídricas.Foram aplicados 0, 50, 100, 150 e 200 mg dm-3 de K2O combinados com duas condições hídricas: 30 e 70% da capacidade máxima de retenção de água do solo em vaso, no delineamento inteiramente casualizado e esquema fatorial 5 x 2, com cinco repetições. Aos 180 dias, as plantas apresentaram maior eficiência do uso do potássio, condutância estomática, transpiração, fotossíntese, altura, diâmetro, área foliar, matéria seca de raiz, caule e folhas, a 70% de umidade do que a 30%. A 30% de umidade, doses crescentes de K aumentaram a área foliar e matéria seca de folhas. Com restrição hídrica, a máxima eficiência de uso da água foi obtida com a dose 71 mg dm-3 de K2O. A 70% de umidade, doses crescentes de K diminuíram a concentração foliar de nitrogênio e aumentou as concentrações de fósforo e potássio. Plantas de mogno-africano são pouco exigentes em potássio na fase inicial de crescimento desde que as demais necessidades nutricionais sejam atendidas. Nos tratamentos de restrição hídrica, o potássio aumenta a eficiência do uso da água e a biomassa de folhas / The objective this work was the evaluation of effects caused by potassium doses and soil moisture levels on growth of young african mahogany (Khaya senegalensis) plants growing in pots. Doses of 0, 50, 100, 150, and 200 mg dm-3 of K2O, combined with two soil moisture levels, i.e., 30 and 70% of the soil maximum water retention capacity, were the treatments applied to the plants. The treatments were replicated five times and distributed in the greenhouse according to a completely random design in the factorial scheme. When the plants growing in the 70% moisture soil were 180 days of age, they showed values of potassium efficiency use, stomata conductance, transpiration, photosynthesis, height, diameter, leaf area, root and stem and leaves dry matter content larger than those observed when soil moisture was of 30%. When soil moisture was of 30%, increasing doses of K determined increments in leaf area and leaves dry matter. Under conditions of moisture restriction, water use maximum efficiency was attained with a dose of 71 mg dm-3 of K2O. When soil moisture content was of 70%, increasing doses of K reduced the foliar concentration of N whereas P and K had their concentrations increased. Young african mahogany plants demand low amounts of K at their initial stage of growth provided that the other nutritional needs are met. In water restriction treatments, potassium increases the water use efficiency and leaves biomass

Deux voies de transfert cyclique d’électrons ont été décrites chez l’algue verte C.reinhardtii, une implique (PGRL1 et PGR5), l’autre une NADP(H)-plastoquinone oxidoréductase (NDA2). Le TCE participerait à la génération d’ATP et donc à l’équilibration de la balance énergétique cellulaire. Pour mieux comprendre la contribution du TCE à la photosynthèse, différents mutants affectés du TCE ont été étudiés. Dans un premier temps, la photosynthèse et la croissance du mutant pgrl1 de C. reinhardtii déficient dans la voie de TCE PGRL1-dépendente ont été caractérisées. A l’état stationnaire, la productivité en biomasse du mutant est similaire à celle du sauvage, dans une large gamme d’intensités lumineuses et de concentrations en CO2. Basé sur les effets d’inhibiteurs de la respiration mitochondriale sur l’activité photosynthétique, il a été conclu que la coopération avec la respiration mitochondriale et de la photo-réduction d’O2 compensaient l’absence du TCE-PGRL1 dépendent. Cette compensation résulte en une productivité normale de biomasse chez le mutant à l’état stationnaire. Dans la deuxième partie de l’étude, une souche sur-exprimant la NDA2 chloroplastique a été étudiée. Une augmentation de l’activité de réduction non-photochimique des plastoquinones (PQ) en aérobiose et une vitesse de production d’H2 accrue par la voie indirecte en anaérobiose ont été notées. Il a été conclu que la production d’H2 par la voie indirecte est limitée par la capacité de réduction des PQ, soit du fait de la faible disponibilité des donneurs d’électrons, soit du fait d’une activité enzymatique de NDA2 limitée. Ceux-ci contribuerait à améliorer une production d’H2 durable. / Photosynthetic organisms have developed complex mechanisms to ensure an optimal match between the energy supplied and the metabolic demand. Among these mechanisms, cyclic electron flow around PSI (CEF) has been proposed to generate additional proton motive force and participate in the supply of extra ATP for photosynthesis. Two pathways of CEF have been described in the green alga C. reinhardtii, one involving PGRL1 (and PGR5), and the other a NAD(P)H-plastoquinone oxidoreductase (NDA2). In order to better understand the contribution of CEF to photosynthesis, different mutants affected in CEF components were studied. First, photosynthesis and growth performances of a knock-out C. reinhardtii mutant (pgrl1) deficient in PGRL1-mediated CEF have been characterized. Steady-state biomass productivity of the pgrl1 mutant was similar to its wild-type progenitor under a wide range of illumination and CO2 concentrations. From the effects of mitochondrial respiration inhibitors on photosynthesis, it was concluded that increased cooperation with mitochondrial respiration, and increased light-dependent O2 photo-reduction compensates for the absence of PGRL1-CEF. Second, a transplastomic strains over-expressing NDA2 was studied. An increased activity of non-photochemical reduction of plastoquinones (PQ) in aerobiosis and increased rate of H2 production by the indirect pathway in anaerobiosis were reported. It was concluded that activity of the indirect pathway of hydrogen production is limited by the non-photochemical reduction of PQ, either by the pool size of electron donors, or by the activity of NDA2. These data contribute to improvement for the sustainable production of hydrogen.

Doctor of Philosophy / Department of Agronomy / P. V. Vara Prasad / High temperature is a major environmental factor that limits wheat productivity. Climate models predict greater increases in night temperature than in day temperature. The objectives of this research were to quantify the effects of high day and night temperatures during anthesis on physiological (chlorophyll fluorescence, chlorophyll concentration, leaf level photosynthesis, lipid peroxidation and membrane damage), biochemical (reactive oxygen species [ROS] concentration and antioxidant capacity in leaves) and yield traits and membrane lipid profile and identify the lipids that are associated with high temperature response in wheat. Winter wheat genotypes Ventnor (heat tolerant) and Karl 92 (heat susceptible) were grown at optimum temperatures (25/15°C, maximum/minimum) until the onset of anthesis. Thereafter, plants were exposed to high night (HN, 25/24°C), high day (HD, 35/15°C), high day and night (HDN, 35/24°C) or optimum temperatures. Compared with optimum temperature, HN, HD and HDN increased ROS concentration, lipid peroxidation and membrane damage and decreased antioxidant capacity, photochemical efficiency, photosynthesis, seed set, grain number and grain yield. Impact of HN and HD was similar on all traits, when stress was imposed for seven days. High day and night temperatures resulted in significant changes in the amount of plastidic and extra-plastidic lipids and lipids with oxidized acyl chains (ox-lipids) in both genotypes. The decrease in lipid unsaturation levels of complex lipids at high temperatures was predominantly due to decrease in 18:3 fatty acid and increase in 18:1 and 16:0 fatty acids. We identified novel odd-numbered long-chain fatty acid-containing phospholipids, which were highly responsive to high temperature stress. Ventnor had higher amounts of sterol glycosides (SG) and lower amounts of ox-lipids at high temperatures than Karl 92; thus SGs and ox-lipids may be potential biomarkers for heat tolerance and susceptibility, respectively, in wheat. Co-occurring lipids, which are up-or-down-regulated together through time under high day and night temperatures formed groups, which were experiencing coordinated metabolism. These results suggest that high day and night temperatures during anthesis cause damage of a similar magnitude to wheat, if stress is imposed for a short term (seven days) and compositional changes in lipid profile in response to high temperature contribute to heat tolerance.

abstract: Non-photochemical quenching (NPQ) is a photoprotective regulatory mechanism essential to the robustness of the photosynthetic apparatus of green plants. Energy flow within the low-light adapted reaction centers is dynamically optimized to match the continuously fluctuating light conditions found in nature. Activated by compartmentalized decreases in pH resulting from photosynthetic activity during periods of elevated photon flux, NPQ induces rapid thermal dissipation of excess excitation energy that would otherwise overwhelm the apparatus’s ability to consume it. Consequently, the frequency of charge separation decreases and the formation of potentially deleterious, high-energy intermediates slows, thereby reducing the threat of photodamage by disallowing their accumulation. Herein is described the synthesis and photophysical analysis of a molecular triad that mimics the effects of NPQ on charge separation within the photosynthetic reaction centers. Steady-state absorption and emission, time-resolved fluorescence, and transient absorption spectroscopies were used to demonstrate reversible quenching of the first singlet excited state affecting the quantum yield of charge separation by approximately one order of magnitude. As in the natural system, the populations of unquenched and quenched states and, therefore, the overall yields of charge separation were found to be dependent upon acid concentration. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

abstract: As sunlight is an ideal source of energy on a global scale, there are several approaches being developed to harvest it and convert it to a form that can be used. One of these is though mimicking the processes in natural photosynthesis. Artificial photosynthetic systems include dye sensitized solar cells for the conversion of sunlight to electricity, and photoelectrosynthetic cells which use sunlight to drive water oxidation and hydrogen production to convert sunlight to energy stored in fuel. Both of these approaches include the process of the conversion of light energy into chemical potential in the form of a charge-separated state via molecular compounds. Porphyrins are commonly used as sensitizers as they have well suited properties for these applications. A high potential porphyrin with four nitrile groups at the beta positions, a β-cyanoporphyrin (CyP), was investigated and found to be an excellent electron acceptor, as well as have the necessary properties to be used as a sensitizer for photoelectrosynthetic cells for water oxidation. A new synthetic method was developed which allowed for the CyP to be used in a number of studies in artificial photosynthetic systems. This dissertation reports the theories behind, and the results of four studies utilizing a CyP for the first time; as a sensitizer in a DSSC for an investigation of its use in light driven water oxidation photoelectrosynthetic cells, as an electron acceptor in a proton coupled electron transfer system, in a carotene-CyP dyad to study energy and electron transfer processes between these moieties, and in a molecular triad to study a unique electron transfer process from a C60 radical anion to the CyP. It has been found that CyPs can be used as powerful electron acceptors in molecular systems to provide a large driving force for electron transfer that can aid in the process of the conversion of light to electrochemical potential. The results from these studies have led to a better understanding of the properties of CyPs, and have provided new insight into several electron transfer reactions. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

abstract: Humanity’s demand for energy is increasing exponentially and the dependence on fossil fuels is both unsustainable and detrimental to the environment. To provide a solution to the impending energy crisis, it is reasonable to look toward utilizing solar energy, which is abundant and renewable. One approach to harvesting solar irradiation for fuel purposes is through mimicking the processes of natural photosynthesis in an artificial design to use sunlight and water to store energy in chemical bonds for later use. Thus, in order to design an efficient energy conversion device, the underlying processes of the natural system must be understood. An artificial photosynthetic device has many components and each can be optimized separately. This work deals with the design, construction and study of some of those components. The first chapter provides an introduction to this work. The second chapter shows a proof of concept for a water splitting dye sensitized photoelectrochemical cell followed by the presentation of a new p-type semiconductor, the design of a modular cluster binding protein that can be used for incorporating catalysts, and a new anchoring group for semiconducting oxides with high electron injection efficiency. The third chapter investigates the role of electronic coupling and thermodynamics for photoprotection in artificial systems by triplet-triplet energy transfer from tetrapyrroles to carotenoids. The fourth chapter describes a mimic of the proton-coupled electron transfer in photosystem II and confirms that in the artificial system a concerted mechanism operates. In the fifth chapter, a microbial system is designed to work in tandem with a photovoltaic device to produce high energy fuels. A variety of quinone redox mediators have been synthesized to shuttle electrons from an electron donor to the microbial system. Lastly, the synthesis of a variety of photosensitizers is detailed for possible future use in artificial systems. The results of this work helps with the understanding of the processes of natural photosynthesis and suggests ways to design artificial photosynthetic devices that can contribute to solving the renewable energy challenge. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015