LOBO, A. K. M. Photosynthesis regulation by sucrose metabolism under water deficit and source-sink alterations in sugarcane. 2016. 118 f. Tese (Doutorado em Bioquímica)-Universidade Federal do Ceará, Fortaleza, 2016. / Submitted by Anderson Silva Pereira (anderson.pereiraaa@gmail.com) on 2017-01-03T20:20:30Z No. of bitstreams: 1 2016_tese_akmlobo.pdf: 4541762 bytes, checksum: e3450d87e286b1a5213eb866921b6c94 (MD5) / Approved for entry into archive by Jairo Viana (jairo@ufc.br) on 2017-01-09T21:32:52Z (GMT) No. of bitstreams: 1 2016_tese_akmlobo.pdf: 4541762 bytes, checksum: e3450d87e286b1a5213eb866921b6c94 (MD5) / Made available in DSpace on 2017-01-09T21:32:52Z (GMT). No. of bitstreams: 1 2016_tese_akmlobo.pdf: 4541762 bytes, checksum: e3450d87e286b1a5213eb866921b6c94 (MD5) Previous issue date: 2016 / Water deficit stress is the major limiting factor for plant growth and development, constraining food production. In order to survive in such dry conditions, many biochemical and physiological changes must be triggered by plants. In general, the responses to drought are loss of water content, reductions of stomatal conductance and photosynthesis and increase of carbohydrates. Soluble sugars play a key role in plant metabolism, acting as substrates and modulators of enzyme activity in carbon-related pathways and controlling the expression of different genes related to carbon, lipid and nitrogen routs. However, the mechanisms involved with photosynthesis down-regulation by drought and sugars in C4 plants are not fully understood. The aim of this study was to investigate how drought and source-sink perturbation regulate photosynthesis in sugarcane plants. Therefore, two studies were conducted with sugarcane plants with four months old cultivated under greenhouse conditions. In the first study sugarcane plants (cv. IACSP94-2094) were subjected to water deficit for 5 days (WD) with concomitant spraying of 50 mM exogenous sucrose (WD + Suc). While in the second study source-sink relationship was perturbed in two sugarcane cultivars (cv. IACSP94-2094 and cv. IACSP95-5000) by imposing partial darkness, spraying 50 mM exogenous sucrose and their combination for 5 days. The negative effects of WD in the gas exchange and photochemical parameters were aggravated by exogenous sucrose. Photosynthesis reductions were related to both stomatal and biochemical limitations, but exogenous sucrose intensified metabolic restrictions mainly through down-regulation of Rubisco initial activity and PSII effective quantum efficiency in drought-stressed plants. In addition, Rubisco activation state was decreased by WD + Suc, indicating perhaps that the activity of this enzyme was reduced by tight-binding inhibitors, such as sugars phosphates. Sucrose metabolism enzymes and sugars amount were also differently altered by WD and WD + Suc in leaves, sheath and stalk in WD and WD +Suc plants. Interestingly, Sucrose/hexose ratio decreased in both leaf and sheath whereas it was increased in stalk, suggesting that sucrose and related sugars were intensely metabolized and transported in drought-stressed plants. In well-watered conditions, photosynthesis was inhibited by sucrose spraying in both genotypes, through decreases in maximum Rubisco carboxylation rate (Vcmax), initial slope of A-Ci curve (k), stomatal conductance (gs) and ATP production driven by electron transport (Jatp). The partial darkness and sucrose spraying combination did not change photosynthesis in both genotypes. Significant increases in Vcmax, gs and Jatp and marginal increases in k were noticed when combining partial darkness and sucrose spraying compared with sucrose spraying alone. Altogether, these results suggest that CO2 assimilation impairment is aggravated by exogenous sucrose in drought-stressed plants. This limitation was mainly related to biochemical restrictions, specially associated with Rubisco initial activity and PSII quantum efficiency. In contrast, in vitro PEPCase activity and amount were increased in sucrose-treated plants, suggesting that C4 cycle efficiency was reduced in vivo by C3 cycle inhibition under drought conditions. Moreover, sucrose amount was increased in the stalk, suggesting the feedback regulation from stalk to source leaves in drought-stressed plants. Our data also revealed that increases in sink strength due to partial darkness offset the inhibition of sugarcane photosynthesis caused by sucrose spraying, enhancing the knowledge on endogenous regulation of sugarcane photosynthesis through the source-sink relationship. / A deficiência hídrica é o principal fator limitante para o crescimento e desenvolvimento das culturas. Para sobreviver nessas condições adversas, várias modificações bioquímicas e fisiológicas são desencadeadas pelas plantas. Em geral, os efeitos da seca em plantas são diminuição do status hídrico, reduções da condutância estomática, fotossíntese e crescimentos e aumentos nos níveis de carboidratos. Os açúcares solúveis desempenham papéis chave no metabolismo das plantas, atuando como substratos e moduladores da atividade enzimática em vias relacionadas com o carbono. Além disso, os açúcares controlam a expressão de genes associados com as rotas do metabolismo do carbono, lipídios e nitrogênio. Entretanto, os mecanismos envolvidos com a regulação negativa da fotossíntese por deficiência hídrica e açúcares em plantas C4 não estão totalmente entendidos. O objetivo deste estudo foi investigar como a deficiência hídrica e perturbações na relação fonte-dreno regulam a fotossíntese em plantas de cana-de-açúcar. Dois estudos foram conduzidos com plantas de cana-de-açúcar com quatro meses de idade cultivadas sob condições de casa de vegetação. No primeiro estudo, plantas de cana-de-açúcar (cv. IACSP94-2094) foram submetidas a deficiência hídrica por 5 dias (WD) com subsequente aplicação de sacarose exógena 50 mM (WD + Suc). Enquanto que no segundo estudo a relação fonte-dreno foi perturbada em duas cultivares de cana-de-açúcar (cv. IACSP94-2094 and cv. IACSP95-5000) pela imposição parcial de sombreamento, aplicação de sacarose exógena 50 mM e por suas combinações por 5 dias. Os efeitos negativos de WD nos parâmetros de trocas gasosas e fotoquímicos foram agravados por sacarose exógena. As reduções na fotossíntese foram relacionadas com limitações estomáticas e bioquímicas, porém a sacarose exógena intensificou as restrições bioquímicas principalmente por reduções na atividade inicial de Rubisco e eficiência quântica do PSII em plantas sob seca. Além disso, o estado de ativação de Rubisco foi inibido por WD + Suc, sugerindo que a atividade inicial dessa enzima foi possivelmente reduzida por inibidores que se ligam fortemente em seu sitio ativo, tais como açúcares fosfato. As enzimas do metabolismo de sacarose e a concentração de açúcares foram modificados diferentemente por WD e WD + Suc em folhas, bainha e colmo. Interessantemente, a relação sacarose/hexose decresceu em folhas e bainha, enquanto que no colmo essa relação aumentou, sugerindo que sacarose e outros açúcares relacionados foram intensamente metabolizados e transportados. Em condições irrigadas a fotossíntese foi inibida pela aplicação de sacarose nos dois genótipos, através de decréscimos da taxa máxima de carboxilação de Rubisco (Vcmax), inclinação inicial da curva A-Ci (k), condutância estomática (gs) e produção de ATP direcionada pelo transporte de elétrons (Jatp). A combinação de sombreamento parcial e sacarose não alterou a fotossíntese em ambos os genótipos. Significantes aumentos em Vcmax, gs, Jatp e k foram observados quando sombreamento parcial e sacarose foram combinados em comparação com plantas tratadas apenas com sacarose. Em conclusão, esses resultados sugerem que o impedimento da assimilação de CO2 é agravada por adição de sacarose exógena em plantas sob estresse hídrico. Essa limitação foi relacionada principalmente com restrições bioquímicas, especialmente associadas com reduções na atividade inicial de Rubisco e eficiência quântica do FSII. Em contraste, a atividade in vivo e concentração de PEPCase foram aumentadas em plantas tratadas com sacarose e estresse hídrico, sugerindo que a eficiência do ciclo C4 foi reduzida in vivo por inibições do ciclo C3 sob condições de seca. Além disso, o conteúdo de sacarose aumentou no colmo, indicando uma regulação de feedback do colmo para as folhas em plantas sob seca. Nossos dados revelam ainda que aumentos na força do dreno devido ao sombreamento parcial aliviaram os efeitos inibitórios na fotossíntese de cana-de-açúcar causados pela aplicação de sacarose, aumentando o conhecimento na regulação endógena da fotossíntese de cana-de-açúcar através da relação fonte-dreno.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A cana-de-aÃÃcar possui importÃncia mundial por armazenar grande quantidade de sacarose no colmo. Entretanto, sua produtividade à limitada por regulaÃÃo negativa na taxa fotossintÃtica modulada pela acumulaÃÃo de aÃÃcares no colmo (diminuiÃÃo na forÃa de dreno) ou pela acumulaÃÃo nas folhas (âfeedbackâ negativo). Outro fator responsÃvel pela reduÃÃo na fotossÃntese e acumulaÃÃo de sacarose no colmo à a presenÃa de deficiÃncia hÃdrica. Os mecanismos envolvidos com a reduÃÃo na produÃÃo de sacarose por acumulaÃÃo de aÃÃcares e seca ainda nÃo foram completamente esclarecidos. O objetivo deste trabalho foi avaliar os processos de inibiÃÃo da fotossÃntese e alteraÃÃes no metabolismo de aÃÃcares induzidos por aÃÃcares e deficiÃncia hÃdrica em plantas de cana-de-aÃÃcar. Para tanto, foram realizados dois estudos com plantas de cana-de-aÃÃcar com quatro meses de idade. No primeiro, foi aplicada soluÃÃo exÃgena de sacarose (50 mM) nas folhas expandidas de plantas mantidas em condiÃÃes de casa de vegetaÃÃo, seguidos de experimentos de dose e tempodependente de sacarose em segmentos foliares e finalizado por um experimento com aplicaÃÃo de aÃÃcares exÃgenos (sacarose, glicose e frutose 50 mM) nas folhas expandidas de plantas mantidas em condiÃÃes ambientais controladas em cÃmara de crescimento (fitotron). No segundo estudo, as plantas foram submetidas à suspensÃo de rega por cinco dias em duas condiÃÃes ambientais: casa de vegetaÃÃo com condiÃÃes naturais de temperatura elevada, alto dÃficit de pressÃo de vapor e alta densidade de fluxo de fÃtons fotossintÃticos (estresse severo) e o segundo em condiÃÃes controladas no fitotron (estresse moderado). A aplicaÃÃo de sacarose exÃgena causou mudanÃas no metabolismo de aÃÃcares [alteraÃÃo nos nÃveis de aÃÃcares e atividade de invertase Ãcida solÃvel (SAI) e neutra (NI), sintase de sacarose (SuSy) e sintase de sacarose fosfato (SPS)]. A sacarose causou forte reduÃÃo na assimilaÃÃo de CO2 e em parÃmetros da atividade do fotossistema II. Quando comparada com glicose e frutose, a sacarose causou maior reduÃÃo na fotossÃntese mÃxima, velocidade mÃxima de carboxilaÃÃo da PEPcase (Vpmax) e taxa mÃxima de regeneraÃÃo de PEP (Vpr). AlÃm disso, a sacarose causou forte inibiÃÃo na atividade de Rubisco, diminuiÃÃo no seu estado de ativaÃÃo e reduÃÃo em sua concentraÃÃo (expressÃo), enquanto que a atividade in vitro de PEPcase nÃo foi alterada. A deficiÃncia hÃdrica causou reduÃÃo das taxas fotossintÃticas com decrÃscimos dos parÃmetros de trocas gasosas e de fotoquÃmica, sugerindo limitaÃÃes estomÃticas e nÃo estomÃticas da fotossÃntese. As trocas gasosas foram mais afetadas nas condiÃÃes de casa de vegetaÃÃo em comparaÃÃo com o ambiente controlado. O tratamento de seca causou aumentos nos nÃveis de aÃÃcares solÃveis nas folhas apenas em condiÃÃes ambientais naturais e sob condiÃÃes controladas este tratamento gerou aumentos das atividades de NI e SPS enquanto que as atividades de SuSy e SPS em folhas nÃo foram alteradas. A fotossÃntese mÃxima foi diminuÃda acompanhando os decrÃscimos de Vpmax e Vpr, que foram associadas com diminuiÃÃo nas atividades e expressÃes de PEPcase e Rubisco. Diante dos resultados, concluise que sacarose modula negativamente a fotossÃntese em cana-de-aÃÃcar por exercer uma regulaÃÃo na expressÃo e atividade de Rubisco. Esse efeito induz uma reduÃÃo na taxa de carboxilaÃÃo in vivo de PEPcase provavelmente por um mecanismo indireto via modulaÃÃo da enzima. Por outro lado, a seca modula negativamente a fotossÃntese por mecanismos distintos, afetando as expressÃes e atividades de PEPcase e Rubisco que refletem em reduÃÃo nas taxas de carboxilaÃÃo do PEP. Nas duas situaÃÃes estudadas nÃo foi possÃvel elucidar o papel das mudanÃas no metabolismo de aÃÃcares na regulaÃÃo da fotossÃntese. Portanto, o presente estudo nÃo conseguiu elucidar como sacarose e/ou hexoses modificam a expressÃo e atividade de Rubisco e a seca altera as expressÃes e atividades de PEPcase e Rubisco. / The sugarcane has worldwide importance for storing large amounts of sucrose in the stalk. However, its production is limited by negative regulation in photosynthetic rate modulated by the sugars accumulation in the stalk (decrease in sink strength) or by the accumulation in the leaves (negative feedback). Another factor responsible for the reduction in photosynthesis and sucrose accumulation in the culm is the water deficiency presence. The mechanisms involved in the reduction in sucrose production by accumulation of sugars and drought are not yet completely understood. The aim of this study was to evaluate the inhibition processes of photosynthesis and changes in the metabolism of sugars induced by sugars and water stress in sugarcane plants. Therefore, two studies were conducted with sugarcane plants with four months old. At first, it was applied exogenous sucrose solution (50 mM) in the expanded leaves of plants grown in greenhouse conditions, followed by experiments on dose and timedependent sucrose in leaf segments and finalized by experiment with application of exogenous sugars (50 mM sucrose, glucose and fructose) in the expanded leaves of plants grown in controlled environmental conditions (phytotron). In the second study, the plants were subjected to irrigation suspension for five days in two environmental conditions: a greenhouse with natural conditions of high temperature, high vapor pressure deficit and high photosynthetic photon flux density (severe stress) and the second in phytotron conditions (moderate stress). The exogenous sucrose application caused changes in the sugars metabolism [alteration in sugars levels and activities of invertase acid soluble (SAI) and neutral (NI), sucrose synthase (SuSy) and sucrose phosphate synthase (SPS)]. Sucrose caused a strong reduction in CO2 assimilation and parameters of the activity of photosystem II. When compared with glucose and fructose, the sucrose caused greater reduction in maximum photosynthesis, carboxylation efficiency of PEP (Vpmax) and maximum rate of regeneration of PEP (Vpr). Furthermore, sucrose caused strong inhibition of Rubisco activity, decrease in its state of activation and reduction in its concentration (expression), whereas the PEPcase activity in vitro was unchanged. Water deficit caused decreases in photosynthetic rates, leaf gas exchange and photochemical, suggesting stomatal and non-stomatal limitations of photosynthesis. Gas exchanges were more affected in greenhouse conditions compared to the controlled environment of phytotron. Drought treatment caused increases in the soluble sugars levels in the leaves only in natural environmental conditions and under controlled conditions this treatment led to increases in NI and SPS activities while the activities of SuSy and SPS sheets were not changed. The maximum photosynthesis was decreased following the decrease of Vpmax and Vpr that were associated with a decrease in the PEPcase and Rubisco activities and expressions. Considering the results, it is concluded that sucrose negatively modulates photosynthesis of sugarcane per exercise a regulation in the Rubisco expression and activity. This effect leads to a reduction in the rate of carboxylation in vivo PEPcase probably by an indirect mechanism via modulation of the enzyme. Moreover, drought negatively modulates photosynthesis by different mechanisms affecting the Rubisco and PEPcase expression and activities reflecting reduction in the rates of carboxylation of PEP. In both cases studied was not possible to elucidate the role of changes in the metabolism of sugars in the regulation of photosynthesis. Therefore, the present study did not elucidate as sucrose and/or hexoses modify the Rubisco expression and activity and drought alters the Rubisco and PEPcase expression and activity.

Made available in DSpace on 2017-07-10T17:48:10Z (GMT). No. of bitstreams: 1 Sandra_Mara_Stroher.pdf: 2306116 bytes, checksum: f6ae6a3b2246936d07a30abb120d43d7 (MD5) Previous issue date: 2015-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aimed to evaluate the gas exchange, enzyme activity, dry matter production and nutritional value over the grass growth Vaquero and Tifton 85 grass depending on the age of regrowth, between the months of August to October 2014 hay production area. The experimental design was a randomized block with split plot with two treatments and five replications. The treatments correspond to forage (Tifton 85 and Vaquero) and the times were the days of regrowth (15, 22, 29, 36 and 43 days). The analyzed nutritional variables were dry matter production, in vitro dry matter digestibility (IVDMD), crude protein (CP), dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), insoluble protein neutral detergent (IPND), insoluble protein, acid detergent (IPAD), lignin, cellulose, hemicellulose and mineral matter (MM). The analysis of gas exchange were made from the net assimilation rate of CO2, stomatal conductance, internal CO2 concentration, leaf transpiration, relative humidity, leaf temperature, efficiency in water use, intrinsic efficiency in water use and efficiency intrinsic carboxylation. For the structural characteristics were collected plant height data, stem diameter, number of green leaves and the number of dead leaves. The biochemical assessments are based on variables such as total protein, insoluble carbohydrate, peroxidase activity (POX) activity and catalase (CAT), and analyzes for the SPAD index and electrical conductivity. It was found that the dry matter production was similar (P> 0.05) between the two fodder. PB Vaquero grass has performed better (P <0.05) at 15 and 29 days of regrowth. The ADF contents were higher in Tifton 85 grass at 15 and 36 days of regrowth. IVDMD concerning the grass Tifton 85 was higher than 29, 36 and 43 days of age, while the Vaquero grass showed better levels at 15 and 22 days of regrowth. The net CO2 assimilation was similar between the forage, except at 22 days of age in the grass Vaquero was superior, where it expressed greater stomatal conductance at 29 days of age when compared to the Tifton 85 grass and greater concentration CO 2 for 22 and 29 days of regrowth. As for the efficient use of water and intrinsic efficiency of water use, the Tifton 85 grass showed the best values at 22 and 29 days of regrowth, similar to Vaquero in other times, however, the Tifton 85 grass was superior to 22 and 29 days of growth when assessing the intrinsic efficiency of carboxylation. Tifton 85 grass had higher plant height to 15, 22 and 36 days of regrowth, with average values of 16.3; 18.8 and 25.1 cm, respectively. For the SPAD index, the grass Tifton 85 was superior for all time periods, showing also lower electrical conductivity. On days 15, 29 and 36 days of regrowth, the grass Tifton 85 had higher carbohydrate values soluble to those found for the Vaquero. The evaluated grasses expressed similar production of dry matter, but were influenced by low night temperature recorded during the experiment. As for nutritional value, the grass Vaquero has better nutritional value until 29 days of age and the Tifton 85 grass, despite the high NDF, demonstrates proper digestibility during the 43 days of regrowth. Vaquero grass externalizes greater stomatal conductance and internal CO2 concentration at 22 and 29 days, however, the Tifton 85 grass shows a more efficient use of water and intrinsic efficiency of water use at 22 and 29 days of regrowth, and thus more efficient, i.e., less loss of water in CO2 fixation. The recommended height for cutting and grass Tifton 85 and Vaquero grass were between 30 and 25 cm, respectively. The grass Tifton 85 has a higher SPAD index and thus shows have better photosynthetic characteristics due to higher concentration of chlorophyll, in addition to lower electrical conductivity. The grass Tifton 85 exposed higher catalase activity (CAT) and appeared to suffer greater stress at nights with low temperatures. The contents peroxidase (POX) increased with peak activity lignification and catalase (CAT) after 29 days of regrowth to Tifton 85. The grass Vaquero expressed higher resistance to cold stress, but on the other hand, suffered stress with increased catalase activity (CAT) caused by leafhopper-of-grazing herbivory / Objetivou-se avaliar as trocas gasosas, atividade enzimática, produção de matéria seca e valor nutricional durante o crescimento do capim Vaquero e capim Tifton 85 em função da idade de rebrota, entre os meses de agosto a outubro de 2014 em área de produção de feno. O delineamento experimental foi em blocos casualizados com parcelas subdivididas no tempo, com dois tratamentos e cinco repetições. Os tratamentos corresponderam às forragens (Tifton 85 e Vaquero) e os tempos foram os dias de rebrota (15, 22, 29, 36 e 43 dias). As variáveis nutricionais analisadas foram produção de matéria seca, digestibilidade in vitro da matéria seca (DIVMS), proteína bruta (PB), matéria seca (MS), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), proteína insolúvel em detergente neutro (PIDN), proteína insolúvel em detergente ácido (PIDA), lignina, celulose, hemicelulose e matéria mineral (MM). As análises de trocas gasosas foram feitas a partir da taxa de assimilação líquida de CO2, condutância estomática, concentração interna de CO2, transpiração foliar, umidade relativa do ar, temperatura foliar, eficiência no uso da água, eficiência intrínseca no uso da água e eficiência intrínseca de carboxilação. Para as características estruturais foram coletados dados de altura de planta, diâmetro de colmo, número de folhas verdes e número de folhas mortas. As avaliações bioquímicas basearam-se nas variáveis como proteína total, carboidrato insolúvel, atividade de peroxidase (POX) e atividade de catalase (CAT), além de análises realizadas para o índice SPAD e a condutividade elétrica. Verificou-se que, a produção de matéria seca foi semelhante (P>0,05) entre as duas forrageiras. A PB do capim Vaquero apresentou-se melhor (P<0,05) aos 15 e 29 dias de rebrota. Os teores de FDA foram maiores no capim Tifton 85 aos 15 e 36 dias de rebrota. A DIVMS referente ao capim Tifton 85 foi superior aos 29, 36 e 43 dias de rebrota, enquanto que, o capim Vaquero exibiu melhores teores aos 15 e 22 dias de rebrota. A assimilação líquida de CO2 foi semelhante entre as forrageiras, exceto aos 22 dias de rebrota em que o capim Vaquero mostrou-se superior, onde o mesmo expressou maior condutância estomática aos 29 dias de rebrota quando comparado ao capim Tifton 85, além de maior concentração de CO2 durante os 22 e 29 dias de rebrota. Quanto à eficiência no uso da água e eficiência intrínseca do uso da água, o capim Tifton 85 manifestou melhores valores aos 22 e 29 dias de rebrota, sendo semelhante ao Vaquero nos demais tempos, porém, o capim Tifton 85 foi superior aos 22 e 29 dias de rebrota quando se avaliou a eficiência intrínseca de carboxilação. O capim Tifton 85 teve maior altura de planta aos 15, 22 e 36 dias de rebrota, com valores médios de 16,3; 18,8 e 25,1 cm, respectivamente. Para o índice SPAD, o capim Tifton 85 foi superior para todos os tempos avaliados, exibindo também menor condutividade elétrica. Aos dias 15, 29 e 36 dias de rebrota, o capim Tifton 85 apresentou maiores valores de carboidratos solúveis aos encontrados para o Vaquero. Os capins avaliados expressaram produção de matéria seca semelhantes, mas, foram influenciados pela baixa temperatura noturna registrada durante o experimento. Quanto ao valor nutricional, o capim Vaquero apresenta melhor valor nutricional até os 29 dias de rebrota e o capim Tifton 85, apesar do alto teor de FDN, demonstra digestibilidade adequada durante os 43 dias de rebrota. O capim Vaqueiro externa maior condutância estomática e concentração interna de CO2 aos 22 e 29 dias, entretanto, o capim Tifton 85 mostra uma maior eficiência no uso da água e eficiência intrínseca no uso da água aos 22 e 29 dias de rebrota, sendo desta forma mais eficiente, ou seja, com menor perda de água na fixação de CO2. A altura recomendada para corte do capim Tifton 85 e do capim Vaquero situaram-se entre 30 e 25 cm, respectivamente. O capim Tifton 85 apresenta maior índice SPAD e assim, evidencia possuir melhor característica fotossintética devido a maior concentração de clorofilas, além do menor valor de condutividade elétrica. O capim Tifton 85 expos maior atividade de catalase (CAT) e mostrou sofrer maior estresse em baixas temperaturas noturnas. Os teores de peroxidase (POX) foram crescentes com pico de lignificação e atividade de catalase (CAT) aos 29 dias de rebrota para o capim Tifton 85. O capim Vaquero manifestou maior resistência ao estresse pelo frio, mas por outro lado, sofreu estresse com aumento de atividade de catalase (CAT) causado pela herbivoria da cigarrinha-da-pastagem

The main aim of this study was to investigate the effects of water availability and SO2 pollution, imposed separately or simultaneously, on the photosynthetic metabolism of Augea capensis Thunb., a succulent of the Namib Desert in the region of Skorpion Zinc mine, Namibia. The main driver for this investigation was the need to distinguish between the effects of water availability on plants native to a desert environment, where water availability dominates plant response, but where the possibility of anthropogenic SO2 pollution poses a new threat to the unique succulent vegetation. Fifteen measuring sites were selected in the vicinity of the mine to determine how rainfall influenced the physiological status of the vegetation. Chlorophyll a fluorescence measurements, and analysis of recorded OJlP fluorescence transients with the JIP-test, were used for this purpose. A series of laboratory experiments were also conducted on A. capensis to determine the precise physiological response that water deprivation and SO2 pollution had under controlled growth conditions. Potted plants were exposed to water deprivation or SO2 fumigation in the light or dark. Besides chlorophyll a fluorescence, photosynthetic gas exchange and Rubisco activity were also measured. Changes in fast fluorescence rise kinetics observed under field conditions suggest considerable modulation of photosystem II function by rainfall with concomitant involvement of a heat stress component as well. In both the field and laboratory experiments, one of the JIP-test parameters, the so-called performance index (PIABS), was identified as a very sensitive indicator of the physiological status of the test plants. Moreover, under laboratory conditions, a good correlation existed between the water deprivation-induced decline in CO2 assimilation rates and the decline in PIABS values. The JIP-test in general, and the PIABS in particular, shows considerable potential for application in the investigation of water availability influences on desert ecosystems. In the laboratory experiments, water deprivation caused stomatal closure but also a slight elevation in intercellular C02 concentration and inhibition of Rubisco activity, suggesting that mesophyll limitation was the dominant factor contributing to the decrease in C02 assimilation rates. Following re-watering, A. capensis showed remarkable recovery capacity. Fumigation of A. capensis with 1.2 ppm SO2 in the dark or light revealed relatively small effects on C02 assimilation. The inhibitory effects on photosynthesis were also fully reversible, indicating no permanent metabolic/structural damage. The effects on photosynthesis were more pronounced when fumigation occurred in the dark. This phenomenon might be related to diurnal differences in cellular capacity for SO2 detoxification. When long-term moderate water deprivation was combined with simultaneous SO2 fumigation, there was no additional inhibitory effect on photosynthesis. These findings suggest that water deprivation do not increase sensitivity towards SO2 pollution in A. capensis. Fumigation with SO2, singly or in combination with water deprivation also had no major effect on chloroplast ultrastructure. It appears that A. capensis is remarkably resistant to SO2 pollution even in the presence of low water availability, which is a common phenomenon in desert ecosystems. Since A, capensis seems to be highly tolerant to S02, its suitability as an indicator species for the detection of SO2 pollution effects at Skorpion Zinc mine is questionable. Because water availability dominates the physiological/biochemical response in this species, subtle SO2 pollution effects might be difficult to detect against this dominant background. The high water content of A. capensis and similar succulents might act as a substantial sink for SO2 and could convey considerable tolerance against this form of air pollution. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2006.

The average Brazilian soybean yield increased considerably from the beginning of the green revolution to the present day. Among the factors that contributed to the yield increase are the new technologies and agricultural practices, as well as the genetic gain provided by plant breeding. While soybean yield increased through breeding efforts, morphophysiological changes in Brazilian cultivars that contributed to yield increase are largely unknown. The objective of this study was to understand how morphophysiological changes increased yield in soybean cultivars grown in the last 50 years in Southern Brazil. The study was divided into three chapters: the first chapter refers to the experiment conducted in the field to evaluate yield and its components in 26 cultivars; the second chapter refers to the experiment conducted in pots to evaluate the roots of 25 cultivars; and the third chapter refers to two experiments in which attributes of energy conversion efficiency, foliar aging and plant response to elevated CO2 in the atmosphere were evaluated in 5 cultivars. The results showed that the yield increase was consistent throughout the years of cultivar release and the rate of increase was 46 kg ha-1 year-1. Among the yield components contributing to this increase we include the increase of biomass per area and harvest index, which therefore provide more seeds per area, due to a greater number of pods and seeds per pod. The lodging resistance improved during the year of cultivar release. For further increases in soybean yield, potential targets in future cultivars are increasing leaf nitrogen content at the R5 growth stage and the biological nitrogen fixation. Mean root diameter was reduced throughout the years of cultivar release, while the attributes total length, volume, projected area and root length were not consistently modified. The evaluated soybean cultivars presented consistent changes under elevated CO2 atmosphere [720 ppm]: the leaf chlorophyll content was reduced, the specific leaf area reduced, and the stem biomass partition increased. The old leaves presented less assimilation, less stomatal conductance, and lower leaf temperature in relation to the new leaves. However, they presented higher concentration of intercellular CO2, higher specific leaf area and chlorophyll content. The results obtained in this study will certainly contribute to strategies in breeding programs in the development of soybean cultivars that are more productive in the future. The results obtained identified morphophysiological changes in a selection of soybean cultivars grown in Southern Brazil. / A produtividade média brasileira de soja aumentou consideravelmente desde o início da revolução verde até a época atual. Entre os fatores que contribuíram no aumento da produtividade, estão as novas tecnologias e práticas agrícolas, bem como o ganho genético propiciado pelo melhoramento vegetal. Enquanto a produtividade de soja aumentou através dos esforços do melhoramento, as modificações morfofisiológicas ocorridas nos cultivares brasileiros que contribuíram para o aumento da produtividade são amplamente desconhecidas. Neste estudo objetivou-se compreender como as mudanças morfofisiológicas aumentaram a produtividade em cultivares de soja cultivadas nos últimos 50 anos no sul do Brasil. O estudo foi dividido em três capítulos: o primeiro capítulo refere-se ao experimento conduzido a campo para avaliar produtividade e seus componentes em 26 cultivares; o segundo capítulo refere-se ao experimento conduzido em vasos para avaliar as raízes de 25 cultivares; e o terceiro capítulo refere-se a dois experimentos em que avaliou-se atributos de eficiência de conversão de energia, envelhecimento foliar e resposta das plantas a elevação do CO2 atmosférico em 5 cultivares. Os resultados obtidos demonstram que o aumento da produtividade foi consistente ao longo do ano de lançamento dos cultivares e a taxa de aumento foi de 46 kg ha-1 ano-1. Entre os componentes de produtividade que contribuem para este aumento destacam-se o aumento da biomassa por área e do índice de colheita que, por consequência, propiciam maior número de sementes por área, em decorrência de um maior número de vagens e sementes por vagem. A resistência ao acamamento melhorou ao longo do ano de lançamento dos cultivares. Para aumentos futuros na produtividade, alvos potenciais para serem buscados nos cultivares futuros são maior teor de nitrogênio foliar no estádio R5 e maior fixação biológica de nitrogênio. O diâmetro médio de raízes reduziu ao longo do ano de lançamento de cultivares, enquanto os atributos comprimento, volume, área projetada e comprimento total da raiz principal não foram modificados de modo consistente. Os cultivares de soja avaliados apresentam mudanças consistentes sob atmosfera de CO2 elevado [720 ppm]: o teor de clorofila nas folhas reduziu, a área foliar específica reduziu e a partição de biomassa para haste aumentou. As folhas velhas apresentaram menor assimilação, menor condutância estomática, e menor temperatura foliar em relação as folhas novas. Entretanto elas apresentaram maior concentração de CO2 intercelular, maior área foliar específica e maior teor de clorofila. Os resultados obtidos neste estudo contribuem para estratégias em programas de melhoramento no desenvolvimento de cultivares de soja mais produtivas para o futuro. Os resultados obtidos identificaram mudanças morfofisiológicas ocorridas em uma seleção de cultivares de soja cultivadas na região sul do Brasil.

The main aim of this study was to investigate the effects of water availability and SO2 pollution, imposed separately or simultaneously, on the photosynthetic metabolism of Augea capensis Thunb., a succulent of the Namib Desert in the region of Skorpion Zinc mine, Namibia. The main driver for this investigation was the need to distinguish between the effects of water availability on plants native to a desert environment, where water availability dominates plant response, but where the possibility of anthropogenic SO2 pollution poses a new threat to the unique succulent vegetation. Fifteen measuring sites were selected in the vicinity of the mine to determine how rainfall influenced the physiological status of the vegetation. Chlorophyll a fluorescence measurements, and analysis of recorded OJlP fluorescence transients with the JIP-test, were used for this purpose. A series of laboratory experiments were also conducted on A. capensis to determine the precise physiological response that water deprivation and SO2 pollution had under controlled growth conditions. Potted plants were exposed to water deprivation or SO2 fumigation in the light or dark. Besides chlorophyll a fluorescence, photosynthetic gas exchange and Rubisco activity were also measured. Changes in fast fluorescence rise kinetics observed under field conditions suggest considerable modulation of photosystem II function by rainfall with concomitant involvement of a heat stress component as well. In both the field and laboratory experiments, one of the JIP-test parameters, the so-called performance index (PIABS), was identified as a very sensitive indicator of the physiological status of the test plants. Moreover, under laboratory conditions, a good correlation existed between the water deprivation-induced decline in CO2 assimilation rates and the decline in PIABS values. The JIP-test in general, and the PIABS in particular, shows considerable potential for application in the investigation of water availability influences on desert ecosystems. In the laboratory experiments, water deprivation caused stomatal closure but also a slight elevation in intercellular C02 concentration and inhibition of Rubisco activity, suggesting that mesophyll limitation was the dominant factor contributing to the decrease in C02 assimilation rates. Following re-watering, A. capensis showed remarkable recovery capacity. Fumigation of A. capensis with 1.2 ppm SO2 in the dark or light revealed relatively small effects on C02 assimilation. The inhibitory effects on photosynthesis were also fully reversible, indicating no permanent metabolic/structural damage. The effects on photosynthesis were more pronounced when fumigation occurred in the dark. This phenomenon might be related to diurnal differences in cellular capacity for SO2 detoxification. When long-term moderate water deprivation was combined with simultaneous SO2 fumigation, there was no additional inhibitory effect on photosynthesis. These findings suggest that water deprivation do not increase sensitivity towards SO2 pollution in A. capensis. Fumigation with SO2, singly or in combination with water deprivation also had no major effect on chloroplast ultrastructure. It appears that A. capensis is remarkably resistant to SO2 pollution even in the presence of low water availability, which is a common phenomenon in desert ecosystems. Since A, capensis seems to be highly tolerant to S02, its suitability as an indicator species for the detection of SO2 pollution effects at Skorpion Zinc mine is questionable. Because water availability dominates the physiological/biochemical response in this species, subtle SO2 pollution effects might be difficult to detect against this dominant background. The high water content of A. capensis and similar succulents might act as a substantial sink for SO2 and could convey considerable tolerance against this form of air pollution. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2006.

Παρά τη σημαντική της συνεισφορά στο συνολικό κέρδος σε άνθρακα των φυτών και τις λειτουργικές της ιδιαιτερότητες, η φωτοσύνθεση βλαστού δεν έχει μελετηθεί στην έκταση που της αναλογεί. Για το λόγο αυτό εφαρμόσαμε ένα συνδυασμό ανατομικών και φυσιολογικών μεθόδων για το χαρακτηρισμό του φωτοσυνθετικού μηχανισμού των πράσινων μίσχων και των στελεχών του άνθους του μονοκοτυλήδονου γεώφυτου Zantedeschia aethiopica και των πράσινων βλαστών του δικοτυλήδονου ημιξυλώδους Dianthus caryophyllus, σε σύγκριση με τα αντίστοιχα φύλλα. Οι μίσχοι και τα στελέχη του άνθους του Z. aethiopica και οι βλαστοί του D. caryophyllus διαθέτουν όλα τα ανατομικά χαρακτηριστικά ενός φωτοσυνθετικά αποδοτικού οργάνου, όπως σημαντικό αριθμό στομάτων με τυπικούς υποστομάτιους θαλάμους, χλωρεγχυματικά κύτταρα παρόμοιας μορφολογίας με τα δρυφακτοειδή κύτταρα των φύλλων, επαρκείς μεσοκυττάριους χώρους και σημαντικό ποσοστό ελεύθερων κυτταρικών τοιχωμάτων. Ωστόσο, η διάταξη των δρυφακτοειδών κυττάρων των μίσχων/στελεχών του Z. aethiopica είναι ασυνήθιστη, καθώς διευθετούνται παράλληλα με τον κατά μήκος άξονα των οργάνων. Επιπλέον, οι μίσχοι/στελέχη επέδειξαν φωτοσυνθετικά χαρακτηριστικά που προσομοιάζουν με εκείνα φύλλων σε συνθήκες καταπόνησης, όπως μειωμένο περιεχόμενο/ενεργότητα της Rubisco, αυξημένο ρυθμό του κύκλου C2 και αυξημένη κυκλική ροή ηλεκτρονίων γύρω από το PSI. Τα χαρακτηριστικά αυτά φαίνεται πως είναι εγγενή στα συγκεκριμένα φωτοσυνθετικά όργανα, εξυπηρετώντας την αυξημένη αζωτοδεσμευτική ικανότητα του είδους, την ποιοτική ρύθμιση του περιεχομένου τους σε αμινοξέα, την αποκαρβοξυλίωση C4-οργανικών οξέων του διαπνευστικού ρεύματος και την ταχεία επαγωγή της μη-φωτοχημικής απόσβεσης. Σε αντίθεση με το Z. aethiopica, η φωτοσυνθετική απόδοση των βλαστών του D. caryophyllus βρέθηκε ανώτερη αυτής των φύλλων, ως αποτέλεσμα των υψηλότερων ρυθμών του κύκλου C3 και μιας πιθανής οργανο-ειδικής ποικιλότητας του παράγοντα εξειδίκευσης της Rubisco. Η μειωμένη ένταση του προσπίπτοντος φωτός in vivo, λόγω του κάθετου προσανατολισμού των βλαστών, ενδεχομένως να οδηγεί σε χαμηλότερα επίπεδα φωτοπροστασίας σε σύγκριση με τα φύλλα και στην υιοθέτηση μιας στρατηγικής βελτιστοποίησης του ρυθμού καθήλωσης C, η οποία πιθανώς περιλαμβάνει και την καθήλωση CO2, που προέρχεται από την αποκαρβοξυλίωση C4-οργανικών οξέων του διαπνευστικού ρεύματος. / Despite its significant contribution to the net carbon gain of plants and its distinct functional properties, stem photosynthesis has not yet received adequate scientific attention. For this reason, a combination of anatomical and physiological methods was used to characterize the photosynthetic machinery of the green petioles and pedicels of the monocotyledonous geophyte Zantedeschia aethiopica and the green stems of the dicotyledonous semi-woody species Dianthus caryophyllus, in comparison to the corresponding leaves. Both the green petioles/pedicels of Z. aethiopica and the green stems of D. caryophyllus possess all the anatomical prerequisites of an actively photosynthesizing organ i.e. considerable number of stomata with typical underlying substomatal chambers, chlorenchyma cells which are similar to the leaf palisade chlorenchyma cells and considerable amount of both intercellular spaces and palisade free cell walls. Yet, the palisade cells of Z. aethiopica petioles/pedicels show a peculiar arrangement with their long axis parallel to the longitudinal organ axis. Furthermore, petiole/pedicel photosynthetic characteristics resemble those of leaves under adversity i.e. reduced Rubisco activity/content, high photorespiration rates and significant cyclic electron flow around PSI. It is concluded that these are innate attributes of petiole/pedicel photosynthesis serving particular functions like the increased nitrogen fixing activity of the species, the qualitative adjustment of the petiole/pedicel amino acid content, the active decarboxylation of C4-organic acids and the rapid induction of non-photochemical quenching. Stem photosynthesis in D. caryophyllus was more efficient than leaf photosynthesis, as a result of the greater rates of stem C3 cycle and a possible organ-specific variation of the specificity factor of Rubisco. In general, D. caryophyllus stems display a photosynthetic pattern of optimal carbon assimilation in the expense of photoprotection. It could be hypothesized that this kind of adaptation could be due to the vertical orientation of stems, which results in lower incident light intensities in vivo and may include the use of C4-organic acids coming up with the transpiration stream as an additional carbon source.

LOBO, A. K. M. Modulação da fotossíntese por açúcares e deficiência hídrica em plantas de cana-de-açúcar. 2012. 107 f. Dissertação (Mestrado em Bioquímica) - Centro de Ciências, Universidade Federal do Ceará, 2012. / Submitted by JOANA BEZERRA (joanabib@yahoo.com.br) on 2013-01-07T21:12:50Z No. of bitstreams: 1 2012_dis_akmlobo.pdf: 1013862 bytes, checksum: fed127e369a87a9e494a73a02c5d60f4 (MD5) / Approved for entry into archive by Érica Barros(ericabarros@ufc.br) on 2013-01-09T17:00:27Z (GMT) No. of bitstreams: 1 2012_dis_akmlobo.pdf: 1013862 bytes, checksum: fed127e369a87a9e494a73a02c5d60f4 (MD5) / Made available in DSpace on 2013-01-09T17:00:27Z (GMT). No. of bitstreams: 1 2012_dis_akmlobo.pdf: 1013862 bytes, checksum: fed127e369a87a9e494a73a02c5d60f4 (MD5) / The sugarcane has worldwide importance for storing large amounts of sucrose in the stalk. However, its production is limited by negative regulation in photosynthetic rate modulated by the sugars accumulation in the stalk (decrease in sink strength) or by the accumulation in the leaves (negative feedback). Another factor responsible for the reduction in photosynthesis and sucrose accumulation in the culm is the water deficiency presence. The mechanisms involved in the reduction in sucrose production by accumulation of sugars and drought are not yet completely understood. The aim of this study was to evaluate the inhibition processes of photosynthesis and changes in the metabolism of sugars induced by sugars and water stress in sugarcane plants. Therefore, two studies were conducted with sugarcane plants with four months old. At first, it was applied exogenous sucrose solution (50 mM) in the expanded leaves of plants grown in greenhouse conditions, followed by experiments on dose and timedependent sucrose in leaf segments and finalized by experiment with application of exogenous sugars (50 mM sucrose, glucose and fructose) in the expanded leaves of plants grown in controlled environmental conditions (phytotron). In the second study, the plants were subjected to irrigation suspension for five days in two environmental conditions: a greenhouse with natural conditions of high temperature, high vapor pressure deficit and high photosynthetic photon flux density (severe stress) and the second in phytotron conditions (moderate stress). The exogenous sucrose application caused changes in the sugars metabolism [alteration in sugars levels and activities of invertase acid soluble (SAI) and neutral (NI), sucrose synthase (SuSy) and sucrose phosphate synthase (SPS)]. Sucrose caused a strong reduction in CO2 assimilation and parameters of the activity of photosystem II. When compared with glucose and fructose, the sucrose caused greater reduction in maximum photosynthesis, carboxylation efficiency of PEP (Vpmax) and maximum rate of regeneration of PEP (Vpr). Furthermore, sucrose caused strong inhibition of Rubisco activity, decrease in its state of activation and reduction in its concentration (expression), whereas the PEPcase activity in vitro was unchanged. Water deficit caused decreases in photosynthetic rates, leaf gas exchange and photochemical, suggesting stomatal and non-stomatal limitations of photosynthesis. Gas exchanges were more affected in greenhouse conditions compared to the controlled environment of phytotron. Drought treatment caused increases in the soluble sugars levels in the leaves only in natural environmental conditions and under controlled conditions this treatment led to increases in NI and SPS activities while the activities of SuSy and SPS sheets were not changed. The maximum photosynthesis was decreased following the decrease of Vpmax and Vpr that were associated with a decrease in the PEPcase and Rubisco activities and expressions. Considering the results, it is concluded that sucrose negatively modulates photosynthesis of sugarcane per exercise a regulation in the Rubisco expression and activity. This effect leads to a reduction in the rate of carboxylation in vivo PEPcase probably by an indirect mechanism via modulation of the enzyme. Moreover, drought negatively modulates photosynthesis by different mechanisms affecting the Rubisco and PEPcase expression and activities reflecting reduction in the rates of carboxylation of PEP. In both cases studied was not possible to elucidate the role of changes in the metabolism of sugars in the regulation of photosynthesis. Therefore, the present study did not elucidate as sucrose and/or hexoses modify the Rubisco expression and activity and drought alters the Rubisco and PEPcase expression and activity. / A cana-de-açúcar possui importância mundial por armazenar grande quantidade de sacarose no colmo. Entretanto, sua produtividade é limitada por regulação negativa na taxa fotossintética modulada pela acumulação de açúcares no colmo (diminuição na força de dreno) ou pela acumulação nas folhas (“feedback” negativo). Outro fator responsável pela redução na fotossíntese e acumulação de sacarose no colmo é a presença de deficiência hídrica. Os mecanismos envolvidos com a redução na produção de sacarose por acumulação de açúcares e seca ainda não foram completamente esclarecidos. O objetivo deste trabalho foi avaliar os processos de inibição da fotossíntese e alterações no metabolismo de açúcares induzidos por açúcares e deficiência hídrica em plantas de cana-de-açúcar. Para tanto, foram realizados dois estudos com plantas de cana-de-açúcar com quatro meses de idade. No primeiro, foi aplicada solução exógena de sacarose (50 mM) nas folhas expandidas de plantas mantidas em condições de casa de vegetação, seguidos de experimentos de dose e tempodependente de sacarose em segmentos foliares e finalizado por um experimento com aplicação de açúcares exógenos (sacarose, glicose e frutose 50 mM) nas folhas expandidas de plantas mantidas em condições ambientais controladas em câmara de crescimento (fitotron). No segundo estudo, as plantas foram submetidas à suspensão de rega por cinco dias em duas condições ambientais: casa de vegetação com condições naturais de temperatura elevada, alto déficit de pressão de vapor e alta densidade de fluxo de fótons fotossintéticos (estresse severo) e o segundo em condições controladas no fitotron (estresse moderado). A aplicação de sacarose exógena causou mudanças no metabolismo de açúcares [alteração nos níveis de açúcares e atividade de invertase ácida solúvel (SAI) e neutra (NI), sintase de sacarose (SuSy) e sintase de sacarose fosfato (SPS)]. A sacarose causou forte redução na assimilação de CO2 e em parâmetros da atividade do fotossistema II. Quando comparada com glicose e frutose, a sacarose causou maior redução na fotossíntese máxima, velocidade máxima de carboxilação da PEPcase (Vpmax) e taxa máxima de regeneração de PEP (Vpr). Além disso, a sacarose causou forte inibição na atividade de Rubisco, diminuição no seu estado de ativação e redução em sua concentração (expressão), enquanto que a atividade in vitro de PEPcase não foi alterada. A deficiência hídrica causou redução das taxas fotossintéticas com decréscimos dos parâmetros de trocas gasosas e de fotoquímica, sugerindo limitações estomáticas e não estomáticas da fotossíntese. As trocas gasosas foram mais afetadas nas condições de casa de vegetação em comparação com o ambiente controlado. O tratamento de seca causou aumentos nos níveis de açúcares solúveis nas folhas apenas em condições ambientais naturais e sob condições controladas este tratamento gerou aumentos das atividades de NI e SPS enquanto que as atividades de SuSy e SPS em folhas não foram alteradas. A fotossíntese máxima foi diminuída acompanhando os decréscimos de Vpmax e Vpr, que foram associadas com diminuição nas atividades e expressões de PEPcase e Rubisco. Diante dos resultados, concluise que sacarose modula negativamente a fotossíntese em cana-de-açúcar por exercer uma regulação na expressão e atividade de Rubisco. Esse efeito induz uma redução na taxa de carboxilação in vivo de PEPcase provavelmente por um mecanismo indireto via modulação da enzima. Por outro lado, a seca modula negativamente a fotossíntese por mecanismos distintos, afetando as expressões e atividades de PEPcase e Rubisco que refletem em redução nas taxas de carboxilação do PEP. Nas duas situações estudadas não foi possível elucidar o papel das mudanças no metabolismo de açúcares na regulação da fotossíntese. Portanto, o presente estudo não conseguiu elucidar como sacarose e/ou hexoses modificam a expressão e atividade de Rubisco e a seca altera as expressões e atividades de PEPcase e Rubisco.

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