Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item Photosynthetic acclimation of coffee in response to water availability and fruiting: a hydraulic and hormonal approach(Universidade Federal de Viçosa, 2018-09-25) Almeida, Wellington Luiz de; Matta, Fábio Murilo da; http://lattes.cnpq.br/1352377403804748The overall coordination between gas exchanges and plant hydraulics may be affected by the soil availability of water and source-to-sink relationships. Here we evaluated how coffee (Coffea arabica L. cv. Catimor) trees are able to acclimate their photosynthesis in response drought and fruiting. The plants, which were 6-yr- old at the beginning of trials, were grown in the field at full sunlight, and subjected to four treatment combinations: irrigated plants with fruits (I*F); irrigated plants with no fruits (I*NF); non-irrigated plants with fruits (NI*F) and non-irrigated plants with no fruits (NI*NF). A range of traits, encompassing from photosynthesis traits, water relations, growth and hormonal profile, were assessed. Over the course of the experiment, the non-irrigated plants displayed lower averaged values of predawn water potentials (-0.5 MPa) than their irrigated counterparts (-0.2 MPa). We showed that under mild water deficit conditions, irrigation per se did not impact growth rates but could reduce branch death significantly. These findings were unrelated to changes in leaf assimilate pools. We also demonstrated that fruiting provoked a feedforward effect on net photosynthesis rate that was fundamentally coupled to an enhanced stomatal conductance. Indeed both the mesophyll conductance and maximum rate of carboxylation by RuBisCO remained unchanged in response to the applied treatments. The increase in stomatal conductance was unrelated to varying abscisic acid levels or differential sensitivity to abscisic acid, although it was likely associated with a lower stomatal sensitivity to leaf-to-air vapor pressure difference. In parallel, the increases in transpiration rate were supported by coordinated alterations in plant hydraulics which should to a large extent explain the maintenance of plant water status regardless of fruiting-related variations in stomatal conductance and transpiration rate. In summary, we showed that stomatal conductance played a major role in the coordination between source capacity and sink demand regardless of irrigation, with concomitant changes in plant hydraulics. Therefore, these aspects should be considered in breeding programs to improve drought tolerance in coffee in face of the present and ongoing climate changes.Item Identificação de fatores genéticos envolvidos no controle da respiração e potencialização da fotossíntese em folhas de tomate(Universidade Federal de Viçosa, 2012-07-10) Silva, Franklin Magnum de Oliveira; Nesi, Adriano Nunes; http://lattes.cnpq.br/4636590232692168Para identificar regiões genômicas envolvidas na regulação de importantes parâmetros fisiológicos como fotossíntese, respiração e processos relacionados. Sessenta e seis linhagens introgredidas de S. pennellii em fundo genético de S. lycopersicum, foram cultivadas em condições semicontroladas até o estádio vegetativo. Nesse estudo, examinaram-se os parâmetros de trocas gasosas e florescência da clorofila a, acúmulo de biomassa e o conteúdo de alguns metabólitos relacionados com o metabolismo do carbono e do nitrogênio. 23 ILs apresentaram taxas fotossintéticas superiores ao parental M82. Essa maior assimilação líquida de CO 2 foi fortemente correlacionada com condutância estomática. Em adição, uma correlação positiva entre a fotossíntese e os parâmetros de fluorescência sugere que maior taxa fotossintética pode estar associada a alterações nos parâmetros de fluorescência. Quanto ao metabolismo do carbono, verificou-se uma alta correlação negativa entre a produção de biomassa e o acúmulo de amido indicando que amido também pode atuar como um importante metabólito integrador na regulação do crescimento vegetativo. Em relação ao metabolismo do nitrogênio, constatou-se que a maior eficiência na incorporação do N inorgânico esteve fortemente relacionada ao acúmulo de amido. Por meio de análises multivariadas, foi possível identificar 21 ILs que diferiram da espécie parental S. lycopersicum. Dentre estas, a IL 7-5 diferiu de modo mais relevantes das demais ILs e do M82. Em virtude de estudos anteriores relatarem um alto rendimento de frutos por parte desta IL, esta região cromossômica torna-se promissora na identificação de fatores genéticos envolvidos no controle da respiração e potencialização da fotossíntese em folhas de tomate.Item Manipulation of source-to-sink ratios in girdled coffee branches evidences lack of photosynthetic down-regulation: the interplay of photosynthesis with respiration and photorespiration pathways and amino acid metabolism(Universidade Federal de Viçosa, 2016-02-25) Avila, Rodrigo Teixeira; Matta, Fábio Murilo da; http://lattes.cnpq.br/6404622647636394We aimed to gain a better understanding on how the regulation of photosynthesis in coffee depends on sink activity or carbohydrate build-up in source leaves and how the coffee tree adjusts its photosynthetic performance and primary metabolism to varying source-to-sink ratios. For these purposes, we use integrative approaches combining gas- exchange and chlorophyll a fluorescence measurements, analyses of carbohydrates and major metabolites, activities of a range of enzymes and the expression of some genes encoding for key enzymes of the carbon metabolism to achieve a holistic view of the whole leaf metabolism in response to long-term source-to-sink manipulation. We designed a field experiment by girdling coffee branches that were further manipulated by controlled defoliation and/or defruiting so that three highly varying source-to-sink ratios were created. We found that under remarkably high source-to-sink ratios photosynthesis rates were chiefly limited by diffusive factors (that were apparently unrelated to whole-leaf abscisic acid) with no apparent signs of feedback down- regulation. Lack of down-regulation was associated with an enormous capacity for starch accumulation coupled with maintenance of low levels of soluble sugars. Chronic Chronic photoinhibition and photodamage could be avoided through adjustments in leaf photochemistry, photorespiration and respiration amongst other processes. No major metabolic reprograming was found at the level of key enzymes associated with carbon metabolism. Metabolic adjustments in source leaves were more evident under high-sink demand conditions and centered more on nitrogen metabolism than on carbon metabolism. In conclusion, our results offer novel insights on the high coordination between the source supply and sink demand in coffee trees, with no evident signs of photosynthetic down-regulation even under dramatically low-sink conditions.Item Thermal oscillations provoke physiological and biochemical changes on wheat plants infected by Pyricularia oryzae(Universidade Federal de Viçosa, 2019-07-25) Silva, Bruno do Nascimento; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/1954041792535980Wheat blast, caused by Pyricularia oryzae, is the most important wheat disease nowadays. High temperatures, as a consequence of climatic changes, can potentially cause physiological and biochemical changes on plants by altering their resistance to diseases. This study aimed to determine whether thermal oscillations could cause physiological and biochemical changes on wheat plants when infected with P. oryzae. Plants were submitted to different thermal acclimations (19°C and 28°C) for five days before being inoculated with P. oryzae. After inoculation, plants were kept at 25°C for 24 h and then either transferred to the initial temperature conditions or transferred to different temperature combinations (19oC→28°C and 28°C→19°C) during three days. Non-inoculated plants were submitted to these same conditions. Blast development was reduced on plants submitted to thermal acclimatization of 19oC→19oC compared to plants exposed to 28°C→28°C. There was no significant difference for blast severity between the thermal acclimations of 19oC→28°C and 28°C→19°C. Plants submitted to 28°C before or after inoculation showed impairments on photosynthesis with lower values for maximum photosystem PSII photochemical efficiency and effective PSII quantum yield, but high values for quantum yield of non-regulated energy dissipation besides lower concentration of pigments, reduction on stomatal conductance and an increase in the internal CO 2 concentration. There was high superoxide dismutase and lower ascorbate peroxidase activities for inoculated plants submitted to thermal acclimatization of 28°C→28°C. Low and high concentrations of superoxide anion and hydrogen peroxide, respectively, occurred for inoculated plants acclimated at 28°C→28°C. High chitinase, phenylalanine ammonia-lyase, and peroxidase activities occurred for inoculated plants acclimated at 28°C→28°C and 19°C→28°C. Polyphenoloxidase activity was lower for inoculated plants submitted to 28°C after or before fungal inoculation. Lipoxygenase increased on inoculated plants exposed at thermal acclimatization of 19oC→19oC. The malondialdehyde concentration was high for inoculated plants submitted to 28°C after or before fungal inoculation. In conclusion, blast development was favored on plants pre-acclimated at 28°C before fungal inoculation and kept at this same temperature during fungal infection process. By contrast, blast development was quite similar on plants pre-acclimated at 19 and 28°C before inoculation with P. oryzae and submitted, respectively, to temperatures of 28 or 19°C after inoculation. Wheat plants exposed at 28°C during the fungal infection process showed damage to the photosynthetic apparatus, a less efficient antioxidative system, and a minor contribution of the enzymes related to host defense. Key words: Defense enzymes. High temperatures. Host resistance. Photosynthesis. Wheat blastItem Trocas gasosas, relações hídricas e composição bioquímica em clones de eucalipto com tolerância diferencial à seca(Universidade Federal de Viçosa, 2019-08-08) Silva, Nágila Campos; Martins, Samuel Cordeiro Vitor; http://lattes.cnpq.br/0595145943191804Devido às mudanças climáticas globais, eventos de mortalidade de árvores estão cada vez mais recorrentes. Diante disso, a busca por bioindicadores para seleção precoce de genótipos tolerantes à seca é crucial. Dada a importância do eucalipto para o setor florestal, foram investigados os mecanismos fisiológicos de tolerância à seca em clones com tolerância diferencial ao déficit hídrico. Foram usados os clones VM01 (tolerante), CO1275 (tolerante), I144 (intermediário) e CNB16 (sensível) crescidos em casa de vegetação em vasos de 20 L. Foi imposto déficit hídrico a 60% da capacidade de campo (seca moderada) por três meses, posteriormente as mesmas plantas tiveram a irrigação suspensa (seca severa) por 8 dias, e logo após foram reidratas durante 15 dias e comparadas com as plantas mantidas na condição controle. Durante o período de seca moderada foram analisados o crescimento em altura, diâmetro do caule e número de ramos, parâmetros de relações hídricas e a caracterização fotossintética. Ao final de cada regime hídrico foram medidas as trocas gasosas, fluorescência da clorofila e coletas para análises bioquímicas foram realizadas. Os clones sob seca moderada apresentaram similar redução do crescimento e não foram observados ajustamentos osmótico e elástico. Foram encontradas diferenças no potencial fotossintético em que os clones CO1275 e I144 apresentaram os maiores e menores investimentos na quantidade de rubisco ativa e taxa máxima de transporte de elétrons. Além disso, foi clara a tendência de maior investimento em potencial fotossintético sob déficit hídrico, o que foi associado com maiores valores de fotossíntese observados após reidratação. Ambos regimes hídricos promoveram redução similar nas trocas gasosas, não havendo diferenças significativas entre os genótipos. Não houve redução do pool de carboidratos não- estruturais sob seca moderada e severa, mas foi identificado maior conversão de amido em sacarose, provavelmente para fins osmóticos. Houve plasticidade em resposta à seca dos teores de prolina e compostos fenólicos, em que os genótipos apresentaram diferentes estratégias. No entanto, dentre os parâmetros avaliados, não foram encontrados bioindicadores robustos para seleção de genótipos tolerantes. Palavras-chave: açúcares, déficit hídrico, fotossíntese.Item Tolerância ao alagamento em clones de Coffea canephora: respostas hídricas, fotossintéticas e metabólicas(Universidade Federal de Viçosa, 2019-05-31) Toral Juárez, Marco Antonio; Matta, Fábio Murilo daO alagamento do solo impacta negativamente o desempenho da planta devido à redução da disponibilidade de oxigênio na raiz e acúmulo de espécies reativas de oxigênio (ERO). Nesta pesquisa, avaliou-se a relação entre a tolerância ao alagamento e a expressão do sistema antioxidante em dois clones (120 e 109A) de Coffea canephora caracterizados, respectivamente, como tolerante (com sistema antioxidante mais robusto) e sensível (com sistema antioxidante menos robusto) à seca. A hipótese basou-se no fato de que clones mais tolerantes à seca, que apresentam um sistema antioxidante mais eficiente, também mostrariam maior tolerância ao alagamento. Os clones foram submetidos a dois tratamentos de irrigação (controle e alagado), por seis dias, seguidos de 40 dias de recuperação. Foram avaliados: potencial hídrico, condutância hidráulica, trocas gasosas, fluorescência da clorofila a, partição de carboidratos, concentração de ácido 1- aminociclopropano-1-carboxílico (ACC) e alguns fitormônios, dano oxidativo e sobrevivência. Em resposta ao alagamento, a atividade antioxidante nas raízes dos clones envolveu incrementos na atividade da dismutase do superóxido e da peroxidase do ascorbato (APX). Entretanto, foi observado apenas aumento de APX foliar do clone 120. O alagamento ocasionou diminuição de absorção de água radicular com perda de 70% na condutância hidráulica em ambos os clones, reduções nas suas taxas de fotossíntese líquida (A) e condutância estomática, esgotamento de açúcares e altas concentrações de ACC e etileno em raízes. Entretanto, no clone 120, houve uma queda mais tênue de A ao longo da imposição do estresse, menor afetação por déficit hídrico, menor alteração no fluxo de elétrons, dissipação eficiente de excesso de energia por meio de processos não fotoquímicos e acúmulo tardio de ACC em raízes. As diferenças entre clones foram maiores na fase de recuperação, sendo as plantas do clone 109A as mais afetadas em danos à maquinaria fotossintética, menor taxa de transporte de elétrons, maior dano oxidativo acompanhado de redução de área foliar, e menor taxa de sobrevivência. Contudo, houve pouca diferença na capacidade antioxidante entre os dois clones, sugerindo que o melhor desempenho do clone 120, durante o alagamento, possivelmente não esteja associado com o metabolismo antioxidante; outras estratégias, portanto, devem estar envolvidas na diminuição do dano oxidativo e no retardo na queda de A, bem como maior dissipação de excesso de energia, na fase de alagamento.Item Physiological and biochemical changes on rice plants supplied with glutamate in response to Pyricularia oryzae infection(Universidade Federal de Viçosa, 2018-07-20) Dias, Carla da Silva; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/0497776503129914Considering the importance of blast, caused by Pyricularia oryzae, to decrease rice yield worldwide, this study aimed to assess the photosynthetic performance (leaf gas exchange and chlorophyll (Chl) a fluorescence as well as the photosynthetic pigments concentration), the activities of antioxidant enzymes (ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione-S-transferase (GST)) and concentrations of hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) in leaves of plants non-supplied (-Glu) or supplied (+Glu) with glutamate (Glu). Blast severity and the number of lesions per cm 2 of leaf were significantly lower for +Glu plants in comparison to -Glu plants. On the infected leaves of +Glu plants, the values for internal CO 2 concentration were lower while the values for net carbon assimilation rate, stomatal conductance as well as for the concentrations of Chl a, Chl b, and carotenoids were higher in comparison to infected leaves of -Glu plants. The functionality of the photosynthetic apparatus was preserved on the infected leaves of +Glu plants. The activities of CAT, GPX, GR, POX, and SOD increased on the infected leaves of both -Glu and +Glu plants compared to their non-inoculated counterparts, but their activities were lower for +Glu plants. The lower activities of these antioxidative enzymes was triggered by the reduced hydrogen peroxide concentration on the infected leaves of +Glu plants that resulted in lower malondialdehyde concentration. For inoculated +Glu plants, the activities of β-1-3- glucanase, chitinase, phenylalanine ammonia-lyase, and polyphenoloxidases as well as the concentrations of total soluble phenolics and lignin-thioglycolic acid derivatives were significantly higher for inoculated +Glu plants in comparison to inoculated -Glu ones. Based on the data from the present study, it can be concluded that photosynthesis was less impaired on plants supplied with glutamate and infected by P. oryzae due to the lower biochemical constraints for CO 2 fixation. There was a need for lower activities of reactive oxygen species scavenging enzymes on the infected leaves of plants supplied with glutamate due to the lower oxidative stress as a result of P. oryzae infection. Moreover, blast severity was reduced on Glu supplied plants due to an increase on the activities of defense enzymes and high concentrations of phenolics and lignin.Item Enhanced photosynthetic efficiency in a Solanum pennellii chromosome 2 QTL(Universidade Federal de Viçosa, 2018-07-30) Costa, Jaciara Lana; Nesi, Adriano Nunes; http://lattes.cnpq.br/0658989361665824Photosynthesis, one of the most important physiological processes, may be limited both by variations in diffusive and biochemical properties. Several studies have demonstrated that the genetic variation in these properties possibility to increase rates of carbon assimilation and plant yield. In a previous study utilizing a Solanum pennellii introgression lines (IL) population of 71 lines, the IL 2-5 and 2-6 displayed photosynthetic rates increased by up to 22% in comparison with control plants. However, understanding the genetic and physiological basis of potential mechanisms involved in the enhanced CO 2 assimilation exhibited by these lines is essential for further biotechnological applications. Thus, this study aimed to uncover the physiological factors involved in the up regulation of photosynthesis in the IL 2-5 and IL 2-6. The ILs have increased photosynthetic capacity followed by higher biomass production when compared to M82. Despite the higher photosynthetic capacity, any difference in relation to stomatal and mesophyll conductance was observed. Nevertheless, the maximum carboxylation velocity, maximum electron transport capacity and chloroplastidic CO 2 concentration correlated positively with carbon isotope composition. Further metabolite analysis also revealed that the higher photosynthetic capacity was associated with higher levels of Rubisco as well as of starch. Analysis of Western blot and data from A/C i curve confirmed that biochemical properties are involved in genetic variation on chromosome 2 which has been related to positive effects on photosynthesis and carbon metabolism.Item Evaluation of arsenic tolerance in Pistia stratiotes L. (ARACEAE): photosynthetic and respiratory metabolism(Universidade Federal de Viçosa, 2019-02-26) Ribeiro, Patrícia Cury; Oliveira, Juraci Alves de; http://lattes.cnpq.br/1324659681042980Arsenic (As) is a toxic element known to impair the development and growth of plants, as well as triggering various physiological changes when absorbed by plants. The plants, cultivated in nutrient solution, pH 6,5 and 1⁄2 ionic strength, were exposed in two treatments for 24, 48 and 72 hours: control (nutrient solution only) and As (1.5 mg L -1 ). After each day, a part of the experiment was collected for later physiological analyzes. The plants exposed to As presented lower biomass gain over the days, as effect of the damages caused by the contaminant in both leaves and roots. Roots accumulated more As and lower concentrations were found in the leaves. Once As is absorbed by the roots and translocated to the leaves, As changes photosynthesis, respiration, photorespiration and in turn, changes in the synthesis and accumulation of carbohydrates were also observed. Among the effects of As on metabolism, leaves displayed decreased in proteins and increased amino acids contents, while sugars and starch were accumulated. In roots, however, decreases in the concentrations of proteins, amino acids and sugars, mainly after 24 hours were observed. Starch decreased in roots during the 72 hours of exposure to As. Although the pigments did not show differences between control and As, net assimilation rate and the efficiency of photosystem II declined in presence of As. The photorespiration and carboxylation/ oxygenation rates of Rubisco followed the photosynthetic parameters, and decreased leaf stress due to the inhibition of specific enzymes in the presence of As. In contrast, both dark and mitochondrial respiration were higher in stressed leaves, possibly due to the chemical similarity of arsenate to phosphate, which may have led to increased respiration and subsequent collapse throughout the respiratory process. As a consequence of the changes observed in photosynthesis and respiration caused by oxidative stress, the activity of TCA enzymes, TCA intermediates and the NAD, NADH, NADP and NADPH balance also showed differences between the control and As. In leaves, there was an increase in the activity of the enzymes of the TCA cycle, which is in agreement with the respiration results. In roots, the activity of enzymes decreased under stress. Fumarate concentrations were higher for contaminated roots and leaves. However, in leaves with As, an increase in malate was observed, and for roots with As was observed a decrease in the concentration of malate, which suggests that malate can be diverted to other pathways within the cell. Among the pyridine nucleotides, all showed an increase between the contaminated leaves and in roots, the NAD + was not detected. Probably it was not regenerated during the respiratory process in roots with As, and as a consequence, the decrease of NADH was observed. Roots were more severely damaged, which can be explained by the greater accumulation of As in this part of the plant. Complementary analyzes related to leaf and root respiration are necessary to better understand the behavior of organic acids during As stress.Item O papel do silício na redução dos impactos da toxidez de ferro em arroz: uma abordagem morfoanatômica e fisiológica(Universidade Federal de Viçosa, 2017-05-04) Santos, Martielly Santana; Matta, Fábio Murilo da; http://lattes.cnpq.br/9769898875861142A toxidez por excesso de ferro (Fe) é uma das mais importantes desordens nutricionais que afetam processos vitais como respiração e fotossíntese, acarretando reduções no crescimento e na produção de arroz. A nutrição com silício (Si) tem-se revelado como uma alternativa promissora na mitigação de fatores de estresse abióticos, tal como metais tóxicos. Informações preliminares sugerem que o Si pode também mitigar os efeitos da toxidez de Fe em arroz, mas não se conhecem os mecanismos envolvidos nesse contexto. Diante disso, o presente trabalho objetivou determinar o potencial mitigatório do Si sobre a toxidez por Fe em arroz, por meio de caracterização detalhada dos aspectos fotossintéticos, bioquímicos, morfofisiológicos e de produtividade. Para isso, dois experimentos independentes foram montados e analisados como tal (o primeiro com plantas no estádio vegetativo; o segundo, até o fim do estádio reprodutivo) utilizando duas cultivares com respostas contrastantes para excesso de Fe (EPAGRI-109 e BR-IRGA-409, tolerante e sensível a toxidez, respectivamente). As plantas foram cultivadas em solução nutritiva não-aerada e suplementadas com Si (0 e 2 mmol L-1) e Fe (25 μmol L-1 e 5 mmol L-1). No estádio vegetativo, a toxidez por Fe impactou negativamente a taxa fotossintética líquida (A) ao reduzir as condutâncias estomática (gs) e mesofílica (gm), além de aumentar a fotorrespiração em ambas as cultivares. Além disso, alterações na arquitetura radicular e na anatomia foram correlacionados com maiores teores de Fe. Por outro lado, a fertilização com Si atenuou tais efeitos da toxidez ao reduzir o teor de Fe em folhas e raízes, o que se refletiu em menores fatores de translocação e de bioconcentração, particularmente na cultivar sensível. Reduções nos teores de Fe favoreceram aumentoa em A por reduzir as limitações difusionais à fotossíntese, com aumentos correspondentes em gs e gm. Registre-se que os parâmetros fotoquímicos e bioquímicos da fotossíntese, bem como a atividade das s enzimas do metabolismo do carbono, foram minimamente afetados pelos tratamentos com Si/Fe. Saliente-se ainda que alterações nos fatores de translocação e de bioconcentração foram associadas ao decréscimo na expressão dos genes que codificam para os transportadores de Fe (IRT1 e IRT2), bem como a maior retenção do Fe nas paredes celulares da exoderme e endoderme na raiz, e em células parenquimáticas do xilema em folhas. Além disso, a redução da placa de Fe nas cultivares +Si+Fe foi relacionada, aparentemente, ao espessamento da parede celular da faixa esclerenquimática da raiz. Nos experimentos conduzidos na fase reprodutiva, a toxidez por Fe promoveu variações expressivas nos teores de alguns nutrientes, especialmente Ca e Mg nas folhas, fato parcialmente revertido pelo Si, porém com alterações mínimas na composição nutricional dos grãos. A toxidez por Fe acarretou decréscimos em A em paralelo a reduções em gs e na taxa de transporte de elétrons (ETR), em especial na cultivar sensível. Contudo, tais respostas foram revertidas parcialmente em ambas as cultivares pela aplicação de Si. O menor acúmulo de Fe nas plantas +Si foi associado ao maior rendimento de grãos, suportado pelo aumento em A acoplado ao incremento em gs e ETR. Além disso, os resultados sugerem que o Si tenha reduzido o impacto negativo do Fe sobre a esterilidade das espiguetas. Em síntese, recomenda-se o emprego do Si como uma estratégia de manejo efetiva para reduzir os impactos negativos da toxidez por Fe sobre o desempenho fotossintético e a produção de grãos em arroz.
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