Salt stress is one of the major problems in the present world’s agriculture. Plants encounter drought stress even in the availability of water because of osmotic imbalance in the cell due to excess salts. Plants avoid water uptake, which in turn decreases the photosynthetic activity. In this work, we measured the effect of salt stress on three accessions of Arabidopsis thaliana (Columbia (Col-0), Landsberg erecta (Ler-0), Wassilewskija (Ws-4)) by subjecting the plants to stress with 0-150 mM NaCl followed by recovery. The impact of the stress was clearly observed in all three accessions during stress and recovery period. Chlorophyll content in leaves decreased with increasing salt concentration. Proline levels increased during salt stress conditions. Non-photochemical quenching and PSII activity slightly decreased under stress conditions. Salt treated plants showed slow acidification of lumen with delayed Non-photochemical quenching in recovery phase. Ler-0 was the most sensitive ecotype to salt stress followed by Ws-4 and Col-0.

Ozone is known to be the most widespread phytotoxic air pollutant. Ozone causes visible injury, reductions in photosynthesis, growth, and yield. Plant response to ozone may vary with species, varieties, and physiological age. Comparison between sensitive and tolerant cultivars has a key role in assessing ozone damage, investigating the sites of cellular injury, and identifying ozone tolerance mechanism. The objectives of this study were to investigate the effects of high ozone concentration (200 ppb) as well as ambient ozone concentrations (under field conditions) on net CO2 assimilation and PSII function in plants with different sensitivities to ozone. Two species of plants, tobacco (Nicotiana tabacum L.) and black cherry (Prunus serotina) were studied. Gas exchange analysis and chlorophyll fluorometry were utilized to characterize physiological function. Two tobacco cultivars, Bel-B and Bel-W3, tolerant and sensitive to ozone, respectively, were grown in a greenhouse supplied with charcoal filtered air and then exposed to 200 ppb ozone for 4hr. Effects on chlorophyll fluorescence, net photosynthesis, and stomatal conductance are described. Quantum yield was calculated from chlorophyll fluorescence and the initial slope of the assimilation-light curve measured by the gas exchange method. Only the sensitive cultivar, Bel-W3, developed visible injury symptoms involving up to 50% of the 5th leaf. The maximum net photosynthetic rate of ozone-treated plants of the tolerant cultivar was reduced 40% compared to control plants immediately after ozone fumigation; however, photosynthesis recovered by 24 hr post fumigation and remained at the same level as control plants. In the sensitive cultivar, on the other hand, ozone exposure reduced maximum net photosynthesis up to 50%, with no recovery, apparently causing permanent damage to the photosystem. Reductions in apparent quantum efficiency, calculated from the assimilation-light curve, differed between cultivars. Bel-B showed an immediate depression of 14% compared to controls, whereas Bel-W3 showed a 27% decline. Electron transport rate (ETR), at saturating light intensity, decreased 58% and 80% immediately after ozone treatment in Bel-B and Bel-W3, respectively. Quantum yield decreased 28% and 36% in Bel-B and Bel-W3, respectively. It can be concluded that ozone caused a greater relative decrease in linear electron transport than maximum net photosynthesis, suggesting greater damage to PSII than the carbon reduction cycle. Two different sensitivity classes of black cherry, tolerant and sensitive, growing under natural environmental conditions in Giles County, VA were assessed for physiological responses to ambient ozone concentrations. Additional measurements were made at two other sites near Blacksburg. Leaf gas exchange rates and visible foliar injury were determined monthly during the growing seasons of 2000, 2001, and 2002 to characterize the relationship of injury to altered photosynthetic function. Ambient ozone levels were sufficient to induce visible symptoms which were highly correlated with a reduction in PnMAX (maximum net photosynthetic rate under saturating light conditions) and à CO2 (quantum yield for carbon reduction) only in sensitive black cherry. Electron transport rate (ETR) and quantum yield of PSII (à PSII) were also reduced in sensitive black cherry. Maximum photochemical efficiency (Fv/Fm) in sensitive trees was severely damaged by ambient ozone. There were positive correlations between increasing cumulative ozone concentration and substantial reductions in PnMAX and in à CO2 of sensitive trees compared to tolerant trees. There was a negative correlation between chlorophyll content and percent leaf injury in sensitive black cherry / Ph. D.

Adequate nutrition plays a key role in the phytoextraction of soil contaminants and may influence the response of plants to heavy metal toxicity. Nevertheless, there is no information on the influence of nitrogen (N), particularly in the forms of nitrate (NO3-) and ammonium (NH4+), on tanzania guinea grass (Panicum maximum cv. Tanzania) under cadmium (Cd) stress. Thus, in the present work, it was aimed to study the effect of these ions on the mitigation of Cd toxicity in this grass. Plants were grown in a greenhouse, using plastic pots containing nutrient solution and ground quartz as substrate. The experiment was laid out in a randomized complete block design, in a 3 × 3 factorial arrangement, with six replications. The factors tested were NO3-/NH4+ ratios (100/0, 70/30 and 50/50) and Cd rates (0.0, 0.5 and 1.0 mmol L-1). Morphological, physiological and biochemical changes in the plants were studied throughout two growth periods. In addition to causing oxidative stress and visual toxicity symptoms, Cd exposure resulted in reduced chlorophyll content and photosynthetic activity, negatively affecting shoot and root growth. Moreover, it altered N metabolism and induced the accumulation of NO3- and NH4+ mainly in shoots, increasing plant total N concentration. The exclusive use of NO3- mitigated toxicity symptoms by favoring Cd accumulation in roots, maintaining normal N metabolism and increasing guaiacol peroxidase activity. On the other hand, although the simultaneous supply of NO3- and NH4+ increased the uptake, transport and accumulation of this metal by the grass, it also increased the photosynthetic capacity along with the synthesis of proline and protein. The use of these N forms at a 50/50 ratio increased the tolerance of the plants to Cd by inducing high superoxide dismutase and glutathione reductase activities in shoots and roots, respectively, maintaining cellular homeostasis and reducing oxidative stress. Cd uptake and accumulation in tanzania guinea grass are strongly related to the form of N available, and the negative effects of this metal on photosynthesis and on the balance between oxidants and antioxidants are attenuated by the partial replacement of NO3- by NH4+ in the nutrient solution. / A nutrição adequada desempenha papel fundamental na fitoextração de contaminantes do solo e pode influenciar a resposta das plantas à toxidez por metais pesados. No entanto, não há informações sobre a influência do nitrogênio (N), particularmente nas formas de nitrato (NO3-) e amônio (NH4+), no capim tanzânia (Panicum maximum cv. Tanzânia) sob estresse por cádmio (Cd). Assim, no presente trabalho, objetivou-se estudar o efeito desses íons na mitigação da toxidez por Cd nesse capim. As plantas foram cultivadas em casa de vegetação, utilizando vasos plásticos contendo solução nutritiva e quartzo moído como substrato. O experimento foi arranjado em delineamento de blocos completos ao acaso, em esquema fatorial 3 × 3, com seis repetições. Os fatores testados foram proporções de NO3-/NH4+ (100/0, 70/30 e 50/50) e doses de Cd (0,0, 0,5 e 1,0 mmol L-1). Foram estudadas alterações morfológicas, fisiológicas e bioquímicas nas plantas ao longo de dois períodos de crescimento. Além de causar estresse oxidativo e sintomas visuais de toxidez, a exposição ao Cd resultou em baixos teor de clorofila e atividade fotossintética, afetando negativamente o crescimento da parte aérea e das raízes. Além disso, ela alterou o metabolismo do N e induziu o acúmulo de NO3- e NH4+ principalmente na parte aérea, aumentando a concentração de N total na planta. O uso exclusivo do NO3- mitigou sintomas de toxidez favorecendo o acúmulo de Cd nas raízes, mantendo o metabolismo normal do N e aumentando a atividade da guaiacol peroxidase. Por outro lado, embora o suprimento simultâneo de NO3- e NH4+ tenha aumentado a absorção, o transporte e o acúmulo desse metal pelo capim, também aumentou a capacidade fotossintética juntamente com a síntese de prolina e proteína. O uso dessas formas de N na proporção de 50/50 aumentou a tolerância das plantas ao Cd induzindo altas atividades da superóxido dismutase e da glutationa redutase na parte aérea e nas raízes, respectivamente, mantendo a homeostase celular e reduzindo o estresse oxidativo. A absorção e o acúmulo de Cd no capim tanzânia estão fortemente relacionados à forma de N disponível, e os efeitos negativos desse metal na fotossíntese e no balanço entre oxidantes e antioxidantes são atenuados pela substituição parcial de NO3- por NH4+ na solução nutritiva.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-15T18:16:10Z No. of bitstreams: 1 marcelaaparecidacamposnevesmiranda.pdf: 2269537 bytes, checksum: 9bf86ff2517e2014e98028114505af4e (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-22T14:58:32Z (GMT) No. of bitstreams: 1 marcelaaparecidacamposnevesmiranda.pdf: 2269537 bytes, checksum: 9bf86ff2517e2014e98028114505af4e (MD5) / Made available in DSpace on 2016-07-22T14:58:32Z (GMT). No. of bitstreams: 1 marcelaaparecidacamposnevesmiranda.pdf: 2269537 bytes, checksum: 9bf86ff2517e2014e98028114505af4e (MD5) Previous issue date: 2011-04-12 / Alterações no padrão de distribuição de luz em ambientes aquáticos podem afetar as características fisiológicas das cianobactérias, e com isso, influenciar na ocorrência de suas florações. Microcystis e Cylindrospermopsis estão entre os gêneros mais comuns formadores de florações em sistemas brasileiros. Conhecer e entender os requerimentos por luz e seu efeito no crescimento dessas duas cianobactérias é de fundamental importância para a compreensão e manejo de florações em ambientes aquáticos continentais. Este trabalho buscou avaliar o efeito de diferentes intensidades luminosas (25, 50, 300, 600 μmol de fótons m-2 s-1) na ecofisiologia de M.aeruginosa (cepa MIRF-01) e de C. raciborskii (cepa CYRF-01) e a interação entre uma cepa de M. aeruginosa (MIRF-01) com duas cepas de C. raciborskii (CYRF-01 e T3) em duas intensidades luminosas (50 e 500 μmol de fótons m-2 s-1). Para avaliar a ecofisiologia as células das duas espécies foram previamente aclimatadas por três gerações as intensidades luminosas utilizadas e os parâmetros avaliados foram turbidez, densidade do fluxo de fótons, densidade celular, pigmentos totais, atividade fotossintética e a morfologia das duas espécies. A interação entre as espécies foi verificada através da taxa de crescimento. O aumento na densidade celular ao longo do tempo promoveu aumento da turbidez e reduziu a disponibilidade da intensidade luminosa por volta de 50% em todos os tratamentos, devido ao auto-sombreamento. MIRF apresentou taxa de crescimento maior do que CYRF (0,38 ± 0,015 e 0,29 ± 0,019 respectivamente) em todos os tratamentos. Em ambas as cepas houve um aumento na concentração de pigmentos ao longo do tempo e uma diminuição com o aumento da intensidade luminosa. O aumento na relação carotenóide/clorofila, nas culturas de CYRF cultivadas em alta intensidade luminosa (CYRF-300 e CYRF-600), justifica a mudança na coloração de “verde” viii para “verde-amarelada” das culturas de C. raciborskii. As duas espécies apresentaram taxa de transferência de elétrons semelhantes entre os tratamentos, não sendo verificados mecanismos de dissipação de energia. Em relação a morfologia MIRF apresentou agregação celular em baixas intensidade luminosas (25 e 50 μmol de fótons m-2 s-1) e CYRF apresentaram alterações nos tricomas cultivados as altas intensidade luminosas (300 e 600 μmol de fótons m-2 s-1), levemente curvados com diferenciação nas extremidades e filamentos bifurcados. A interação entre M.aeruginosa e C. raciborskii foi evidente para as cepas coexistentes MIRF e CYRF. Em baixa intensidade luminosa (50 μmol de fótons m-2 s-1), CYRF apresentou menor taxa de crescimento quando na presença de MIRF; em alta intensidade luminosa (500 μmol de fótons m-2 s-1) MIRF apresentou maiores taxas de crescimento quando na presença de CYRF do que quando em monocultura. M.aeruginosa e C. raciborskii quando aclimatadas não apresentaram diferenças em relação à ecofisiologia nas diferentes intensidades luminosas utilizadas. E a interação entre cepas coexistentes pode refletir no crescimento das espécies com a alteração da intensidade luminosa. / Changes in the distribution pattern of light in aquatic environments can affect the physiological characteristics of cyanobacteria and, thus, influence on the occurrence of blooms. Cylindrospermopsis and Microcystis are among the most common bloomforming genera in Brazilian systems. Knowing and understanding the requirements for light and its effect on the growth of these two cyanobacteria are important for the understanding and management of algal blooms in freshwater ecosystems. This study evaluated (1) the effect of different light intensities (25, 50, 300, 600, μmol photons m-2 s-1) on growth, physiology and morphology of the species M. aeruginosa (strain MIRF) and C. raciborskii (strain CYRF) and; (2) the interaction between one strain of M.aeruginosa (MIRF-01) with two strains of C. raciborskii (CYRF-01 and T3) at two light intensities (50 and 500 μmol photons m-2 s-1). Both strains were previously acclimated. Cell density, total pigments, turbidity, density of photon flux, photosynthetic activity and morphology of the two species were analized. The interaction between two species was verified by changes in growth rates. The increase in cell density over time promoted increase in turbidity and reduced the availability of light intensity by about 50% in all treatments, due to self-shading. MIRF showed higher growth rate than CYRF (0.38 ± 0.29 ± 0.015 and 0.019 respectively) in all treatments. There was no difference in the growth rates between treatments for MIRF and CYRF in different light intensities. In both strains, there was an increase in pigment concentration over time and decrease with increasing irradiance. The increase in the ratio carotenoid/chlorophyll-a in cultures grown in high irradiance CYRF (CYRF-300 and CYRF-600) explains the change in color from green to green-yellow of cultures of C. raciborskii. The rapid light curves were similar among treatments, and was not verified x down regulation mechanisms. It was also noted that while MIRF showed cell aggregation at low light intensities (25 and 50 mmol photons.m-2.s-1), CYRF showed morphological changes in the trichomes at high light intensities (300 and 600 μmol photons.m-2.s-1), slightly curved filaments and bifurcate at the ends. The interaction between M.aeruginoa and C.raciborskii was evident for coexisting MIRF and CYRF strains. In low light intensity (50 μmol photons.m-2.s-1), CYRF showed a lower growth rate in the presence of MIRF. In high light-intensity (500 μmol photons.m-2.s-1) MIRF growth rates were higher in the presence of CYRF than in monoculture. When M.aeruginosa and C.raciborskii are acclimated there is no ecophysiology difference in different light intensities. The interaction between coexisting strains may reflect the growth of species in different light intensity.

Pour répondre à la demande mondiale croissante en huile et en protéines, le tournesol apparaît comme une culture très compétitive grâce à la diversification de ses débouchés et son attractivité environnementale et nutritionnelle. Pourtant, les teneurs en huile et protéines sont soumises à des effets génotypiques et environnementaux qui les rendent fluctuantes et difficilement prédictibles. Nous argumentons qu’une meilleure connaissance des effets les plus importants et leurs interactions devrait permettre de mieux prédire ces teneurs. Deux approches de modélisation ont été développées. Dans la première, trois modèles statistiques ont été construits puis comparés à un modèle simple existant. L’approche dynamique est basée sur l’analyse des relations source-puits au champ et en serre (2011 et 2012) pendant le remplissage. Les performances et domaines de validité des deux types de modélisation sont comparés. / Considering the growing global demand for oil and protein, sunflower appears as a highly competitive crop, thanks to the diversification of its markets and environmental attractiveness and health. Yet the protein and oil contents are submitted to genotypic and environmental effects that make them fluctuating and hardly predictable. We argue that a better knowledge of most important effects and their interactions should permit to improve prediction. Two modeling approaches are proposed: statistical one, where we compared three types of statistical models with a simple existing one. The dynamic approach is based on source-sink relationships analysis (field and greenhouse experiments in 2011 and 2012) during grain filling. Performances of both modeling types and their validity domain are compared.