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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Características ecofisiológicas de crambe em condições de estresse hídrico / Ecophysiological characteristics of crambe under water stress conditions

Boiago, Nayara Parisoto 20 June 2012 (has links)
Made available in DSpace on 2017-07-10T19:25:10Z (GMT). No. of bitstreams: 1 Nayara.pdf: 589475 bytes, checksum: f2c35283a861de2856bf3240ffe1381c (MD5) Previous issue date: 2012-06-20 / The seeds produced by Crambe abyssinica Hochst (crambe) species have great potential in the biodiesel industry that currently searches for new sources of biomass to reach its production goals. As this culture species is rarely developed, it is essential to carry out researches on ecophysiological behavior to implement it in the Brazilian energy matrix. In order to characterize the ecophysiological behavior of crambe, this study evaluated the growth and allelopathic potential of crambe under conditions of water stress in two stages. vi Crambe plants were submitted to different levels (4, 8, 12, 16 and 20 days) of irrigation cancelation during the vegetative and flowering stages. At each level, the following parameters were analyzed: number of leaves, plants heights, leaf area and total dry weight and calculated physiological indexes of leaf area ratio (LAR), specific leaf area (SLA), net assimilation rate (NAR) and relative growth rate (RGR), all analyzed by linear exponential regression. In addition, it was carried out a leaf constitution analysis of micro and macronutrients by atomic absorption spectrophotometry. The static aqueous extract was prepared from its shoots to evaluate the allelopathic potential of crambe under water stress, at 2 and 4% concentration and then added to Petri dishes with 25 seeds of lettuce for each one. Experiments were carried out in a germination chamber with distilled water and osmotic potential (PEG 6000) as control treatments, based on a completely randomized design. The obtained data were percentage (%G) and germination speed index (GSI), root (RL) and shoot lengths (SL) of seedlings and averages were compared by Tukey test at 5% significance level. Crambe plants showed some decrease on leaf area and total dry matter in the vegetative stage, in the last level of stress. For the same developmental stage, an effect of water stress was observed at LAR, SLA, NAR and RGR indexes, concluding that this stage of development is more sensitive to drought effects. The extracts that were prepared at 4% concentration showed higher allelopathic effects. During vegetative development, there was a decrease in allelopathic potential of plants along the stress, but, during flowering, crambe plants affected negatively germination and seedling initial development of lettuce during the 4th and 16th days of water stress. Thus, it was concluded that the cancelation of irrigation on crambe plants differed in terms of development period and intensity of water stress / As sementes produzidas pela espécie Crambe abyssinica Hoscht (crambe) apresentam grande potencial na indústria do biodiesel que, atualmente, procura novas fontes de biomassa vegetal para atingir as metas de produção. Por ser uma espécie de cultivo pouco desenvolvida, pesquisas sobre seu comportamento ecofisiológico são importantes para auxiliar a implementar tal cultura na matriz energética brasileira. A fim de caracterizar o comportamento ecofisiológico do crambe, o presente estudo avaliou o crescimento e a potencialidade alelopática do crambe em condições de estresse hídrico em dois estádios de desenvolvimento. Plantas de crambe foram submetidas a diferentes níveis (4, 8, 12, 16 e 20 dias) de suspensão de irrigação durante o estádio vegetativo e a floração. Em cada nível, foram analisados os seguintes parâmetros: número de folhas, altura das plantas, área foliar e massa seca total e calculados os índices fisiológicos de razão de área foliar (RAF), área foliar específica (AFE), taxa de assimilação liquida (TAL) e taxa de crescimento relativa (TCR), submetidos à análise de regressão linear exponencial. Além disso, fez-se análise da constituição foliar de micro e macronutrientes por espectrofotometria de absorção atômica. Para avaliar a potencialidade alelopática do crambe em condições de estresse hídrico, foi preparado extrato aquoso estático a partir de suas partes aéreas, em concentração de 2 e 4%, os quais foram adicionados em placas de Petri contendo 25 sementes de alface em cada uma. Os experimentos foram conduzidos em câmara de germinação, com testemunha de água destilada e de potencial osmótico (PEG 6000) e delineamento inteiramente casualizado. Obtiveram-se porcentagem (%G), índice de velocidade de germinação (IVG), comprimento médio de raiz (CMR) e de parte aérea (CMPA) das plântulas e as médias comparadas pelo teste Tukey a 5% de significância. As plantas de crambe apresentaram redução de área foliar e massa seca total no estádio vegetativo, no último nível de estresse. Para o mesmo estádio de desenvolvimento, foi observado efeito do estresse hídrico nos índices RAF, AFE, TAL e TCR, haja vista esse estádio de desenvolvimento ser mais sensível aos efeitos do déficit hídrico. Os extratos preparados a 4% de concentração apresentaram maiores efeitos alelopáticos. Durante o desenvolvimento vegetativo, observou-se redução na potencialidade alelopática das plantas ao longo do estresse. Porém, na floração, as plantas afetaram negativamente o processo de germinação e desenvolvimento inicial das plântulas de alface durante o 4° e 16° dia de estresse hídrico. Assim, conclui-se que os efeitos da suspensão de irrigação sobre as plantas de crambe variaram quanto ao período de desenvolvimento e à intensidade do estresse hídrico
102

Prospecção de compostos orgânicos voláteis e seus efeitos na auto-regulação fisiológica em cianobactérias / Prospection of volatile organic compounds and their effects on physiological self-regulation in cyanobacteria.

Simone Vieira da Silva 07 December 2017 (has links)
Apesar dos diversos estudos sobre a presença de cianobactérias e a correlação entre fatores ambientais que influenciam ou desencadeiam florações, é ainda incipiente a informação sobre o controle fisiológico e bioquímico da produção de metabólitos secundários, cianotoxinas e compostos orgânicos voláteis (COVs) nestes organismos. Os COVs mais comumente encontrados em cianobactérias são a geosmina e o 2- metil-isoborneol, compostos que resistem ao tratamento convencional da água, causam mau cheiro e alteram seu gosto, além de bioacumular em peixes e moluscos. Estudos sobre possíveis sistemas de competição (alelopatia) entre linhagens de cianobactérias, ou entre elas e outros organismos, podem contribuir para elucidação do papel da produção de COVs por cianobactérias. Dessa forma, os objetivos deste projeto foram (i) prospectar a produção de COVs e seus efeitos na auto-regulação fisiológica em cianobactérias mantidas em laboratório; e (ii) desenvolver um método analítico, por microextração em fase sólida (SPME) e cromatografia em fase gasosa com detecção por espectrometria de massas (GC-MS), para a determinação destes compostos. Foram realizados ensaios para avaliar os perfis de produção dos COVs em duas linhagens de M. aeruginosa em diferentes fases de crescimento, sob diferentes intensidades luminosas (50, 150 e 250 ?µmol.fótons.m-2.s-1) e também ao longo do ritmo circadiano, avaliando a influência dos períodos claro e escuro. Para avaliar efeitos alelopáticos, exsudatos de uma linhagem de M. aeruginosa produtora de microcistinas foram testados em culturas de outra linhagem de M. aeruginosa não produtora de toxinas por meio de técnicas tradicionais de cultivo com monitoramento do crescimento. Na análise da produção de COVs, por GC-MS, observou-se que se destacam, majoritariamente, os compostos α-ciclocitral, &#946-ciclocitral e β-ionona, sendo o β-ciclocitral o mais abundante, em todas as condições testadas, para as ambas as linhagens estudadas. A linhagem não toxigênica, no entanto, apresentou produção mais elevada de todos os compostos identificados. Dentre as intensidades luminosas testadas, a intensidade de 250 µmol.fótons.m-2s-1 foi a que apresentou a maior taxa de crescimento para a linhagem LTPNA 08 e relação negativa entre o aumento da irradiância e a produção de β-ciclocitral. Foram identificadas, também, variações na produção dos compostos α-ciclocitral, β-ciclocitral e β-ionona nas linhagens ao longo do ritmo circadiano, sendo as maiores concentrações encontradas no período escuro. Observou-se morte celular e redução na produção de COVs 24 horas após adição de exsudatos pertencentes à linhagem de M. aeruginosa toxigênica em cultivos da linhagem não-toxigênica. Sendo assim, pode-se inferir que a produção dos COVs pode sofrer alterações qualitativas e quantitativas dependendo do estímulo ambiental presente, tanto por interações bióticas (com outros organismos e ritmo circadiano), quanto por fatores abióticos (intensidade luminosa). / There are several studies on the presence of cyanobacteria and the correlation between environmental factors that may influence or trigger blooms. However, information concerning the physiological and biochemical control of the production of secondary metabolites, toxins and volatile organic compounds (VOC) by cyanobacteria is poorly understood. Geosmin and 2-methyl-isoborneolare are commonly found VOC in cyanobacteria, they resist to conventional water treatment and can cause bad smell and taste in the final water. In addition, VOC can bioaccumulate in fish and shellfish. Studies on possible competition systems (allelopathy) either among strains of cyanobacteria or among them and other organisms such as green microalgae, may help to elucidate the role of VOC production by cyanobacteria. Thus, the main objectives of this study are: (i) prospect the production of VOCs and their effects on physiological self-regulation in cyanocrobacteria kept in the laboratory; and (ii) to develop an analytical method, by solid phase microextraction (SPME) and gas chromatography with mass spectrometry detection (GC-MS), for the determination of these compounds. The assays were carried out to evaluate the production profiles of VOCs in two strains of M. aeruginosa at different growth stages under different light intensities (50, 150 and 250 µmol.fótons.m-2.s-1) and also along of the circadian rhythm, evaluating the influence of light and dark periods. To assess allelopathic effects, exudates from a microcystin-producing strain of M. aeruginosa were tested on cultures of another non-toxin producing M. aeruginosa strain by traditional growth monitoring culture techniques. In the analysis of VOC production by GC-MS, it was observed that α-cyclocyclal, β-cyclocyclal and β-ionone compounds were the most prominent, with β-cyclocitral being the most abundant in all conditions tested, for both strains studied. The non-toxigenic lineage, however, showed higher production of all the identified compounds. Among the light intensities tested, the intensity of 250 µmol.fótons.m-2s-1 was the one with the highest growth rate and positive relation between the irradiance increase and the β-cyclocitral production. Variations in the production of the α-cyclocyclal, β-cyclocyclal and β-ionone compounds were also identified in the lines along the circadian rhythm, being the highest concentrations found in the dark period. Cell death and reduction in VOC production were observed 24 hours after addition of exudates belonging to the toxigenic M. aeruginosa lineage in cultures of the non-toxigenic lineage. Thus, it can be inferred that the production of VOCs can undergo qualitative and quantitative changes depending on the environmental stimulus present, both by biotic interactions (with other organisms and circadian rhythm) and by abiotic factors (luminous intensity).
103

Análise fitoquímica, antioxidante e fitotóxica dos extratos de folhas de salvia officinalis l. sobre lycopersicon esculentum / Phytochemical, antioxidant and phytotoxic analyses of leaves extracts from salvia officinalis l. on lycopersicon esculentum

Silva, Claudia Tatiana Araujo da Cruz 18 January 2016 (has links)
Made available in DSpace on 2017-05-12T14:47:35Z (GMT). No. of bitstreams: 1 Claudia Tatiana_ silva.pdf: 2022908 bytes, checksum: a04e53fead9716247a3d90eaa7333faf (MD5) Previous issue date: 2016-01-18 / Allelochemicalare substances present in plants, released into the environment that influence on the community, since the allelopathic potential of one plant can inhibit the development of others. Medicinal plants that have essential oils in their composition have typically been promising in weed control. Thus, this study evaluated the phytotoxic potential of dried leaves, extracts and essential oil of sage on germination and growth of tomato, guinea grass and chia plants, under laboratory conditions and at greenhouse as well as identified the chemical composition and antioxidant activity. For the bioassays in laboratory, dried leaves were soaked using hexane, ethyl acetate, acetone and methanol solvents and extracts were submitted to reactions for phytochemical characterization. The essential oil was obtained by hydro-distillation of leaves and its composition was determined by gas chromatography coupled to mass spectrometry. Antioxidant activity was measured by free radicals as DPPH. Allelopathic tests used extracts at 1% concentration and essential oil at concentrations of 0, 100, 200, 400, 600, 800, 1,000 and 2,000 mg L-1 (v/v). In greenhouse, dry mass of sage was tested at 3.75; 7.5 and 15 t ha-1 rates and the control (no mass). Phytochemical analysis revealed the occurrence of tannins, flavonoids, saponins and triterpenoids on extracts. Acetone and methanolic extracts have registered some high antioxidant activity. All extracts reduced tomato germination parameters and the extracts produced with hexane and ethyl acetate also reduced tomato shoot growth. The acetone extract had no effect on germination of guinea grass, while other extracts tested inhibited the answers and hexane extract decreased seedling growth of this specie. Hexane extract reduced the germination of chia seeds. However, the other parameters of germination were affected by the other extracts without any effect on growth. Twenty-eight compounds were recorded (corresponding to 98.82% essential oil) and the highest were: camphor (27.59%), camphene (23.70%), α-pinene (13.75%), β-pinene (6.28%) and limonene (5.38%). Monoterpenes (68%) have been prevalent in essential oil. The essential oil showed 85.3% of DPPH radical seizing activity and a 3.67 μg mL-1IC50value characterizing it as a great antioxidant. The final germination percentage of the three species was not inhibited by the essential oil at the tested concentrations. However, germination speed, time indices and average speed of germination rates were adversely affected in most tested concentrations for tomato and chia seeds. The same behavior was not observed for guinea grass seeds. In greenhouse, chlorophyll contents of tomato and guinea grass plants were reduced with 7.5 and 15 t ha-1 sage as cover crop. Tomato shoot length was inhibited in all tested rates, and guinea grass plants showed some growth decrease when using 15 t ha-1 sage mass. The dry mass of tomato plants was reduced when 15 t ha-1 sage and 7.5 and 15t ha-1 guinea grass were used as cover crops. In general, the extracts showed better phytotoxic activity to parameters of germination than the seedling growth. The effect varied due to the target specie and solvent used to prepare the extract. Sage as cover crop reduced the evaluated variables in tomato and guinea grass, but there was no effect on chia plants. It is suggested that planting in sequence or too close must be avoided. On the other hand, the essential oil showed no influence on guinea grass seeds. But, it is worth noting that botanical species respond differently and, usually, there is no allelopathic effect on germination percentage / Aleloquímicos são substâncias presentes nos vegetais, liberadas no ambiente e influenciam a comunidade ao redor, visto que, o potencial alelopático de uma planta pode se manifestar inibindo ou estimulando o desenvolvimento de outras. As plantas medicinais que apresentam óleos essenciais em sua composição, normalmente, têms e mostrado promissoras no controle de plantas. Assim, o objetivo deste trabalho foi avaliar o potencial alelopático de folhas secas, extratos e óleo essencial de sálvia sobre a germinação e o desenvolvimento de tomate, capim mombaça e chia, em condições de laboratório e casa de vegetação bem como identificar a composição química e atividade antioxidante. Para os testes de laboratório, folhas de sálvia foram submetidas à extração com os solventes hexano, acetato de etila, acetona e metanol que passaram por reações de caracterização fitoquímica. O óleo essencial foi obtido por hidrodestilação e sua composição foi determinada usando cromatografia gasosa/espectrometria de massa. A atividade antioxidante foi medida pela eliminação de radicais livres DPPH. Os testes alelopáticos utilizaram extratos na concentração de 1% e o óleo nas concentrações: 0, 100, 200, 400, 600, 800, 1000 e 2000 mg L-1 (v/v). Nos testes em casa de vegetação, a massa seca de sálvia foi utilizada nas proporções de 3,75; 7,5 e 15 t ha-1, além da testemunha. A análise fitoquímica indicou a presença de taninos, saponinas, flavonóides e triterpenóides nos extratos. Os extratos acetônico e metanólico apresentaram maior atividade antioxidante. Todos os extratos influenciaram negativamente os parâmetros germinativos do tomate e os produzidos com hexano e acetato de etila reduziram o crescimento aéreo. O extrato acetônico não influenciou os parâmetros germinativos de capim mombaça, enquanto os demais extratos inibiram as respostas e o extrato hexânico reduziu o crescimento da plântula. As sementes de chia tiveram a germinação inibida pelo extrato hexânico. Entretanto, os demais parâmetros germinativos foram afetados pelos demais extratos, sem efeito sobre o crescimento. No óleo essencial, foram detectados 28 compostos (98,82% do óleo) e os majoritários foram: cânfora (27,59%), canfeno (23,70%), α-pineno (13,75%), β-pineno (6,28%) e limoneno (5,38%). Monoterpenóides foram predominantes no óleo essencial (68%). O óleo apresentou 85,3% de capacidade de sequestro do radical DPPH e EC50 de 3,67 μg mL-1, caracterizando-o como ótimo antioxidante. O percentual final de germinação das três espécies não foi inibido pelo óleo essencial nas concentrações testadas. Entretanto, os índices de velocidade, tempo e velocidade média de germinação foram influenciados de forma negativa na maioria das concentrações testadas, para as sementes de tomate e chia. O mesmo não foi observado para sementes de capim mombaça. Em casa de vegetação, o teor de clorofila das plantas de tomate e capim mombaça foi reduzido com 7,5 e 15 t ha-1 de sálvia em cobertura. O comprimento da parte aérea do tomate foi inibido em todas as proporções testadas e as plantas de capim mombaça apresentaram redução do crescimento quando foram utilizados15 t ha-1desálvia. A massa seca das plantas de tomate reduziu com o uso de 15 t ha-1 de sálvia como cobertura e a de capim mombaça com 7,5 e 15 t ha-1. De forma geral, os extratos apresentaram melhores respostas alelopáticas para os parâmetros germinativos do que para o crescimento das plântulas. O efeito variou em função da espécie alvo e do solvente utilizado para preparo do extrato. A sálvia em cobertura reduziu as variáveis avaliadas em tomate e capim mombaça. Assim, a semeadura em sequência ou muito próxima deve ser evitada. Entretanto, não apresentou efeito nas plantas de chia. Ao passo que o óleo essencial não influenciou o capim mombaça. Deve ser destacado que as espécies botânicas respondem de forma diferenciada e muitas vezes o efeito alelopático não está sobre o percentual de germinação
104

Características ecofisiológicas de crambe em condições de estresse hídrico / Ecophysiological characteristics of crambe under water stress conditions

Boiago, Nayara Parisoto 20 June 2012 (has links)
Made available in DSpace on 2017-05-12T14:48:34Z (GMT). No. of bitstreams: 1 Nayara.pdf: 589475 bytes, checksum: f2c35283a861de2856bf3240ffe1381c (MD5) Previous issue date: 2012-06-20 / The seeds produced by Crambe abyssinica Hochst (crambe) species have great potential in the biodiesel industry that currently searches for new sources of biomass to reach its production goals. As this culture species is rarely developed, it is essential to carry out researches on ecophysiological behavior to implement it in the Brazilian energy matrix. In order to characterize the ecophysiological behavior of crambe, this study evaluated the growth and allelopathic potential of crambe under conditions of water stress in two stages. vi Crambe plants were submitted to different levels (4, 8, 12, 16 and 20 days) of irrigation cancelation during the vegetative and flowering stages. At each level, the following parameters were analyzed: number of leaves, plants heights, leaf area and total dry weight and calculated physiological indexes of leaf area ratio (LAR), specific leaf area (SLA), net assimilation rate (NAR) and relative growth rate (RGR), all analyzed by linear exponential regression. In addition, it was carried out a leaf constitution analysis of micro and macronutrients by atomic absorption spectrophotometry. The static aqueous extract was prepared from its shoots to evaluate the allelopathic potential of crambe under water stress, at 2 and 4% concentration and then added to Petri dishes with 25 seeds of lettuce for each one. Experiments were carried out in a germination chamber with distilled water and osmotic potential (PEG 6000) as control treatments, based on a completely randomized design. The obtained data were percentage (%G) and germination speed index (GSI), root (RL) and shoot lengths (SL) of seedlings and averages were compared by Tukey test at 5% significance level. Crambe plants showed some decrease on leaf area and total dry matter in the vegetative stage, in the last level of stress. For the same developmental stage, an effect of water stress was observed at LAR, SLA, NAR and RGR indexes, concluding that this stage of development is more sensitive to drought effects. The extracts that were prepared at 4% concentration showed higher allelopathic effects. During vegetative development, there was a decrease in allelopathic potential of plants along the stress, but, during flowering, crambe plants affected negatively germination and seedling initial development of lettuce during the 4th and 16th days of water stress. Thus, it was concluded that the cancelation of irrigation on crambe plants differed in terms of development period and intensity of water stress / As sementes produzidas pela espécie Crambe abyssinica Hoscht (crambe) apresentam grande potencial na indústria do biodiesel que, atualmente, procura novas fontes de biomassa vegetal para atingir as metas de produção. Por ser uma espécie de cultivo pouco desenvolvida, pesquisas sobre seu comportamento ecofisiológico são importantes para auxiliar a implementar tal cultura na matriz energética brasileira. A fim de caracterizar o comportamento ecofisiológico do crambe, o presente estudo avaliou o crescimento e a potencialidade alelopática do crambe em condições de estresse hídrico em dois estádios de desenvolvimento. Plantas de crambe foram submetidas a diferentes níveis (4, 8, 12, 16 e 20 dias) de suspensão de irrigação durante o estádio vegetativo e a floração. Em cada nível, foram analisados os seguintes parâmetros: número de folhas, altura das plantas, área foliar e massa seca total e calculados os índices fisiológicos de razão de área foliar (RAF), área foliar específica (AFE), taxa de assimilação liquida (TAL) e taxa de crescimento relativa (TCR), submetidos à análise de regressão linear exponencial. Além disso, fez-se análise da constituição foliar de micro e macronutrientes por espectrofotometria de absorção atômica. Para avaliar a potencialidade alelopática do crambe em condições de estresse hídrico, foi preparado extrato aquoso estático a partir de suas partes aéreas, em concentração de 2 e 4%, os quais foram adicionados em placas de Petri contendo 25 sementes de alface em cada uma. Os experimentos foram conduzidos em câmara de germinação, com testemunha de água destilada e de potencial osmótico (PEG 6000) e delineamento inteiramente casualizado. Obtiveram-se porcentagem (%G), índice de velocidade de germinação (IVG), comprimento médio de raiz (CMR) e de parte aérea (CMPA) das plântulas e as médias comparadas pelo teste Tukey a 5% de significância. As plantas de crambe apresentaram redução de área foliar e massa seca total no estádio vegetativo, no último nível de estresse. Para o mesmo estádio de desenvolvimento, foi observado efeito do estresse hídrico nos índices RAF, AFE, TAL e TCR, haja vista esse estádio de desenvolvimento ser mais sensível aos efeitos do déficit hídrico. Os extratos preparados a 4% de concentração apresentaram maiores efeitos alelopáticos. Durante o desenvolvimento vegetativo, observou-se redução na potencialidade alelopática das plantas ao longo do estresse. Porém, na floração, as plantas afetaram negativamente o processo de germinação e desenvolvimento inicial das plântulas de alface durante o 4° e 16° dia de estresse hídrico. Assim, conclui-se que os efeitos da suspensão de irrigação sobre as plantas de crambe variaram quanto ao período de desenvolvimento e à intensidade do estresse hídrico
105

Installation d'espèces feuillues en forêt de pins d'Alep : interactions avec les strates arborées et arbustives / Broadleaved seedling establishment in Aleppo pine forests : overstorey and understorey interactions

Gavinet, Jordane 08 December 2016 (has links)
L’installation de plantules est une phase critique fortement influencée par les interactions avec la végétation établie, compétition ou facilitation. Dans cette thèse, nous montrons que l’effet du pin d’Alep ou d'arbustes sur l’installation d’espèces feuillues dépend de la densité du couvert, de la stratégie des espèces cibles et nurses et des conditions locales. Sous couverts très denses, la survie et la croissance des plantules sont drastiquement limitées par compétition lumineuse et hydrique, le stress hydrique étant renforcé par une faible allocation de biomasse aux racines. À l’autre extrémité du gradient, en milieu ouvert, la photoinhibition et la concurrence avec les herbacées peuvent limiter l'installation des plantules. Les espèces sclérophylles sempervirentes sont peu sensibles aux fortes irradiances, températures et demandes évaporatives et peuvent profiter de conditions favorables momentanées par polycyclisme en milieu ouvert. L’effet d’un couvert végétal sur ces espèces est principalement compétitif, tandis que les espèces décidues à fort SLA bénéficient d’un couvert modéré. En pépinière, la litière des principales espèces ligneuses modifie les propriétés physico-chimiques et microbiologiques du sol sous-jacent mais sans effet sur des plantules de chêne au bout de 2 ans, montrant un faible effet allélopathique. L’éclaircie des peuplements de pin d’Alep denses est une stratégie pour faciliter l’installation d’espèces feuillues et ainsi améliorer la diversité et la résilience au feu des forêts. L’optimum de couvert semble se déplacer vers des couverts plus denses dans des sites à conditions climatiques ou édaphiques plus sévères et pour les espèces décidues. / Seedling establishment is a critical demographic phase, strongly influenced by plant-plant interactions. This thesis shows that the effect of Aleppo pine and shrubs on broadleaved seedling establishment depends on vegetation cover density, target and nurse species strategies and local conditions. A dense vegetation cover strongly limits seedling establishment by light and water competition, seedlings water stress being worsened by a low biomass allocation to roots. At the other extreme, in the open, photoinhibition and competition with grasses can limit seedling establishment. Sclerophyllous species are poorly sensitive to high temperature, irradiance and evaporative demand and can take advantage of favorable conditions at any time of the year by polycyclism in the open: interactions with pine are thus mostly competitive. In contrast, deciduous species with high SLA are more sensitive to photo-inhibition and benefit from the protection of a moderate cover, under which they are able to grow faster. In a nursery experiment, pine and shrub litters modified soil chemical and microbiological properties but without feedback on oak seedlings, indicating a poor allelopathic effect. Pine thinning is a strategy to enhance broadleaved seedling establishment and increase Mediterranean forest diversity and fire-resilience. However, the optimum thinning intensity seems to decrease in harsher climatic or edaphic conditions and for deciduous species.
106

Seaweed allelopathy against coral: surface distribution of seaweed secondary metabolites by imaging mass sepctrometry

Andras, Tiffany D. 16 August 2012 (has links)
Coral reefs are in global decline, with seaweeds increasing as corals decrease. Though seaweeds have been shown to inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly known. Here we use field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting treatment effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, Neurymenolide A, as the main allelopathic agent. For allelopathy of lipid soluble metabolites to be effective, the metabolites would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify Neurymenolide A on the surface of P. neurymenioides and found the metabolite on all surfaces analyzed. The highest concentrations of Neurymenolide A were on basal portions of blades where the plant is most likely to contact other benthic competitors.
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Chemically-mediated interactions in the plankton: defenses against grazing and competitors by a red tide dinoflagellate

Prince, Emily Katherine 19 March 2008 (has links)
The species composition of planktonic communities is determined not only by abiotic factors, such as nutrient availability, temperature, and water column stratification but also by biotic interactions between hosts and parasites, predators and prey, and among competitors. Blooms of the red tide dinoflagellate, Karenia brevis, can dramatically alter the planktonic community, reaching densities of millions of cells per liter and occurring nearly monospecifically. I investigated whether K. brevis uses chemical compounds to defend against grazing or to inhibit the growth of competitors. Because K. brevis is known to produce brevetoxins which act as potent neurotoxins in mammals, I also investigated whether brevetoxins played a role in competition or predator resistance. Experiments revealed that copepods fed diets rich in Karenia brevis experienced lowered fitness, however, nutritional inadequacy, rather than toxicity, was responsible for the decrease in grazer fitness. Compounds exuded from natural samples of K. brevis blooms did, however, inhibit the growth of four of five model competitors. Compounds exuded from K. brevis cultures were similarly allelopathic to competitors. Exposure to these allelopathic compounds resulted in lowered photosynthetic efficiency of all competitors, and decreased cell membrane integrity of three competitors. The allelopathic potency of K. brevis blooms was variable between collections and years, but allelopathy did not correlate with bloom density or concentration of brevetoxins. However, the variability of allelopathy could partially be explained by the presence of specific competitors. The diatom Skeletonema costatum reduced the growth-inhibiting effects of K. brevis bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Allelopathic compounds exuded by K. brevis that inhibited the growth of the diatom Asterionellopsis glacialis were partially characterized. K. brevis produced multiple, polar, organic compounds that inhibited A. glacialis growth. Exuded brevetoxins, on the other hand, had no effect on A.glacialis growth. Taken together, these results indicate that K. brevis is not chemically defended against grazing, but does produce yet-unidentified allelopathic compounds that inhibit the growth of competing phytoplankton. Blooms of K. brevis may be facilitated by the exudation of potent allelopathic compounds, but the specific phytoplankton assemblage has the potential to alter bloom dynamics.
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Avaliação do efeito inibitório de extratos hidroalcoólicos de macrófitas aquáticas sobre o crescimento de Microcystis aeruginosa Kutzing

Silveira, Augusto Lima da 15 August 2012 (has links)
CAPES / As cianobactérias se proliferam rapidamente em ambientes eutrofizados e podem ser capazes de sintetizar toxinas que inviabilizam a utilização dos recursos hídricos. A espécie Microcystis aeruginosa apresenta ampla distribuição, além de ser potencial produtora de hepatotoxinas denominadas microcistinas. O risco à saúde humana destas substâncias faz com que os métodos para controle destes microrganismos na água adquiram fundamental importância. De forma a verificar possíveis efeitos inibitórios de compostos fitoquímicos produzidos por macrófitas aquáticas sobre o crescimento e a produção de microcistinas da cianobactéria Microcystis aeruginosa, o presente estudo utilizou extratos hidroalcoólicos de sete espécies de macrófitas aquáticas (Eichhornia azurea, Eleocharis cf. acutangula, Ludwigia cf. peruviana, Myriophyllum cf. aquaticum, Pontederia cordata, Sagittaria montevidensis e Typha domingensis). O meio de cultura ASM-1 foi otimizado em relação ao pH, nitrogênio, fósforo e ferro através de planejamento fatorial. Para o preparo dos extratos, as sete espécies de macrófitas aquáticas foram coletadas, processadas e submetidas ao processo de extração com solução hidroetanólica 80% (v/v). Os extratos obtidos foram liofilizados e aplicados em concentrações conhecidas aos cultivos de M. aeruginosa, em meio ASM-1 otimizado. O monitoramento da concentração celular foi realizado a cada 48 h por 10 dias. As diferenças estatísticas foram avaliadas através do método estatístico ANOVA repeated. A determinação da concentração de microcistina-LR foi realizada nas culturas contendo a concentração de extrato de maior efeito inibitório. Para a verificação de efeitos bacteriostáticos e bactericidas, ao final do período testado, os cultivos foram reinoculados em tubos de ensaio contendo apenas o meio de cultura estéril. Os extratos foram avaliados quanto à presença de metabólitos secundários e à toxicidade aguda sobre Daphnia magna. Os experimentos apresentaram valores de crescimento elevados no meio que continha maiores concentrações de P e Fe. Os extratos inibiram significativamente o crescimento da cepa quando foram aplicados na concentração de 500 mg.L-1, com exceção do extrato obtido a partir de S. montevidensis em que o efeito inibitório sobre as células foi o menor observado. O extrato com maior efeito inibitório foi obtido de partes aéreas de M. cf. aquaticum pois a taxa de inibição foi de 99,1% na concentração de 500 mg.L-1. As análises de microcistina evidenciaram que para o extrato de E. cf. acutangula a redução do crescimento foi acompanhada de aumento na produção de microcistina-LR de 216 para 610 ppb. Nos testes com o extrato de S. montevidensis a concentração de toxina sofreu pouca alteração, aumentando de 216 para 222 ppb. Efeitos bactericidas foram verificados para a exposição aos extratos de E. cf. acutangula, L. cf. peruviana e M. cf. aquaticum, uma vez que após reinoculadas não foram verificados crescimentos celulares. Para os extratos de E. azurea, P. cordata e T. domingensis não foram observados efeitos tóxicos, por outro lado, a maior toxicidade ocorreu para S. montevidensis, pois 100% dos organismos apresentaram imobilidade na concentração de 50 mg.L-1. Considerando os dados de inibição e de toxicidade foi possível constatar que o extrato obtido de L. cf. peruviana apresentou maiores vantagens em sua aplicação. Os resultados obtidos indicam a possibilidade futura da aplicação de extratos para a remediação de florações e mostram, também, a necessidade de investigações fitoquímicas e toxicológicas mais detalhadas no sentido de identificar as substâncias ativas no controle de florações, de forma a potencializar a ação destas e minimizar seus efeitos tóxicos. / Cyanobacteria proliferate rapidly in eutrophic environments and may be able to synthesize toxins that block water resources use. The cyanobacterium Microcystis aeruginosa is widely distributed, being a potential producer of hepatotoxins called microcystins. The risks to human health of these substances demands methods to control these microorganisms in water. In order to investigate possible inhibitory effects of phytochemical compounds produced by aquatic macrophytes on the growth and microcystin production of Microcystis aeruginosa, the present study used aquatic macrophytes hydroalcoholic extracts of seven species (Eichhornia azurea, Eleocharis cf. Acutangula, Ludwigia cf. peruviana, yriophyllum cf. aquaticum, Pontederia cordata, Sagittaria montevidensis and Typha domingensis). The culture medium ASM-1 was optimized with respect to pH, nitrogen, phosphorus and iron through a factorial design. For extracts preparation, the seven species of aquatic macrophytes were collected, processed and submitted to extraction process solution ethanol 80% (v/v). The extracts were lyophilized and applied in known concentrations to cultures of M. aeruginosa, in optimized ASM-1 medium. Cell concentration was determined every 48 h for 10 days. Statistical differences were evaluated using ANOVA repeated. The microcystinLR concentration was determined in cultures containing greater inhibitory effect extract concentration. Evaluation of bacteriostatic and bactericidal effects at the end of tested period, the cultures were reinoculated into test tubes containing only sterile culture medium. The extracts were evaluated for the presence of secondary metabolites and acute toxicity on Daphnia magna. The experiments showed high growth rates in medium containing higher concentrations of P and Fe. Hydroalcoholic extracts inhibited the growth of Microcystis aeruginosa strain, more effective when applied at a concentration of 500 mg L-1, except for tests performed with S. montevidensis in that the mean inhibitory effect on the cells was the lowest observed. The extract with the highest inhibitory effect was obtained from aerial parts of M. cf. aquaticum in which the inhibition rate was 99.1%. The analyzes showed that microcystin for the extract of E. cf. acutangula the greatest cellular inhibition was accompanied by an increase in microcystin-LR production from 216 to 610 ppb. In tests with S. montevidensis extract the concentration of toxin was few changed, increasing from 216 to 222 ppb. Bactericidal effects were observed for exposure to extracts of E. cf. acutangula, L. cf. peruviana and M. cf. aquaticum. For extracts of E. azurea, P. cordata and T. domingensis toxic effects were not observed. The major toxicity was observed for S. montevidensis, in which 100% of organisms presented immobility in concentration of 50 mg.L-1. Considering inhibition and toxicity data was found that L cf. peruviana extract showed more advantages on its application. The results indicate the possibility of future application of extracts for blooms remediation and also show the need for detailed toxicological and phytochemical investigations in order to identify the active compounds in blooms control and minimize their toxic effects.
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Studiu klíčivosti a vzcházivosti semen technického konopí / Study of germination and emergence of industial hemp seeds

ŘEZÁČOVÁ, Veronika January 2018 (has links)
Nowadays hemp is listed among plants with a wide range of potentials. It can be used as a source of fibre, oil, food or medicine. The aim of this work was to investigate optimal conditions for hemp seed germination grown in laboratory as well as field conditions and to propose the application of acquired findings. Hemp seed was split into 2 size groups: above 3 mm and 2 - 3 mm. Divided seeds with the humidity level of 6, 9 and 12% were stored at the temperature of 0, 8 and 20? 1°C for half a year. In 2 months interval, there were evaluated: germination, energy of sprouting, speed of sprouting, further seed viability and laboratory emergence. From next influences were evaluated the influence of dryness, wetting, autotoxicity, exudates of perennial weeds, seed treatment with the infusion of field horsetail and the grown stimulator. The best germination and laboratory emergence had seeds stored at 0°C. Test of seed viability confirmed significant decline in live seeds stored over 4 months at the 0°C temperature. The best germination was achieved by seed size 2 - 3 mm. Hemp requires sufficient amount of water for germination. Leachates from rhizomes of couch grass inhibited germination of hemp by 10%. On the other hand, germination was significantly increased by the stimulator.
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ALELOPATIA DE CARQUEJA (Baccharis trimera Less) E AÇÃO DE FUNGOS EM CAPIM-ANNONI (Eragrostis plana Ness) / ALLELOPATHY OF CARQUEJA (Baccharis trimera Less) AND ACTION OF FUNGI IN TOUGH LOVEGRASS (Eragrostis plana Ness)

Gonçalves, Carlos Eduardo Prates 12 March 2014 (has links)
Livestock in southern Brazil is sustained largely by native pastures, which have large species diversity. This area is part of the Pampa biome. However, invasive species Eragrostis plana (tough lovegrass) threat to native grasslands of this biome. Becomes necessary to develop alternative methods of control of this species, since conventional control practices, although fairly efficient, has no as a principle the preservation of native vegetation. The present work aimed to study the control of tough lovegrass through biocontrol method for isolation of potentially pathogenic fungi, as well as the allelopathic effects of aqueous extract of carqueja (Baccharis trimera) on the germination of tough lovegrass. The fungi were isolated from seeds of tough lovegrass and incubated for eight days of growth at 25 °C and a photoperiod of 12 hours, then identified to genus chamber. Five genera were identified: Alternaria sp., Curvularia sp., Aspergillus sp., Penicillium sp. e Fusarium sp. To test the interaction of these fungi with the seeds of E. plana, fungi inoculation was performed in seeds through deposition technique, which were previously sterilized with 1% NaClO, and seeded on two types of substrates: filter paper (in vitro experiment) and substrate and sand mixture (ex vitro experiment). Treatments consisted of the five identified fungi, inoculated separately in seeds of E. plana. The genera showed that the best results were: Fusarium sp., Curvularia sp. e Penicillium sp. The carqueja belongs to the Asteraceae family, possessing compounds with many properties. Among the compounds present in B. trimera can highlight the presence of flavonoids, tannins, fatty acids, steroids, triterpenoids. To evaluate the allelopathic effect of B. trimera on E. plana different doses of the crude aqueous extract (CAE) of carqueja were applied on the seeds of tough love-grass. The concentrations where 0; 25; 50; 75 and 100 g.L-1. The experiments were conducted in vitro and ex vitro. The High-performance liquid chromatography (HPLC) was also conducted to identify the compounds present in the CAE. Were found in larger amounts: caffeic acid, chlorogenic acid, ellagic acid and isoquercitina. In the in vitro experiment the inhibition of the germination appeared from the concentration of 25 g.L-1 upwards, causing a diminishing germination with increasingly higher concentrations of the CAE. In the ex vitro experiment the reduction of emergence was lower, but was statistically significant. The data show that the carqueja extracts interfere on the development of the tough lovegrass by reducing leaf length and the dry mass of the aerial part and of the roots. / A pecuária na Região Sul do Brasil é sustentada, em grande parte, por pastagens nativas, que apresentam grande diversidade de espécies. Esse território faz parte do bioma Pampa. A espécie invasora capim-annoni ameaça essas pastagens. Torna-se necessário o desenvolvimento de métodos alternativos de controle dessa espécie, pois práticas convencionais de controle, embora relativamente eficientes, não tem a preservação da vegetação nativa como princípio. O presente trabalho teve por objetivo estudar o controle de capim-annoni, através do biocontrole por método de isolamento de fungos potencialmente fitopatogênicos, bem como dos efeitos alelopáticos do extrato aquoso de carqueja (Baccharis trimera) sobre a germinação do capim-annoni. Os fungos foram isolados a partir de sementes de E. plana e incubados por oito dias em câmara de crescimento, a 25 °C e fotoperíodo de 12 horas, em seguida identificados até gênero. Foram identificados cinco gêneros: Alternaria sp., Curvularia sp., Aspergillus sp., Penicillium sp. e Fusarium sp. Para testar a interação desses fungos com as sementes de E. plana, foi realizada a inoculação dos fungos nas sementes através da técnica de deposição, sendo elas previamente desinfestadas com NaClO 1%, e semeadas em dois tipos de substratos: papel-filtro (experimento in vitro) e mistura de substrato e areia (experimento ex vitro). Os tratamentos constaram dos cinco fungos identificados, inoculados separadamente nas sementes de E. plana. Os gêneros que apresentaram os melhores resultados foram Fusarium sp., Curvularia sp. e Penicillium sp. A carqueja, pertencente à família Asteraceae, apresenta vários compostos na sua composição. Dentre os compostos presentes em B. trimera pode-se destacar a presença de flavonóides, taninos, ácidos graxos, esteróides, triterpenóides. Para avaliar o efeito alelopático de B. trimera em E. plana foram aplicadas diferentes doses de extrato bruto aquoso (EBA) de carqueja nas sementes de capim-annoni. As concentrações foram 0; 25; 50; 75 e 100 g.L-1. Os experimentos foram conduzidos in vitro e ex vitro. Também foi realizada a técnica Cromatografia Líquida de Alta Eficiência (HPLC) para identificar os compostos presentes no EBA. Foram encontrados em maior quantidade: ácido cafeico, ácido clorogênico, isoquercitina e ácido elágico. No experimento in vitro a inibição da germinação deu-se a partir da concentração 25 g.L-1, sendo que a germinação diminuiu conforme a concentração do EBA aumentou. No experimento ex vitro a redução da emergência de plântulas foi estatisticamente significativa. Os dados obtidos mostram que os extratos de carqueja interferem no desenvolvimento do capim-annoni para comprimento de folhas e massa seca de parte aérea e raiz.

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