The thesis is a summary and discussion of six papers. The purpose of the investigation was to study the influence of (i) environmental factors and (ii) the physiological condition of the thallus on nitrogen fixation in the lichen Stereocaulon paschale (L.) Fr. The nitrogen input to the site, a sparsely stocked pine forest in northern Sweden, was also studied. Nitrogen fixation (nitrogenase activity) was measured as acetylene reduction both in the field and in the laboratory. Usually intact lichen thalli were used, but also excised cephalodia were studied. All nitrogenase activity was located in the external cephalodia containing the blue-green alga Stigonema sp. There was always a reduction in nitrogenase activity when the cephalodia were quantitatively excised from the thallus. Moisture was found to be the most important environmental factor in the field during the snow free part of the year. At the site, with 14 % of the ground covered by S. paschale3 the yearly nitrogen fixation was estimated to c. 0.1 g nitrogen per m^. The lichen thalli could withstand several months in a very dry condition and at a low temperature without significant decrease in nitrogenase activity. A higher capacity for nitrogenase activity was found in lichen thalli collected from bare ground than in thalli collected under the snow. The light conditions before as well as during the nitrogenase activity measurements affected the nitrogenase activity. Thalli incubated with acetylene in the dark had only c. two thirds of their activities in the light. Lichen thalli pretreated in the light showed increased nitrogenase activities, probably due to raised content of carbohydrates available for nitrogenase activity. The necessary energy for nitrogenase activity is supplied by either oxidative phosphorylation or photophosphorylation. / digitalisering@umu

Cyanobacteria are widely distributed in marine, freshwater and terrestrial habitats. Some cyanobacterial genera can convert di-nitrogen gas (N2) to bioavailable ammonium, i.e. perform nitrogen (N) fixation, and are therefore of profound significance for N cycling. N fixation by summer blooms of cyanobacteria is one of the largest sources of new N for the Baltic Sea. This thesis investigated N fixation by cyanobacteria in the Baltic Sea and explored the fate of fixed N at different spatial and temporal scales. In Paper I, we measured cell-specific N fixation by Aphanizomenon sp. at 10 ºC, early in the season. Fixation rates were high and comparable to those in late summer, indicating that Aphanizomenon sp. is an important contributor to N fixation already in its early growth season. In Paper II, we studied fixation and release of N by Aphanizomenon sp. and found that about half of the fixed N was rapidly released and transferred to other species, including autotrophic and heterotrophic bacteria, diatoms and copepods. In Paper III, we followed the development of a cyanobacterial bloom and related changes in dissolved and particulate N pools in the upper mixed surface layer. The bloom-associated total N (TN) increase was mainly due to higher particulate organic N (PON) concentrations, but also to increases in dissolved organic nitrogen (DON). About half the PON-increase could be explained by the sum of N-fixing cyanobacteria, other phytoplankton (&gt;2µm) and zooplankton, indicating that production was stimulated by the N fixation. In Paper IV, we used a growth model based on measured photosynthesis–irradiance relationships to explore the production potential of Aphanizomenon sp. The model included data on irradiance, biomass, temperature and light attenuation (1999–2013). Until the bloom peak, the modelled production matched the measured biomass, indicating low production losses. Over the whole season, the modelled production could explain a substantial part of the summer TN increase, assuming that plausible losses (such as grazing or cell lysis) are retained within the upper mixed layer. Complementing the other data, we also investigated the nutrient content (Paper I) and varying cell width (Paper IV) of Aphanizomenon sp. By a combination of approaches, this thesis has contributed new information on cyanobacterial N fixation rates, the transfer of fixed N to other organisms in the food web and shown the potential for fixed N to stimulate summer primary and secondary production in the Baltic Sea. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

Woody plant expansion has been documented for decades in many different ecosystems, often due to anthropogenic disturbances to the environment and yielding vast changes in ecosystem functioning. While causes and consequences of woody expansion have been well documented, few studies have investigated functional traits of woody species that promote rapid expansion in range. My objective was to determine if hydraulic efficiency confers enhanced photosynthetic efficiency so that functional traits representing light and water use may be possible mechanisms facilitating woody encroachment into grasslands and forest understories. I quantified leaf-level light environment, photosynthetic activity, and hydraulic characteristics of three sympatric broadleaf evergreens of varying leaf life span (Ilex opaca, Kalmia latifolia, and Myrica cerifera) in a deciduous forest understory to understand seasonal intra- and interspecific ranges of broadleaf evergreen physiology. Additionally, I investigated the effects of age on physiological efficiency of M. cerifera across a chronosequence (i.e., space for time substitution) of shrub thicket development in order to understand possible age-related physiological mechanisms facilitating shrub expansion. Lastly, I determined functional traits and resulting physiology that contribute to rapid expansion and thicket formation of an invasive, deciduous, N-fixing shrub, Elaeagnus umbellata, and a native, evergreen, N-fixing shrub M. cerifera. When compared to co-occurring evergreen species, electron transport rate (ETR) of M. cerifera was nearly double that of I. opaca or K. latifolia in summer. Photosynthetic capacity was positively related to hydraulic capacity among understory evergreens. Furthermore, photosynthetic and hydraulic efficiency of M. cerifera remained consistent despite considerable differences in thicket age and development. Both similar and contrasting functional traits of E. umbellata and M. cerifera allowed for enhanced light capture and water movement, and reductions in subcanopy light penetration. Enhanced hydraulic and photosynthetic efficiency relative to co-occurring species contributes to rapid range expansion and thicket formation by promoting enhanced productivity and limiting successful colonization of other species. My results indicate that there may be suites of functional traits linked to expansive success and thicket-formation, yet differences in functional traits between native and invasive species represent alternative strategies leading to rapid growth and thicketization.

In the nutrient-poor soils characteristic of coastal environments, symbiotic association with the nitrogen-fixing root endosymbiont Frankia is essential to establishment and survival of the woody shrub Morella cerifera. Nutrient deficiency quickly becomes severe unless seedlings are infected by Frankia soon after germination. However, the means of arrival of Frankia prior to shrub establishment has not been determined. Using sterilized lab-grown M. cerifera seedlings and fecal samples collected from passerine birds on the Eastern Shore of Virginia, viability of avian dispersal of the bacteria was tested. Although passerine fecal samples did produce nodules on some sterilized M. cerifera seedlings, these experimental inoculations did not lead to significantly higher likelihood of nodulation, relative to sterilized reference seedlings. Non-sterilized seedlings displayed greatest percent nodulation; results suggest that passerines contribute to Frankia dispersal, but also that the actinomycete is contained on or within viable seeds or fruits of M. cerifera, and therefore may be co-dispersed directly from the parent plant.

Shrub expansion in herbaceous ecosystems is emerging as an important ecological response to global change, especially in mesic systems where increases in canopy biomass are greatest. Two consequences of woody encroachment are increases in belowground resources, such as carbon and nitrogen, and reductions in above-ground resources such as light, which affect diversity, community trajectory, and ecosystem function. My objective was to determine how expansion of the nitrogen-fixing shrub Morella cerifera affected the resource environment across a chronosequence of shrub expansion on a Virginia barrier island. I quantified changes in carbon (C) and nitrogen (N) cycling, canopy structure and understory light associated with M. cerifera expansion. Litterfall in shrub thickets exceeded litterfall for other woody communities in the same region, and due to high N concentration, resulted in a return of as much as 169 kg N ha-1 yr-1 to the soil, 70% of which was from symbiotic N fixation. Litter and soil C and N pools were 3-10 times higher in shrub thickets than in adjacent grasslands. Understory light in shrub thickets decreased to as low as 0.5% of above-canopy light. Sunflecks in shrub thickets were shorter, smaller and less intense than sunflecks in forest understories. However, relative to other shrub species such as Elaeagnus umbellata, M. cerifera was less efficient at intercepting light. Although M. cerifera had the highest leaf area index (LAI) of five shrub species studied, M. cerifera was relatively inefficient at light attenuation due to low levels of branching, steep leaf angles and a relatively shallow canopy. The shift from grassland to shrub thicket on barrier islands, and in other mesic systems, results in a significant change in canopy structure that alters understory resource availability and greatly alters ecosystem function and trajectory.

A Araucaria angustifolia possui alto valor madeireiro e resinífero, é fonte de alimento e espécie característica da Floresta Ombrófila Mista, um ecossistema rico em espécies endêmicas e detentor de alta diversidade. Devido à intensa exploração durante décadas, atualmente a araucária é considerada espécie em perigo crítico de extinção, sendo fundamental a compreensão deste ecossistema para sua preservação e regeneração. As minhocas, os fungos micorrízicos arbusculares (FMA) e as bactérias diazotróficas são organismos edáficos que desempenham funções essenciais no processo de ciclagem de nutrientes e podem favorecer o desenvolvimento vegetal. Muitos trabalhos avaliam o efeito de cada um destes organismos separadamente, mas o estudo das interações entre eles é escasso. Portanto, este trabalho teve como objetivo avaliar o efeito da inoculação de minhocas invasoras Amynthas corticis, do FMA Gigaspora rosea e de um isolado de bactéria diazotrófica sobre o desenvolvimento de mudas de araucária, considerando suas interações. O experimento foi realizado em vasos, em casa de vegetação, sob delineamento em blocos casualizados, em esquema fatorial 2x2x2, sendo: presença e ausência de minhoca (A. corticis), presença e ausência de FMA (G. rosea), e presença e ausência de bactéria diazotrófica (isolado S32274), com oito repetições cada, sendo que a metade dos vasos foi avaliada 150 dias após o transplantio (Época 1) e o restante aos 250 dias após o transplantio (Época 2) das mudas de araucária. Os parâmetros de avaliação foram: altura e diâmetro das plantas, massa seca das raízes e da parte aérea, concentração e conteúdo total de nitrogênio e fósforo da parte aérea, densidade de esporos de G. rosea no substrato, taxa de colonização radicular pelo FMA e sobrevivência, reprodução e massa fresca das minhocas. A biomassa e o conteúdo de N e P das plantas foram afetados pela interação dos organismos. A inoculação de G. rosea propiciou melhor desenvolvimento das mudas de araucária, entretanto, não houve efeito significativo da inoculação de somente diazotróficos. As plantas inoculadas com minhocas apresentaram tendência de menor biomassa e a sobrevivência das minhocas foi baixa. O estudo das interações de microrganismos e macrofauna deve ser considerado na pesquisa e desenvolvimento de práticas de manejo mais sustentáveis para reflorestamento e manutenção de florestas de araucária. / Araucaria angustifolia is a tree of high lumber and resin values, a source of food, and the most important tree in the Mixed Subtropical Ombrophilous forest, a rich ecosystem with many endemic species. However, due to intense exploration for decades, the Araucaria is presently considered a critically endangered species, and the understanding of this ecosystem is fundamental for conservation and regeneration purposes. Soil organisms such as earthworms, arbuscular mycorrhizal fungi (AMF) and diazotrophic bacteria play an essential role in nutrient cycling and can increase plant performance. Many studies have evaluated the impact of each of these organisms independently, but few have studied their interactions. Therefore, the aim of this study was to evaluate the inoculation effects of invasive earthworms (Amynthas corticis), AMF (Gigaspora rosea) and an isolated of diazotrophic bacteria, and the interactions between each of these, on the performance of A. angustifolia seedlings. The plants were grown in greenhouse conditions in a block-type randomized design with a factorial layout of 2x2x2, being: presence and absence of earthworms (A. corticis), presence and absence of AMF (G. rosea) and presence and absence of diazotrophic bacteria (isolated S32274), in eight replicates, evaluated at 150 and 250 d after transplanting. The following parameters were evaluated: plant height and diameter, shoot and root biomass, shoot nutrient content (P, N), number of AMF spores, root mycorrhizal colonization rate and earthworm survival, reproduction and fresh biomass. Plant biomass and shoot nutrient content were affected by the three-way interaction of earthworms, AMF and bacteria. AMF inoculation enhanced A. angustifolia performance, while bacterial inoculation alone had no significant effect on plants and earthworms had low survival rates and tended to reduce plant biomass. Microbial-faunal interactions can lead to important changes in plant growth and should be considered in future research and development of sustainable Araucaria forest management practices.

Enterobactérias são comumente encontradas em simbiose com plantas, promovendo o crescimento vegetal, através da redução do nitrogênio atmosférico a amônia. Entretanto, são os principais patógenos na medicina humana e veterinária. O objetivo deste estudo foi buscar marcadores genéticos e fisiológicos que caracterizem espécies de enterobactérias isoladas de cana-de-açúcar (n=24) e de origem clínica (n=15). Foram submetidas a testes moleculares e fisiológicos como: capacidade de reduzir N2; perfil de susceptibilidade a antibióticos; atividade hemolítica; produção de substâncias promotoras de crescimento e liberação de enzimas extracelulares. Atividades metabólicas e fisiológicas altamente conservadas, sustentadas pelo ponto vista genético, permitem a distribuição destas espécies em diferentes ecossistemas, e, em condições favoráveis, esta adaptação pode contribuir para o estabelecimento de processos patogênicos ou simbióticos em plantas. Então, enterobacterias ambientais podem se tornar patogênicas, enquanto isolados clínicos podem se adaptar a condições ambientais. / Enterobacteria are commonly found in symbiosis with plants, promoting their growth by reducing atmospheric nitrogen to ammonia. However, they are also major pathogens in human and veterinary medicine. The aim of this study was to characterize physiological and genetic markers that distinguish enterobacteria species isolated from sugarcane (n= 24) and clinical sources (n= 15). The samples were characterized regarding their molecular and physiological assays as: ability to reduce N2, antibiotic susceptibility profile; screen for hemolytic activity; production of plant-growth promoting compounds and release of extracellular enzymes. Finally, highly conserved physiological and metabolic activities are supported on genetic backgrounds that allow a wide distribution along different ecosystems and, in favorable conditions, this adaptation could contribute to the establishment of a pathogenic process or symbiosis in plants. So, environmental enterobacteria isolates can become pathogenic, whereas clinical strains can adapt to environmental conditions.

Raramente plantações de eucalipto respondem à adubação nitrogenada. Contudo, por se tratar de povoamentos monoespecíficos, com baixa capacidade de fixação de N, depois de algumas rotações de cultivo a probabilidade de resposta a este nutriente aumenta, devido ao esgotamento das reservas naturais de nitrogênio do solo acumuladas no ecossistema anterior. O presente estudo teve como objetivos avaliar i) o crescimento, o desenvolvimento de raízes finas de Eucalyptus grandis e de Acacia mangium em povoamentos monoespecíficos e mistos; ii) a nodulação da A. mangium nestes povoamentos. As árvores foram plantadas em maio de 2003 no espaçamento 3m x 3m. O delineamento experimental foi o de blocos completamente aleatorizados (4 blocos), sendo avaliados 3 tratamentos: povoamentos monoespecíficos de E. grandis e A. mangium e um povoamento em que essas espécies foram consorciadas (1100 plantas por ha de E. grandis e 550 árvores por ha de A. mangium). Quando consorciada, a A. mangium foi plantada no meio da distância entre as árvores de E. grandis na mesma linha de plantio. Foram amostradas raízes finas vivas (&#8804;3 mm) em 5-16 posições (dependendo do tratamento), de uma árvore de área basal média em doze parcelas (3 tratamentos x 4 blocos), até 1 m de profundidade aos 6 e 12 meses pós-plantio e até 2 m de profundidade aos 18 e 30 meses pós-plantio, por meio de uma sonda de aço com 4,5 cm de diâmetro interno. O E. grandis foi diferente da A. mangium quanto ao desenvolvimento radicular nos diferentes períodos de amostragem, principalmente na camada superficial do solo (0-10 cm). No povoamento misto, aos 30 meses pós-plantio, o E. grandis foi 64% maior em altura do que a A. mangium e 75% maior em área basal, produzindo 94% mais biomassa do que esta leguminosa. A assimetria do crescimento radicular foi elevada entre as espécies, reflexo da grande competição por luz na parte aérea. Não houve clara estratificação de exploração das camadas do solo pelo sistema radicular das espécies. O E. grandis apresentou maior exploração radicular em todas as camadas do solo, fazendo com que o desenvolvimento radicular da A. mangium ficasse restrito a proximidade da árvore. O elevado grau de assimetria no desenvolvimento radicular entre as espécies resultou, aos 30 meses, na camada 0-10 cm, numa diferença de 91% na densidade de raízes finas (drf) entre as espécies. A nodulação foi sensível a competição com o E. grandis, aparentemente, devido à variação de umidade e temperatura sazonal. Aos 18 meses, no povoamento monoespecífico, houve tendência de maior densidade de nódulos na linha de plantio, camada 0-10 cm. Aos 30 meses os nódulos foram encontrados próximos às árvores. No misto, aos 18 e 30 meses ocorreu diminuição da densidade de nódulos na camada 10-30 cm e aumento entre 30 e 50 cm. / Eucalypts plantations rarely answer to the nitrogen fertlization. However, for being of monospecific stands, with low capacity of N fixation, after some cultivation rotations the answer probability to this nutritious one increases, due to the exhaustion of the natural reservations nitrogen of the soil accumulated in previous ecosystem. The present study had as objectives to evaluate i) the growth, the development of Eucalyptus grandis and Acacia mangium fine-root in monospecific and mixed stands; ii) the A. mangium nodulation in these stands. The trees were planted in may of 2003 in the spacing 3m x 3m. The experimental design was it of completely randomized blocks (4 blocks), between assessed 3 treatments: Monospecific stands of E. grandis and A. mangium and a stand in that those species were mixed (1100 plants for ha of E. grandis and 550 trees for ha of A. mangium). When mixed, to A. mangium was planted in the middle of the distance among the trees of E. grandis in the same plantation line. They were sampling live fine-root (&#8804; 3 mm) in 5-16 positions (depending on the treatment), of a tree of medium basal area in twelve portions (3 treatments x 4 blocks), until 1 m of depth to the 6 and 12 months powder-plantation and until 2 m of depth to the 18 and 30 months powder-plantation, by means of a sledgehammer with 4,5 cm of internal diameter. The E. grandis was different from the A. magium with relationship to the roots development in the different sampling periods, mainly in the superficial layer of the soil (0-10 cm). In the mixed stand, between 29 and 30 months after plantation, E. grandis was 64% larger in height than at A. mangium and 75% larger in basal area, producing 94% more biomass than this leguminous. The asymmetry of the root growth was elevated between the species, reflex of the great competition for light in the aerial part. There was not clear stratification of exploration of the layers of the soil for the roots system of the species. The E. grandis presented larger roots exploration radicular in all the layers of the soil, doing with that the roots development of the A. mangium was restricted in the proximity of the tree. The high asymmetry degree in the roots development between the species, resulted to the 30 months in the layer 0-10 cm, a difference of 91% in the density of fine roots (dfr) between the species. The nodulation was sensitive the competition with the E. grandis , seemingly, due to the humidity variation and seasonal temperature. To the 18 months, in the monospecific stands, there was tendency of larger density of nodules in the plantation line, layer 0-10 cm. To the 30 months the nodules were found close to the trees. In the mixed, to the 18 and 30 months it happened decrease of the density of nodules in the layer 10-30 cm and increase between 30 and 50 cm.

Submitted by Eunice Novais (enovais@uepg.br) on 2018-03-05T18:23:35Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Leandro Tullio.pdf: 1410480 bytes, checksum: b92ca948d0810d08208334b6703b86c9 (MD5) / Made available in DSpace on 2018-03-05T18:23:35Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Leandro Tullio.pdf: 1410480 bytes, checksum: b92ca948d0810d08208334b6703b86c9 (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O pH é o principal determinante da diversidade microbiana do solo. Rhizobium freirei é um notável endossimbionte de feijão e reconhecido por sua elevada capacidade de tolerância a estresses ambientais, como o pH ácido. O objetivo deste trabalho foi analisar alterações na expressão gênica, em nível transcricional e traducional, de R. freirei cultivada em pH ácido. A bactéria foi cultivada em caldo TY até alcançar a fase exponencial em pH 6,8 e pH 4,8 e, submetida à extração de proteínas totais. As proteínas foram separadas por eletroforese bidimensional e os perfis proteicos obtidos foram analisados em imagens de alta resolução. Os spots diferencialmente expressos (p ≤ 0,05) foram selecionados para análise em espectrometria de massa e identificação in silico. A expressão diferencial dos genes gshB, gstA e ropB foi analisada após 0, 30 e 60 min de exposição de R. freirei ao pH ácido. De acordo com os resultados, o principal mecanismo de tolerância de R. freirei ao pH ácido parece estar associado à alteração de vias metabólicas centrais, devido ao aumento na expressão de proteínas envolvidas com vias oxidativas (ZwF, KDPG e PckA), relacionadas ao Ciclo do Ácido Tricarboxílico. A maior expressão destas enzimas sugere um aumento no consumo de carboidratos e consequente formação de NADH, que pode ser corroborado pelo aumento na expressão da subunidade NuoC do Complexo 1 da cadeia respiratória, que cataliza a conversão de NADH em NAD+ acoplada ao transporte de prótons para o periplasma, reduzindo a acidificação citosólica. O Complexo 1 é considerado o principal formador de radical superóxido, além disso a maior expressão das enzimas antioxidativas AhpC e GstA em nível traducional, bem como a maior expressão de gstA em nível transcricional, sugere fortemente que o pH ácido induz ao estresse oxidativo em R. freirei. Por outro lado, a menor expressão da proteína AccC pode estar relacionada a um direcionamento do metabolismo central ao consumo de ácidos em detrimento à biossíntese de ácidos graxos, processo em que AccC é fundamental. A menor expressão da subunidade β do Complexo ATPase (AtpD) pode estar direcionada à redução na acidificação do pH interno, por meio da diminuição na entrada de prótons. Tal abrangência de vias metabólicas envolvidas sugere que a resposta adaptativa ao pH ácido possui caráter multigênico, cuja predominância de proteínas citoplasmáticas reforça a importância do metabolismo central para sua capacidade de tolerar pH acidificado. Ao contrário de trabalhos que enfocam genes ou mecanismos específicos de tolerância, nossos resultados mostraram, pela primeira vez, que o metabolismo central parece ser o principal mecanismo de tolerância ao pH ácido em R. freirei e que há fortes indícios da correlação entre estresse ácido e oxidativo. / The pH is the main controller of microbial diversity of soil. Rhizobium freirei is a remarkable bean endosymbiont and recognized by its ability to tolerate environmental stresses, such as acidic pH. The aim of this study was to analyze changes in gene expression at transcriptional and translational level of R. freirei grown in acidic pH. Bacteria was grown in TY medium until exponential phase in two treatments: pH 6,8 and pH 4,8. The protein extraction was performed and the extract was separated by two-dimensional electrophoresis. High-resolution images of the profiles were analyzed and the spots that showed statistical difference in the relative volume (%vol) between treatments were selected for identification by mass spectrometry (MS) and in silico identification. Differential expression of R. freirei was assessed by analysis of gshB, gstA and ropB genes after 0, 30 and 60 min of exposure in acidic pH. According to the results, the changing of central metabolic pathways seems to be the main mechanism of tolerance to acid stress in R. freirei, due to the increased expression of proteins involved in oxidative pathways (Zwf, aldolase KDPG and PckA) related to the Tricarboxilic Acid cicle (TCA). The increased expression of these proteins suggests higher carbohydrate consumption and NADH formation, reinforced by elevated expression of NuoC subunit of respiratory chain Complex 1, that converts NADH into NAD+ coupled to proton transport to periplasm and consequent decreases the cytosolic acidification. The Complex 1 of the respiratory chain is the main superoxide former; moreover the higher expression of the antioxidative enzymes AhpC and GstA at translational level, and the higher expression of gstA at transcriptional level, strongly suggests an oxidative stress induced by acid pH condition. On the other hand, the decreased AccC protein expression supports the trend of the central metabolism to acid-consuming reactions, in contrast to fatty acids biosynthesis pathways, where AccC is essential. Down-regulation of the β subunit of ATPase Complex can be related to regulation of cytosolic acidity by reduction of proton entry through ATPase Complex. Such broad range of pathways involved in the response to acid conditions suggests an adaptive response of multigenic character mainly involving cytoplasmic proteins, and reinforces the importance of the central metabolism for R. freirei ability to tolerate acidic pH conditions. In contrast to studies focused in few genes or specific mechanisms of tolerance, our results shows by the first time that the central metabolism appears to be the main mechanism of acid tolerance in R. freirei and suggests a correlation between acid and oxidative stress responses.

O presente estudo teve por objetivo analisar os efeitos da inoculação de Acinetobacter sp. ICB117 no desenvolvimento da cana-de-açúcar variedade SP791011. As plantas foram cultivadas a partir de toletes com uma gema e fornecidas pelo Centro de Tecnologia Canavieira. Aos 30 dias de idade, foram submetidas aos seguintes tratamentos: controle (C) sem inoculação e solução de Hoagland sem nitrogênio; nitrato (N) sem inoculação e solução de Hoagland com nitrato (15 mM); bactéria (B) inoculação bacteriana e solução de Hoagland sem nitrogênio; bactéria + nitrato (BN) inoculação bacteriana e solução de Hoagland com nitrato (15 mM). Antes da realização da inoculação, foi inserido em ICB117 um plasmídio que contém um gene de expressão para o GFP. O material vegetal foi coletado mensalmente (2 coletas), sendo os seguintes parâmetros analisados: altura, nº de folhas, massa seca, composição de aminoácidos na seiva xilemática, razão C/N das raízes e folhas, atividade da nitrato redutase foliar, assimilação máxima de CO2 e estimativa da população endofítica de ICB117. / Acinetobacter sp. ICB117 is a nitrogen-fixing bacterium isolated from Brazilian sugarcane (Saccharum sp. variety SP791011) which releases amino acids, polyamines and indole-3-acetic acid (IAA) when grown in vitro. The present study aimed to evaluate the effects of Acinetobacter sp. ICB117 (a diazotrophic endophytic bacterium) inoculation on the growth of Saccharum sp. variety SP791011 (sugarcane). Sugarcane plants were obtained from stools with one bud, provided by CTC (Centro de Tecnologia Canavieira). Plants with 30 days old were submitted to the following treatments: control (C) - no bacterium inoculation and Hoagland solution without nitrogen; nitrate (N) - no bacterium inoculation and Hoagland solution with nitrate (15 mM); bacteria (B) - bacterium inoculation and Hoagland solution without nitrogen; Bacteria + nitrate (BN) - bacterial inoculation and Hoagland solution with nitrate (15 mM). Previously to the inoculation procedure, Acinetobacter sp. ICB117 was transformed with plasmid containing a gene that expresses the Green Fluorescent Protein (GFP). Plant material were sampled monthly (2 sampling times) in order to evaluate the following parameters: hight, number of leaves, dry mass, amino acids composition on xylem sap, leaf and root nitrogen and carbon content, leaf nitrate reductase activity, photosynthetic CO2 assimilation and ICB117 endophytic population estimative. The results showed a very similar pattern along experimental period: inoculation with bacterium increased plant total dry mass (evidenced by roots), number of leaves and the assimilation of CO2, but it did not influece significantly the shoot size of the plants and the leaf nitrate reductase activity. The endophytic ICB117 population was larger in plants treated without nitrate than in plants with nitrate inputs. Among the different treatments, alterations were not verified in the amino acids composition on xylem sap prevailing arginine in the sap of all the plants. In the roots, the carbon nitrogen (C/N) ratio was smaller in the plants treated with nitrate (N and BN); in the leaves, the C/N ratio was smaller only in the plants treated with nitrate without inoculation (N).