Made available in DSpace on 2015-03-26T13:53:12Z (GMT). No. of bitstreams: 1 texto completo.pdf: 214329 bytes, checksum: 81d4e9290b3370fc5e7508c542c24c7d (MD5) Previous issue date: 2009-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The literature presents a great deal of controversy regarding increase and/or reduction of organic C supply in soil or of its fractions as a result of implantation of forest species. In this context, the physical methods for separation of soil organic matter (SOM), associated with the isotopic composition of C, allow the understanding of C alteration in soil and also in the different compartments of SOM, such as evaluation and quantification of possible entries of C through implanted culture and, in addition, the losses that the new cultivation brings about C derived from the former culture. This is facilitated when there is a vegetation substitution of C3 for C4, or the contrary, seeing that these plant metabolism presents differences of 13C, which in turn, affects the soil when this residue in left on the soil. Thus, the purpose of this work was to determine the C changes in fractions of organic matters in soils cultivated with eucalyptus. Samples of eucalyptus, pasture and native forest layers of 0-10, 10-20, 20-40, 40-60, 60-80 e 80-100 cm, in four repetitions, were collected. The selected uses were: native forest (NF), fifth rotation eucalyptus (Euc. 5R) eucalyptus in the first rotation at the age of five, (Euc. 1R5A) and adjacent pasture (Past. 1R5A) and also first rotation eucalyptus at the age of two (Euc. 1R2A) and adjacent pasture (Past. 1R2A) The collected samples were submitted to physical fractionation divided into two distinct fractions: particulate organic matter (POM) and mineral-associated organic matter (MAM). These fractions had their C and natural abundance of 13C analyzed by using a mass spectrometer (Continuous Flow Isotope Ratio MS). The data were analyzed considering a sampling design, and from these four repetitions, the average and respective standard errors were obtained for each of the soil layers and their different use. The contents were, in a general way, higher in NF, although, in some comparisons, these values were close to the ones under eucalyptus and pasture. The C contents of Euc. 5R and Euc. 1R5A were not as high as the ones under NF, while in the soil under Euc. 1R2A, these contents were similar or higher for the first collected layers. Among the uses of collected soil, NF and Euc. 5R presented the highest values of C for POM. The soils with Euc. 1R5A, Euc. 1R2A and Past. 1R5A presented the highest decrease, of C content in this fraction when compared to NF. The alteration of soil use resulted in expressive increase in C content of MAM in relation to NF, especially in areas under Euc. 1R5A, Euc. 1R2A, Past. 1R5A e Past. 1R2A. The natural abundance of 13C allowed the cycling rate measurement of POM and MAM fraction cyclings which were nearly, 8,33 e 0,5 % per year, respectively, indicating a greater sensibility of POM to the alterations in the soil use. / A literatura apresenta muita controvérsia no que se refere ao aumento e, ou, diminuição dos estoques de C orgânico no solo ou de suas frações devido à implantação de espécies florestais. Nesse contexto, os métodos físicos de separação da matéria orgânica do solo (MOS), aliados à técnica de composição isotópica do C permitem o entendimento da alteração que o C sofre no solo e nos diferentes compartimentos da MOS, tais como a avaliação e quantificação das possíveis entradas de C por meio da cultura implantada e, também, das perdas que o novo cultivo causa ao C do solo oriundo da cultura anterior. Tudo isso é facilitado quando ocorre a substituição de vegetação C3 por C4 ou o contrário, visto que o metabolismo dessas plantas apresenta discriminação diferenciada do 13C, diferença que também ocorre no solo quando esses resíduos são nele aportados. Assim, o objetivo desse trabalho foi determinar as mudanças do C nas frações da MO em solos cultivados com eucalipto. Foram coletadas amostras em solos com eucalipto, pastagem e mata nativa nas camadas de 0-10, 10-20, 20-40, 40-60, 60-80 e 80-100 cm em quatro repetições. Os usos selecionados foram: mata nativa (MN), eucalipto na 5ª rotação (Euc. 5R), eucalipto na 1ª rotação aos cinco anos (Euc. 1R5A) e pastagem adjacente (Past. 1R5A) e também eucalipto na 1ª rotação aos dois anos (Euc. 1R2A) e pastagem adjacente (Past. 1R2A). As amostras coletadas foram submetidas a um fracionamento físico, dando origem a duas frações distintas: matéria orgânica particulada (MOP) e matéria orgânica associada aos minerais (MAM). Essas frações tiveram o C e a abundância natural de 13C analisados em espectrômetro de massas de razão isotópica de fluxo contínuo. Os dados foram analisados considerando-se um delineamento de amostragem, e, à partir das quatro repetições, foram obtidas as médias e os respectivos erros-padrão, para cada camada dos solos nos diferentes usos. Os teores de C foram, de modo geral, maiores nos solos sob a mata nativa, embora em algumas comparações esses valores tenham sido próximos daqueles sob o eucalipto e pastagem. Os teores de C do solo do Euc. 5R (Eucalipto na 5ª rotação) e Euc. 1R5A (Eucalipto 1ª rotação aos cinco anos de idade) foram menores que aqueles sob a MN (Mata nativa), enquanto para o solo sob o Euc. 1R2A (Eucalipto 1ª rotação aos doisanos de idade), esses teores foram semelhantes ou maiores para as primeiras camadas amostradas. Dentre os usos do solo amostrados, a MN e o Euc. 5R apresentaram os maiores teores de C na MOP. Os solos com o Euc. 1R5A, Euc. 1R2A e Past. 1R5A foram aqueles que apresentaram os maiores decréscimos dos teores de C nessa fração quando comparados à MN. A alteração do uso do solo acarretou aumentos expressivos nos teores de C da MAM em relação à MN, principalmente nas áreas sob o Euc. 1R5A, Euc. 1R2A, Past. 1R5A e Past. 1R2A. A abundância natural do 13C possibilitou o cálculo da taxa de ciclagem de ciclagem das frações MOP e MAM que foram de, aproximadamente, 8,33 e 0,5 % ao ano, respectivamente, indicando a maior sensibilidade da MOP às alterações de uso do solo.

O presente estudo teve como objetivo avaliar o efeito da inoculação com rizóbio no estabelecimento, crescimento inicial e em alguns aspectos da dinâmica de N em folhas de leguminosas (Fabaceae) arbóreas nativas plantadas por semeadura direta no campo, em área de mata ciliar no Estado de São Paulo. Foi avaliada a emergência de plântulas (% em relação ao número de sementes plantadas) até os 3 meses após a semeadura (MAS) e o crescimento em altura aos 13 MAS. O fracionamento isotópico do N foliar também foi avaliado, pelo método da abundância natural do 15N, além da concentração de N e a razão C/N foliar. Acacia polyphylla foi usada como planta-referência não-fixadora de N2. Em relação ao desenvolvimento inicial, houve grande variação entre as espécies estudadas. Acacia polyphylla e Enterolobium contortisiliquum apresentaram taxa de germinação mediana e rápido crescimento. Mimosa bimucronata e Parapiptadenia rigida tiveram crescimento relativamente rápido, porém baixo potencial germinativo. Erythrina speciosa e Poecilanthe parviflora, com crescimento lento, apresentaram germinação elevada no campo. As espécies fixadoras de N2 mostraram &#948;15 N médio de 2,7&#8240;, enquanto que a referência Acacia polyphylla se mostrou cerca de 4,0&#8240; mais enriquecida em 15N . Erythrina speciosa e Ormosia arborea apresentaram os menores valores de &#948;15N, enquanto que Parapiptadenia rigida, enriquecida em 15N, mostrou estar obtendo N exclusivamente do solo. Poecilanthe parviflora, Mimosa bimucronata e Enterolobium contortisiliquum apresentaram valores intermediários de &#948;15N, com grande variação entre os indivíduos amostrados. A concentração de N nos tecidos foliares variou entre 1,5% e 3,6%. De forma geral, esta variável não mostrou relação direta com o &#948;15N das plantas. A menor razão C/N foi observada em Enterolobium contortisiliquum e Erythrina speciosa, seguida por M. bimucronata. Nas condições experimentais locais, as plantas não responderam à inoculação com rizóbio em nenhum dos parâmetros avaliados (estabelecimento, crescimento inicial, &#948;15N, concentração de N e razão C/N). As espécies de crescimento mais lento e com alta incidência de herbivoria observados no campo (E. speciosa e O. arborea) foram também as que apresentaram &#948;15N na faixa considerada como de ocorrência da fixação biológica de nitrogênio. Os resultados indicam, para as outras espécies, maior aquisição de N proveniente do solo. / The aim of this work was to assess the effect of rhizobia inoculation on the establishment, early growth and some aspects of N dynamics in direct-seeded native legume (Fabaceae) trees in a riparian zone of São Paulo State, Southeastern Brazil. Seedling emergency (% of total planted seeds) was evaluated until three months after sowing (MAS), and the height of the trees were measured at 13 MAS. Isotopic N fractionation was also assessed by the 15N natural abundance method, as well as foliar N content and C/N ratio. Acacia polyphylla was used as a non-N2-fixing reference plant. Acacia polyphylla and Enterolobium contortisiliquum grew most rapidly, with moderate germination rate. Mimosa bimucronata and Parapiptadenia rigida were fast-growing but with low establishment rate. Erythrina speciosa and Poecilanthe parviflora showed low growing rate, but high germination potential. The N2-fixers showed an average foliar &#948;15N of 2,7&#8240;, while the reference-plant was 4,0&#8240; more <sup15>N enriched. Erythrina speciosa and Ormosia arborea showed the lowest &#948;15N values. The high &#948;15N of Parapiptadenia rigida probably indicated that it is obtaining N exclusively from the soil. Poecilanthe parviflora, Mimosa bimucronata and Enterolobium contortisiliquum showed intermediate &#948;15N values, with strong variations among the sampled individuals. Foliar N concentrations varied from 1,5% to 3,6%. In general, N concentrations were not correlated with foliar &#948;15N . The lowest C/N ratio was observed on E. contortisiliquum and E. speciosa , followed by M. bimucronata. In this field trial conditions, rhizobia inoculation did not show differences in all surveyed parameters (establishment, early growth, foliar &#948;15N, total N content and C/N ratio of trees). The slow-growing species, E. speciosa and O. arborea , that also had a high herbivore attack observed in the field, showed foliar &#948;15N in the biological N2 fixation range. The results suggested, for the other species, a larger soil N acquisition.

No description available.

La spectroscopie RMN 2D du deutérium en abondance naturelle (DAN) en utilisant les cristaux liquides chiraux comme solvant de RMN est une méthodologie efficace pour deux raisons: i) l’interaction quadrupolaire (interaction RMN sensible à l’ordre orientationnel des molécules et spécifique aux noyaux de spin I>1/2) n’est plus nulle en moyenne comme dans les liquides; ii) la chiralité du milieu permet de discriminer spectralement des énantiomères (molécule chirale) ou des directions énantiotopes (molécule prochirale). L'objectif principal de ce travail de Thèse était d'explorer le potentiel analytique de cette technique pour analyser le fractionnement isotopique naturel deutérium dans le cas d’ester d’acides gras saturés (AGS) et (poly)insaturés (AGI). Le but ultime de ce travail est de fournir de nouvelles informations (de nature stéréochimique) pour améliorer la compréhension de certains mécanismes enzymatiques impliqués au cours de leur biosynthèse. Dans ce contexte, nous avons montré que l'utilisation de solutions organiques orientées de polypeptides (mésophases chirales) utilisant des co-solvants polaires comme le DMF ou la pyridine (Py) fournissait les meilleurs résultats en termes d’(énantio)discrimination spectrale (nombre de sites et amplitude) sur la base des déplacements chimiques et des éclatements quadrupolaires du deutérium. Ainsi, la mésophase chirale (PBLG/Py) a été utilisée avec succès pour analyser les AGI comme le linoléate de méthyle (C18), pour lequel nous avons pu mesurer l'excès énantio-isotopomèrique (eei) au niveau de chaque site méthylène de la molécule. Pour la première fois, d'importantes informations relatives à la stéréochimie des mécanismes enzymatiques, inaccessibles par la méthode conventionnelle SNIF-NMR®, ont été déterminées. La même méthodologie impliquant la mésophase achirale (PBG/Py) et chirale (PBLG/Py) s’est révélée également être un excellent outil pour l'analyse des SAFA sous leur forme libre (C14 à C18) ou sous leur forme de triglycérides (3*C4 et 3*C14). L'attribution des doublets 2H détectés sur les spectres RMN 2D anisotropes des SAFA a été confirmée par l'élaboration d'un modèle théorique capable de prédire le comportement orientationnel de ces molécules flexibles. Comme exemple illustratif, la méthode a été appliquée pour étudier les mécanismes enzymatiques convertissant le linoléate en vernoléate dans deux plantes différentes. Enfin, pour améliorer la compréhension des interactions «soluté-polypeptide» impliquées dans les mécanismes d'orientation et d’énantio-discrimination, nous avons étudié par RMN 2D DAN, l'évolution des paramètres d'ordre (matrice de Saupe) de deux molécules prochirales, rigides et apolaires dissoutes dans une mésophase chirale préparée en mélangeant deux polypeptides de même stéréochimie (L), mais dont la nature chimique des chaînes latérales est différente, en fonction de leur proportion massique respective. / Natural abundance deuterium (NAD) 2D-NMR spectroscopy using (a)chiral liquid crystals as NMR solvent is a powerful method for two reasons: i) the quadrupolar interaction (an order-sensitive NMR interaction specific to spins I > ½) is not averaged to zero anymore as in liquids; ii) the chirality of medium allows enantiomers (chiral molecule) or enantiotopic directions (prochiral molecule) to be spectrally discriminated. The main objective of this Thesis work was to explore the analytical potential of this technique to analyze the natural distribution of deuterium in the case of esters of saturated fatty acids (SAFA) and (poly)unsaturated fatty acids (PUFA). The ultimate goal of this research is to collect new (stereochemical) information to improve the understanding of some enzymatic mechanisms involved during their biosynthesis. In this context, we have shown that the use of oriented solutions of polypeptide (chiral mesophases) using polar co-solvents such as DMF or pyridine (py) provided better results in terms of spectral (enantio)discrimination (number of sites and magnitude) on the the basis of chemical shifts and deuterium quadrupole splittings. Thus, the chiral mesophase (PBLG/py) has been applied successfully to analyse PUFA’s like the methyl linoleate (C18) for which we could measure the enantio-isotopomeric excess (eie) at each methylen site of the molecule. For the first time, important information related to the stereochemistry of enzymatic mechanisms, inaccessible by the conventional method SNIF-NMR®, have been determined. The same methodology using achiral (PBG / py) and chiral (PBG / py) mesophases, revealed also to be an excellent tool for analysing SAFA in their free form (C14 to C18), or in triglyceride forms (3*C4 and 3*C14). The assignment of 2H doublets detected on 2D-NMR spectra of SAFA’s was confirmed by developing a theoretical model predicting the orientational ordering behavior of these flexible molecules. As illustrative exemple, the method was applied for investigating the enzymatic mechanisms converting the linoleate into vernoleate in two different plants. Finally, to improve the understanding of “solute/polypeptide" interactions involved in the orientation and enantiodiscrimination mechanisms, we have investigated by NAD 2D-NMR the evolution of the order parameters (Saupe matrix) of two apolar, rigid prochiral molecules dissolved in a chiral mesophase made by mixing two polypeptides having the same stereochemistry (L) but different type of side chains, versus their respective mass proportion.

No description available.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-09-11T19:30:41Z No. of bitstreams: 1 2017 - Marcius Nei Zanin Cesar.pdf: 3447328 bytes, checksum: 098490a3674208d8609db17b18d3c285 (MD5) / Made available in DSpace on 2018-09-11T19:30:41Z (GMT). No. of bitstreams: 1 2017 - Marcius Nei Zanin Cesar.pdf: 3447328 bytes, checksum: 098490a3674208d8609db17b18d3c285 (MD5) Previous issue date: 2009-04-30 / Cap. I The aim of this work is to evaluate the agronomic behavior of different legume species under cerrado conditions in Mato Grosso do Sul. Seven experiments were carried out, all of them in the experimental field of the (Ag?ncia de Desenvolvimento Agr?rio e Extens?o Rural de MS), (Agency of rural development and extension of MS). Two of these experiments referred to the performance of legumes evaluation. The first experiment was carried out during the Spring- Summer period, and the second one during the Fall- Winter period. The treatments were constituted by the legume species (Crotalaria juncea, Crotalaria ochroleuca, Crotalaria mucronata, Crotalaria reviflora, Mucuna pruriens, Mucuna aterrima, Cajanus cajan (L.) Millsp Cv Fava larga and Cv IAPAR Arat? 43 an?o, Canavalia ensiformes and Canavalia brasiliensis). The third experiment was carried out to determine the dry phytomass decomposition rate and the nitrogen release of the species that were evaluated; this happened during the Fall-Winter period, and the treatments were the mulching of the legumes cited above, except C. breviflora, which was severely attacked by Fusarium sp. The experimental design adopted was randomized blocks, with eleven treatments and nine harvest dates disposed with four replicates. The forth and the fifth experiments were carried out in the subsequent year, their aim was qualifying the Biological Nitrogen Fixation (hereinafter called BNF) and determining the isotope discrimination value ?B value?; their treatments were seven legume species previously selected due to their performances on the former experimental actions and three checks, Brachiaria decumbens, Helianthus annuus, and Zea mays cv BR 106, disposed in randomized blocks with four replicates. The sixth and the seventh experiments were carried out to evaluate the performance of the cabbage cv Astrus under organic management in no-tillage system. The treatments of the sixth experiment were maize-velvet bean intercrop. The later was sown in five different times after maize germination, mucuna alone, maize alone, spontaneous vegetation, and cultivation with conventional tillage of the soil. The treatments of the seventh experiment were maize intercropped with Crotalaria juncea, the latter was slashed, slashed and pruned, maize with basic fertilizer, maize with basic and dressing fertilizers, crotalaria alone, maize alone, spontaneous vegetation, and cultivation with conventional tillage of the soil. The experimental design adopted for both experiments was randomized blocks. The evaluation of the aerial phytomass production was determined when the legume species flowered and when the non-legume ones underwent the grain filling process. The quantification of BNF and the determination of the B value were estimated by using natural abundance 15N and the 15N dilution technique. Functional growth analyses were also carried out as well as soil cover rates, digestion time of the plant tissues, and the phytosociology were determined. On the sixth and seventh experiments the green manure contributions on the agronomic behavior of the cabbage cultivated in no-tillage system under organic management were evaluated. The results obtained have demonstrated the viability for the cultivations of these legume species at the Cerrado Biome, with the contribution of the BNF varying between 75 and 85% of the nitrogen found in the plant tissue originating from the air. They have also demonstrated the viability of using C. juncea and velvet bean when both are intercropped with maize in the mulching formation to the organic cultivation of the cabbage in no-tillage system Cap. II Two experiments were carried out to evaluate the agronomic behavior of legume species in which several components of plant growth were evaluated, such as aerial phytomass production, soil cover rate, seed production, besides phytosociology and in situ decomposition rate under cerrado conditions in Mato Grosso do Sul in two periods of the year. One experiment was carried out during the Spring-Summer period and the other one was carried out during the Fall-Winter period. Both experiments were carried out at the Centro de Pesquisa da Ag?ncia de Desenvolvimento Rural e Extens?o Rural de Mato Grosso do Sul (Mato Grosso do Sul Research center of the Agency of rural development and extension), in Campo Grande ? MS. The experimental design adopted for both was randomized blocks, formed by eleven treatments made up by the species C. juncea, C. ochroleuca, C. mucronata, C. spectabilis, C. breviflora, Mucuna aterrima, Mucuna pruriens, Canavalia brasiliensis, Canavalia ensiformis, Cajanus Cajans cv ?IAPAR an?o?, and Cajanus Cajans cv. giant broad bean. The agronomic behavior of the species that were studied was evaluated by the analysis of the stem and the leaf separately. It was observed that the aerial phytomass productions differed significantly with the species of the genus Crotalaria, showing the best results. Crotalaria juncea stands out with 14.16 Mg ha-1, followed by the Cajanus cajan cv. Fava larga with 11.58 Mg ha-1; there were no significant differences among the species of prostrate habit, mucunas and Brazilian jackbean (Canavalia brasiliensis). The later obtained 3.56 Mg ha-1 and the former did 2.85 Mg ha-1. Regarding seed production, the best performances were obtained during the Fall-Winter period for all legume species, except jack bean and feij?o-bravo (Capparis flexuosa), both obtained similar performances on the two periods of sowing, probably because they might be more tolerant to the drought stress. Regarding the decomposition rate, the results have revealed that the decomposition constants and the residue half-lives had different behaviors on the species that were studied; the Crotalaria species obtained higher decomposition rates when compared to the other species, differentiated behaviors were also noticed on the stem and on the leaf. The C. juncea, jack bean, and the two species of mucuna obtained higher soil cover rate, which reflected a higher suppression of spontaneous plants Cap. III Two experiments related to the quantification of BNF and the determination of the isotope discrimination, ?B value?, in legume species previously selected were simultaneously carried out in the experimental field of the AGRAER-MS, in Campo Grande-MS, during the Spring/Summer period in the 2005/2006 year of production. The experimental design adopted was randomized blocks, formed by ten treatments made up by the species C. juncea, C. ochroleuca, C. mucronata, C. spectabilis, velvet bean, Brazilian jackbean, and Pigeon pea; there have been also, as checks, Sunflower, Maize, and Brachiaria species. The aerial phytomass productions were determined when each legume species flowered and when the non-legume ones underwent the grain filling process. With the samples of legumes and check plants, the quantities of N and the BNF were estimated by using the 15N dilution technique. Afterwards, when the BNF values were known, they were applied to the equation used in natural abundance 15N with the aim of estimating the B value. Regarding the aerial phytomass production, the Pigeon pea had the best performance, followed by the C. ochroleuca, reaching averages of 16.24 Mg ha-1 against 14.44 Mg ha-1. The legume species behaved similarly to the amount of accumulated nitrogen; the Pigeon pea, C. ohcroleuca, and C. mucronata reached values of 346.57 kg ha-1, 333.25 kg ha-1, and 277.35 kg ha- 1 respectively, and they deserve a distinction. Regarding the %BNF, it was observed that the 15N dilution technique could not be applied in all the species that were studied since the cycle of most legumes species was different from the checks; in this way, the checks were not appropriate because the technique demands that legumes and checks grow simultaneously and under the same conditions. However, to the varieties which were more precocious that the checks, the BNF value must be at least between 73 to 87%. Just on the specie C. mucronata it was possible to estimate the BNF and the B value with the rigor that the applied isotopic methodologies demand. The B value of this specie was -3.69. Cap. IV The aim of this study is to evaluate the agronomic behavior of the cabbage in no-tillage system under organic management and the contribution of the prior cultivation of two legumes with different growing habits intercropping with maize in the mulching formation. Both experiments were carried out in the experimental field of AGRAER-MS, in Campo Grande-MS. The first experiment was the maize-C. juncea intercrop, the latter was managed, slashed, pruned, and slashed afterwards; besides the cultivation of single maize, single C. juncea, cultivation with conventional tillage of the soil with and without fertilization with equivalent amounts of 100 Kg N ha-1 at planting and sidressed 30 days after the maize cultivation, making up eight treatments with four replications in randomized blocks. The dry matter productions in the aerial part of the cover crops and the spontaneous vegetation were evaluated. Agronomic characteristics that were evaluated on the cabbage: productivity, commercial standard, fresh and dry weight, besides the dry phytomass of the prior cultivation. On this experiment it was possible to verify better yields regarding the fresh weight and head diameter when we used single, pruned C. juncea maize with basic fertilizer, and maize with base and dressing fertilizers, reaching a fresh weight over 1.0 Kg and heads diameter over 10 cm. Regarding maize and cabbage productivity, they were not influenced by the different kinds of intercrop systems; there were no significant statistic difference of treatments, which also reflected on the dry matter production of the prior cultivations. On the second experiment, the experimental design which was adopted was randomized blocks, with nine treatments and four replicates. The treatments were: maize-velvet bean intercrop, the later was planted in five different times: after the maize germination, maize alone, mucuna alone, cultivation with conventional tillage of the soil, and fallow with spontaneous vegetation, making up a total number of nine treatments. The parameters that were evaluated were similar to the ones of the former experiment.The cabbage production showed the most promising yield 2.06 Kg of head average weight and when cultivated as a sequential crop to the maize-velvet bean intercrop sown 15 days after the maize germination, differing significantly from the other treatments. When we analyzed the maize productivities, we noticed fall of productivity around 29% when it was intercropped with velvet bean at 15 and 30 days after its germination when it was compared to the other prior cultivations in which the intercrop system was used. / Cap. I O presente trabalho teve como finalidade avaliar o comportamento agron?mico de diferentes esp?cies de leguminosas nas condi??es do cerrado de Mato Grosso do Sul. Foram conduzidos sete experimentos, todos no campo experimental da Ag?ncia de Desenvolvimento Agr?rio e Extens?o Rural de MS, sendo que dois deles foram referentes ? avalia??o do desempenho das leguminosas. O primeiro foi instalado no per?odo de primavera-ver?o e o segundo no outonoinverno. Os tratamentos foram constitu?dos das esp?cies de leguminosas Crotal?ria juncea, Crotal?ria ochroleuca, Crotal?ria mucronata, Crotal?ria reviflora, Mucuna pruriens, Mucuna aterrima, Cajanus cajan (L.) Millsp cv Fava larga e Cv IAPAR Arat? 43 an?o, Canavalia ensiformes e Canavalia brasiliensis. O terceiro experimento foi realizado para determinar a taxa de decomposi??o da fitomassa seca e libera??o de nitrog?nio das esp?cies avaliadas, realizado no per?odo de outono-inverno, com os tratamentos constituindo-se da palhada das leguminosas descrita acima, exceto C. breviflora, pois a leguminosa sofreu ataque severo de Fusarium sp. O delineamento experimental foi em blocos ao acaso, com onze tratamentos e nove ?pocas de coleta distribu?dos em quatro repeti??es. O quarto e o quinto experimentos foram realizados no ano subsequente e tiveram como finalidade quantificar a Fixa??o Biol?gica de Nitrog?nio (FBN) e determinar o valor de discrimina??o isot?pica ?Valor B?, tendo como tratamentos sete esp?cies de leguminosas previamente selecionadas pelos seus desempenhos nas a??es experimentais anteriores e tr?s testemunhas, Brachiaria decumbens, Helianthus annuus e Zea mays cv BR 106, dispostos em blocos ao acaso com quatro repeti??es. O sexto e o s?timo experimentos foram conduzidos para avaliar o desempenho do repolho cv Astrus sob manejo org?nico em sistema plantio direto, sendo que o sexto experimento teve como tratamentos cons?rcio milho x mucuna cinza, sendo esta semeada em cinco ?pocas diferentes, ap?s germina??o do milho, mucuna em monocultivo, milho em monocultivo, vegeta??o espont?nea e cultivo com preparo convencional do solo. O s?timo experimento teve como tratamentos milho consorciado com Crotal?ria juncea, sendo esta ro?ada, ro?ada e podada, milho com aduba??o de base, milho com aduba??o de base e cobertura, crotal?ria em monocultivo, milho em monocultivo, vegeta??o espont?nea e cultivo com preparo convencional do solo. O delineamento experimental adotado em ambos os experimentos foi o de blocos ao acaso. A avalia??o da produ??o de fitomassa a?rea foi determinada por ocasi?o do florescimento para as esp?cies de leguminosas e de enchimento de gr?os para as n?o-leguminosas. A quantifica??o da FBN e determina??o do valor ?B? foram estimadas utilizando-se a t?cnica de abund?ncia natural 15N e da dilui??o isot?pica de 15N. Foram tamb?m realizadas an?lises funcionais de crescimento, bem como determinadas as taxas de cobertura do solo, tempo de decomposi??o dos tecidos vegetais e a fitossociologia. No sexto e no s?timo experimentos, foram avaliadas as contribui??es da aduba??o verde no desempenho agron?mico do repolho cultivado em sistema de plantio direto, sob manejo org?nico. Os resultados obtidos demonstraram a viabilidade do cultivo destas leguminosas no bioma cerrado, com a contribui??o da FBN, variando entre 75 e 85% do nitrog?nio encontrado no tecido vegetal proveniente do ar. Tamb?m, demonstraram a viabilidade do uso da C. juncea e M. cinza quando cultivadas em cons?rcio com milho para obten??o de palhada ao cultivo org?nico do repolho em sistema plantio direto. Cap. II Dois experimentos foram conduzidos para avaliar o comportamento agron?mico de esp?cies de leguminosas, onde foram avaliados diferentes componentes do crescimento vegetal, como produ??o fitomassa a?rea, taxa de cobertura de solo, produ??o de sementes, al?m da fitossociologia e taxa de decomposi??o ?in situ?, nas condi??es do cerrado de Mato Grosso do Sul, em duas ?pocas do ano. Os experimentos foram conduzidos no Centro de Pesquisa da Ag?ncia de Desenvolvimento Agr?rio e Extens?o Rural de Mato Grosso do Sul, localizado em Campo Grande - MS, sendo um no per?odo de primavera-ver?o e outro no outono-inverno. Em ambos, o delineamento experimental adotado foi o de blocos ao acaso, formado de onze tratamentos constitu?dos das esp?cies C. juncea, C. ochroleuca, C. mucronata, C. spectabilis, C. breviflora, Mucuna aterrima, Mucuna pruriens, Canavalia brasiliensis, Canavalia ensiformis, Cajanus Cajans cv. IAPAR an?o e Cajanus Cajans cv. fava larga gigante. O comportamento agron?mico das esp?cies estudadas foi avaliado analisando-se separadamente haste e folha. Observou-se que as produ??es de fitomassa a?rea diferiram de forma significativa com as esp?cies do g?nero crotal?ria, obtendo-se melhores desempenhos. Destacam-se a Crotal?ria juncea com 14,16 Mg ha-1, seguida do Guandu cv fava-larga com 11,58 Mg ha-1; entre as esp?cies de h?bito prostrado, n?o houve diferen?as significativas, mucunas e o feij?o-bravo-do Cear?, sendo que esse obteve 3,56 Mg ha-1 contra 2,85 Mg ha-1 da M. preta. Com rela??o ? produ??o de sementes, os melhores desempenhos foram obtidos no per?odo de outono-inverno para todas as leguminosas, com exce??o do feij?o-de-porco e feij?o-bravo, que obtiveram desempenhos semelhantes nas duas ?pocas de semeadura, provavelmente, por serem mais tolerantes ao estresse h?drico. No tocante ? taxa de decomposi??o, os resultados revelaram que as constantes de decomposi??o e tempo de meia-vida tiveram comportamentos diferentes para as esp?cies estudadas, com esp?cies de crotal?ria obtendo maiores velocidades de decomposi??o quando comparadas ?s demais esp?cies, notou-se tamb?m comportamentos diferenciados para haste e folha. A C. juncea, feij?o de porco e as duas esp?cies de mucuna obtiveram maior taxa de cobertura de solo, o que refletiu em uma maior supress?o da vegeta??o de ocorr?ncia espont?nea Cap III Foram conduzidos simultaneamente dois experimentos relacionados ? quantifica??o da FBN e determina??o do valor de discrimina??o isot?pica, valor ?B?, em esp?cies de leguminosas previamente selecionadas. Os experimentos foram conduzidos no campo experimental da AGRAER-MS, localizado em Campo Grande-MS, no per?odo de primavera-ver?o, no ano agr?cola 2005/06. O delineamento estat?stico utilizado foi o de blocos ao acaso, constitu?dos de dez tratamentos, sendo este compostos pelas esp?cies C. juncea, C. ochroleuca, C. mucronata, C. spectabilis, Mucuna cinza, Feij?o-bravo-do-cear? e Guandu fava larga; e como testemunhas as esp?cies Girassol, Milho e Braqui?ria. Por ocasi?o do florescimento de cada esp?cie de leguminosa e enchimento de gr?os das n?o-leguminosas, foram determinadas as produ??es de fitomassa a?rea. A partir das amostras de leguminosas e plantas testemunhas, estimaram-se as quantidades de N e a FBN, para tanto usando a t?cnica de dilui??o isot?pica de 15N . Posteriormente, conhecendo-se os valores de FBN, aplicou-se aos mesmos a equa??o utilizada na t?cnica de abund?ncia natural de 15N com a finalidade de estimar o valor B. Com rela??o ? produ??o de fitomassa a?rea, o Guandu fava larga obteve melhor desempenho seguido da C. ochroleuca, atingindo m?dias de 16,24 Mg ha -1 contra 14,44 Mg ha-1. Para a quantidade de nitrog?nio acumulada as esp?cies de leguminosas se comportaram de maneira semelhante, com destaque para o Guandu fava larga, C. ohcroleuca e C. Mucronata, atingido valores de 346,57 kg ha-1, 333,25 kg ha-1 e 277,35 kg ha-1 respectivamente. No tocante ? %FBN, observou-se que a t?cnica de dilui??o isot?pica de 15N n?o poderia ser aplicada para todas as esp?cies estudadas, uma vez que a maioria das esp?cies de leguminosas teve ciclo diferenciado das testemunhas, desta forma, as testemunhas n?o foram apropriadas, visto que a t?cnica exige que tanto as leguminosas como as testemunhas cres?am nas mesmas condi??es e de forma simult?nea. Contudo, para as variedades mais precoces que as testemunhas, o valor de FBN deve estar no m?nimo entre 73 a 87%. Somente na esp?cie C. Mucronata, foi poss?vel estimar a FBN e o valor B com o rigor que exigem as metodologias isot?picas aplicadas. O valor B para esta esp?cie foi de -3,69. Cap. IV O presente estudo teve o objetivo de avaliar o desempenho agron?mico do repolho em sistema plantio direto, sob manejo org?nico, e a contribui??o do pr?-cultivo de duas leguminosas de h?bitos de crescimento distintos em cons?rcio com milho, na forma??o de palhada. Ambos experimentos foram implantados no Campo Experimental da AGRAER, em Campo Grande-MS. O primeiro experimento consistiu no cons?rcio entre milho e C. juncea, sendo esta manejada, somente com ro?ada (taratamento 6), podada e posteriormente ro?ada (tratamento 5), al?m do cultivo do milho solteiro, C. juncea solteira, cultivo com preparo convencional do solo, com aus?ncia e presen?a de aduba??o, em quantidades equivalentes a 100 Kg N ha-1 no plantio e em cobertura 30 dias ap?s plantio do milho, perfazendo oito tratamentos com quatro repeti??es, dispostos em blocos ao acaso. Avaliaram-se as produ??es de mat?ria seca na parte a?rea das plantas de cobertura e da vegeta??o espont?nea. As caracter?sticas agron?micas avaliadas no repolho foram: produtividade, padr?o comercial, peso fresco e seco, al?m da fitomassa seca do pr?-cultivo. Neste experimento, verificaram-se melhores rendimentos quanto ao peso m?dio e di?metro da cabe?a quando se utilizaram C. juncea solteira, C.juncea ro?ada, milho com aduba??o de base e milho com aduba??o de base e cobertura, alcan?ando peso m?dio acima de 1,0 kg e di?metro das cabe?as acima de 10 cm. Quanto ? produtividade do milho e do repolho, estes n?o foram influenciados pelos diferentes tipos de cons?rcios, n?o havendo diferen?a estat?stica significativa entre os tratamentos, o que refletiu tamb?m na produ??o de mat?ria seca dos pr?-cultivos. No segundo experimento, o delineamento experimental utilizado foi o de blocos ao acaso com nove tratamentos e quatro repeti??es. Os tratamentos foram: o cons?rcio entre milho e mucuna cinza, sendo esta plantada em cinco ?pocas diferentes - ap?s a germina??o do milho, monocultivo do milho, monocultivo da mucuna, cultivo com preparo convencional do solo e pousio com vegeta??o espont?nea -, perfazendo um total de nove tratamentos. Os par?metros avaliados foram semelhantes aos do experimento anterior. A produ??o do repolho alcan?ou melhores rendimentos, 2,06 kg de peso m?dio da cabe?a; e, quando cultivado em sucess?o ao cons?rcio milho x M. Cinza, semeada aos 15 dias ap?s germina??o do milho, diferiu significativamente dos demais tratamentos. Ao se analisarem as produtividades do milho, notouse uma queda de rendimento em torno de 29% quando este foi consorciado com M. Cinza, aos 15 e 30 dias ap?s sua germina??o, ao comparar-lo aos demais pr?-cultivos utilizando-se cons?rcios

La mesure de couplage dipolaire permet d’accéder à la structure tridimensionnelle d’un composé solide. Cependant, en présence d’une forte densité de spins couplés, le phénomène de troncature dipolaire rend difficile l’obtention de ces informations par RMN du solide. Ce problème peut être affranchi par l’étude de spins rares en abondance naturelle. En effet, avec une abondance naturelle de 1.1 %, la probabilité que trois 13C soient couplés, et avec elle la troncature dipolaire, devient négligeable. Une méthodologie basée sur la séquence de recouplage dipolaire POST-C7 permet d’accéder à des informations structurales d’échantillons en abondance naturelle sensibles à la fois à la conformation moléculaire et à l’empilement cristallin par mesure de couplages dipolaires 13C-13C. La sensibilité de détection des signaux RMN 13C est augmentée à l’aide la polarisation dynamique nucléaire ce qui permet de réduire considérablement les temps d’expériences. De plus, la séquence de recouplage R20_9_2 aidée de supercycles s’est montrée être plus robustes que POST-C7 face à de fortes anisotropies de déplacement chimique ou de forts couplages hétéronucléaires 1H-13C. La seconde problématique abordée concerne l’attribution de signaux 13C. En effet, il existe seulement quelques exemples de détermination de connectivités 13C -13C en abondance naturelle. Nous montrons ici que des spectres de corrélations dipolaires 13C-13C peuvent être obtenus en quelques jours à l’aide de la séquence de recouplage R20_9_2. Contrairement aux méthodologies basées sur le couplage J, notre séquence requiert un temps d’excitation DQ plus court ce qui la rend adaptée à l’étude de solides désordonnés. / Measurment of dipolar coupling provides 3D structural information of powder samples. However, in practice, the high density of spins in organic compounds prevents the measurements of long-range dipolar couplings in solid-state NMR by the so-called dipolar truncation effect. The study of rare spins on natural abundance allows to overcome this problem. In fact, with a natural abundance of 1.1 %, the probability for three 13C to be coupled is negligible. We developed a methodology based either on the dipolar recoupling NMR pulse sequence POST-C7 or on the dramatic increase in sensitivity provided by dynamic nuclear polarization. We demonstrated that its methodology provides a measure of 13C-13C dipolar couplings in natural abundance powder samples and that the so-obtained distance information is sensitive to both molecular conformation and crystal packing of powder samples. Moreover, we show that the recoupling pulse sequence R20_9_2 is more robust to strong chemical shift anisotropy and also to strong 1H-13C heteronuclear dipolar couplings than POST-C7. The second challenge involves 13C signal assignment for natural abundance. In fact, there are only a few examples of 13C-13C correlation spectra obtained for natural abundance samples. Here, we show that 13C-13C correlation spectra sequence based on the reintroduction of 13C−13C dipolar couplings can be obtained with standard MAS probe and within few days using R20_9_2 pulse sequence. Contrary to pulse sequences based on 13C-13C J coupling, our pulse sequence requires shorter DQ excitation time and hence, is more suitable for samples having short T2 relaxation times such as amorphous solids.