Submitted by GABRIELA CAROLINA VILLAMAGUA VERGARA (g_villamagua@yahoo.com) on 2018-07-28T04:37:09Z No. of bitstreams: 1 Tese Gabriela Villamagua 3.2.pdf: 1881061 bytes, checksum: 7701b89454927308fd0bc3786253c83a (MD5) / Approved for entry into archive by Ana Lucia de Grava Kempinas (algkempinas@fca.unesp.br) on 2018-07-30T13:27:32Z (GMT) No. of bitstreams: 1 vergara_gcv_dr_botfca.pdf: 1881061 bytes, checksum: 7701b89454927308fd0bc3786253c83a (MD5) / Made available in DSpace on 2018-07-30T13:27:32Z (GMT). No. of bitstreams: 1 vergara_gcv_dr_botfca.pdf: 1881061 bytes, checksum: 7701b89454927308fd0bc3786253c83a (MD5) Previous issue date: 2018-06-04 / Outra / Com a necessidade de buscar espécies florestais mais eficientes na utilização dos recursos naturais como luz, água e nutrientes, o que pode possibilitar um incremento da biomassa da parte aérea, o objetivo do presente trabalho foi o de quantificar as taxas de crescimento, eficiência da utilização da luz, água e nutrientes de florestas energéticas sob mesmas condições de solo, altitude e manejo. Foram utilizados plantios adensados de Bambusa vulgaris, híbrido espontâneo de Eucalyptus urophylla – clone AEC-144, híbrido interespecífico de Eucalyptus grandis × Eucalyptus urophylla - clone LW07 e Salix nigra. A determinação da produtividade primária líquida do tronco (PPLT), eficiência do uso da luz (EUL), eficiência do uso da água (EUA) foram obtidas através de acompanhamentos mensais e individuais em 15 plantas por espécie, no período de 12 meses. Foi obtido dados de: diâmetro e altura total das plantas, e posteriormente, taxa fotossintética (A), taxa transpiratória (E) e condutância estomática (gs). Foi realizada ainda a determinação do índice de vegetação e a coleta de amostras para determinação de macro e micronutrientes em laboratório. A espécie B. vulgaris apresentou o maior valor de biomassa por planta e, consequentemente, os maiores incrementos em matéria seca por planta (8,07 kg pl-1 e 1,56 kg pl-1 ano-1, respectivamente), no entanto, observou-se que clone de E. urophylla AEC-144 obteve maior eficiência no uso da luz por área (1,80 g MJ-1) e maior eficiência intrínseca no uso da água (68,09 μmol CO2 mol H2O-1). Em relação à eficiência do uso da água, o clone E. grandis × E. urophylla - LW07 apresentou o maior valor (4,93 μmol CO2 mol H2O-1). Nota-se que houve diferença em relação ao acúmulo de nutrientes entre as espécies estudadas, sendo que os maiores valores obtidos foi observado em B. vulgaris. / In the search for forest species more efficient in the use of resources (light, water and nutrients) to increase aerial biomass, this study aimed to quantify the growth, light, water and nutrients use efficiency of short rotation plantations under the same conditions of soil altitude and management of Bambusa vulgaris, the spontaneous hybrid of Eucalyptus urophylla - clone AEC-144, interspecific hybrid of Eucalyptus grandis × Eucalyptus urophylla - clone LW07 and Salix nigra. To determine truck net primary productivity trunk (TNPP), light use efficiency (LUE) and water use efficiency (WUE), 15 plants per treatment were monitored monthly for 12 months. Plants diameter and total height were collected, as well as photosynthetic rate (A), transpiration rate (E) and stomatal conductance (gs), using infrared gas analyzer (IRGA) (LI-COR 6400). Vegetation index was also obtained using AccuPAR (LP-80) ceptometer and were collected samples for determination of macro and micronutrients in the laboratory. Bambusa vulgaris was the species that obtained the highest biomass per plant ratio and consequently higher net primary productivity (8.07 kg pl-1 and 1.56 kg pl-1 year-1, respectively), however, clone AEC-144 showed higher light use efficiency per area (1.80 g MJ-1) and higher intrinsic water use efficiency (68.09 μmol CO2 mol H2O-1). Clone LW07 obtained the highest value (4.93 μmol CO2 mol H2O-1) of instantaneous water use efficiency, when compared to other species. There was a difference in nutrient accumulation between species, and the highest values were observed in Bambusa vulgaris.

Comprendre le devenir du carbone organique stable du sol (COS) dans un environnement globalement plus chaud est un défi majeur pour prévoir sur le long terme la concentration en CO2 atmosphérique. Pour cela il apparaît nécessaire de mieux comprendre ce qu'est ce COS stable à l'échelle pluri-décennale et comment sa cinétique de minéralisation est modulée par la température. C'est avec cette ambition que cette thèse se propose (1) d'étudier la sensibilité à la température de la minéralisation du COS stable; (2) d'étudier la réponse à la température de la communauté microbienne qui minéralise le COS et (3) d'établir un lien entre âge et décomposabilité du COSLes échantillons issus de 4 essais de jachère nue ont été utilisés dans cette thèse. Des échantillons prélevés en début de chacun de ces essais et après plusieurs décennies de jachère nue ont été incubés à différentes températures pendant 427 jours. La respiration de ces échantillons a été suivie régulièrement. En fin d'incubation, la structure des communautés microbiennes a été déterminée par pyroséquençage. D'autre part, une datation du COS contenu dans les échantillons de la chrono-séquence de l'essai de jachère nue de Versailles a été réalisée.Les résultats obtenus mettent en évidence une relation générale entre vitesse de décomposition du carbone et sensibilité à la température. Ces travaux ont également mis en lumière une plus grande diversité et une plus grande sensibilité à la température des communautés microbiennes associées au carbone stable. Enfin, cette thèse met en lumière les difficultés rencontrées lors de l'utilisation de la technique de datation de la matière organique du sol par le 14C. / To understand the fate of stable soil organic carbon (SOC) in a warmer world is a major challenge to be able to predict future atmospheric CO2 concentrations. To do so, it is of prime importance to understand what the stable SOC is exactly and how its mineralization rate is modulated by temperature. This thesis proposed to study (1) the temperature sensitivity of stable SOC mineralization; (2) the response of soil microbial communities to temperature and (3) to establish a link between SOC decomposability and its age. Soil samples from four long term bare fallow experiments were used for work. We incubated soils sampled at the beggining of each experiment and after several decades of bare fallow at different temperatures for 427 days and we regularly monitored soil respiration. At the end of the incubation, soil microbial communities were assessed using pyrosequencing techniques. Finally, we determined the age of soil organic carbon by radiocarbon dating in soil samples from the chrono-sequence located at Versailles, France. The results obtained brought evidence for a general relationship between the mineralization rate of soil organic carbon and its temperature sensitivity. We also found that microbial communities linked to stable organic carbon are more diverse but also more sensitive to a temperature increase. Some bacterial phyla were particularly impacted by the temperature increase and the organic resource rarefaction. Finally, this thesis highlighted the difficulties met with the radiocarbon dating technique.

Selection of optimum nitrogen (N) fertilizer timing, rate, and placement strategies by corn (Zea mays L.) producers are among their most important annual management decisions. Much research has been conducted on pre-plant, at-plant, and one or more sidedress timings for N application to corn, but few public-sector studies employ modern technological approaches for N placement in their experimental designs. Research gaps on optimum placements for at-plant N systems are especially acute when N banding quantity exceeds 20% of the intended season-long N rate. Previous sidedress research has rarely utilized modern N placement tools with high clearance delivery devices for early and late in-season sidedress timings when >50% of the season-long N rate was already applied at planting. Therefore, this 2017 and 2018 Indiana-based field research addressed three questions i) are corn planters that deliver 50% to 100% of a full-season N rate at traditional or alternate band placements capable of matching or exceeding grain yields achieved by lower starter fertilizer N rates, ii) what is the impact of split N management on grain yield and/or N fertilizer recovery efficiency (NRE) when ≥50% of the total N rate is supplied at-plant, and iii) do alternate sidedress N placements (i.e. soil-surface streaming versus injection versus broadcast at multiple timings) in split-N sidedress applications influence grain yield and aboveground plant recovery of N fertilizer?<p></p> <p>To evaluate the consequences of moderate to high N rates banded at planting, urea-ammonium nitrate (UAN) was coulter-banded with a prototype Deere DB20 row-crop planter as close as 5cm x 5cm (5x5) (distance from soil surface x distance from seed row) to as far as 10x20 at planter applied N rates of 34, 101, and/or 202 kg ha-1. These at-plant applications were followed by a V5 to V6 stage mid-row sidedress application (if required) to achieve a uniform total N rate of 202 kg N ha-1. Analyses were primarily focused on 5x5 and 10x5 starter band positions as these were the only placements represented at the 34 kg N ha-1 rate. In these placement comparisons, 5x5 banding yielded similarly to 10x5 banding in 2017, but increased yield 6.6% (averaged across 34, 101, and 202 kg N ha-1 rates) in 2018. Corn grown in 2018 with at-plant rates of 101 and 202 kg N ha-1 produced grain yields statistically similar to or greater than that obtained with the 34 kg N ha-1 rate (averaged across 5x5 and 10x5 placements). In 2018, the 101 kg N ha-1 rate increased yields by 14.8% and NRE by 18.5 g g-1 compared to banding of 34 kg N ha-1. A secondary analysis included 6 placements (5x5, 5x13, 5x20, 10x5, 10x13, and 10x20) at just the 101 and 202 kg N ha-1 rates. Among these additional placement treatment combinations (averaged across 101 and 202 kg N ha-1 rates), both 5x13 and 10x20 banding reduced grain yield in 2018 by 12.5% and 10.1%, respectively, when compared to 5x5 banding. No yield differences among these 6 at-plant placements were found in 2017. Therefore, moderate to high N rates can be banded safely at-planting with the typically close starter fertilizer placements, but higher NRE and optimum yields can be achieved when a 50:50 split N fertilizer management approach is used.</p> <p>The optimal sidedress experiment targeted placement and/or timing impacts on corn yields and NRE when at-plant N was ≥50% and sidedress N was ≤50% of the total N rate. Single at-plant (AP) applications at total N rates of 26 (Zero), 112 (AP_112) and 224 (AP_224) kg N ha-1 were compared to split applications of 202 kg N ha-1 (with ~55% of total N applied at-plant plus the balance at sidedress). Sidedress N was applied at V5 or V12 timings with surface streamed versus subsurface injection of UAN, or via high-clearance broadcasting of urea at the V8-stage. In nearly every split sidedress approach, apart from the V12 injection treatment in 2017, grain yields and NRE with split-N sidedress responded similarly to AP_224 each year despite the reduced total N rate at 202 kg N ha-1. Both V12 streaming and AP_224 yielded 6.7% more than the V12 injection approach in 2017. The reduced yield in 2017 from late-season injection contributed to the 4.6% grain yield gain for surface-streaming applications (averaged across timings) with no apparent NRE advantage.</p> <p>These responses confirmed that in-season sidedress N placement influenced yield and, in our case, the surface-streaming advantage over injection was most evident at V12 where late vegetative to flowering rainfall was plentiful. Similarly, planter N placement was not influenced by N band depth as much as by N band distance from the seed row where 13 and 20cm distances occasionally decreased yield in 2018. This research provided evidence of modern placement technology impacts at planting and sidedress times where UAN placed near corn seeds in the seed-furrow and/or plants in the row never reduced, and occasionally increased, grain yield and/or N recovery in corn cropping systems.</p> <p> </p>

The PROTEOLYSIS 6 (PRT6) branch of the N-end rule pathway is a well-characterized negative regulator of flooding and low oxygen tolerance in plants. This study investigated the role of this pathway in adaptation to salinity stress in Arabidopsis and maize via physiological and molecular characterization of Arabidopsis prt6-1 and maize prt6 MU insertion mutants, respectively. Our study demonstrated that the loss of function mutation of prt6 in Arabidopsis activated hormonal and transcriptional responses associated with adaptation to salinity stress, enhancing high salt tolerance at seed germination, seedling, and adult plant stages. Our data also indicated that salinity tolerance conferred by the prt6 mutation is attributed to increased mRNA abundance of key transcriptional factors in ABA-dependent (AREB/ABFs) and independent (DREBs) pathways, together with the dominant expression of downstream dehydrins. Furthermore, this study revealed that the prt6 mutation enhances ethylene and brassinosteroid responses, resulting in restricted Na+ accumulation in roots and shoots as well as increased expression of dehydrin genes such as RD29A and RD29B. Maize prt6 mutant plants, contrary to our observation in Arabidopsis, showed lower seed germination, primary root elongation, and shoot biomass growth along with increased malondialdehyde (MDA) accumulation under high salt. Moreover, maize prt6 mutants exhibited reduced grain yield and yield-related components under high salt. These results indicate that PRT6 functions as a negative regulator for salinity tolerance in Arabidopsis, whereas this gene plays a positive role in salinity tolerance in maize. In wheat, we compared two genotypes with contrasting nitrogen-use-efficiency (NUE), VA08MAS-369 and VA07W-415, to dissect physiological and molecular mechanisms underlying NUE regulation. Our agronomic data revealed that line 369 maintained yield and yield-related parameters and exhibited greater NUE indexes relative to line 415 under N deficient conditions. Furthermore, our analyses suggested that the significantly higher nitrogen use efficiency (NUE) in line 369 could be attributed to the greater N uptake efficiency in this genotype. In fact, line 369 was able to maintain the development of root systems under N limitation. Consistently, genes encoding high-affinity nitrate transporters such as TaNRT2.1 and TaNRT2.2 were expressed more abundantly in the roots of line 369 than line 415 at limited N. Overall, the results of this study characterized physiological and molecular phenotypes associated with high N uptake efficiency in line 369. This is useful information for the development of new wheat accessions with improved NUE. / Doctor of Philosophy / In coastal areas, sea-level rise increases the chances of saltwater intrusion into cultivable lands, making a hostile environment for crop growth and production by imposing flooding and salinity stresses simultaneously. Identification of central regulators that regulate the adaptation to both flooding and salinity is a critical step for the development of new crop genotypes with enhanced tolerance to these stresses. Previous studies have characterized the function of the PROTEOLYSIS 6 (PRT6) gene in adaptation to flooding stress in plants. This study assessed whether this gene is involved in adaptation to salinity stress in Arabidopsis and maize by evaluating the growth and survival of their respective prt6 mutants under high salt. Consistent with the flooding tolerance data, our study showed that the PRT6 gene also functions as a negative regulator of salinity stress tolerance in Arabidopsis. The prt6 mutation in Arabidopsis activated the key transcriptional and hormone response pathways associated with adaptation to both salinity/osmotic stress and sodium toxicity, expressed as enhanced tolerance to excess salt at seed germination, seedling, and adult plant stages. In maize, disruption of the PRT6 gene decreased seed germination, primary root elongation, and shoot biomass growth under high salt, which is opposite to our observations in Arabidopsis. Additionally, the maize mutant plants encountered more oxidative stress, as demonstrated by the higher accumulation of malondialdehyde (MDA) under high salt. Moreover, maize prt6 mutants exhibited reduced grain yield under high salt. Overall, these results indicate that disruption of the PRT6 gene confers increased tolerance to high salt in Arabidopsis, whereas it conversely reduced salinity tolerance in maize. In wheat, we compared two genotypes with distinct nitrogen use efficiency (NUE), VA08MAS-369 and VA07W-415, to determine critical traits involved in NUE regulation. Our study showed that grain yield and yield-related parameters were significantly higher in line 369 than line 415 under low N. Moreover, high NUE in line 369 was attributed to efficient N uptake in this genotype under limited N. Our root architecture analysis demonstrated that line 369 was able to maintain root depth, volume, and thickness even under N limitation. Consistently, line 369 highly induced expression of genes associated with nitrogen transport at low N. Altogether, this study identified key traits involved in high NUE in wheat, facilitating the breeding of new wheat genotypes with enhanced NUE.

O melhor entendimento sobre os aspectos metabólicos, nutricionais e produtivos das gramíneas forrageiras quanto ao uso do nitrogênio é necessário para aumentar a eficiência de uso do nutriente e para a sustentabilidade da produção pecuária. Com isso, objetivou-se analisar alguns cultivares de gramíneas forrageiras utilizados em pastagens no Brasil, quanto a: I) modificações morfológicas e produtivas da parte aérea e das raízes; II) formas de partição do nitrogênio absorvido para melhorar a eficiência de uso do nitrogênio e III) forma de assimilação do nitrogênio absorvido, sendo avaliados pelas variáveis: produção de massa seca, números de folhas e perfilhos, área foliar, concentração e conteúdos de nitrogênio total, nitrato e amônio, eficiência de uso do nitrogênio, atividades das enzimas nitrato redutase e glutamina sintetase e concentração de aminoácidos livres totais na parte aérea e nas raízes dessas gramíneas, quando submetidas a alta e baixa dose de nitrogênio. Na baixa dose de nitrogênio os cultivares Marandu, Xaraés, Piatã, Basilisk e Mombaça mantiveram o número de perfilhos constante e diminuíram o número de folhas e a área foliar, enquanto o cultivar Tanzânia manteve o número de perfilhos e área foliar constantes e reduziu o número de folhas e os cultivares Aruana e Massai aumentaram o número de perfilhos e de folhas e reduziram a área foliar. A baixa dose de nitrogênio resultou em proporções da massa seca da parte aérea e das raízes distintas entre os cultivares quando comparada à alta dose de nitrogênio, favorecendo o crescimento das raízes. Os cultivares estudados modificaram a partição de nitrogênio, nitrato e amônio da parte aérea e raízes, quando em alto e baixo suprimento de nitrogênio. Essas diferenças refletiram na mais alta eficiência de uso do nitrogênio pelos cultivares Mombaça e Tanzânia. A assimilação do nitrato ocorreu principalmente na parte aérea desses capins. Os cultivares Mombaça e Aruana apresentaram elevadas atividades da enzima nitrato redutase nas folhas diagnósticas. A atividade da enzima glutamina sintetase nas folhas diagnósticas foi mais elevada nos cultivares de Panicum. A concentração de amônio nas raízes foi mais alta nos cultivares Piatã e Xaraés, na baixa dose de nitrogênio, e nos capins Aruana e Mombaça, na dose alta de nitrogênio. A concentração de aminoácidos totais nas folhas diagnósticas foi mais elevada nos cultivares de Panicum, quando submetidos à alta dose de nitrogênio, enquanto nas raízes foi maior nos cultivares de Brachiaria, nas duas doses de nitrogênio. / A better understanding of the metabolic, nutritional and production aspects of nitrogen use by grasses are needed to increase nutrient use efficiency and livestock production sustainability. Thus, this study aimed to analyze some forage grasses cultivars used in Brazilian pastures, for: i) morphological and production changes in shoots and roots; II) absorbed nitrogen partition to improve nitrogen use efficiency and III) nitrogen assimilation, evaluated by the variables: dry matter production, number of leaves and tillers, leaf area, concentration and content of total nitrogen, nitrate and ammonium, nitrogen use efficiency, nitrate reductase and glutamine synthetase activities and free amino acids concentration in shoots and roots of these grasses, when supplied with high and low nitrogen rates. At low nitrogen rate, Marandu, Xaraés, Piatã, Basilisk and Mombaça cultivars kept the number of tillers constant and decreased the number of leaves and leaf area, while Tanzânia cultivar kept the number of tillers and leaf area constant and reduced the number of leaves, and Aruana and Massai cultivars increased the number of tillers and leaves and reduced leaf area. The low nitrogen rate resulted in different shoots to roots proportions among cultivars when compared to the higher nitrogen rate, which favored roots growth. The cultivars changed the partition of nitrogen, nitrate and ammonium between roots and shoots, in both nitrogen rates. These differences reflect the higher nitrogen use efficiency by Mombaça and Tanzânia cultivars. The nitrate assimilation occurred mainly in the shoots of these grasses. Mombaça and Aruana cultivars showed high nitrate reductase activity in diagnostic leaves. The glutamine synthetase activity in diagnostic leaves was higher in Panicum cultivars. Ammonium concentration in the roots was high in Piatã and Xaraés, at low nitrogen rate, and Aruana and Mombaça grasses, at high nitrogen rate. The total amino acids concentration in diagnostic leaves was higher in Panicum cultivars than in Brachiaria cultivars, when high nitrogen rate was supplied, whereas Brachiaria cultivars had this concentration high in the roots, at the two nitrogen rates.

O melhor entendimento sobre os aspectos metabólicos, nutricionais e produtivos das gramíneas forrageiras quanto ao uso do nitrogênio é necessário para aumentar a eficiência de uso do nutriente e para a sustentabilidade da produção pecuária. Com isso, objetivou-se analisar alguns cultivares de gramíneas forrageiras utilizados em pastagens no Brasil, quanto a: I) modificações morfológicas e produtivas da parte aérea e das raízes; II) formas de partição do nitrogênio absorvido para melhorar a eficiência de uso do nitrogênio e III) forma de assimilação do nitrogênio absorvido, sendo avaliados pelas variáveis: produção de massa seca, números de folhas e perfilhos, área foliar, concentração e conteúdos de nitrogênio total, nitrato e amônio, eficiência de uso do nitrogênio, atividades das enzimas nitrato redutase e glutamina sintetase e concentração de aminoácidos livres totais na parte aérea e nas raízes dessas gramíneas, quando submetidas a alta e baixa dose de nitrogênio. Na baixa dose de nitrogênio os cultivares Marandu, Xaraés, Piatã, Basilisk e Mombaça mantiveram o número de perfilhos constante e diminuíram o número de folhas e a área foliar, enquanto o cultivar Tanzânia manteve o número de perfilhos e área foliar constantes e reduziu o número de folhas e os cultivares Aruana e Massai aumentaram o número de perfilhos e de folhas e reduziram a área foliar. A baixa dose de nitrogênio resultou em proporções da massa seca da parte aérea e das raízes distintas entre os cultivares quando comparada à alta dose de nitrogênio, favorecendo o crescimento das raízes. Os cultivares estudados modificaram a partição de nitrogênio, nitrato e amônio da parte aérea e raízes, quando em alto e baixo suprimento de nitrogênio. Essas diferenças refletiram na mais alta eficiência de uso do nitrogênio pelos cultivares Mombaça e Tanzânia. A assimilação do nitrato ocorreu principalmente na parte aérea desses capins. Os cultivares Mombaça e Aruana apresentaram elevadas atividades da enzima nitrato redutase nas folhas diagnósticas. A atividade da enzima glutamina sintetase nas folhas diagnósticas foi mais elevada nos cultivares de Panicum. A concentração de amônio nas raízes foi mais alta nos cultivares Piatã e Xaraés, na baixa dose de nitrogênio, e nos capins Aruana e Mombaça, na dose alta de nitrogênio. A concentração de aminoácidos totais nas folhas diagnósticas foi mais elevada nos cultivares de Panicum, quando submetidos à alta dose de nitrogênio, enquanto nas raízes foi maior nos cultivares de Brachiaria, nas duas doses de nitrogênio. / A better understanding of the metabolic, nutritional and production aspects of nitrogen use by grasses are needed to increase nutrient use efficiency and livestock production sustainability. Thus, this study aimed to analyze some forage grasses cultivars used in Brazilian pastures, for: i) morphological and production changes in shoots and roots; II) absorbed nitrogen partition to improve nitrogen use efficiency and III) nitrogen assimilation, evaluated by the variables: dry matter production, number of leaves and tillers, leaf area, concentration and content of total nitrogen, nitrate and ammonium, nitrogen use efficiency, nitrate reductase and glutamine synthetase activities and free amino acids concentration in shoots and roots of these grasses, when supplied with high and low nitrogen rates. At low nitrogen rate, Marandu, Xaraés, Piatã, Basilisk and Mombaça cultivars kept the number of tillers constant and decreased the number of leaves and leaf area, while Tanzânia cultivar kept the number of tillers and leaf area constant and reduced the number of leaves, and Aruana and Massai cultivars increased the number of tillers and leaves and reduced leaf area. The low nitrogen rate resulted in different shoots to roots proportions among cultivars when compared to the higher nitrogen rate, which favored roots growth. The cultivars changed the partition of nitrogen, nitrate and ammonium between roots and shoots, in both nitrogen rates. These differences reflect the higher nitrogen use efficiency by Mombaça and Tanzânia cultivars. The nitrate assimilation occurred mainly in the shoots of these grasses. Mombaça and Aruana cultivars showed high nitrate reductase activity in diagnostic leaves. The glutamine synthetase activity in diagnostic leaves was higher in Panicum cultivars. Ammonium concentration in the roots was high in Piatã and Xaraés, at low nitrogen rate, and Aruana and Mombaça grasses, at high nitrogen rate. The total amino acids concentration in diagnostic leaves was higher in Panicum cultivars than in Brachiaria cultivars, when high nitrogen rate was supplied, whereas Brachiaria cultivars had this concentration high in the roots, at the two nitrogen rates.

L’usufruit est essentiellement envisagé comme un droit réel portant sur un bien immobilier.Jadis, les immeubles constituaient l’élément le plus important du patrimoine des particuliers. Depuis un siècle, il y a une transformation de la nature des patrimoines caractérisé par le développement des fortunes mobilières à côté de celle immobilières.L'objet de l'usufruit des droits sociaux se trouve au confluent de deux disciplines totalement étrangères l’une à l’autre : le droit des biens et le droit des sociétés.Le droit des biens tend à privilégier l’approche réelle de la matière, ce qui peut conduire à négliger la spécificité de l’objet de l’usufruit. Alors que le droit des sociétés met l’accent sur les mécanismes internes de la société et du droit d’associé, ce qui peut perdre de vue que ce droit est envisagé comme un bien.L’ouvrage explore les différents mécanismes d’utilisation de ce procédé d’ingénierie patrimoniale aussi bien en matière d’optimisation qu’en matière de transmission fiscales. Il envisage aussi d’expliciter les différents aspects de conciliation que requiert l’application de cet outil juridique et financier au sein de la société.Cette thèse encouragera le législateur libanais à introduire et adopter la notion de l’usufruit des droits sociaux au Liban et permettra de mettre en place une étude mise à jour et plus riche en la matière. / Usufruct is a right in rem allowing to use and to enjoy the property of another. Whilst previously, real estates and immovable properties were one’s most valuable assets, with time we have witnessed a shift in the market environment and the development of wealth in movables.In light of the foregoing, usufruct which was initially applicable in real estate, has been applied in other types of property such as corporate shares and stocks. Being relatively a recent development, there is an absence in the French system of adequately applicable legal texts to the usufruct of shares and stocks and accordingly it is subject to both the property law and company law. This gives rise to a number of difficulties because whereas the property law focuses on the various forms of ownership and the legal relationship with the rem, and emphasizes on proprietorship rights; the company law studies the interaction of the shareholders and other stakeholders with the company specifying their rights and duties and thus may lose sight that the usufruct is a property right. With this research I intend to explore the different mechanisms and contexts in which usufruct is used as a legal & financial tool for tax optimization and cost cutting mostly elucidated during inheritance. On the other hand, I will elaborate the way of utilizing it by a shareholder within the company.Finally, I hope that my thesis will contribute to encourage the Lebanese legislator in introducing this notion into Lebanon by developing the relevant laws and will provide an updated and thorough study of shares and stocks usufruct.

The bulk of Zimbabwe’s groundnut (Arachis hypogaea L.) crop is grown on sandy soils in the smallholder sector where sustainable production is hindered by acid soil infertility. The study goal was thus to examine the effects of soil acidity amelioration by four Ca-containing materials on nutrient composition, vegetative and reproductive growth, and quality of groundnut to formulate ameliorative strategies to improve productivity on acid soils. The effectiveness of calcitic lime (CL), dolomitic lime (DL), gypsum (G) and single superphosphate (SSP) in ameliorating soil acidity was determined in field experiments conducted for three seasons at two Research Stations in Zimbabwe, and in greenhouse experiments conducted for two seasons at Harare Research Station. In both experiments the lime application rates were from 0 to 4000 kg ha-1, while G application rates were from 0 to 3450 kg ha-1, and those of SSP were from 0 to 250 kg ha-1. Calcitic or dolomitic lime applied at 2000 or 4000 kg ha-1 increased soil pH and Ca and Mg contents in the pod and root zones, and in the plant material. Gypsum and SSP applications at 200 and 250 kg ha-1 respectively, had no significant effects on pH, Ca and Mg levels, but when applied in equivalent amounts of Ca as lime, gypsum improved soil Ca status. Effects of the four ameliorants on the N, P and K levels in the soils and in plant material were generally neither significant nor consistent. The direct and residual benefits of application of CL or DL were manifested in improved plant stands, better growth, nodulation, productivity and quality of groundnut. Gypsum applied at equal Ca rates as CL or DL was the superior Ca-source in improving pod and kernel quality. By the end of the third season, the increases in cumulative kernel yields due to application of 4000 kg ha-1 lime over non-application were up to 319%. The major growth-limiting factors on the studied acid soils were identified as deficiencies of Ca and Mg, and low pH per se. In a field experiment conducted to evaluate the tolerance of 15 groundnut genotypes to soil acidity, significant differences in yield and nutrient utilization efficiency of the genotypes were observed, implying that productivity on acid soils can be increased by growing genotypes efficient in uptake and utilization of nutrients. Results from greenhouse and growth chamber studies conducted to examine the effects of pH (3.0 - 7.0) and its interactions with Ca (0 - 2000 µM Ca) on early seedling growth and reproductive growth of groundnut indicated that low pH per se has a major detrimental impact on seedling survival, growth, pod formation, yield and quality of groundnut, but not on germination. The adverse effects of low pH were more pronounced in the absence of Ca, and became progressively less as the solution Ca concentrations increased. Further experiments showed that it is feasible to mitigate the adverse effects of soil acidity on groundnut germination and seedling survival by pelleting seeds with small amounts of CaCO3, or priming with CaSO4. / Dissertation (PhD (Plant Production: Agronomy))--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

A better way to improve understanding and quantification of nitrous oxide (N₂O) emitted from intensive maize cropping systems is to develop an advanced emissions measurement method This study developed an open path (OP) method to measure N₂O emissions from four adjacent maize plots managed by tillage practices of no-till (NT) and chisel plow (ChP), and different nitrogen (N) treatments from 2014 to 2016. Anhydrous ammonia (220 kg NH₃-N ha^-1) was applied in once or equally split (full vs. split rate) and applied in different timing (Fall vs. Spring). The spring N application occurred either before planting (pre-plant) or in season (side-dress). Emissions measurements were conducted by using the OP method (the scanning OP Fourier transform infrared spectrometry (OP-FTIR) + the gas point-sampling system + a backward Lagrangian stochastic (bLS) dispersion model) and static closed chamber methods. The performance and feasibility of the OP measurements were assessed by a sensitivity analysis, starting with errors associated with the OP-FTIR for calculating N₂O concentrations, and then errors associated with the bLS model for estimating N₂O emissions. The quantification of N₂O concentrations using the OP-FTIR spectrum was influenced by ambient humidity, temperature, and the path length between a spectrometer and a retro-reflector. The optimal quantitative method mitigated these ambient interference effects on N₂O quantification. The averaged bias of the calculated N₂O concentrations from the spectra acquired from wide ranges of humidity (0.5 – 2.0 % water vapor content), temperature (10 – 35 °C), and path length (100 – 135 meters) was 1.4 %. The precision of the OP-FTIR N₂O concentrations was 5.4 part per billion(3σ) in a stationary flow condition for a 30-minute averaging period. The emissions measurement from multiple sources showed that the field of interest was likely interfered by adjacent fields. Fields with low emission rates were more sensitive to the adjacent fields with high emissions, resulting in substantial biases and uncertainties. The minimum detection limit of the N₂O emission rates was 1.2 µg m^-2 s^-1 (MDL; 3σ). The OP measurements showed that the NT practice potentially reduced N₂O emission compared with ChP. Under the long-term NT treatments, the split-N rate application (110 kg NH₃-N ha^-1 in the fall and spring) resulted in lower N₂O emissions than the full application (220 kg NH₃-N ha^-1 in the fall). The management of NT coupled with split-N rate application minimized N₂O emissions among treatments in this study, resulting in N₂O-N losses of 3.8, 13.2, and 6.6 N kg ha^-1 over 9-, 35-, and 20-days after the spring NH₃ application in 2014, 2015, and 2016, respectively. The spring pre-plant N application in 2015 also resulted in higher N₂O emissions than the spring side-dress application in 2016, and the increased N₂O-N loss was corresponding to lower N recovery efficiency in 2015 measurements. A comparison of chamber and OP measurements showed that soil N₂O emissions were likely underestimated by 10x without considering the wind-induced effect on gas transport at the ground-atmospheric interface. This study showed that the OP method provides a great opportunity to study agricultural N₂O emissions as well as management optimization for the sustainability of the agroecosystems.

Sur la montagne nue est un recueil de huit nouvelles à la forme particulière: les textes sont divisés en paragraphes qui présentent, en alternance, deux voix, deux femmes distinctes. Ces femmes parlent d’elles-mêmes à la troisième personne du singulier. Il n’y a pas de dialogues, seulement des voix qui se donnent l’une après l’autre et qui se rejoignent par le biais de la mémoire. Il s’agit de nouvelles certes, mais elles ont été écrites pour la scène, pour des comédiennes, pour être entendues. De surcroît, les propos de ces textes sont généralement autofictionnels. Dans la partie théorique, je questionne le choix d’une narration à la troisième personne pour l’écriture de l’autofiction. Pour ce faire, je compare mon travail avec la pratique de Gabrielle Roy, Marguerite Duras et Annie Ernaux qui ont elles aussi, dans certains moments de leurs oeuvres, choisi ce type de narration pour l’écriture de soi.