Durch den in den letzten Jahren in Deutschland stark ausgeweiteten Spargelanbau wird der Kostendruck auf die Erzeuger immer größer. Um eine Spargelfläche ökonomisch erfolgreich zu bewirtschaften sind Anbauempfehlungen die auf einer objektiven Grundlage beruhen unersetzlich. Eine Möglichkeit hierzu ist das Messen der Reservekohlenhydratkonzentration (RKH-Konzentration) in den Speicherwurzeln. Ein sehr großer Nachteil dieser Methode ist, dass die Speicherwurzelmasse, die einen erheblichen Einfluss auf die verfügbare Gesamtmenge an Reservekohlenhydraten hat unberücksichtigt bleibt. Hinsichtlich der Wurzelmasse und der Wurzelverteilung im Boden bestanden bislang große Wissenslücken. Um den Einfluss der Bewässerung auf die Wurzelmasse und die Wurzelverteilung zu ermitteln, wurde ein Praxisversuch angelegt. Zu bestimmten Zeitpunkten in der Vegetationsperiode wurden Proben auf einer bewässerten und einer unbewässerten Variante entnommen. In der bewässerten Variante waren zu jedem Zeitpunkt signifikant mehr Speicherwurzeln vorhanden. Auch die Speicherwurzelfrischmasse war signifikant größer. In der Tiefenverteilung unterschieden sich jedoch die Varianten nicht. Auch in Gefäßversuchen konnten diese Ergebnisse bestätigt werden. Die Faserwurzelverteilung unter Praxisbedingungen unterschied sich jedoch erheblich von der Speicherwurzelverteilung. In der bewässerten Variante war der Boden im untersuchten Profil komplett mit Faserwurzeln durchwachsen, während in der unbewässerten Variante die Faserwurzeln lediglich in den oberen Bodenschichten zu finden waren. In Gefäßversuchen durchwurzelten die Faserwurzeln unabhängig von der Bewässerungssteuerung das gesamte Bodenvolumen. Unter mehrjährigen Praxisbedingungen lag die RKH-Konzentration in der unbewässerten Variante immer über der Konzentration in der bewässerten Variante. Die Gesamtmenge an RKH lag jedoch aufgrund der größeren Speicherwurzelmasse in der bewässerten Variante höher. Daher muss bei der Verwendung der RKH-Methode als Steuerinstrument im Spargelanbau unbedingt auch die Speicherwurzelmasse berücksichtigt werden. / The cultivation of asparagus in Germany has strongly expanded over the last years. Hence the cost pressure is increasing vastly on the producers. For the cultivation of asparagus, impartial cultivation recommendations are necessary. One possibility is measuring the carbohydrate concentration (CHO-concentration) in the storage roots. A great disadvantage of this method is that the root mass, which has a substantial influence on the total quantity of available carbohydrates, remains unconsidered. Regarding to the root mass and the distribution of roots in the soil so far large gaps in the grower’s knowledge are existent. In order to determine the influence of the irrigation on the root mass and the distribution of roots, a trial was prepared. Samples of a watered and an unwatered variant were taken at certain points in the vegetation period. In the watered variant were significantly more storage roots were present at each time. Further the storage root fresh mass was significantly bigger. However, in the vertical distribution the variants did not differ, which could also be confirmed in container trials. The distribution of fibre roots under practical conditions did indeed differ substantially from the storage root distribution. In the watered variant the soil profile was completely filled with fibre roots, whereas in the unwatered variant the fibre roots were only found in the upper soil layer. In container trials the fibre roots were distributed throughout the entire soil volume independently of the irrigation control. Under practical conditions the CHO concentration was always higher for the unwatered variant compared to the watered variant. However, the total quantity of CHO was higher in the watered variant due to the larger storage root mass. Therefore the storage root mass has to be considered when using the CHO method as an instrument in the cultivation of asparagus.

Le système racinaire des arbres peut établir des symbioses ectomycorhiziennes (ECM) avec des champignons rhizosphériques. La mise en place de la symbiose est accompagnée d'une stimulation de la formation des racines latérales (RLs), et d'une modification de la croissance racinaire. Ces processus développementaux conduisent à la formation de racines courtes typiques des ECMs. Il a été montré que l'auxine est une phytohormone clef dans la formation des RLs ainsi que dans la croissance racinaire. Notre projet s'est focalisé sur l'étude de la régulation des voies de l'auxine dans la racine de peuplier en réponse à L. bicolor. Dans cette étude, nous avons mis en évidence un arrêt de croissance des RLs et des racines adventives du peuplier Populus tremula x P. alba, après deux semaines de co-culture avec L. bicolor. De plus, nous avons aussi montré que cet arrêt n'est pas conditionné par la présence du réseau de Hartig. Une analyse de l'expression globale des gènes de peuplier dans la mycorhize a été réalisée au cours de la formation de la mycorhize. Cette analyse, couplée à des observations du gradient auxinique via le patron d'expression du promoteur DR5, montre que la signalisation auxinique est affectée dans l'organe symbiotique. La quantification de l'auxine (acide indole 3-acétique, AIA) et des métabolites associés a permis de mettre en évidence un environnement symbiotique riche en auxine dans la mycorhize, qui pourrait expliquer les modifications de la signalisation auxinique. De plus, un changement de la conjugaison et de la dégradation de l'AIA est détecté dans la racine, ainsi qu'une dégradation de l'AIA dans les hyphes de L. bicolor. En parallèle, une analyse fonctionnelle de PtaPIN9, un orthologue de AtPIN2, responsable du transport basipète de l'auxine à l'apex racinaire chez Arabidopsis thaliana, a été réalisée au cours de la mycorhization avec L. bicolor. L'immunolocalisation de PtPIN9 dans les racines de peuplier a montré une localisation similaire à AtPIN2, dans les cellules épidermiques. Les lignées transgéniques ayant une modification de l'expression de ce gène ne répondent pas à L. bicolor en terme de stimulation de RLs. Dans les racines mycorhizées, PtaPIN9 n'est plus observée, mais les modifications de l'expression de PtaPIN9 ne modifient ni l'arrêt de croissance racinaire, ni la formation du réseau de Hartig. Ces résultats montrent des modifications majeures des voies de l'auxine du peuplier par le champignon symbiotique L. bicolor. Cette étude ouvre des perspectives sur la compréhension du rôle de l'auxine dans le développement racinaire ainsi que dans le contexte des interactions plantes-microorganismes / Root systems of host trees are known to establish the ectomycorrhizal (ECM) symbiosis with rhizospheric fungi. This mutualistic association leads to modifications of root development that including a stimulation of lateral host roots, and a modification in root growth. The phytohormone auxin (Indole-3-acetic acid, IAA) is known to regulate LRs formation and root growth. Our research focussed on auxin pathways in poplar root in response to L. bicolor. In this study, our data showed that the poplar-Laccaria bicolor interaction leads to the arrest of LRs and adventitious root growth after two weeks of interaction. We also showed that this arrest is not regulated by the Hartig net. Differential auxin responses were analyzed by using an auxin-responsive DR5::GUS marker line and revealed a loss of auxin response in ECM roots. An oligoarray-based transcript profiling of poplar roots in contact with L. bicolor highlights a differential expression of auxin asociated genes in ECM. Measurement of auxin metabolite in ECM and in the free living partners revealed an IAA accumulation, an activation of the IPyA (Indol-3-Pyruvic Acid) dependant IAA biosynthesis pathway in both partners, as well as changes in IAA conjugation pathways in poplar and in IAA degradation pathways in L. bicolor. Our findings illustrate the impact of L. bicolor colonization on root auxin metabolism and response, and also suggest a role of auxin as a signal in the formation of ECM and in the regulation of ECM function. In parallel, PtaPIN9 function analysis in response to L. bicolor has been performed. PtaPIN9 immunolocalization in poplar roots showed similar localization to AtPIN2 in epidermis cells. Transgenic lines having a modification in PtaPIN9 expression, did not formed new LRs in respond to L. bicolor. In ECM roots, the loss of PtaPIN9 signal is observed but modifications of PtaPIN9 expression did not modify the root growth arrest and the Hartig net formation. These results show major changes in auxin associate pathways in poplar root by the symbiotic fungus L. bicolor, during the formation of the mycorrhiza root. Our results offer perspectives on the role of auxin in root development and in the context plants-microbes interactions

A soja no Brasil está entre as culturas agrícolas que apresentam crescimento mais expressivo em área de cultivo e na encomia do país. O que se deve ao fato da cultura apresentar diversas finalidades desde a produção de biodiesel até consumo humano. Dentre os fatores que afetam a produtividade de soja, o déficit hídrico é tido como o principal. Desta forma, a absorção de água pelo sistema radicular não é capaz de suprir a evapotranspiração apenas com o regime pluviométrico durante o ciclo de soja, logo a planta depende da absorção de água disponível pelo solo, que é diretamente proporcional a profundidade do sistema radicular. Estudos realizados pelo Comitê Estratégico Soja Brasil (CESB) demostraram que o sistema radicular de soja de alta produtividade se estende a profundidade superiores a100 cm. Portanto, a hipótese deste trabalho é de que a absorção de água pela planta ocorre majoritariamente em profundidades superiores à de 15 cm para áreas de alta produtividade, associado a um solo sem restrição química, física ou biológica para o crescimento radicular. Assim, o objetivo desse trabalho foi determinar a profundidade efetiva do sistema radicular (80% da evapotranspiração real, ETr) de soja em duas áreas distintas de alta e baixa produtividade. O cálculo para quantificar a ETr baseia-se na quantidade de água presente no solo e massa específica do mesmo por camada. Para isso o solo foi saturado com água e após 24 horas foi realizada a coletas de amostras de solo indeformadas através de anéis volumétricos em 10 profundidades distinta do solo espaçadas a cada 10 cm (5 a 95 cm), a qual foi repetida após três dias, sem a ocorrência de irrigação ou chuva. A área de baixa produtividade estava localizada em Piracicaba, SP, caracterizada por Latossolo Vermelho-Amarelo distrófico típico, e a área de alta produtividade em Goiatuba-GO, sendo um Latossolo Vermelho eutrófico típico, ambos com textura médioarenosa. Após a coleta das amostras, as mesmas foram pesadas e alocadas em estufas de ventilação forçada até atingir massa constante, determinando o conteúdo de água em cada amostra, e a partir da diferença entre os dois dias determinar o consumo hídrico total. Os resultados da análise química do solo demonstraram que a área de Piracicaba apresentava restrição química ao crescimento radicular pela alta concentração de alumínio abaixo de 40 cm profundidade, e pela resistência do solo a penetração, observando-se valores altos de compactação na camada entre 20 e 40 cm. Tais limitações não estavam presenta na área de Goiatuba. O sistema radicular obteve um crescimento mais expressivo em Goiatuba, tendo 175% e 188%, respectivamente, maior comprimento e área superficial que Piracicaba. A evapotranspiração real da cultura acumulada em três dias foi de 23,7 e 24,4 mm, respectivamente, para Goiatuba e Piracicaba, sendo que Goiatuba obteve o acumulado de 80% entre 70 e 80 cm de profundidade, enquanto que Piracicaba, esse acumulado ocorreu entre 10 e 20 cm. Na área de Goiatuba, a produtividade foi de 91 sc ha-1, contra 61 sc ha-1 na área de Piracicaba. Ademais, a ausência de restrição física e química no solo para crescimento radicular permitiu aumentar a capacidade de água disponível no solo para a planta, reduzindo as perdas de produtividade ocasionadas pelo déficit hídrico. / Soybean is among the agricultural crops that show more expressive growth in the area of cultivation and economy in Brazil. This is because the crop has several purposes from the production of biodiesel to human consumption. Among the factors that affect soybean yield, the water deficit was considered the main one. Thus, the water uptake by the root system is not able to supply the evapotranspiration only using rainfall during the soybean cycle, this way, crop depends on the water uptake available in the soil, which is directly proportional to the root depth. Researches carried out by the Soybean Brazil Committee showed that the soybean root system extends below 100 cm of depth. Therefore, the work hypothesis is that the water uptake by the soybean occurs mainly in depths greater than 15 cm for the areas of high yield, associated with a soil without chemical, physical or biological restriction for root growth. This way, the aim of this research was quantify the effective root depth (80% of the actual crop evapotranspiration, ETr). The ETr was quantified based on the amount of water in the soil and its specific mass by layer. The soil was sutured with water and after 24 hours was made the soil samples in 10 different soil depths spaced every 10 cm (from 5 to 95 cm), which was replicated three days after the first one, without occurrence of irrigation or rainfall. The area of low yield was located in Piracicaba, SP, characterized by typical dystrophic Red-Yellow Latosol, and the area of high yield in Goiatuba, GO, being typical Eutrophic Red Latosol. The both soil were medium-sandy texture. The soil samples were weighed and allocated in forced ventilation greenhouses until reaching constant mass, determining the percentage of water and by the difference from day 0 and day 3 was quantified the total water uptake. The chemical soil analysis showed that the area in Piracicaba had restriction for root growth by high aluminum concentration below 40 cm, and also by high soil compaction between 20 e 40 cm. These limitations were not observed in the area of Goiatuba, which had 175% e 188%, respectively, more root length and superficial area than Piracicaba. The actual crop evapotranspiration accumulated in three days were 23.7 and 24.4 mm, respectively, for Goiatuba e Piracicaba, where the 80% accumulated was between 70 e 80 cm for Goiatuba, and 10 e 20 cm for Piracicaba. In Goiatuba, the yield was 91 sc ha-1 against 61 sc ha-1 in Piracicaba. Thus, the no chemical and physical restriction for the root growth helped to increase the water available for the crop, reducing the yield losses by water deficit.

Made available in DSpace on 2017-07-25T19:29:50Z (GMT). No. of bitstreams: 1 CarolineJesusCoelho.pdf: 3922070 bytes, checksum: 06fa3d69d093ea4840c9056afcb2a9ff (MD5) Previous issue date: 2011-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aluminum toxicity has limited the potential yield in most crops, especially damage caused by the root system as inhibiting the growth, elongation and absorption of nutrients. The objectives were to standardize the concentration of aluminum and exposure of the roots of seedlings in minimal solution (Ca2+ + Al3+) and subsequently characterize the genetic variability of tolerance to the element in different germplasm (hybrids and landraces). The experiments of the approach of minimal solution in DBC were implanted with three replications. The treatments were arranged in a split plot where the plot studied the effect of doses of Al3+ (0, 2, 4 and 6 mg L-1) and the subplot effect of hybrids, which were exposed for a period of 96 h (1 and 2 experiments) and 48 h (experiment 3). The variables analyzed were the DIF1 (root net growth), DIF2 (root final growth) and their relative differences (DIFR1 and DIFR2). The variables analyzed were effective for assessing the tolerance / sensitivity to aluminum in minimal solution. The results revealed dramatic decline in root growth of all the hybrids with increasing doses of Al3+, based on the square root regression model. The starting dose of 4 mg L-1 the damage is so pronounced that virtually paralyzed the root growth when exposed for 96 h. On the other hand, when the hybrids were exposed for 48 h and the differences in tolerance or sensitivity were seen. In this sense, we standardized for the other experiments (characterization of germplasm), the minimal solution containing 4 mg L-1 + Al3+ + 40 mg L-1 Ca2+ implanted in the DBC with three replications. Germplasm in hybrid maize were carried out two experiments (48 and 96 h of exposure) with a total of 52 hybrids and germplasm experiment with landraces, with 54 treatments: 50 landraces + 4 hybrid control (48 h exposure). The genotypes were evaluated for the same variables as well as classified for the tolerance on the aluminum (ITRAl). Germplasm in hybrid, the analysis showed genetic variability for tolerance or sensitivity to, and Al+3. In general, the exposure period of 96 h significantly reduced the growth / root regrowth. The majority of the hybrids (35) showed a reduction in the value of ITRAl due to the increase of the exposure period, while 15 hybrids responded with an increase in this index. The evaluation of landraces showed very high values of growth / root regrowth as well as a predominance of genotypes (50%) classified as ITRAl ≥ 4, are considered excellent sources of aluminum tolerance. Featured very positive for the landrace Dente de Ouro 2 that showed a value of more than control ITRAl tolerant H 44. Estimates of genetic parameters in two maize germplasm showed high levels of genetic variance and heritability coefficients. These indices indicate very favorable conditions for development and selection of populations improved with increase in frequency of alleles of aluminum tolerance. / A toxidez pelo alumínio tem limitado o potencial de rendimento de grãos na maioria das culturas, principalmente pelos danos ocasionados no sistema radicular como: inibição do crescimento, da elongação e da absorção dos nutrientes. Os objetivos foram padronizar a concentração de alumínio e o tempo de exposição das raízes de plântulas em solução mínima (Al3+ + Ca2+) e posteriormente caracterizar a variabilidade genética para tolerância ao elemento em diferentes germoplasmas (híbridos e variedades crioulas). Os experimentos de adequação da metodologia de solução mínima foram implantados no DBC com três repetições. Os tratamentos foram arranjados em esquema de parcela subdividida, onde na parcela estudou-se o efeito de doses de Al3+ (0, 2, 4 e 6 mg L-1) e na subparcela o efeito de híbridos, que foram expostos por período de 96 h (1° e 2° experimentos) e de 48 h (3° experimento). As variáveis analisadas foram o DIF1 (crescimento radicular líquido), DIF2 (crescimento radicular final) e as respectivas diferenças relativas (DIFR1 e DIFR2). As variáveis analisadas foram eficientes para a avaliação da tolerância/sensibilidade ao alumínio em solução mínima. Os resultados revelaram queda drástica no crescimento radicular de todos os híbridos avaliados com o aumento das doses de Al3+, baseados no modelo de regressão raiz quadrada. A partir da dose 4 mg L-1 os danos são tão acentuados que praticamente paralisaram o crescimento radicular quando expostos por 96 h. Por outro lado, quando os híbridos foram expostos por 48 h as diferenças de tolerância e ou sensibilidade foram visualizadas. Neste sentido, padronizou-se para os demais experimentos (caracterização de germoplasma), a solução mínima contendo 4 mg L-1 de Al3+ + 40 mg L-1 de Ca2+ implantados no DBC com três repetições. No germoplasma de milho híbrido foram realizados dois experimentos (48 e 96 h de exposição) com total de 52 híbridos e um experimento com germoplasma crioulo, com 54 tratamentos: 50 variedades crioulas + 4 híbridos testemunhas (48 h exposição). Os diferentes genótipos foram avaliados para as mesmas variáveis bem como classificados para o índice de tolerância relativa ao alumínio (ITRAl). Na avaliação dos híbridos, a análise revelou variabilidade genética para tolerância e ou sensibilidade ao Al+3. De maneira geral, a exposição por período de 96 h reduziu sensivelmente o crescimento/recrescimento radicular. A grande maioria dos híbridos (35) apresentou redução no valor do ITRAl em função do aumento do período de exposição, embora 15 híbridos responderam com incremento neste índice. A avaliação das variedades crioulas demonstrou valores bastante elevados de crescimento/recrescimento radicular bem como um predomínio de genótipos (50%) classificados com ITRAl ≥ 4, sendo consideradas excelentes fontes de tolerância ao alumínio. Destaque muito positivo para a variedade Dente de Ouro 2 que apresentou valor de ITRAl superior a testemunha tolerante H 44. As estimativas dos parâmetros genéticos nos dois germoplasmas de milho demonstraram elevados valores de variância genética e dos coeficientes de herdabilidade. Estes índices indicam condição muito favorável para o desenvolvimento e seleção de populações melhoradas com incremento na frequência de alelos de tolerância ao alumínio.

As substâncias húmicas (SH) podem alterar o crescimento das plantas bem como estimular a absorção de nutrientes. A ureia é o fertilizante nitrogenado mais utilizado na agricultura, porém, apresenta baixa eficiência de uso. Sabe-se que as substâncias húmicas podem aumentar a eficiência de uso da ureia por meio de efeito bioestimulante no crescimento radicular. Somado a isso, as SH atuam nas bombas de próton das raízes estimulando a absorção de nitrogênio e também alteram a dinâmica de hidrólise e mineralização do N-ureia. O objetivo deste trabalho foi verificar se as SH extraídas de turfa, associadas ou não ao N-ureia, alteram as transformações do N-ureia no solo, assim como o crescimento radicular e da parte aérea no desenvolvimento inicial da cana-planta. Nesse sentido, foram instalados dois experimentos em casa de vegetação, um com a presença de plantas para aferir parâmetros morfológicos e nutricionais e outro, sem plantas, para verificar a dinâmica de hidrólise e mineralização do N-ureia. Os experimentos foram planejados em delineamento experimental inteiramente casualizado com 16 tratamentos e cinco repetições, correspondendo a um esquema fatorial completo com quatro doses de nitrogênio na forma de ureia: 0; 100; 200 e 300 mg dm-3 e quatro doses de SH: 0; 13,8; 27,6; 41,7 mg dm-3 de C, e o experimento sem plantas utilizando o mesmo delineamento porém com 3 repetições e análises feitas em duplicatas. As substâncias húmicas aumentaram a hidrólise da ureia elevando a concentração de NH4+ no solo. O processo de nitrificação da ureia foi reduzido na presença das substâncias húmicas. As aplicações isoladas de N e SHs estimularam o crescimento radicular e da parte aérea da cana-de-açúcar, bem como modificaram as características morfológicas das raízes e parte aérea da cana-planta. A associação dos produtos resultou em decréscimos no crescimento vegetal devido às altas concentrações de amônio causadas pela maior hidrólise da ureia e também atuaram na redução do acúmulo e teor de nitrogênio na planta. Tanto a ureia quanto as SHs se mostraram eficientes no estímulo do crescimento inicial da cana-de-açúcar, no entanto, devido às altas doses de N-ureia utilizadas, o possível efeito sinérgico dos produtos não foi verificado. / Humic substances (HS) can alter plant growth and stimulate the absorption of nutrients. Urea is the most widely used nitrogen fertilizer in agriculture, however, has low use efficiency. It is known that humic substances can increase the efficiency of urea through bio-stimulant effect on root growth. Added to this, the SH proton pumps operate in the roots stimulating the uptake of nitrogen and also alter the dynamics of urea\'s hydrolysis and mineralization. The aim of this study was to verify whether the HS extracted from peat, associated or not with N-urea, alter the dynamics of transformation of urea-N in the soil and the growth of roots and shoots in the cane-plant cropcycle. In this direction, two experiments were carried out in a greenhouse, with the presence of plants to assess morphological and nutritional parameters and one without plants, to verify the dynamics of hydrolysis and mineralization of N-urea. The experiments were designed in a completely randomized design with 16 treatments and five replications, corresponding to a full factorial design with four rates of nitrogen as urea: 0, 100, 200 and 300 mg dm-3 and four rates of HS: 0, 13.8, 27.6, 41.7 mg dm-3 C, and experiment without plants using the same design but with three replications and analyzes performed in duplicates. The humic substances increased hydrolysis of urea by raising the concentration of NH4+ in soil. The nitrification of urea was reduced in the presence of humic substances. Individual applications of N and SHs stimulated root and shoot of sugar cane growth and modified the morphological characteristics of roots and shoots in the crop cycle of the cane-plant. The association of the product resulted in decreases in plant growth due to high ammonium concentrations caused by increased hydrolysis of urea and also reduced accumulation and nitrogen content in the plant. Both urea and the SHs were effective in stimulating early growth of sugar cane , however , due to high doses of N-urea used, the synergistic effect of the products has not been verified.

Le nitrate, source majeur d’azote pour la plupart des plantes,n’est pas seulement un élément nutritif mais est aussi une molécule signale. Il existe cependant des réponses au nitrate contrastées entre les différentes plantes supérieures. Chez Medicago truncatula, espèce modèle de la famille des légumineuses, le nitrate a un effet inhibiteur sur la croissance de la racine primaire en phase post-germinative. Une étude de génétique quantitative a montré qu’un transporteur de nitrate se situe au pic d’un QTL impliqué dans la croissance de la racine primaire. La caractérisation fonctionnelle de ce transporteur, nommé MtNRT1.3 et renommé MtNPF6.8, a montré que celui-ci est à double affinité pour le nitrate. Ce transporteur est alors susceptible de participer à l’influx de nitrate dans la plante. Après l’obtention de trois génotypes mutants RNAi stables, les expérimentations utilisant duK15NO3 ont montré que ce transporteur participe effectivement à l’influx de nitrate lié au système de transport à faible affinité inductible dans la plante (iLATS). En revanche,la mutation de MtNPF6.8 ne semble pas avoir de conséquence sur le métabolisme azoté. Par ailleurs, les études sur la croissance de la racine primaire ont permis de confirmer l’implication du transporteur sur ce caractère phénotypique. L’inhibition de croissance de la racine primaire observée sur nitrate chez le génotype sauvage est alors imputée, à l’échelle cellulaire, à une modulation de l'élongation cellulaire. La possibilité que l’ABA, hormone végétale, joue un rôle dans la médiation de cette réponse dépendant du nitrate, est fortement favorisée. L’ensemble de résultats, conforté par une étude de mutants exprimant ce transporteur chez A. thaliana, indique donc que MtNPF6.8 est un senseur de nitrate pour la plante en phase post germinative,ceci indépendamment de sa fonction de transport de nitrate. / Nitrate, a major nitrogen source for most plants, is not only anutrient but also a signaling molecule. However, there arecontrasting responses to nitrate between different higherplants. In the model legume Medicago truncatula, nitrate hasan inhibitory effect on the primary root growth in postgerminationphase. A quantitative genetic study has shownthat a nitrate transporter is localized at the peak of a QTLinvolved in the primary root growth. Functionalcharacterization of the transporter, named MtNRT1.3 andrenamed MtNPF6.8, showed that it encodes a dual affinitynitrate transporter. MtNPF6.8 is likely to participate in thenitrate influx in the plant. After obtaining three knockdownlines by RNA interference, experiments using K15NO3 showedthat this transporter is effect involved in nitrate influx relatedto the inducible low affinity transport system (iLATS).However, mutation in MtNPF6.8 does not any effect onnitrogen metabolism. In addition, studies on the primary rootgrowth have confirmed the involvement of the transporteron phenotypic trait. In wild-type plants, cortical cell sizedecreased after nitrate treatment, showing that primary rootgrowth was due to this reduced cell elongation. Thepossibility that ABA also plays a role in mediating this nitratedependent response is heavily favored. All these results,reinforced by a study of mutants expressing this transporterin A. thaliana, indicate that MtNPF6.8 is a nitrate sensor forMedicago in the post-germination phase, independently ofits nitrate transport activity.

Made available in DSpace on 2014-06-11T19:27:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-01Bitstream added on 2014-06-13T19:55:59Z : No. of bitstreams: 1 lemos_mto_me_jabo.pdf: 967680 bytes, checksum: a6c9fc3231a065465ff531a2097edf51 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A conservação da biodiversidade, implica em cultivar espécies arbóreas nativas que possam ser utilizadas em projetos de reflorestamento, recuperação de áreas degradadas e com o objetivo de obter produtos secundários importantes como madeira e produtos medicinais. O uso de rizobactérias promotoras de crescimento em plantas, vem sendo muito estudado em culturas de importância econômica, devido a sua aplicabilidade em beneficiar o desenvolvimento destas. Neste trabalho foram escolhidas quatro espécies arbóreas nativas, leguminosas não nodulantes: Pterogyne nitens (Amendoim-bravo), Albizia hasslerii (Farinha-seca), Copaifera langsdorffii (Copaíba), e Stryphnodendron adstringens (Barbatimão). O objetivo deste trabalho foi avaliar in vitro as diferentes bactérias isoladas destas espécies florestais que possam ter efeito benéfico no crescimento e desenvolvimento inicial das plantas e caracterizálas pelo sequenciamento do gene 16S rRNa e perfil eletroforético do gene BOX-A 1R. As bactérias foram isoladas da rizosfera e da raiz de mudas de cada espécie, em meio de cultura NFb. No total, 29 isolados foram cultivados em meio de cultura DYGS enriquecido com triptofano. A estimativa colorimétrica do Ácido Indolacético (AIA) foi feita no espectrofotômetro, utilizando o sobrenadante da cultura de células e solução de Salkowski, com resultado positivo para o isolado Pn 6 Sphingobium chlorophenolicum com 61,69 μg.mL-1. Os isolados também foram testados para a eficiência de solubilização de fosfato de cálcio que foi realizado e contabilizado até o 15° dia após a inoculação em placas de Petri com meio de cultura NBRIP sólido, onde 27 isolados apresentaram resultados positivos. A caracterização genética permitiu a diferenciação em gêneros e também em espécies de um mesmo gênero. Os isolados que deram resultados positivos para AIA e solubilização de fosfato... / The biodiversity conservation implies cultivating native forest species that can be used in reforestation projects, recovery of degraded areas as well as getting others like wood and medicinal products. The plant growth promoting rhizobacteria (PGPR) use is being studied in cultures of economic importance. In this work four native forest species, no nodulating leguminous had been chosen: Pterogyne nitens, Albizia hasslerii, Copaifera langsdorffii, and Stryphnodendron adstringens. The aim of this work was the in vitro evaluation of the different isolates from those forest species with beneficial effects in growth and initial development of the plants and characterizes them by 16S rRNA gene sequencing and BOX-A 1R. The bacteria had been isolated from the rhizosphere and from the roots (endophytic) of each species seedlings on NFb growth media. A total of 29 isolates had been cultivated in growth media DYGS enriched with tryptophan. The indolacetic acid (IAA) production was estimated by colorimetric test in the spectrophotometer, using the supernatant of the cells culture and Salkowski´s reagent, with positive result for the isolated Pn 6 Sphingobium chlorophenolicum with 61,69 μg.mL-1. Isolates had been also tested for the efficiency of P- solubilizing that was carried through and measured until the 15 º day after the inoculation in Petri plates with solid growth media NBRIP, where 27 isolates had presented positive results. The genetic characterization allows us to differentiate by the genus and species from the same genus. The isolates that had positive results for IAA and P-solubilizing had not matched between itself, what suggests nursery tests with combinations between them to evaluate the isolate efficiency as a possible PGPRs.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Soil water availability is one of the major factors affecting the success or failure of an agricultural crop. Stresses caused by water deficit or surplus are harmful to the growth and sunflower yield. Plant growth pattern is changed and the yield is reduced with the growth of the intensity corresponding to stress. The main aims of this study were to evaluate the grain yield and quality of sunflower oil, root growth, deepening and distribution of roots in the soil, growth of shoot and roots in dry matter and modeling of sunflower plant growth, in response to stress caused by water surplus and water deficit in two sowing dates and two soils of Rio Grande do Sul. The experiments were carried out at early sowing date (sowing in early September) and late sowing date (sowing in early January), in two soils in the municipalities of Santa Maria (Ultisol) and Panambi (Oxisol). Three treatments of water availability were applied: water deficit (maintaining soil moisture between 40 and 60% of the available water capacity (AWC)), water surplus (maintained between 90% of AWC and the determine saturation point) and control (maintained between 75 and 100% of the AWC). To determine the water condition of the soil along the cycle was held daily sequential water balance. The water inlet by rain in the treatment of water deficit was controlled. The analyzed variables were yield and yield components, oil content and oil yield, fatty acid profile, root depth, root distribution, dry matter of different plant parts, in addition to intrinsic variables of growth analysis. Modeling of the root depth and sunflower growth in dry matter was held of different plant parts. The drought level applied was more harmful than the level of water surplus applied, with significant reduction in yield, yield components and sunflower growth. Sowing date had influence on yield, where the early sowing date produced more than late sowing date. Soil had great influence on the root deepening which was higher in Ultisol compared to Oxisol, which impacted the yield gap under water deficit. Water deficit was responsible for increased Oleic Acid and reduction of Linoleic Acid. The sowing at early sowing date enables deepening and increased dry matter production of roots than sowing at late sowing date. Sunflower growth models in dry matter and root depth had good fit to the measured data. In this way, it is concluded that soil water availability and sowing dates influences the yield and quality of sunflower and should be taken measures to mitigate the problems caused. / A disponibilidade hídrica do solo é um dos principais fatores responsáveis pelo sucesso ou insucesso de um cultivo agrícola. A ocorrência de estresses causados por déficit ou por excesso hídrico é prejudicial ao crescimento e à produtividade do girassol. O padrão de crescimento das plantas é alterado e a produtividade é reduzida com o aumento da intensidade correspondente ao estresse. Os principais objetivos deste trabalho foram avaliar a produtividade de grãos e de óleo e a qualidade do óleo do girassol, o crescimento, aprofundamento e distribuição de raízes no solo, o crescimento da parte aérea e raiz em matéria seca e a modelagem do crescimento de plantas de girassol, em resposta ao estresse causado por excesso e déficit hídrico, em duas épocas de semeadura e dois solos do Rio Grande do Sul. Os experimentos foram realizados na Safra (semeadura em início de setembro) e na Safrinha (semeadura em início de janeiro), em dois solos nos municípios de Santa Maria (Argissolo) e Panambi (Latossolo). Foram aplicados três tratamentos de disponibilidade hídrica: déficit hídrico (mantendo-se a umidade do solo entre 40 e 60% da capacidade de armazenamento de água disponível (CAD)), excesso hídrico (mantido entre 90% da CAD e o ponto de saturação determinado) e controle (mantido entre 75 e 100% da CAD). Para determinar a condição hídrica do solo ao longo do ciclo, realizou-se o balanço hídrico sequencial diário. A entrada de água por chuva no tratamento de déficit hídrico foi controlada. As variáveis analisadas foram a produtividade, os componentes da produtividade, o teor e o rendimento de óleo, o perfil de ácidos graxos, a profundidade radicular, a distribuição radicular, a matéria seca das diferentes partes da planta, além das variáveis intrínsecas a análise de crescimento. Foi realizada a modelagem do aprofundamento radicular e do crescimento do girassol em matéria seca das diferentes partes da planta. Verificou-se que o nível de déficit hídrico aplicado foi mais prejudicial do que o nível de excesso hídrico aplicado, com redução significativa da produtividade, dos componentes da produtividade e do crescimento do girassol. A época de semeadura teve influencia sobre a produtividade, em que a Safra produziu mais do que a Safrinha. O solo teve grande influencia sobre o aprofundamento radicular que foi maior no Argissolo em comparação ao Latossolo, o que impactou na diferença de produtividade. O déficit hídrico foi responsável pelo aumento do Ácido Oleico e pela redução do Ácido Linoleico. A semeadura na Safra possibilita um maior aprofundamento e maior produção de massa seca de raízes do que a semeadura da Safrinha. Os modelos de crescimento do girassol em matéria seca e em profundidade radicular apresentaram bom ajuste aos dados medidos. Dessa forma, conclui-se que a disponibilidade hídrica do solo e a época de semeadura influenciam na produtividade e na qualidade do girassol e se devem tomar medidas para mitigar os problemas causados.

Os solos ácidos (pH < 5,0) representam cerca de 40 % das áreas agricultáveis no mundo. Nestes solos ocorre a solubilização de formas tóxicas de alumínio que inibe o crescimento radicular. Independente da presença do Al, o baixo pH pode ser tóxico à raiz, afetando a viabilidade celular no ápice e o crescimento radicular. Há evidências de que o estresse por H+ e/ou Al³+ afetam a parede celular. Por outro lado, modificações na parede podem determinar o grau de tolerância da planta quando submetidos a estes estresses. Assim, utilizou-se de duas abordagens para investigar se possíveis modificações na parede celular melhorariam o crescimento e viabilidade celular na exposição a H+ e Al³+. Na primeira, raízes de plantas do cultivar Micro-Tom (MT) de tomateiro (Solanum lycopersicum L.), com 2 e 13 dias de desenvolvimento, foram expostas de forma direta ou gradual ao baixo pH. Na segunda abordagem, as raízes foram submetidos a um tratamento hipo-osmótico antes de serem expostas a pH 4,0 ou 4,5 + Al. Em plantas com 2 e 13 dias, a exposição gradual foi realizada alterando o pH ao longo de 12 e 24 h, respectivamente. No tratamento hipo-osmótico (priming), as plantas foram transferidas de uma solução de alta osmolaridade (150 mM) para uma com baixa osmolaridade (0,5 mM), a pH 5,8, por 0; 0,5; 1 e 2 h antes de serem expostas a pH 4,0 ou 4,5 + Al por 12h. Como controles, raízes não receberam tratamento osmótico ou foram mantidas continuamente em alta osmolaridade. O crescimento de raízes expostas diretamente a pH 4,5 foi cerca de metade do controle a pH 5,8 e a pH 4,0 foi nulo. Ao contrário do esperado, na exposição gradual a pH 4,5, as raízes cresceram menos do que aquelas expostas diretamente a este pH e a pH 4,0 o crescimento continuou insignificante. No entanto, raízes expostas gradualmente ao pH 4,0 mantiveram a viabilidade das células do ápice, ao contrário daquelas expostas diretamente. Assim, a redução do crescimento radicular pela exposição a baixo pH pode ser uma resposta gerada pela própria planta, não sendo necessariamente decorrente da ação direta do pH. O priming hipo-osmótico antes da exposição a pH 4,0 permitiu a manutenção da viabilidade celular e um crescimento radicular de até 38% das raízes controle a pH 5,8, enquanto que nos controles a pH 4,0 as células morreram e o crescimento foi praticamente nulo. Em pH 4,5 + 5 ?M de Al o priming não reverteu a inibição do crescimento radicular, indicando que as respostas para H+ e Al³+ são diferentes. Ficou evidente que a atividade de GPX está envolvida nas respostas encontradas tanto na exposição gradual a baixo pH como no tratamento hipo-osmótico anterior ao baixo pH, mas não foi possível determinar se é consequência ou uma das possíveis causas destas respostas. No seu conjunto, os dados indicam que possíveis mudanças na parede celular podem estar envolvidas na melhoria do crescimento radicular e viabilidade celular do ápice durante o estresse. / Acidic soils (pH <5.0) represent about 40% of the arable land in the world. In these soils, toxic aluminum becomes soluble and inhibits root growth. Regardless of Al, low pH is, in itself, also toxic, decreasing cell viability and root growth. There is evidence that H+ and Al3+ can affect the cell wall. Reversely, modifications in the wall may determine the degree of tolerance of roots subjected to these stresses. Therefore, we used two approaches to investigate whether possible changes in the cell wall improve growth and cell viability upon exposure to H + and Al³+. In the first approach, roots of plants of the Micro-Tom (MT) cultivar of tomato (Solanum lycopersicum L.), at 2 and 13 days of development, were exposed directly or gradually to low pH. In the second approach, the roots were subjected to hypoosmotic treatment prior to being exposed to pH 4.0 or 4.5 + Al. In 2- and 13-day plants, gradual exposure was achieved by changing the pH over a 12 and 24 h period, respectively. In the hypo-osmotic pre-treatment (priming), plants were transferred from a high osmolarity solution (150 mM) to another with low osmolarity (0.5 mM), at pH 5.8, for 0, 0.5, 1 and 2 h before being exposed to pH 4.0 or 4.5 + Al for 12h. As controls, roots did not receive any osmotic treatment or were maintained continuously at high osmolarity. Growth of roots exposed directly to pH 4.5 was about half that of control roots at pH 5,8 and at pH 4.0 root growth was suppressed. Different from expected, roots exposed gradually to pH 4.5 grew less than those exposed directly to pH 4.5 and at pH 4.0, root growth remained negligible. However, cell viability was maintained in roots exposed gradually to pH 4.0, unlike those exposed directly. Thus, decreased root growth upon exposure to low pH may be a response generated by the plant itself rather than the direct effect of pH. In roots subjected to hypo-osmotic priming prior to exposure to pH 4.0, cell viability was maintained and root growth was up to 38% of that of control roots at pH 5.8, whereas in control roots at pH 4.0, cell death occurred and root growth was insignificant. At pH 4.5 + 5 uM Al, priming did not reverse the inhibition of root growth, suggesting that responses to H+ and Al3+ are different. GPX was involved in responses to both gradual exposure to low pH and to hypo-osmotic treatment prior to low pH, but it was not possible to determine whether this was a consequence or one of the possible causes of these responses. Taken together, the data indicate that possible changes in the cell wall may be involved in improving root growth and cell viability of the root apex during stress.

Le sujet de l’adaptation aux changements climatiques est devenu l’un des sujets contemporains les plus importants dans la vigne. Une grande focalisation a été mise sur la compréhension des effets du porte-greffe sur la croissance du scion, l’absorption des nutriments, et la tolérance au stress, dans l’objectif final de développer de nouveaux porte-greffes qui facilitent l’adaptation au changement climatique. L’objectif de cette thèse est d’examiner comment les différences dans la résistance à la sécheresse entre les génotypes peut résulter en de grandes différences dans leur capacité à maintenir leur croissance racinaire en situation de stress. Une meilleure compréhension sur la manière dont la structure, la croissance racinaire et l’absorption d’eau répondent au stress nous permettra de mieux comprendre quels sont les aspects de la physiologie racinaire qui contribuent à la tolérance face à la sécheresse. Des recherches précédentes qui s’étaient focalisées sur l’absorption d’eau racinaire chez la vigne ont suggéré que l’absorption d’eau racinaire pouvait être fortement liée à la vitesse de croissance racinaire instantanée (voir Gambetta et al. 2013). Cette observation implique que des différences entre les génotypes dans la résistance face à la sécheresse pourrait largement résulter de leur capacité à maintenir la croissance racinaire en conditions de stress. Deux porte-greffes de vigne avec des capacités contrastées en matière de résistance à la sécheresse, le Riparia Gloire de Montpellier (RGM) et le 110 Richter (110R) ont été sélectionnés pour étudier dans cette thèse. RGM est considéré comme sensible à la sécheresse, tandis que 110R est fortement résistant à la sécheresse (Carbonneau 1985). La thèse a examiné la relation entre la croissance racinaire et la capacité de résistance à la sécheresse en évaluant la vitesse de croissance racinaire, la conductivité hydraulique à travers deux variétés de porte-greffe en conditions de déficit en eau. Le niveau de l’expression des gènes d’aquaporines (via la qPCR et l’ARNseq) et leur contribution à la conductivité hydraulique racinaire ont été analysés dans les radicelles afin d’obtenir une meilleure compréhension sur les mécanismes impliqués dans la régulation de l’absorption de l’eau racinaire et la conductivité hydraulique au cours du développement et en réponse à un manque d’eau.Le traitement de stress d’eau prolongé a diminué le potentiel hydraulique de la plante. La croissance racinaire individuelle est très hétérogène : bien que le traitement de sécheresse réduise l’élongation racinaire en moyenne, la vitesse de croissance racinaire varie tout de même énormément. Un haut niveau de stress hydrique a réduit significativement la vitesse de croissance racinaire moyenne à la fois pour RGM et 110R. Globalement, la vitesse de croissance racinaire moyenne a montré une tendance réduite au cours du développement de la plante. La température du sol est aussi un facteur qui affecte la croissance racinaire. Pour RGM et 110R, en conditionsIIde bon arrosage et de stress hydrique, la vitesse de croissance quotidienne moyenne a été positivement corrélée avec la température du sol quotidienne moyenne. En conditions de bon arrosage, des vitesses de croissance racinaires plus importantes ont été constamment observées chez 110R par rapport à RGM, ce qui pourrait être une explication possible de sa meilleure résistance à la sécheresse par rapport à 110R. [...] / The subject of adaptation to climate change has become one of the most important contemporary topics in grapevine. Much focus has been placed on the understanding of rootstocks effects on scion growth, nutrient uptake, and tolerance to stress, with the ultimate goal of developing novel rootstocks that facilitate adaptation to a changing climate. The purpose of this thesis is to examine how differences in drought resistance between genotypes could result largely from differences in their ability to maintain root growth under stress. A better understanding of how root structure, growth, and water uptake respond to stress will allow us to better understand what aspects of root physiology contribute to drought tolerance. Previous research focused on root water uptake in grapevine suggested that root water uptake could be tightly coupled to a root’s instantaneous rate of growth (see Gambetta et al. 2013). This observation implies that differences in drought resistance between genotypes could result largely from their ability to maintain root growth under stress. Two grapevine rootstocks with contrasting drought resistance capacity, Riparia Gloire de Montpellier (RGM) and 110 Richter (110R), were selected to study in this thesis. RGM is considered as sensitive to drought, while 110R is highly resistant to drought (Carbonneau 1985). The thesis examined the relationship between root growth and drought resistant capacity by assessing root growth rate, hydraulic conductivity across two rootstock varieties subjected to water deficit. The role of aquaporin gene expression (via qPCR and RNAseq) and their contribution to root hydraulic conductivity were analyzed in fine roots in order to obtain a better understanding on the mechanisms involved in the regulation of root water uptake and hydraulic conductivity across development and in response to water deficit.Prolonged water stress treatment decreased plant water potential. Individual root growth is very heterogeneous, although drought treatment reduces root elongation on average, individual root growth rate still varies enormously. High level of water stress significantly reduced average root growth rate for both RGM and 110R. Globally, average root growth rate showed a decreased trend over plant development. Soil temperature is also a factor that affects root growth. For both RGM and 110R, under both well-watered and water-stressed conditions, average daily root growth rate was positively correlated with average daily soil temperature. Under well-watered conditions, higher root growth rates were constantly observed in 110R compared to RGM, which could be one possible explanation for the higher capacity in drought resistance of 110R.Root hydraulic conductivity (Lpr) was influenced by both water stress treatment and plant developmental stage. Generally, for both RGM and 110R, Lpr was significantly reduced under water stress in early stage. In mid and late stages, no significant differences in Lpr were observedIVbetween well-watered and water-stressed plants. Changes in individual root Lpr in response to pre-dawn leaf water potential (ᴪpredawn) were investigated as well. Lpr showed a fast drop in the beginning of water stress treatment when ᴪpredawn was higher than -0.5 MPa. However, with ᴪpredawn getting more negative, e.g. from -0.4 MPa to -2.0 MPa, the range of Lpr values measured in our study maintained constant. Lpr of well-watered plants decreased as well even though their ᴪpredawn was maintained at a high level (< 0.1 MPa) during the period of the experiment. [...]