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250 p. + anexos, El pino radiata es una conífera de crecimiento rápido originario de la costa de California que se ha importado en muchos países, en concreto en España se empezó a emplear en reforestaciones a mediados del sigo XX y desde entonces su uso se ha popularizado debido a la rentabilidad económica. Sin embargo, el fututo incierto debido al cambio climático, así como la necesidad de mejorar su productividad hacen evidente la necesidad de su investigación. En esta tesis doctoral hemos tratado desde un enfoque genético tratar de avanzar en el entendimiento de la especie en la Comunidad Autónoma Vasca, así como en el resto de España, útil para su mejora en aspectos de productividad y sostenibilidad. Todo ello se ha abordado en primer lugar mediante la caracterización genética de la especie en España analizando su diversidad genética neutral y analizando de la misma manera el material disponible y que se seleccionó en los inicios del programa de mejora del Pino radiata en el País Vasco allá en 1984. Asimismo, esta tesis se ha centrado en dos caracteres relacionados con la productividad de la especie, así como la sostenibilidad como son la calidad de madera para uso estructural y la respuesta a la sequía respectivamente. Los resultados aportan información útil para la mejora genética del Pinus radiata en la Comunidad Autónoma Vasca y el resto de las plantaciones españolas. Finalmente y colateralmente se diseñó un flujo de trabajo útil para la evaluación de procesos bioinformáticos empleados en el marco de este estudio.

Con objeto de realizar tareas de servicio en órbita de manera autónoma y sin necesidad de personal humano, este trabajo presenta el desarrollo de un sistema robótico de auto-acoplamiento basado en cámaras y marcadores visuales que permiten facilitar el ensamblaje de la interfaz multifuncional SIROM (Standard Interface for Robotic Manipulation), diseñada por SENER Aeroespacial. Para ello se ha implementado un control servo visual, logrando realizar el acoplamiento de manera autónoma entre un dispositivo SIROM activo utilizado como herramienta de un manipulador robótico y su homólogo SIROM pasivo acoplado a un módulo espacial. Este desarrollo permitirá que en el futuro dicha interfaz robótica sea una solución de referencia vanguardista para la realización de estas tareas. La solución presentada ha sido validada mediante la realización de ensayos independientes para cada uno de los subsistemas que componen el prototipo desarrollado y, posteriormente, se ha verificado el funcionamiento del sistema al completo en diferentes escenarios de ensamblaje y ante situaciones de gran desalineamiento. El análisis de los resultados obtenidos en este trabajo permiten corroborar que el prototipo diseñado logra cumplir con el objetivo principal de manera satisfactoria.

231 p., Ammonium (NH4+) is a nitrogen source of great interest in the context of sustainable agriculture. Its application in the field together with nitrification inhibitors has been extensively proven efficient to limit detrimental N losses compared to the use of nitrate (N03). NH4+ is a common intermediate involved in numerous metabolic routes. However, high NH4 concentrations may lead to a stress situation provoking a set of symptoms collectively known as "ammonium syndrome" mainly characterized by growth retardation. Those symptoms are caused by a combination of, among others, a profound metabolic reprogramming, disruption of photosynthesis, pH deregulation and ion imbalance. Numerous studies have described the way plant copes to ammonium nutrition. However, the organ developmental stage has been generally neglected.To fill in this gap, in the first chapter we first aimed studying how the metabolism is adapted in function of the leaf position in the vertical axis of the tomato plants (Solanum lycopersicum) grown with NH4+, N03- or NH4N03 supply. To do so, we dissected leaf biomass composition and metabolism through a complete analysis of metabolites, ions and enzyme activities. The results showed that C and N metabolic adjustment in function of the nitrogen source was more intense in older leaves compared to younger ones. Importantly, we propose a trade-off between NH4+ accumulation and assimilation to preserve young leaves from ammonium stress. Besides, NH4+-fed plants exhibited a rearrangement of carbon skeletons with a higher energy cost respect to plants supplied with N03-. We explain such reallocation by the action of the biochemical pH-stat, to compensate the differential proton production that depends on the nitrogen form provided.Ammonium nutrition may limit cell expansion, suggesting that the cellular processes involved would be altered. Among others, cell growth is largely dependent of the internal pressure exerted on the cell wall by the vacuole. However, the

[EN] Agriculture faces the considerable challenge of having to adapt to a progressively changing climate (including the increase in CO2 levels and temperatures); environmental impact must be reduced while at the same time crop yields need to be maintained or increased to ensure food security. Under this scenario, increasing plants' nitrogen (N) use efficiency and minimizing the energy losses associated with photorespiration are two goals of crop breeding that are long sought after. The plastidic glutamine synthetase (GS2) enzyme stands at the crossroads of N assimilation and photorespiration, and is therefore a key candidate for the improvement of crop performance. The GS2 enzyme has long been considered essential for angiosperm survival under photorespiratory conditions. Surprisingly, in Arabidopsis GS2 is not essential for plant survival, and its absence confers tolerance towards ammonium stress, which is in conflict with the idea that NH4+ accumulation is one of the main causes of ammonium stress. Altogether, it appears that the 'textbook' view of this enzyme must be revisited, especially regarding the degree to which it is essential for plant growth under photorespiratory conditions, and the role of NH4+ assimilation during ammonium stress. In this article we open the debate on whether more or less GS2 is a desirable trait for plant productivity.

Phosphoenolpyruvate carboxylase (PEPC) is a carboxylating enzyme with important roles in plant metabolism. Most studies in C-4 plants have focused on photosynthetic PEPC, but less is known about non-photosynthetic PEPC isozymes, especially with respect to their physiological functions. In this work, we analyzed the precise roles of the sorghum (Sorghum bicolor) PPC3 isozyme by the use of knock-down lines with the SbPPC3 gene silenced (Ppc3 lines). Ppc3 plants showed reduced stomatal conductance and plant size, a delay in flowering time, and reduced seed production. In addition, silenced plants accumulated stress indicators such as Asn, citrate, malate, and sucrose in roots and showed higher citrate synthase activity, even in control conditions. Salinity further affected stomatal conductance and yield and had a deeper impact on central metabolism in silenced plants compared to wild type, more notably in roots, with Ppc3 plants showing higher nitrate reductase and NADH-glutamate synthase activity in roots and the accumulation of molecules with a higher N/C ratio. Taken together, our results show that although SbPPC3 is predominantly a root protein, its absence causes deep changes in plant physiology and metabolism in roots and leaves, negatively affecting maximal stomatal opening, growth, productivity, and stress responses in sorghum plants. The consequences of SbPPC3 silencing suggest that this protein, and maybe orthologs in other plants, could be an important target to improve plant growth, productivity, and resistance to salt stress and other stresses where non-photosynthetic PEPCs may be implicated.

Ammonium (NH4+)-based fertilization efficiently mitigates the adverse effects of nitrogen fertilization on the environment. However, high concentrations of soil NH4+ provoke growth inhibition, partly caused by the reduction of cell enlargement and associated with modifications of cell composition, such as an increase of sugars and a decrease in organic acids. Cell expansion depends largely on the osmotic-driven enlargement of the vacuole. However, the involvement of subcellular compartmentation in the adaptation of plants to ammonium nutrition has received little attention, until now. To investigate this, tomato (Solanum lycopersicum) plants were cultivated under nitrate and ammonium nutrition and the fourth leaf was harvested at seven developmental stages. The vacuolar expansion was monitored and metabolites and inorganic ion contents, together with intracellular pH, were determined. A data-constrained model was constructed to estimate subcellular concentrations of major metabolites and ions. It was first validated at the three latter developmental stages by comparison with subcellular concentrations obtained experimentally using non-aqueous fractionation. Then, the model was used to estimate the subcellular concentrations at the seven developmental stages and the net vacuolar uptake of solutes along the developmental series. Our results showed ammonium nutrition provokes an acidification of the vacuole and a reduction in the flux of solutes into the vacuoles. Overall, analysis of the subcellular compartmentation reveals a mechanism behind leaf growth inhibition under ammonium stress linked to the higher energy cost of vacuole expansion, as a result of alterations in pH, the inhibition of glycolysis routes and the depletion of organic acids.

Background: Agriculture relies on the intensive use of synthetic nitrogen (N) fertilizers to maximize crop yields, which has led to the transformation of agricultural soils into high-nitrifying environments. Nevertheless, nitrification inhibitors (Nis) have been developed to suppress soil-nitrifier activity and decrease N losses. The Nis 3,4-dimethylpyrazole phosphate (DMPP) and 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) are able to reduce N2O emissions and maintain soil NH4+ for a longer time. Although both Nls have been proven to be effective to inhibit soil nitrification, their exact mode of action has not been confirmed. We aimed to provide novel insights to further understand the mode of action of DMP-based Nis. We evaluated the performance of DMPP and DMPSA in soil and pure cultures of nitrifying bacteria Nitrosomonas europaea. Results: DMPSA did not inhibit nitrification in pure cultures of N. europaea. In the soil, we evidenced that DMPSA needs to be broken into DMP to achieve the inhibition of nitrification, which is mediated by a soil biological process that remains to be identified. Moreover, both DMPP and DMPSA are thought to inhibit nitrification due to their ability to chelate the Cu2+ cations that the ammonia monooxygenase enzyme (AMO) needs to carry on the first step of NH4+ oxidation. However, the efficiency of DMPP was not altered regardless the Cu2+ concentration in the medium. In addition, we also showed that DMPP targets AMO but not hydroxylamine oxidoreductase enzyme (HAO). Conclusions: The inability of DMPSA to inhibit nitrification in pure cultures together with the high efficiency of DMPP to inhibit nitrification even in presence of toxic Cu2+ concentration in the medium, suggest that the mode of action of DMP-based Nis does not rely on their capacity as metal chelators.