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In their natural environment, leaves are exposed to rapid fluctuations of irradiance. Research on CO2 assimilation under fluctuating irradiance often relies on measurements of gas exchange during transients where irradiance is rapidly increased or decreased, after the leaf has adapted to a particular set of environmental conditions. In the field, such increases and decreases occur mostly because of sunflecks (rapid increases in irradiance on a low irradiance background) created by gaps in the canopy and plant movement by wind, and cloudflecks (rapid decreases in irradiance on a high irradiance background) generated by clouds that transiently block the sun. In this dissertation, the metabolic regulation of photosynthesis and how this may limit dynamic CO2 assimilation is studied in silico with the development and application of simulation models. In order to support the development of the models, a review of the literature was performed as well as an experiment designed to generate data on dynamic CO2 assimilation for different photosynthetic mutants of Arabidopsis thaliana. In addition to providing these models to the research community, this dissertation also identifies multiple targets that may be used for improving dynamic CO2 assimilation in plants. It further demonstrates that the dynamic responses of CO2 assimilation to changes in irradiance has a significant effect on canopy CO2 assimilation, even for dense canopies exposed to open skies, resembling the conditions of commercial crops. In Chapter 1, the context of this dissertation is presented. The societal relevance of this research is argued, making reference to the role that photosynthesis could play in addressing global problems such as food and energy security. The necessary background on the physiology of photosynthesis is provided, with special emphasis on the terminology and concepts required to understand the rest of the dissertation, with the aim of making the contents more accessible to a wider aud

A better understanding of the metabolic and diffusional limitations of photosynthesis in fluctuating irradiance can help identify targets for improving crop yields. We used different genotypes of Arabidopsis thaliana to characterise the importance of Rubisco activase (Rca), stomatal conductance (g s), non-photochemical quenching of chlorophyll fluorescence (NPQ) and sucrose phosphate synthase (SPS) on photosynthesis in fluctuating irradiance. Leaf gas exchange and chlorophyll fluorescence were measured in leaves exposed to stepwise increases and decreases in irradiance. rwt43, which has a constitutively active Rubisco enzyme in different irradiance intensities (except in darkness), showed faster increases than the wildtype, Colombia-0, in photosynthesis rates after step increases in irradiance. rca-2, having decreased Rca concentration, showed lower rates of increase. In aba2-1, high g s increased the rate of change after stepwise irradiance increases, while in C24, low gs tended to decrease it. Differences in rates of change between Colombia-0 and plants with low levels of NPQ (npq1-2, npq4-1) or SPS (spsa1) were negligible. In Colombia-0, the regulation of Rubisco activation and of gs were therefore limiting for photosynthesis in fluctuating irradiance, while levels of NPQ or SPS were not. This suggests Rca and g s as targets for improvement of photosynthesis of plants in fluctuating irradiance.

Los métodos de procesamiento de video como Magnificación Euleriana, Correlación de Fase, Comparación de plantillas y Flujo Óptico permiten extraer de forma cualitativa y cuantitativa información importante a partir de grabaciones de video, tal como la frecuencia de oscilación de construcciones en el campo de ingeniería de civil. En el monitoreo de salud estructural se evalúa dicho aspecto utilizando comúnmente dispositivos electrónicos, que implican un procedimiento invasivo y costoso al instalar y distribuir a lo largo de la estructura múltiples sensores. Este proyecto ofrece una alternativa para estimar la frecuencia de oscilación a través de captura video, en la cual se extrae la frecuencia de oscilación utilizando los cuatro diferentes métodos mencionados, cuyos resultados se comparan con los de un LVDT y se evalúan en cuanto a complejidad computacional, escalabilidad, precisión y funcionamiento.