Impacto del cambio climático sobre la ecofisiología y capacidad fitorremediadora de halófitas

El Cambio Climático está considerado como uno de los principales cambios globales a los que se enfrenta la humanidad, y es consecuencia del incremento exacerbado de la emisión de dióxido de carbono (CO2) a la atmósfera desde la etapa preindustrial. La vegetación es uno de los componentes del ecosistema con mayor vulnerabilidad frente a este fenómeno, habiéndose descrito posibles alteraciones sobre su distribución, fenología, productividad, etc. En este contexto, es de gran importancia estudiar cómo afectan a la ecofisiología de las plantas las interacciones de distintos factores asociados al Cambio Climático (elevado CO2, aumento de las temperaturas y nivel del mar, eventos climáticos extremos, etc.). Las halófitas son especies vegetales que han desarrollado una serie de mecanismos que les permiten completar su ciclo vital en ambientes altamente estresantes. Además, muchas halófitas han demostrado un enorme potencial tecnológico para su empleo como recursos de diferente naturaleza (alimentación, fármacos, etc.) o en fitorremediación de contaminantes. Sin embargo, poco se sabe sobre la respuesta de estas especies frente a la interacción de factores asociados con el Cambio Climático o cómo estas interacciones afectan a su capacidad fitorremediadora; y este es el vacío de conocimiento que trata de llenar esta Tesis Doctoral. Nuestros resultados mostraron cómo el aumento del CO2 (700 ppm) mejoró la tolerancia de una halófita modelo, Salicornia ramosissima, frente a la salinidad (510 mM NaCl). La mejora de la tolerancia se reflejó en el mantenimiento de la tasa de asimilación de CO2 y la funcionalidad de los fotosistemas. Este efecto positivo se hizo patente incluso bajo condiciones de inundación permanente del suelo. Respecto al impacto de eventos térmicos extremos de corta duración (40-28 ºC y 12-5ºC durante tres días), se observó una respuesta termo-dependiente, de forma que S. ramosissima fue más sensible a las bajas temperaturas que a las altas para los dos niveles de salinidad estudiados (171 y 1040 mM). Por otro lado, los resultados de esta Tesis mostraron un efecto específico en la capacidad fitorremediadora de las halófitas Spartina densiflora y Juncus acutus. Así, en el caso de S. densiflora, el elevado CO2 (700 ppm) aumentó su tolerancia frente al exceso de Cu, manteniendo la capacidad para fitoestabilizar Cu en sus raíces. Para J. acutus su mayor tolerancia frente al Zn estuvo en gran parte mediada por la reducción de la concentración de Zn en sus tejidos en presencia de sal (85 mM NaCl). En conclusión, las halófitas crecidas en una atmósfera enriquecida en CO2 en combinación con otros factores ambientales de estrés mostraron mejor respuesta fisiológica que aquellas sometidas solamente a alta salinidad, inundación o al efecto tóxico de un metal pesado. La interacción de factores genera efectos sinérgicos que difieren de las respuestas que se registran cuando se analizan los factores por separado. Por tanto, para poder predecir la respuesta de las plantas frente al Cambio Climático es necesario abordar los ensayos considerando la interacción de factores.Climate Change is considered one of the main global changes facing by humanity, and is the result of the exacerbated increase in the emission of carbon dioxide (CO2) into the atmosphere from the pre-industrial stage. The vegetation is one of the components of the ecosystem with greater vulnerability to this phenomenon, having described possible alterations on its distribution, phenology, productivity, etc. In this context, it is very important to study how the interactions of different factors associated with climate change (high CO2, rising temperatures and sea level, extreme climatic events, etc.) affect the ecophysiology of plants. Halophytes are plant species that have developed a series of mechanisms that allow them to complete their life cycle in highly stressful environments. In addition, many halophytes have demonstrated an enormous technological potential for their use as resources of different nature or in phytoremediation of pollutants. However, little is known about the response of these species to the interaction of factors associated with Climate Change or how these interactions affect their phytoremediation capacity; and this is the knowledge gap that tries to fill this Doctoral Thesis. Our results shown how the increase in CO2 (700 ppm) improved the tolerance of a halophyte model, Salicornia ramosissima, against salinity (510 mM NaCl). The improvement in tolerance was reflected in the maintenance of the CO2 assimilation rate and the functionality of the photosystems. This positive effect became apparent even under conditions of permanent soil flooding. Regarding the impact of extreme thermal events of short duration (40-28ºC and 12-5ºC during three days), a thermo-dependent response was observed, so that S. ramosissima was more sensitive to low temperatures for the two levels of salinity studied (171 and 1040 mM). On the other hand, the results of this Thesis showed a specific effect on the phytoremediation capacity of the halophytes Spartina densiflora and Juncus acutus. Thus, in the case of S. densiflora, high CO2 (700 ppm) increased its tolerance to Cu excess, maintaining the ability to phytostabilize Cu in its roots. For J. acutus, its greater tolerance to Zn was largely mediated by the reduction of the concentration of Zn in its tissues in the presence of salt (85 mM NaCl). In conclusion, halophytes grown in an atmosphere enriched in CO2 in combination with other environmental factors of stress shown a better physiological response than those subjected only to high salinity, flood or the toxic effect of a heavy metal. The interaction of factors generates synergistic effects that differ from the responses that are recorded when the factors are analyzed separately. Therefore, in order to predict the response of plants to climate change it is necessary to address the trials considering the interaction of factors.Premio Extraordinario de Doctorado U

Impact of short-term extreme temperature events on physiological performance of Salicornia ramosissima J. Woods under optimal and sub-optimal saline conditions

Increasing extreme temperature climatic events could exert an important effect on plant photosynthetic performance, which could be modulated by the co-occurrence with other environmental factors, such as salinity, in estuarine ecosystems. Therefore, a mesocosm experiment was designed to assess the impact of temperature events for three days (13/5 °C, 25/13 °C and 40/28 °C) in combination with two NaCl concentrations (171 and 1050 mM NaCl) on the physiological performance of Salicornia ramosissima. Extreme temperature events had a negative impact on S. ramosissima photosynthetic efficiency, this effect being more marked with cold wave at both salinities, compared with heat wave, even in presence of NaCl excess. This differential thermotolerance in the photosynthetic apparatus was ascribed to the greater integrity and functioning of its photosynthetic pathway at high temperature, as indicated by constant gs, Vc,max values at optimal salinity and the higher values of those parameters and gm recorded in combination with NaCl excess. Moreover, S. ramosissima was able to upregulate the energy sink capacity of its photochemical apparatus at elevated temperature and salinity by a greater energy excess dissipation capacity. This could have contributed to reducing the risk of oxidative stress, along with the recorded higher capacity for antioxidant enzyme activity modulation under these conditions.España, MINECO Project CGL2016– 75550-

Effect of Plant Growth-Promoting Rhizobacteria on Salicornia ramosissima Seed Germination under Salinity, CO2 and Temperature Stress

In a scenario of climate change and growing population, halophyte root microbiota interactions may be a sustainable solution to improve alternative crop production while combating abiotic stress. In this work, seeds of the cash crop halophyte Salicornia ramosissima were inoculated with five different plant growth-promoting rhizobacteria consortia, isolated from the rhizosphere of five halophytes in southwestern Spain salt marshes. For the first time, we recorded seed germination response to three interactive abiotic stressors, CO2 (400 and 700 ppm), temperature (25 and 29 ℃) and salinity (171, 510 and 1030 mM NaCl), all of them related to climate change. Salinity played a decisive role, as no significant differences were registered between treatments at 171 mM NaCl and no germination took place at 1030 mM NaCl. At 510 mM NaCl, one rhizobacterial consortium improved seed parameters notably, increasing up to 114% germination percentage and 65% seedlings biomass. These first findings encourage us to think that cash crop halophytes like S. ramosissima and halophyte root microbiota may be valuable resources for human or animal feeding in a future climate reality.Ministerio de Economía y Competitividad (CGL2016-75550-R)Ministerio de Educación, Cultura y Deporte (FPU014/03987

Chitosan-based hydrogels obtained via photoinitiated click polymer IPN reaction

Chitosan (CTS) is a polysaccharide with a wide variety of applications in the biomedical field, owing to its outstanding disinfectant properties, biocompatibility and biodegradability, but with limited mechanical properties. The proposed strategy to improve CTS-based hydrogel properties in this study is the formation of a semi-interpenetrating polymer network (semi-IPN). In this way, a photo-initiated radical click reaction was proposed to obtain a synthetic polymer, whose components were included in a CTS solution, resulting in the semi-IPN network after UV illumination. Different crosslinking degrees (CD) and CTS/polymer ratios were evaluated through rheological characterization, along with an assessment of both variables based on an experimental model design, obtaining that, for every CTS/polymer ratio, intermediate values of CD (8 %) offered the best rheological properties. In addition, chemical and microstructural characterization were carried out for selected hydrogels, obtaining consistent results according to rheological characterization, as the 1/1 CTS/polymer ratio with CD 8 % hydrogel displayed the most homogeneous pore size and distribution, consequently leading to the best rheological performance.This study was financially supported by MCIN/AEI/10.13039/5 01100011033/FEDER, UE, through the project PID2021- 124294OB-C21. The authors gratefully acknowledge their financial support. This work was also possible thanks to the postdoctoral contract of Víctor M. Pérez Puyana from the ‘‘Contratación de Personal Investigador Doctor” supported by the European Social Fund and Junta de Andalucía (PAIDI DOCTOR – Convocatoria 2019–2020, DOC_00586)

Time-frequency analysis based on minimum-norm spectral estimation to detect induction motor faults

Producción CientíficaIn this work, a new time-frequency tool based on minimum-norm spectral estimation is introduced for multiple fault detection in induction motors. Several diagnostic techniques are available to identify certain faults in induction machines; however, they generally give acceptable results only for machines operating under stationary conditions. Induction motors rarely operate under stationary conditions as they are constantly affected by load oscillations, speed waves, unbalanced voltages, and other external conditions. To overcome this issue, different time-frequency analysis techniques have been proposed for fault detection in induction motors under non-stationary regimes. However, most of them have low-resolution, low-accuracy or both. The proposed method employs the minimum-norm spectral estimation to provide high frequency resolution and accuracy in the time-frequency domain. This technique exploits the advantages of non-stationary conditions, where mechanical and electrical stresses in the machine are higher than in stationary conditions, improving the detectability of fault components. Numerical simulation and experimental results are provided to validate the effectiveness of the method in starting current analysis of induction motors.Consejo Nacional de Ciencia y Tecnología (Proyecto 487058)Universidad de Guanajuato (Proyecto 248495/2019

Salinity alleviates zinc toxicity in the saltmarsh zinc-accumulator Juncus acutus

The potential importance of Juncus acutus for remediation of Zn-contaminated lands has been recognized, because of its Zn tolerance and capacity to accumulate Zn. Since it is also a halophyte, the extent to which salinity influences its Zn tolerance requires investigation. A factorial greenhouse experiment was designed to assess the effect of NaCl supply (0 and 85 mM NaCl) on the growth, photosynthetic physiology and tissue ions concentrations of plants exposed to 0, 30 and 100 mM Zn. Our results indicated that NaCl supplementation alleviated the effects of Zn toxicity on growth, as Zn at 100 mM reduced relative growth rate (RGR) by 60% in the absence of NaCl but by only 34% in plants treated also with NaCl. This effect was linked to a reduction in Zn tissue concentrations, as well as to overall protective effects on various stages in the photosynthetic pathway. Thus, at 85 mM NaCl plants were able to maintain higher net photosynthesis (AN) than in the absence of added NaCl, although there were no differences in stomatal conductance (gs). This contributed to preserving the trade-off between CO2 acquisition and water loss, as indicated by higher intrinsic water use efficiency (iWUE). Hence, AN differences were ascribed to limitation in the RuBisCO carboxylation, manifested as higher intercellular CO2 concentration (Ci), together with dysfunction of PSII photochemistry (in term of light harvest and energy excess dissipation), as indicated by higher chronic photoinhibition percentages and variations in the photosynthetic pigment profiles in presence of Zn under non-saline conditions

Impact of Plant Growth Promoting Bacteria on Salicornia ramosissima Ecophysiology and Heavy Metal Phytoremediation Capacity in Estuarine Soils

Salicornia ramosissima is a C3 halophyte that grows naturally in South Western Spain salt marshes, under soil salinity and heavy metal pollution (mostly Cu, Zn, As, and Pb) caused by both natural and anthropogenic pressure. However, very few works have reported the phytoremediation potential of S. ramosissima. In this work, we studied a microbe-assisted phytoremediation strategy under greenhouse conditions. We inoculated plant growth promoting (PGP) and heavy metal resistant bacteria in pots with S. ramosissima and natural non-polluted and polluted sediments collected from Spanish estuaries. Then, we analyzed plant ecophysiological and metal phytoaccumulation response. Our data suggested that inoculation in polluted sediments improved S. ramosissima plant growth in terms of relative growth rate (RGR) (32%) and number of new branches (61%). S. ramosissima photosynthetic fitness was affected by heavy metal presence in soil, but bacteria inoculation improved the photochemical apparatus integrity and functionality, as reflected by increments in net photosynthetic rate (21%), functionality of PSII (Fm and Fv/Fm) and electron transport rate, according to OJIP derived parameters. Beneficial effect of bacteria in polluted sediments was also observed by augmentation of intrinsic water use efficiency (28%) and slightly water content (2%) in inoculated S. ramosissima. Finally, our results demonstrated that S. ramosissima was able to accumulate great concentrations of heavy metals, mostly at root level, up to 200 mg Kg–1 arsenic, 0.50 mg Kg–1 cadmium, 400 mg Kg–1 copper, 25 mg Kg–1 nickel, 300 mg Kg–1 lead, and 300 mg Kg–1 zinc. Bioaugmentation incremented S. ramosissima heavy metal phytoremediation potential due to plant biomass increment, which enabled a greater accumulation capacity. Thus, our results suggest the potential use of heavy metal resistant PGPB to ameliorate the capacity of S. ramosissima as candidate for phytoremediation of salty polluted ecosystems.Ministerio de Economía y Competitividad (CGL2016-75550-R, AEI/FEDER, UE

Diseño y construcción de un banco de pruebas de motores para ensayos de investigación formativa

Con el fin de realizar investigaciones novedosas en motores de combustión interna alternativos, se requieren modernas salas de pruebas con equipos sofisticados para el control de los motores y sus equipos auxiliares. El principal obstáculo para la integración de una sala de éstas es el excesivo costo. Este artículo está dedicado a presentar la construcción de un banco dinamométrico de bajo costo para motores con potencias de hasta 120 kilovatios, diseñado con el principal propósito de atender las necesidades de investigación formativa en los cursos de ingeniería en el área de Máquinas de Combustión Interna. Los componentes necesarios para la construcción, la instrumentación y la operación de este banco se han adquirido con menos de US$12.000. El banco de pruebas se ha integrado teniendo como base un dinamómetro de corrientes parásitas y un motor Hércules G1600 de encendido provocado y cuatro cilindros en línea. En el artículo se describen las características del dinamómetro y el diseño de su sistema de control, así como el sistema de acople al motor, las particularidades constructivas de la estructura y las previstas para el montaje y alineación adecuados de diferentes tipos de motores. La parte mecánica del banco se ha complementado con un sistema de instrumentación y adquisición de información que registra las variables de par, velocidad y temperatura del motor, empleados para la obtención de las características de potencia y carga de los motores a instalar. El banco actualmente se ha instalado en una sala adecuada para la disposición del sistema de refrigeración externa del motor, la alimentación de combustible, la evacuación de los gases de escape, la ventilación del banco y el control del motor y del freno. Se ilustran las características de par y potencia sistematizadas durante la operación del banco de ensayos construido.Eje: Motores de combustión interna.Facultad de Ingenierí

Diseño y construcción de un banco de pruebas de motores para ensayos de investigación formativa

Con el fin de realizar investigaciones novedosas en motores de combustión interna alternativos, se requieren modernas salas de pruebas con equipos sofisticados para el control de los motores y sus equipos auxiliares. El principal obstáculo para la integración de una sala de éstas es el excesivo costo. Este artículo está dedicado a presentar la construcción de un banco dinamométrico de bajo costo para motores con potencias de hasta 120 kilovatios, diseñado con el principal propósito de atender las necesidades de investigación formativa en los cursos de ingeniería en el área de Máquinas de Combustión Interna. Los componentes necesarios para la construcción, la instrumentación y la operación de este banco se han adquirido con menos de US$12.000. El banco de pruebas se ha integrado teniendo como base un dinamómetro de corrientes parásitas y un motor Hércules G1600 de encendido provocado y cuatro cilindros en línea. En el artículo se describen las características del dinamómetro y el diseño de su sistema de control, así como el sistema de acople al motor, las particularidades constructivas de la estructura y las previstas para el montaje y alineación adecuados de diferentes tipos de motores. La parte mecánica del banco se ha complementado con un sistema de instrumentación y adquisición de información que registra las variables de par, velocidad y temperatura del motor, empleados para la obtención de las características de potencia y carga de los motores a instalar. El banco actualmente se ha instalado en una sala adecuada para la disposición del sistema de refrigeración externa del motor, la alimentación de combustible, la evacuación de los gases de escape, la ventilación del banco y el control del motor y del freno. Se ilustran las características de par y potencia sistematizadas durante la operación del banco de ensayos construido.Eje: Motores de combustión interna.Facultad de Ingenierí