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[ES] El uso de la urea como fuente de nitrógeno en sistemas de cultivo hidropónico es muy limitado, debido a que se considera que la absorción de nitrógeno se realiza casi exclusivamente en forma nítrica. Resultados previos sugieren que el producto Nitroplus de la empresa Stoller, que combina una fuente de nitrógeno en forma de urea con aporte de calcio (urea-calcio), supone una forma más eficiente para su absorción y asimilación por las plantas, y permite un mayor crecimiento de las mismas, en comparación con la fertilización por separado de urea y calcio. El presente trabajo tiene como objetivo determinar el efecto de diferentes concentraciones (10 y 7,5 mmol/L) y formas de nitrógeno (NO3-, urea y urea-calcio) en un cultivo de tomate en hidroponía bajo condiciones de invernadero. Para ello, se utilizó un diseño factorial de bloques al azar con dos repeticiones por solución, en el que las plantas se desarrollaron durante 30 días. De forma semanal se recogieron parámetros tales como la altura y peso de la planta, diámetro del tallo, biomasa, contenido en clorofilas, fluorescencia de las clorofilas del fotosistema II y relación C/N para evaluar los efectos de la limitación y disponibilidad del nitrógeno sobre los diferentes tratamientos. Como resultado de la reiterada afección de Fusarium de las plantas en los experimentos realizados, sobre todo en las fases avanzadas del desarrollo, no se sacaron conclusiones claras de los resultados obtenidos con respecto a la influencia de las distintas formas nitrogenadas y/o concentraciones de las mismas estudiadas, aun habiendo detectado relaciones variables entre ellas en los parámetros evaluados. A pesar de ello, el trabajo realizado en los distintos experimentos ha permitido obtener una información valiosa en cuanto a la metodología a aplicar en este tipo de estudio. Estas observaciones van a ser de gran utilidad en la reformulación de un nuevo experimento que permita acometer los objetivos inicialmente planteados., [EN] The use of urea as a nitrogen source in hydroponic growing systems is very limited, because nitrogen uptake is considered to be almost exclusively in nitric form. Previous results suggest that the product Nitroplus from Stoller, which combines a nitrogen source in the form of urea with calcium (urea-calcium), is a more efficient way for its absorption and assimilation by plants, and allows for greater plant growth, compared to the separate fertilization of urea and calcium. The objective of the present work was to determine the effect of different concentrations (10 and 7.5 mmol/L) and forms of nitrogen (NO3-, urea and urea-calcium) on a tomato crop in hydroponics under greenhouse conditions. For this purpose, a randomized block factorial design with two replicates per solution was used, in which plants were grown for 30 days. Parameters such as plant height and weight, stem diameter, biomass, chlorophyll content, photosystem II chlorophyll fluorescence and C/N ratio were collected weekly to evaluate the effects of nitrogen limitation and availability on the different treatments. As a result of the repeated affection of plants by Fusarium in the experiments carried out, especially in the advanced stages of development, no clear conclusions were drawn from the results obtained with respect to the influence of the different nitrogen forms and/or concentrations of the same studied, even though variable relationships between them were detected in the parameters evaluated. In spite of this, the work carried out in the different experiments has made it possible to obtain valuable information regarding the methodology to be applied in this type of study. These observations will be very useful in the reformulation of a new experiment that will allow us to achieve the objectives initially proposed.

[ES] El tomate es uno de los cultivos hortícolas más importantes del mundo. Su producción se ha basado en una sobrefertilización, especialmente nitrogenada, para maximizar las cosechas. Esto ha llevado a una contaminación de los suelos y los acuíferos, y ha contribuido al cambio climático. Los objetivos que se plantean para el desarrollo de una agricultura sostenible requieren una disminución del aporte de nitrógeno a los cultivos, evitando a su vez una reducción significativa de la producción. Además de mejoras en el manejo de los cultivos, en este contexto es de gran importancia la obtención de cultivares con mayor eficiencia en el uso del nitrógeno (NUE), especialmente en condiciones de aporte reducido de nitrógeno. El desarrollo de estos cultivares se ha de basar en un mejor conocimiento de los procesos fisiológicos implicados. La NUE está fundamentalmente definida por procesos de captación y asimilación de nitrógeno (N), así como de distribución y movilización de los compuestos nitrogenados al órgano cosechado, en este caso el fruto. Cabe destacar la estrecha relación del metabolismo del carbono (C), como fuente de esqueletos carbonados para su asimilación, con el de N. En este trabajo se pretende caracterizar la asimilación y partición de C y N en cultivares de tomate que en estudios previos han mostrado una NUE diferencial. Se determinará la captación de ambos elementos midiendo la tasa fotosintética, así como el contenido en C y N elementales en los diferentes órganos durante el desarrollo de la planta. Además, se medirá el contenido en carbohidratos metabolizables (azúcares y almidón), aminoácidos y proteínas totales. Dado que la NUE de las plantas depende del aporte de N, los estudios se realizarán en plantas fertilizadas tanto con niveles de nitrógeno suficientes como subóptimas. Este trabajo permitirá relacionar la capacidad de captación, asimilación y distribución de C/N con su NUE en distintas condiciones de disponibilidad de N., [EN] Tomato is one of the most important horticultural crops in the world. Intensive production systems have been based on an elevated use of fertilizers, especially nitrogenous, to maximize harvests. This has led to pollution of soils and aquifers and has contributed to climate change. The objectives set for the development of sustainable agriculture require a reduction in the nitrogen input to crops, while avoiding a significant reduction in production. In addition to improvements in crop management, in this context it is of great importance to obtain crops with greater nitrogen use efficiency (NUE), especially under conditions of reduced nitrogen supply. The development of these cultivars must be based on a better understanding of the physiological processes involved. The NUE is fundamentally defined by nitrogen (N) uptake and assimilation processes, as well as the distribution and mobilization of nitrogenous compounds to the harvested organ, in this case the fruit. It is worth highlighting the close relationship between the metabolism of carbon (C), as a source of carbon skeletons for their assimilation, with that of N. This work has characterized the assimilation and partition of C and N in tomato crops that in previous studies have shown a differential NUE. The uptake of both elements has been determined by measuring the photosynthetic rate, as well as the content of elemental C and N in the different organs during the development of the plant. In addition, the content of metabolizable carbohydrates (soluble sugars and starch) and free amino acids has been measured. Given that the NUE of the plants depends on the input of N, the studies will be carried out in fertilized plants with both sufficient and suboptimal levels. In this study, the capacity for uptake, assimilation and distribution of C / N has been related to its NUE in different genotypes under different conditions of availability of N. It has been determined that genotype CV70 is of particular intere

[ES] En el contexto actual de aumento de la población mundial y de cambio climático, se hace necesario del desarrollo de nuevos cultivares que permitan incrementar las cosechas bajo condiciones de producción sostenible. Esto es de especial relevancia en el caso del nitrógeno, ya que el sobreabonado realizado para maximizar las cosechas está provocando importantes problemas de contaminación de suelos y atmósfera. El tomate es el principal cultivo hortícola en España, con una producción cercana a los 5 millones de toneladas anuales. Desde su introducción, la mejora de esta especie se ha dirigido a la obtención de variedades tolerantes a enfermedades, con alto índice de cosecha, y más recientemente, con mejor calidad organoléptica. S. pimpinellifolium es una especie antecesora del tomate cultivado que se ha empleado en diversos trabajos de mejora para la introducción en tomate, mediante ILs, de caracteres relacionados con la resistencia a enfermedades y calidad del fruto. Estudios recientes en una colección de ILs de S. pimpinellifolium y tomate han mostrado algunos genotipos con mayor vigor de crecimiento. Además, resultados preliminares del grupo de investigación sugieren que esta especie muestra una menor reducción de crecimiento en condiciones de limitación en el suministro de nitrógeno. En este contexto, el objetivo principal del presente trabajo es la identificación de caracteres de S. pimpinellifolium relacionados con la producción en condiciones de limitación en el aporte de nitrógeno. Para ello, se estudiará el crecimiento, producción y calidad de fruto en una colección de ILs de esta especie silvestre en tomate comercial. Se seleccionarán para su estudio genético y fisiológico posterior aquellas líneas que muestren una mayor eficiencia en la acumulación de biomasa y partición de asimilados al fruto, manteniendo su calidad bajo aporte reducido de nitrógeno., [EN] In the current context of increasing world population and climate change, it is necessary to develop new cultivars that allow increasing yields under sustainable production conditions. This is specially relevant in the case of nitrogen due to over-fertilization carried out to maximize harvests, which is causing important problems of contamination of soils and atmosphere. Tomato is the main horticultural crop in Spain, with a production close to 5 million tons per year. Since its introduction, the improvements of this species has been aimed to obtain varieties that are tolerant to diseases, with a high harvest index and more recently with better organoleptic quality. S.pimpinellifolium is an ancestor species of the cultivated tomato that has been used in various breeding Works for the introduction into tomato by ILs of characters related to resistance to diseases and fruit quality. Recent studies in a collection of S.pimpinellifolium and tomato ILs have shown some genotypes with greater growth vigor. In addition, preliminary results from the research group suggest that this species shows a lower growth reduction under conditions of limited nitrogen supply. In this context, the main goal of this project is the identification os S.pimpinellifolium characters related to production under conditions of limited nitrogen suppley. Therefore, the growth production and quality of fruit will be studied in a collection of ILs of this wild species in commercial tomato. Those lines that show greater efficiency in the accumulation of biomass and partition of assimilates to the fruit will be selected for theis subsequent genetic and physiological study, keeping their quality under reduced nitrogen uptake.

[ES] Debido a la creciente preocupación por la gestión y eliminación de residuos procedentes del uso de hidrocarburos como combustibles, cada vez más estudios se centran en la búsqueda de procedimientos eficaces con el fin de paliar este problema. En este trabajo, se propone una solución desde el punto de vista de la biorremediación, con el fin de reducir o eliminar los residuos resultantes del uso de hidrocarburos en la automoción. Partiendo de la biomasa presente en la superficie de depósitos de coche, se ha analizado y descrito por primera vez el microbioma que coloniza estos ambientes, mediante técnicas de análisis de secuenciación masiva. Así como también, las muestras se han sometido a un cultivo enriquecido con diésel o gasolina durante cuatro semanas, con el fin de analizar los cambios que ocurren en la composición microbiana ante una presión de selección. El microbioma que habita en los depósitos ha resultado ser muy diverso, donde el filo Proteobacteria ha resultado ser el dominante en todas las muestras. Tras el cultivo con presión de selección, el género Pseudomonas obtuvo un notable aumento en abundancia relativa, en las muestras enriquecidas con diésel. Finalmente, se estableció una colección de cepas bacterianas cultivables en placa procedentes de los caldos de cultivo enriquecidos, identificadas por el gen codificante de rRNA 16S. El género Pseudomonas fue al que más cepas aisladas pertenecieron. Así como también, destacaron los géneros Stenotrophomonas, Staphylococcus y Bacillus, entre otros. Queda así demostrado que la biorremediación de estos ambientes mediante la utilización de especies capaces de metabolizar estos hidrocarburos, es una solución con gran potencial para eliminar estos compuestos tan recalcitrantes., [EN] Due to the growing concern about the management and disposal of waste from the use of hydrocarbons as fuels, more and more studies are being focused on the research for effective procedures to put an end to this problem. In this work, we propose a solution from the point of view of bioremediation, in order to reduce or eliminate the resulting waste from the use of hydrocarbons in the automotive industry. Starting from the biomass present in the surface of car deposits, the microbiome that colonizes these environments has been analyzed and described for the first time, by Next Generation Sequencing (NGS) techniques. As well as, the samples have been subjected to an enriched culture with diesel or gasoline for four weeks, in order to analyze the changes that occur in the microbial composition before a selection pressure. The microbiome that inhabits the deposits has turned out to be very diverse, where the Proteobacteria phylum has turned out to be the dominant one in all the samples. After cultivation with selection pressure, the genus Pseudomonas obtained a remarkable increase in relative abundance in the samples enriched with diesel. Finally, a collection of platable bacterial strains from the enriched culture broths, identified by the gene coding for 16S rRNA, was established. The genus Pseudomonas was the one that most isolated strains belonged to. Also, genus as Stenotrophomonas, Staphylococcus and Bacillus were found, among others. It is thus demonstrated that the bioremediation of these environments through the use of species capable of metabolizing these hydrocarbons, is a solution with great potential to eliminate these recalcitrant compounds.

[ES] Actualmente, uno de los temas que causa más controversia en el ámbito de la biotecnología es el de los organismos modificados genéticamente en agricultura. Una de las alternativas posibles para intentar minimizar los inconvenientes en su aceptación social y normativa es el uso de patrones modificados biotecnológicamente para injertos o trans-grafting. Esta técnica implica el uso de patrones mejorados que le confieren al cultivar comercial unos caracteres de mayor tolerancia a estreses, mejor calidad o mayor producción, manteniendo su condición de no modificado biotecnológicamente. Por lo tanto, el objetivo principal del proyecto que se presenta es demostrar la necesidad de un marco regulatorio sólido a nivel mundial respecto al trans-grafting, ya que, se trata de una nueva tecnología surgida a partir de la antigua técnica del injerto, que presenta grandes ventajas gracias a los conocimientos biotecnológicos disponibles en la era moderna. Para ello, en este trabajo se expone un análisis, a través de los cinco continentes, de la legislación vigente en cada uno de ellos que regula esta nueva técnica de fitomejoramiento. Con esto, se realiza posteriormente, una comparación entre el estado actual de la legislación nombrada y la aplicada a los organismos genéticamente modificados, que se presenta también a nivel mundial de forma más genérica. Además, para adentrarse en los aspectos científicos del trans-grafting, se muestran las aplicaciones de esta técnica y las ventajas que supone respecto a métodos convencionales de cultivo. Para ilustrar esta parte se exponen los resultados preliminares realizados en un cultivo de tomate injertado empleando patrones transgénicos de la misma especie., [EN] Currently, one of the most controversial issues in the field of biotechnology is that of genetically modified organisms in agriculture. One of the possible alternatives to try to minimize the inconveniences in its social and normative acceptance is the use of biotechnologically modified rootstocks for grafts or trans-grafting. This technique involves the use of improved rootstocks that give commercial cultivars characters with greater tolerance to stress, better quality or higher production, maintaining their status as biotechnologically unmodified. Therefore, the main objective of the project presented is to demonstrate the need for a solid regulatory framework worldwide regarding trans-grafting, since it is a new technology, arising from the old technique of grafting, It has great advantages thanks to the biotechnological knowledge available in the modern era. To do this, this paper presents an analysis, through the five continents, of the current legislation in each of them to regulate this new technique of plant breeding. With this, a comparison is made between the current state of the appointed legislation and that applied to genetically modified organisms, which is also more globally exposed. In addition, to delve into the scientific aspects of trans-grafting, the applications of this technique and its advantages over conventional methods of cultivation are shown. To illustrate this part, preliminary results in a grafted tomato crop using transgenic rootstocks of the same species are shown.

[EN] The performance of a salt-tolerant pepper (Capsicum annuum L.) accession (A25) utilized as a rootstock was assessed in two experiments. In a first field experiment under natural salinity conditions, we observed a larger amount of marketable fruit (+75%) and lower Blossom-end Root incidence (-31%) in commercial pepper cultivar Adige (A) grafted onto A25 (A/A25) when compared with ungrafted plants. In order to understand this behavior a second greenhouse experiment was conducted to determine growth, mineral partitioning, gas exchange and chlorophyll a fluorescence parameters, antioxidant systems and proline content in A and A/A25 plants under salinity conditions (80 mM NaCl for 14 days). Salt stress induced significantly stunted growth of A plants (-40.6% of leaf dry weight) compared to the control conditions, while no alterations were observed in A/A25 at the end of the experiment. Accumulation of Na+ and Cl- in leaves and roots was similar in either grafted or ungrafted plants. Despite the activation of protective mechanisms (increment of superoxide dismutase, catalase, ascorbate peroxidase activity and non-photochemical quenching), A plants showed severely reduced photosynthetic CO2 assimilation (-45.6% of A(N390)) and substantial buildup of malondialdehyde (MDA) by-product, suggesting the inability to counteract salt-triggered damage. In contrast, A/A25 plants, which had a constitutive enhanced root apparatus, were able to maintain the shoot and root growth under salinity conditions by supporting the maintained photosynthetic performance. No increases in catalase and ascorbate peroxidase activities were observed in response to salinity, and MDA levels increased only slightly; indicating that alleviation of oxidative stress did not occur in A/A25 plants. In these plants the increased proline levels could protect enzymatic stability from salt-triggered damage, preserving the photosynthetic performance. The results could indicate that salt stress was vanished by

[ES] Durante el siglo XX, la mejora de la producción de los cultivo se basó en la optimización de las prácticas de cultivo, incluyendo fertilizantes, pesticidas, riego, y la selección de cultivares. Actualmente, la creciente demanda de producción, junto con la limitación en la disponibilidad de tierras y agua de riego de calidad, hace necesario el desarrollo de nuevas variedades con una capacidad mayor de producción de biomasa y tolerancia a estreses ambientales. Además, en el contexto de una agricultura sostenible y menos agresiva con el medio ambiente, es necesario reducir el uso de fertilizantes. En este sentido, estas variedades deben presentar una mejor eficiencia en el uso del nitrógeno, uno de los principales macronutrientes requeridos por la planta y responsable de la contaminación de acuíferos. La generación de plantas transgénicas con mayor capacidad de producción de biomasa por sobreexpresión de genes individuales relacionados con la fijación fotosintética de carbono o la asimilación de nitrógeno ha dado resultados limitados, ya que se trata de caracteres multigénicos. En este sentido, la utilización de factores de transcripción, que regulan la expresión de múltiples genes simultáneamente, parece una estrategia prometedora. La sobreexpresión de genes de una familia de factores de transcripción específicos de plantas, los genes Dof (DNA-binding with one finger), han incrementado la producción en plantas de maíz o mijo. En el presente trabajo se ha caracterizado el papel del gen Dof21 de Arabidopsis thaliana en el metabolismo de carbono y nitrógeno en tomate. Para ello se han cultivado plantas en condiciones de invernadero, con tres niveles de aporte de nitrógeno (100, 60 y 30% del aporte completo), y se ha determinado la producción de biomasa, la capacidad fotosintética, el contenido en carbohidratos metabolizables, el contenido total en C y N, así como la actividad enzimática de la enzima nitrato reductasa y la expresión del gen PEP carboxilasa y la quina, [EN] During the 20th century, the improvement in the crop production was based on the optimization of the growing techniques, including fertilisers, pesticides, irrigation and cultivars selection. Currently, the increasing demand in production along with the limitation of land and irrigation water availability makes it necessary the development of new varieties with a greater capacity of biomass production and environmental stress tolerance. Furthermore, in the context of a sustainable and less aggressive agriculture, it is essential to reduce the fertilisers used. Accordingly, these new varieties should be more efficiency regarding the use of nitrogen, which is one of the principal macronutrients required by the plant and responsible of the aquifer contamination. The generation of transgenic plants with an increased biomass production capacity through the overexpression of genes related to the photosynthetic fixation of carbon or the nitrogen assimilation has provided limited results, due to the fact that these are multigenic characters. In this regard, the utilization of transcription factors, which regulate the expression of multiple genes simultaneously, could be a promising strategy. The overexpression of a specific plant family of transcription factors, the Dof (DNA-binding with one finger), has increased the production in maize, millet plants. In the present study, it has been characterized the role of the Arabidopsis thaliana gen Dof21 in the carbon and nitrogen metabolism in tomato. For this purpose, tomato plants have been cultivated in greenhouse conditions with three levels of nitrogen input (100, 60 and 30% of the full input). Finally, it has been determinated the biomass production, the photosynthetic capacity, the metabolizable carbohydrates content, the carbon and nitrogen content, the activity of the nitrate reductase enzyme and the expression of PEP carboxylase and the kinase SnRK1. The Dof21 overexpression increases the photosynthetic rate, the av

[EN] The present state of knowledge concerning developmental processes and the secondary metabolism of saffron, Crocus sativus L. (Iridaceae), along with the genes involved in these processes so far known, is reviewed. Flowers and corms constitute the most valuable parts of saffron. Corm and flower development are two key aspects to be studied in saffron to increase the yield and quality of the spice, to raise its reproductive rate, and to implement new production systems. Important knowledge about the physiology of flowering and vegetative growth has been acquired in recent years, but there is still only limited information on molecular mechanisms controlling these processes. Although some genes involved in flower formation and meristem transition in other species have been isolated in saffron, the role of these genes in this species awaits further progress. Also, genes related with the synthesis pathway of abscisic acid and strigolactones, growth regulators related with bud endodormancy and apical dominance (paradormancy), have been isolated. However, the in-depth understanding of these processes as well as of corm development is far from being achieved. By contrast, saffron phytochemicals have been widely studied. The different flower tissues and the corm have been proved to be an important source of phytochemicals with pharmacological properties. The biotechnological prospects for saffron are here reviewed on the basis of the discovery of the enzymes involved in key aspects of saffron secondary metabolism, and we also analyze the possibility of transferring current knowledge about flowering and vegetative propagation in model species to the Crocus genus.

[EN] A fungal gene encoding a transcription factor is expressed from its own promoter in Arabidopsis phloem and improves drought tolerance by reducing transpiration and increasing osmotic potential. Horizontal gene transfer from unrelated organisms has occurred in the course of plant evolution, suggesting that some foreign genes may be useful to plants. The CtHSR1 gene, previously isolated from the halophytic yeast Candida tropicalis, encodes a heat-shock transcription factor-related protein. CtHSR1, with expression driven by its own promoter or by the Arabidopsis UBQ10 promoter, was introduced into the model plant Arabidopsis thaliana by Agrobacterium tumefaciens-mediated transformation and the resulting transgenic plants were more tolerant to drought than controls. Fusions of the CtHSR1 promoter with beta-glucuronidase reporter gene indicated that this fungal promoter drives expression to phloem tissues. A chimera of CtHSR1 and green fluorescence protein is localized at the cell nucleus. The physiological mechanism of drought tolerance in transgenic plants is based on reduced transpiration (which correlates with decreased opening of stomata and increased levels of jasmonic acid) and increased osmotic potential (which correlates with increased proline accumulation). Transcriptomic analysis indicates that the CtHSR1 transgenic plants overexpressed a hundred of genes, including many relevant to stress defense such as LOX4 (involved in jasmonic acid synthesis) and P5CS1 (involved in proline biosynthesis). The promoters of the induced genes were enriched in upstream activating sequences for water stress induction. These results demonstrate that genes from unrelated organisms can have functional expression in plants from its own promoter and expand the possibilities of useful transgenes for plant biotechnology.

[EN] In this work we have done a research study about the annual variation in production of photoassimilates and mobilizing them into sinks in the alternate bearing 'Salustiana' sweet orange (Citrus sinensis (L.) Osb.), and its relation to the reproductive behavior. The alternate bearing of this variety is due to the low intensity of flowering obtained after a year of a high yield, and not to the decreased of fruit set. The photosynthetic rate does not show major seasonal variations, being the changing environmental conditions among the different days in a month the main source of variation. No significant differences were observed in AN among trees on and off, although in the same on tree, the leaves of shoots that bear fruits have a slightly lower photosynthetic rate (10%) than shoots without fruit. The photosynthetic capacity remains stable throughout the first year of life of the leave, and decreases by 20% for the second-one. Soluble sugars in leaves of 'Salustiana' maintain a fairly constant level throughout the year, whereas the excess of fixed carbon is used for the production of starch, which is the carbohydrate with greater variations. The variation in carbohydrates meets the changing demand of the various sinks. In off trees, the starch content is higher than in on trees between March and August, and the maximum difference occurs at the end of fruit drop, in June. From September until March, no differences in carbohydrate content among trees on and off are observed. At the time of full blossom (April), the concentration of carbohydrates in on tree leaves decreases dramatically. Most of the stocks during the off year seem destined to the formation of surplus flowers, with a cost of dry matter of about 6 kg. From these observations it can be concluded that the reserves of carbohydrates in leaves do not have a regulatory role in the floral induction which takes place between November and February, also in flower development, which starts between February and, [ES] En este trabajo se ha estudiado la variación anual de la producción de fotoasimilados y la movilización de los mismos hacia sumideros en la variedad alternante de naranjo dulce 'Salustiana' (Citrus sinensis (L.) Osb.), y su relación con el comportamiento reproductivo. Las observaciones indican que el comportamiento alternante de esta variedad, es debido a la baja intensidad de floración que se obtiene tras un año de elevada cosecha, y no a una disminución del cuajado. La tasa fotosintética no manifiesta grandes variaciones estacionales, siendo las condiciones ambientales cambiantes entre los diferentes días de un mes la principal fuente de variación. No se observan diferencias significativas en AN entre árboles on y off, pero en un mismo árbol on, en las hojas de brotes con fruto es menor (10%). La capacidad fotosintética permanece estable a lo largo del primer año de vida de la hoja, y disminuye un 20% durante el segundo. Los azúcares solubles en hojas mantienen un nivel prácticamente constante durante todo el año, mientras que el exceso de carbono fijado se destina a la producción de almidón, que es el carbohidrato que presenta mayores variaciones. En los árboles off, el contenido de almidón en hojas es superior que en los árboles on entre marzo y agosto, presentando la diferencia máxima al final de la caída de fruto, en junio. Desde septiembre hasta marzo, no se observan diferencias en el contenido en carbohidratos entre árboles on y off. En el momento de plena floración (abril), la concentración de carbohidratos en árboles on disminuye considerablemente, con lo que la mayor parte de las reservas almacenadas durante el año off parecen destinadas a la formación de flores excedentes, cuyo coste es de unos 6 kg de materia seca. Por tanto, las reservas de carbohidratos en hojas no tienen un papel regulador ni durante la inducción floral por bajas temperaturas, que tiene lugar entre noviembre y febrero, ni en el desarrollo de las flores, que se inicia entre febre, [CA] En aquest treball s'ha estudiat la variació anual de la producció de fotoassimilats i la mobilització dels mateixos cap a embornals en la varietat alternant de taronger dolç 'Salustiana' (Citrus sinensis (L.) Osb.), i la seva relació amb el comportament reproductiu. El comportament alternant d'aquesta varietat és a causa de la baixa intensitat de floració que s'obté després d'un any d'elevada collita, i no a una disminució del quallat. La taxa fotosintètica no mostra grans variacions estacionals, sent les condicions ambientals canviants entre els diferents dies d'un mes la principal font de variació. No s'observen diferències significatives en AN entre arbres on i off, però en un mateix arbre on, les fulles de brots amb fruit presenten una taxa fotosintètica lleugerament menor (10%) que les de brots sense fruit. La capacitat fotosintètica roman estable al llarg del primer any de vida de la fulla, i disminueix un 20% durant el segon. Els sucres solubles en fulles de 'Salustiana' mantenen un nivell pràcticament constant durant tot l'any, mentre que l'excés de carboni fixat es destina a la producció de midó, que és el carbohidrat que presenta majors variacions. La variació en carbohidrats s'ajusta als canvis en la demanda dels diferents embornals. En els arbres off, el contingut de midó és superior que en arbres on entre març i agost, sent la diferència màxima al final de la caiguda de fruit, en juny. Des de setembre fins a març, no s'observen diferències en el contingut en carbohidrats entre arbres on i off. En el moment de plena floració (abril), la concentració de carbohidrats en les fulles dels arbres on disminueix considerablement, amb el que la major part de les reserves emmagatzemades durant l'any off semblen destinades a la formació de flors excedents, el cost de les quals és d'uns 6 kg de matèria seca. Per tant, les reserves de carbohidrats en fulles no tenen un paper regulador ni durant la inducció floral per baixes temperatures, que té lloc entre novemb

Background: The increased selection pressure of the herbicide glyphosate has played a role in the evolution of glyphosate-resistance in weedy species, an issue that is becoming a threat to global agriculture. The molecular components involved in the cellular toxicity response to this herbicide at the expression level are still unidentified. Results: In this study, we identify the protein kinase GCN2 as a cellular component that fosters the action of glyphosate in the model plant Arabidopsis thaliana. Comparative studies using wild-type and gcn2 knock-out mutant seedlings show that the molecular programme that the plant deploys after the treatment with the herbicide, is compromised in gcn2. Moreover, gcn2 adult plants show a lower inhibition of photosynthesis, and both seedlings and adult gcn2 plants accumulate less shikimic acid than wild-type after treatment with glyphosate. Conclusions: These results points to an unknown GCN2-dependent factor involved in the cascade of events triggered by glyphosate in plants. Data suggest either that the herbicide does not equally reach the target-enzyme in a gcn2 background, or that a decreased flux in the shikimate pathway in a gcn2 plants minimize the impact of enzyme inhibition.

Tesis por compendio, [EN] Pepper is a vegetable of extraordinary economic and social importance in our country. Unfortunately, the persistent exploitation of the land, the monoculture and the intensification of production processes, lead to the development of soil diseases. This coupled with the abiotic stress, mainly the salinity of waters and soil, suboptimal temperatures and water stress, can induce the appearance of physiological disorders in peppers as the Blossom-end rot (BER) and cracking or cracked, induce plant senescence and decrease not only production, but also the quality of the product. Salinity and water shortages are two among the biggest environmental problems that crops have to face in the Mediterranean area. A way to overcome the stresses under the prism of an ecological or integrated crop management, is the use of grafted plants as adaptation strategy. Although there has been remarkable progress in this technique (mainly in tomato, melon, watermelon), in the cultivation of pepper use remains rare. In this Doctoral thesis several pepper genotypes have been selected through different physiological parameters which indicate tolerance to salt and water stress. Commercial cultivars were grafted onto the selected genotypes and were grown under water stress, salinity and control conditions studying several physiological, agronomic responses and the interaction rootstock/scion. The results obtained concluded that genotypes selected and used as rootstocks improved commercial varieties to salt and water stress tolerance, both in terms of performance (commercial production) compared to other commercial characters and variety without grafting. Different physiological mechanisms explain the tolerance to stress, such as the ability to maintain the water potential through an osmotic adjustment, stimulation of the antioxidant system, exclusion or retention of toxic ions (Na+ and Cl-) in saline in the roots and the maintenance of photosynthesis which allows to maintain the metabolic, [ES] El pimiento es una hortaliza de extraordinaria importancia económica y social en nuestro país. Lamentablemente, la persistente explotación del suelo, el monocultivo y la intensificación de los procesos de producción, conducen al desarrollo de enfermedades del suelo. Esto unido a los estreses abióticos, principalmente la salinidad de las aguas y del suelo, temperaturas subóptimas y estrés hídrico, puede inducir la aparición de fisiopatias en el pimiento como el Blossom-end rot (BER) y cracking o rajado, inducir senescencia vegetal y disminuir no solo la producción, sino también la calidad del producto. La salinidad y la escasez de agua son unos los mayores problemas medio ambientales a los que tienen que hacer frente los cultivos en el área Mediterránea. Un modo de sortear los estreses bajo el prisma de un manejo integrado o ecológico del cultivo, es la utilización de plantas injertadas como estrategia de adaptación. Aunque se ha producido un notable avance en esta técnica (principalmente en tomate, melón, sandía), en el cultivo del pimiento su utilización es poco frecuente aun. En esta Tesis Doctoral se han seleccionado mediante parámetros fisiológicos diferentes genotipos de pimiento tolerantes al estrés salino e hídrico. Los genotipos seleccionados fueron validados como patrones tolerantes a condiciones de estrés hídrico y salino injertados sobre una variedad comercial mediante el estudio de las respuestas fisiológicas, agronómicas y de la interacción patrón/variedad en ambas condiciones de estrés. De los resultados obtenidos se concluye que los genotipos seleccionados y utilizados como patrones mejoraron la tolerancia de las variedades comerciales a la salinidad, en términos de rendimiento (producción comercial) de frutos comparando con otros patrones comerciales y la variedad sin injertar. Diferentes mecanismos fisiológicos explican la tolerancia al estrés, como la capacidad de mantener el potencial hídrico mediante un ajuste osmótico, estimulación del sist, [CA] El pimentó és una hortalissa d'extraordinària importància econòmica i social al nostre país. Lamentablement, la persistent explotació del sòl, el monocultiu i la intensificació dels processos de producció, conduïxen al desenrotllament de malalties del sòl. Açò unit als estressos abiòtics, principalment la salinitat de les aigües i del sòl, temperatures subòptimes i estrés hídric, pot induir l'aparició de fisiopaties en el pimentó com el Blossom-end rot (BER) i cracking, induir senescència vegetal i disminuir no sols la producció, sinó també la qualitat del producte. La salinitat i l'escassetat d'aigua són uns els majors problemes mitjà ambientals als que han de fer front els cultius en l'àrea Mediterrània. Una manera de sortejar els estressos davall el prisma d'un maneig integrat o ecològic del cultiu, és la utilització de plantes empeltades com a estratègia d'adaptació. Encara que s'ha produït un notable avanç en esta técnica (principalment en tomaca, meló, meló d'alger), en el cultiu del pimentó la seua utilització és poc freqüent. En esta Tesi Doctoral s'han seleccionat per mitjà de paràmetres fisiològics diferents genotips de pimentó tolerants a l'estrés salí i hídric. Els genotips seleccionats van ser validats com a patrons tolerants a condicions d'estrés hídric i salí empeltats sobre una varietat comercial per mitjà de l'estudi de les respostes fisiològiques, agronòmiques i de la interacció patrón/variedad en ambdós condicions d'estrés. Dels resultats obtinguts es conclou que els genotips seleccionats i utilitzats com a patrons van millorar la tolerància de les varietats comercials a la salinitat, tant en termes de rendiment (producció comercial) de fruits comparant amb altres patrons comercials i la varietat sense empeltar. Diferents mecanismes fisiològics expliquen la tolerància a l'estrés, com la capacitat de mantindre el potencial hídric per mitjà d'un ajust osmòtic, estimulació del sistema antioxidant, exclusió o retenció dels ions tòxics salins (Na+

[EN] Grafting has been proposed as an interesting strategy that improves the responses of crops under salinity. In pepper, we reported increased fruit yield of the commercial 'Adige' cultivar under salinity when grafted onto accessions Capsicum chinense Jacq. 'ECU-973' (12) and Capsicum baccatum L. var. pendulum 'BOL-58' (14), whereas no,effect was observed when grafted onto accession Capsicum annuum L var. 'Serrano' (5). We also analysed the physiological and biochemical mechanisms related to the tolerance conferred by these rootstocks. Responses to salinity (40 mM NaCl) were studied in the different plant combinations for 30 days by determining water relations, mineral content, proline accumulation, photosynthetic parameters, nitrate reductase activity and antioxidant capacity. Higher salt tolerance was achieved when the 'Adige' cultivar was grafted onto the 12 genotype, which allowed not only lower Na+ and Cl- accumulation in the scion, but also ion selectivity maintenance, particularly Na+/K+ discrimination. These traits led to a minor negative impact on photosynthesis, nitrate reductase activity and lipid peroxidation in grafted scion leaves. This work suggests that using tolerant pepper rootstocks that maintain the scion's ion homeostasis is a promising strategy to provide salinity tolerance and can consequently improve crop yield.

[EN] Soft skills have become part of the curriculum of content courses at the Universities. Evaluating those skills requires working in small groups run by various lecturers and those groups might become biased by the lecturer’s perception of the activities. In this study our hypothesis was that lecturers’ prejudices influence student perception of the course activities and that misguidance from lecturers can be amended with motivating coordination of the lecturers. Two team-based activities were assessed for lab evaluation. Besides, self- and peer-evaluation were carried out to mark students’ soft skills related to teamwork and leadership in relation to these activities. Perception of the activities and their assessment by students and lecturers were analysed. We concluded that lecturer prejudices bias students’ perception of the activities they carry out and that lecturers need to work as a close team for the course to become a successful project., [ES] Las competencias transversales se han convertido en parte del programa de las asignaturas en las Universidades. La evaluación de competencias requiere que los grupos de estudiantes sean reducidos, con lo que intervienen varios profesores en una misma actividad programada. Estas actividades pueden resultar influidas por la percepción que de ellas tenga cada profesor. Partimos de la hipótesis de que los prejuicios de los profesores influyen en la percepción que tiene el alumno de las actividades y que las desviaciones debidas a esos prejuicios pueden ser corregidas mediante una coordinación motivadora entre profesores. Se valoró la adecuación como evaluación de prácticas de laboratorio de dos actividades que los alumnos realizaron en equipos de tres. Además, se llevó a cabo un sistema de autoevaluación y evaluación entre pares para evaluar a los alumnos en la competencia “trabajo en equipo y liderazgo” en relación con esas dos actividades. Analizamos la valoración de alumnos y profesores respecto a las actividades propuestas y al sistema de evaluación en una encuesta abierta. Se concluye que los profesores influimos en la apreciación que los alumnos tienen de las actividades y que los profesores necesitaríamos trabajar estrechamente en equipo para que la asignatura sea un proyecto con éxito.

[EN] Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies. We also asked whether any differences among laboratories were related to the extraction and quantification methods used to determine starch and sugar concentrations. These questions were addressed by sending sub-samples collected from five woody plant tissues, which varied in NSC content and chemical composition, to 29 laboratories. Each laboratory analyzed the samples with their laboratory-specific protocols, based on recent publications, to determine concentrations of soluble sugars, starch and their sum, total NSC. Laboratory estimates differed substantially for all samples. For example, estimates for Eucalyptus globulus leaves (EGL) varied from 23 to 116 (mean = 56) mg g(-1) for soluble sugars, 6-533 (mean = 94) mg g-1 for starch and 53-649 (mean = 153) mg g-1 for total NSC. Mixed model analysis of variance showed that much of the variability among laboratories was unrelated to the categories we used for extraction and quantification methods (method category R-2 = 0.05-0.12 for soluble sugars, 0.10-0.33 for starch and 0.01-0.09 for total NSC). For EGL, the difference between the highest and lowest least squares means for categories in the mixed model analysis was 33 mg g-1 for total NSC, compared with the range of laboratory estimates of 596 mg g-1. Laboratories were reasonably consistent in their ranks of estimates among tissues for starch (r = 0.41-0.91), but less so for total NSC (r = 0.45-0.84) and soluble sugars (r = 0.11-0.83). Our results show that NSC estimates for woody plant tissues cannot be compared among laboratories. The relative changes in NSC between treatments measured within a laboratory may be

[EN] Water stress is a major environmental factor that limits crop production and it is important to develop crop varieties with higher yield under water scarcity. Increased pepper tolerance to water stress through grafting onto robust rootstocks could be an optimal alternative in the context of environmentally friendly agriculture. Our work evaluated the behaviour of 18 pepper genotypes during vegetative and reproductive stages under water stress in order to select tolerant genotypes to be used as rootstocks for pepper cultivation. The pepper tolerance screening was based on photosynthetic parameters. The genotypes Atlante, C-40, Serrano, PI-152225, ECU-973, BOL-58 and NuMex Conquistador were revealed as the most tolerant genotypes to water stress because they maintained net photosynthetic rate levels under water stress conditions. The selected genotypes were validated as rootstocks on a pepper cultivar in terms of productivity under severe water stress. Plants grafted onto cvs Atlante, PI-152225 and ECU-973 showed higher marketable yields when compared with ungrafted cultivar.

[EN] DNA binding with One Finger (DOF) transcription factors are involved in multiple aspects of plant growth and development but their precise roles in abiotic stress tolerance are largely unknown. Here we report a group of five tomato DOF genes, homologous to Arabidopsis Cycling DOF Factors (CDFs), that function as transcriptional regulators involved in responses to drought and salt stress and flowering-time control in a gene-specific manner. SlCDF15 are nuclear proteins that display specific binding with different affinities to canonical DNA target sequences and present diverse transcriptional activation capacities in vivo. SlCDF15 genes exhibited distinct diurnal expression patterns and were differentially induced in response to osmotic, salt, heat, and low-temperature stresses. Arabidopsis plants overexpressing SlCDF1 or SlCDF3 showed increased drought and salt tolerance. In addition, the expression of various stress-responsive genes, such as COR15, RD29A, and RD10, were differentially activated in the overexpressing lines. Interestingly, overexpression in Arabidopsis of SlCDF3 but not SlCDF1 promotes late flowering through modulation of the expression of flowering control genes such as CO and FT. Overall, our data connect SlCDFs to undescribed functions related to abiotic stress tolerance and flowering time through the regulation of specific target genes and an increase in particular metabolites.

[EN] Tomato is one of the most important horticultural crops worldwide, and is cultivated in semi-arid regions in which soil and groundwater salinity is an increasing limitation to yield. The assessment of the responses of new cultivars to salt and the comparisons among cultivars and wild species are of great interest in tomato breeding. This assay provides a reproducible and reliable method for screening tomato responses to NaCl salinity under hydroponic conditions in growth chambers. Although NaCl is the most commonly used salt in salinity studies, other salts such as Na2SO4, MgCl2 or MgSO4, usually found in saline soils, can also be assayed (Nebauer et al., 2013). Plants can be maintained for 30-45 days under the described conditions, although significant effects on growth can be observed after 10 days, depending on the salt and concentration used.

[EN] Salinity is an important environmental constraint to crop productivity in arid and semiarid regions of the world. The evaluation of the responses to salinity of different Arabidopsis ecotypes or transgenic lines is important to identify and investigate the role of different key genes. These new characterized genes involved in the response to salinity stress are of great interest to be incorporated in crops breeding programs. Here we provide a reproducible method to evaluate the performance of Arabidopsis lines to salinity stress by analysing primary and lateral root growth and fresh weight of plants grown under in vitro conditions in growth chambers. Even though NaCl is the most frequent used salinity tests, other salts (e.g. KCl, MgCl2) can be also evaluated by this method. Arabidopsis plants can be maintained for 15-20 days in these conditions, although effects on growth and biomass can be observed, depending on the used salt and concentration, within the first 10 days.

[EN] The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who have some experience with the application of Chl a fluorescence but are still in the process of discovering what it all means and how it can be used. Topics discussed are (among other things) the kind of information that can be obtained using different fluorescence techniques, the interpretation of Chl a fluorescence signals, specific applications of these techniques, and practical advice on different subjects, such as on the length of dark adaptation before measurement of the Chl a fluorescence transient. The paper also provides the physiological background for some of the applied procedures. It also serves as a source of reference for experienced scientists

[EN] Recent studies have shown that tolerance to abiotic stress, including water stress, is improved by grafting. In a previous work, we took advantage of the natural variability of Capsicum spp. and selected accessions tolerant and sensitive to water stress as rootstocks. The behavior of commercial cultivar 'Verset' seedlings grafted onto the selected rootstocks at two levels of water stress provoked by adding 3.5 and 7% PEG (polyethylene glycol) was examined over 14 days. The objective was to identify the physiological traits responsible for the tolerance provided by the rootstock in order to determine if the tolerance is based on the maintenance of the water relations under water stress or through the activation of protective mechanisms. To achieve this goal, various physiological parameters were measured, including: water relations; proline accumulation; gas exchange; chlorophyll fluorescence; nitrate reductase activity; and antioxidant capacity. Our results indicate that the effect of water stress on the measured parameters depends on the duration and intensity of the stress level, as well as the rootstock used. Under control conditions (0% PEG) all plant combinations showed similar values for all measured parameters. In general terms, PEG provoked a strong decrease in the gas exchange parameters in the cultivar grafted onto the sensitive accessions, as also observed in the ungrafted plants. This effect was related to lower relative water content in the plants, provoked by an inefficient osmotic adjustment that was dependent on reduced proline accumulation. At the end of the experiment, chronic photoinhibition was observed in these plants. However, the plants grafted onto the tolerant rootstocks, despite the reduction in photosynthetic rate, maintained the protective capacity of the photosynthetic machinery mediated by osmotic adjustment (based on higher proline content). In addition, water stress limited uptake and further NO3- transfer to the leaves. Increase

[EN] The fruit is the main sink organ in Citrus and captures almost all available photoassimilates during its development. Consequently, carbohydrate partitioning and starch content depend on the crop load of Citrus trees. Nevertheless, little is known about the mechanisms controlling the starch metabolism at the tree level in relation to presence of fruit. The aim of this study was to find the relation between the seasonal variation of expression and activity of the genes involved in carbon metabolism and the partition and allocation of carbohydrates in 'Salustiana' sweet orange trees with different crop loads. Metabolisable carbohydrates, and the expression and activity of the enzymes involved in sucrose and starch metabolism, including sucrose transport, were determined during the year in the roots and leaves of 40-year-old trees bearing heavy crop loads ('on' trees) and trees with almost no fruits ('off' trees). Fruit altered photoassimilate partitioning in trees. Sucrose content tended to be constant in roots and leaves, and surplus fixed carbon is channeled to starch production. Differences between 'on' and 'off' trees in starch content can be explained by differences in ADP-glucose pyrophosphorylase (AGPP) expression/activity and alpha-amylase activity which varies depending on crop load. The observed relation of AGPP and UGPP (UDP-glucose pyrophosphorylase) is noteworthy and indicates a direct link between sucrose and starch synthesis. Furthermore, different roles for sucrose transporter SUT1 and SUT2 have been proposed. Variation in soluble sugars content cannot explain the differences in gene expression between the 'on' and 'off' trees. A still unknown signal from fruit should be responsible for this control.

[EN] Salinity is a major environmental constraint on crop productivity and grafting can be a sustainable strategy to enhance plant tolerance under adverse growth conditions. Screening different graft combinations under field conditions can be a slow and expensive processes. In this study, plants of 18 genotypes of Capsicum spp. were evaluated during 5 months to select salt tolerant plants to be used as rootstocks in greenhouse under controlled conditions. Their net photosynthetic rate was used as a rapid and sensitive methodology for screening their tolerance to salt stress conditions. The germination potential of some genotypes was also tested under different salinity conditions to see if it would be useful to accelerate the screening process. According to photosynthesis rate, the commercial rootstock ‘Tresor’ and the genotypes ‘Serrano’ (C. annuum), ‘ECU-973’ (C. chinense) and ‘BOL-58’ (C. baccatum) were the most tolerant during this period. Nevertheless, the evaluation of pepper genotypes for salinity tolerance based on the germination performance and chlorophyll fluorescence parameter Fv/Fm ratio were not good indicators of the sensitivity along plant ontogeny. Finally, the selected genotypes as salt-tolerant were validated under field conditions as rootstocks of two interesting pepper cultivars, concluding that using the rootstocks selected by the net photosynthetic rate improved the salt tolerance of the scion in terms of marketable yield and fruit quality.

Saffron is a triploid sterile crop with a low vegetative propagation rate, which prevents the widespread use of selected genotypes. Despite efficient in vitro propagation via direct organogenesis being very interesting, high contamination levels and low propagation rates preclude the commercial use of this technique. In order to obtain a source of explants for the in vitro multiplication of saffron that allows low contamination levels and efficient propagation, daughter corms were produced by storing non-planted mother corms at low temperatures (1-3 degrees C) for 9 months. This method avoids field cultivation and yields more corms than field production (8 vs. 3 corms per mother corm). Corms produced under cold storage conditions were in vitro sprouted on media with a high level of cytokinins (5 mg l(-1) 6-benzylaminopurine or 1 mg l(-1) thidiazuron) and 0.5 mg l(-1) naphthalene acetic acid, and sprouted buds were cultivated on the same media. After 8 weeks of culture, multiple shoot primordia emerged from the base of the sprouted buds with no callus formation, and up to 400 shoot primordia were produced from one initial mother corm. These shoot primordia can be elongated and 90% produce corms. The high multiplication rate, lack of contamination, and the fact that multiplication occurs through direct organogenesis make the method suitable for the propagation of selected genotypes. Otherwise shoot clusters can be maintained for 6-7 months. However for longer maintenance periods, shoot proliferation capacity by direct organogenesis diminishes, and the emergence of somaclonal variation cannot be ruled out.

[EN] The objective of this work was to study the influence of fruit load on CO2 assimilation in the leaves of citrus trees presenting alternate bearing habits, and the importance of this factor on photosynthetic rate variability throughout the year and under regular cropping conditions. The photosynthetic rate was measured on 60 days throughout the year on field-grown sweet orange plants under natural conditions in the Valencian Community, the most important citrus-producing area of Spain. The experiments were performed on the 'on' (high crop) and 'off' (low crop) bearing 40-year-old Salustiana sweet orange trees growing in the same orchard. Gas exchange and fluorescence parameters were measured during the year in young and old leaves on sun-exposed branches with and without fruit in the 'on' trees, and in fruitless branches of the 'off' trees. In non-manipulated Citrus trees, fruit load has no significant effect in any season on the photosynthetic rate in the leaves from branches without fruit. However, in high crop trees, the leaves of branches bearing fruit present a slightly lower photosynthetic rates (approx. 10%) than those of fruitless branches. Variations in mineral content (N, K and P) might explain not only these differences, but also the lower photosynthesis rate observed in old leaves (13-24 month-old leaves). Environmental conditions were the main factor for the variation of the photosynthetic rate, with variability of the monthly mean photosynthetic rate being much lower than that between days in the same month.

A major constraint limiting saffron cultivation is the difficulty of obtaining high quality corms for propagation. There is limited knowledge about the physiology of vegetative development of saffron. The aim of this work was to analyse the relative contribution of different carbon sources (leaf photosynthetic activity and mother corm reserves) to the growth of vegetative organs and to analyse the influence of internal and external factors on the photosynthetic processes sustaining corm growth. The photosynthetic rate and changes in biomass were measured over the course of the vegetative growing season. The influence of the size of the mother corm, the cultivation method used (greenhouse versus field) and water availability on saffron production was assessed. Most of the remaining mother corm reserves after flowering were depleted during root and leaf development. After these organs reached their maximum size, the growth of replacement corms was initiated, and this development primarily relied on photosynthesis. Saffron mother corm reserves only contributed 10% to the biomass during vegetative development. The photosynthetic rate was consistently very high (26 mu mol m(-2) s(-1)) throughout the year but was reduced in plants from the largest corms. A sink capacity limitation arose during growth of replacement corms since the increase of biomass was limited before total leaf senescence. Saffron grown under greenhouse conditions exhibited traits characteristic of plants grown under low-irradiance, even after the saffron plants were transferred to the field. This fact limits the production of replacement corms in this environment. A decrease in the photosynthetic rate was observed under water stress, but the supply of water to the leaves from the corms and roots was found to maintain a still high photosynthetic rate (12 mu mol m(-2) s(-1)) even at highly negative soil water potentials.

The photosynthetic responses to a flowering-inductive water-stress period and recovery were studied and compared in two Citrus species. Under greenhouse conditions, Fino lemon and Owari satsuma trees were subjected to moderate (-2 MPa at predawn) and severe (-3 MPa) water stress levels and were re-watered after 60 days. Vegetative growth was inhibited during the stress assays, and strong defoliation levels were reported, especially in Fino lemon. In both species, bud sprouting was induced after re-watering. Flowers and vegetative shoots developed in Owari satsuma after a drought period, and the development was independent of the stress level. In Fino lemon, vegetative shoots and flowers were primarily formed after moderate and severe stress, respectively. The photosynthetic rate and stomatal conductance were reduced by water stress, and a marked increase in water-use efficiency at the moderate water deficit level was observed. Nevertheless, the photosynthetic apparatus was not damaged, since the maximum quantum yield, photosynthetic pigment concentrations and Rubisco level and activity did not change. Furthermore, the measured malonyldialdehyde (MDA) and peroxidase activity indicated that oxidative stress was not specifically triggered by water stress in our study. Therefore, the gas exchange, fluorescence and biochemical parameters suggested that diffusional limitations to photosynthesis predominated in both of the studied Citrus species, and explained the rapid recovery of the photosynthetic parameters after rehydration. The net CO 2 fixation rate and stomatal conductance were recovered within 24 h in Fino lemon, whereas 3 days were required in Owari satsuma. This suggests the presence of some metabolic limitations in the latter species. Furthermore, the sensibility of the defoliation rates, the accumulation of proline and the stomatal behaviour in response to water stress indicated a higher drought tolerance of Fino lemon, according to its better acclimation to h

Photosynthesis down-regulation due to an imbalance between sources and sinks in Citrus leaves could be mediated by excessive accumulation of carbohydrates. However, there is limited understanding of the physiological role of soluble and insoluble carbohydrates in photosynthesis regulation and the elements triggering the down-regulation process. In this work, the role of non-structural carbohydrates in the regulation of photosynthesis under a broad spectrum of source-sink relationships has been investigated in the Salustiana sweet orange. Soluble sugar and starch accumulation in leaves, induced by girdling experiments, did not induce down-regulation of the photosynthetic rate in the presence of sinks (fruits). The leaf-to-fruit ratio did not modulate photosynthesis but allocation of photoassimilates to the fruits. The lack of strong sink activity led to a decrease in the photosynthetic rate and starch accumulation in leaves. However, photosynthesis down-regulation due to an excess of total soluble sugars or starch was discarded because photosynthesis and stomatal conductance reduction occurred prior to any significant accumulation of these carbohydrates. Gas exchange and fluorescence parameters suggested biochemical limitations to photosynthesis. In addition, the expression of carbon metabolism-related genes was altered within 24 h when strong sinks were removed. Sucrose synthesis and export genes were inhibited, whereas the expression of ADP-glucose pyrophosphorylase was increased to cope with the excess of assimilates. In conclusion, changes in starch and soluble sugar turnover, but not sugar content per se, could provide the signal for photosynthesis regulation. In these conditions, non-stomatal limitations strongly inhibited the photosynthetic rate prior to any significant increase in carbohydrate levels. © The Author 2011. Published by Oxford University Press. All rights reserved.

[EN] The aim of this work was to assess the relation between carbohydrate levels and flower and fruit production, as well as the role of carbohydrates on CO(2) fixation activity, by analysis of leaves, twigs and roots from the alternate bearing 'Salustiana' cultivar of sweet orange (Citrus sinensis [L.] Osbeck). A heavy crop load (on year) did not affect photosynthesis activity when compared to non-fruiting trees (off year). Fruiting trees accumulated most of the fixed carbon in mature fruits, whilst no accumulation was observed in roots before harvest. Non-fruiting trees transported part of the fixed carbon to the roots and mobilize it for growth processes and, at the end of the season (December), store it as reserves. Reserve carbohydrates accumulation in leaves started by early December for both tree types, showing the same levels in on and off trees until spring bud sprouting. A heavy flowering after an off year caused the rapid mobilization of the stored reserves, which were exhausted at full bloom. We found no evidence on carbon fixation regulation by either fruit demand or carbohydrate levels in leaves. Carbohydrate reserves played little or no role over fruit set, which actually relied on current photosynthesis

[EN] The Spanish type cultivar 'Piel de Sapo' (Cucumis melo L var. saccharinus), has a limited compatibility with the Cucurbita maxima x Cucurbita moschata hybrids currently used as rootstocks. Double grafting can be used to improve compatibility between rootstock and scion by means of an intermediate rootstock compatible with both. Non-grafted, single, and double grafted melon plants of the cultivar Piel de Sapo were evaluated for water, nutrient absorption, photosynthesis activity, biomass production in early phases, as well as for yields and fruit quality in a long term trial. The hybrid 'Shintoza' (C. maxima x C. moschata) was used as rootstock, and the cantaloupe type melon cultivar 'Sienne' as an intermediate scion. Grafting did not affect net photosynthetic values, yet increased water use efficiency (35%). Double grafted plants increased aerial dry weights (66% and 31% with respect to non-grafted and simple graft plants, respectively), and also increased capacity for uptaking beneficial minerals (between 61% and 13% and particularly for NO(3)(-), P, K, Ca, Mn, and Zn) with respect to non-grafted and single grafted plants. The quantum efficiency PSII photochemistry values increased in double grafted plants (12%) with respect to the control plants. Consequently, double grafting on a vigorous rootstock such as 'Shintoza', with an intermediate scion, results in improved mineral and water absorption and achieves an increase in ion influx to the scion - so enabling an increase in light photosynthetic reaction and biomass. Double grafted plants increased fruit yield when compared to simple grafted and non-grafted plants (12% and 56%, respectively) and did not affect fruit quality in terms of degrees Brix and colour. In conclusion, double grafting presents several beneficial aspects that are counter-balanced by the extra cost of the technique. The difference in yields reflects compatibility problems.