Variation of grain nitrogen content in relation with grain yield in old and modern Spanish wheats grown under a wide range of agronomic conditions in a Mediterranean region

Wheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/ 07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0.75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content ; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0.13 to 0.40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0.22 (mean of the four manipulative experiments) in the oldest cultivar to 0.51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

Comparative performance of the stable isotope signatures of carbon, nitrogen and oxygen in assessing early vigour and grain yield in durum wheat

The present paper studied the performance of the stable isotope signatures of carbon (δ13C), nitrogen (δ15N) and oxygen (δ18O) in plants when used to assess early vigour and grain yield (GY) in durum wheat growing under mild and moderate Mediterranean stress conditions. A collection of 114 recombinant inbred lines was grown under rainfed (RF) and supplementary irrigation (IR) conditions. Broad sense heritabilities (H2) for GY and harvest index (HI) were higher under RF conditions than under IR. Broad sense heritabilities for δ13C were always above 0·60, regardless of the plant part studied, with similar values for IR and RF trials. Some of the largest genetic correlations with GY were those shown by the δ13C content of the flag leaf blade and mature grains. Under both water treatments, mature grains showed the highest negative correlations between δ13C and GY across genotypes. Flag leaf δ13C was negatively correlated with GY only under RF conditions. The δ13C in seedlings was negatively correlated, under IR conditions only, with GY but also with early vigour. The sources of variation in early vigour were studied by stepwise analysis using the stable isotope signatures measured in seedlings. The δ13C was able to explain almost 0·20 of this variation under RF, but up to 0·30 under IR. In addition, nitrogen concentration in seedlings accounted for another 0·05 of variation, increasing the amount explained to 0·35. The sources of variation in GY were also studied through stable isotope signatures and biomass of different plant parts: δ13C was always the first parameter to appear in the models for both water conditions, explaining c. 0·20 of the variation. The second parameter (δ15N or N concentration of grain, or biomass at maturity) depended on the water conditions and the plant tissue being analysed. Oxygen isotope composition (δ18O) was only able to explain a small amount of the variation in GY. In this regard, despite the known and previously described value of δ13C as a tool in breeding, δ15N is confirmed as an additional tool in the present study. Oxygen isotope composition does not seem to offer any potential, at least under the conditions of the present study.

Carbohydrate and nitrogen stores in Festuca paniculata under mowing explain dominance in subalpine grasslands

Cessation of traditional management threatens semi-natural grassland diversity through the colonisation or increase of competitive species adapted to nutrient-poor conditions. Regular mowing is one practice that controls their abundance. This study evaluated the ecophysiological mechanisms limiting short- and long-term recovery after mowing for Festuca paniculata, a competitive grass that takes over subalpine grasslands in the Alps following cessation of mowing. We quantified temporal variations in carbon (C) and nitrogen (N) content, starch, fructan and total soluble sugars in leaves, stem bases and roots of F. paniculata during one growth cycle in mown and unmown fields and related them to the dynamics of soil mineral N concentration and soil moisture. Short-term results suggest that the regrowth of F. paniculata following mowing might be N-limited, first because of N dilution by C increments in the plant tissue, and second, due to low soil mineral N and soil moisture at this time of year. However, despite short-term effects of mowing on plant growth, C and N content and concentration at the beginning of the following growing season were not affected. Nevertheless, total biomass accumulation at peak standing biomass was largely reduced compared to unmown fields. Moreover, lower C storage capacity at the end of the growing season impacted C allocation to vegetative reproduction during winter, thereby dramatically limiting the horizontal growth of F. paniculata tussocks in the long term. We conclude that mowing reduces the growth of F. paniculata tussocks through both C and N limitation. Such results will help understanding how plant responses to defoliation regulate competitive interactions within plant communities.

Carbohydrate and nitrogen stores in Festuca paniculata under mowing explain dominance in subalpine grasslands

Cessation of traditional management threatens semi-natural grassland diversity through the colonisation or increase of competitive species adapted to nutrient-poor conditions. Regular mowing is one practice that controls their abundance. This study evaluated the ecophysiological mechanisms limiting short- and long-term recovery after mowing for Festuca paniculata, a competitive grass that takes over subalpine grasslands in the Alps following cessation of mowing. We quantified temporal variations in carbon (C) and nitrogen (N) content, starch, fructan and total soluble sugars in leaves, stem bases and roots of F. paniculata during one growth cycle in mown and unmown fields and related them to the dynamics of soil mineral N concentration and soil moisture. Short-term results suggest that the regrowth of F. paniculata following mowing might be N-limited, first because of N dilution by C increments in the plant tissue, and second, due to low soil mineral N and soil moisture at this time of year. However, despite short-term effects of mowing on plant growth, C and N content and concentration at the beginning of the following growing season were not affected. Nevertheless, total biomass accumulation at peak standing biomass was largely reduced compared to unmown fields. Moreover, lower C storage capacity at the end of the growing season impacted C allocation to vegetative reproduction during winter, thereby dramatically limiting the horizontal growth of F. paniculata tussocks in the long term. We conclude that mowing reduces the growth of F. paniculata tussocks through both C and N limitation. Such results will help understanding how plant responses to defoliation regulate competitive interactions within plant communities.

Phosphorous and nitrogen changes in compost-amended schist soils in vineyards in the D.O. Priorat wine-producing area (NE Spain)

The impact, on nitrogen and phosphorous dynamics, of applying compost at different rates was investigated in soils developed on schist in new terraced vineyards (NTV) and in undisturbed areas (NC). Repacked soil columns amended with 0 (control), 50 t ha –1 (T1) and 100 t ha–1 (T2) of compost were studied under laboratory conditions simulating both situations. The columns were maintained for 1 year, during which time a total of 300 mm of simulated rainfall was applied in ten 30 mm applications. Soil organic matter (OM), nitrogen and phosphorous contents were analysed at the end of the study period and leachates were analysed after each simulated rainfall event. Significant differences in nitrate leaching were observed between the control and the treated soils and these differences were greater in the NC (control = 1.368 g, T1 = 1.526 g and T2 = 1.686 g) than in the NTV soils (control = 0.61 g, T1 = = 1.068 g and T2 = 1.283 g). The relative effect was greater in the NTV soils (T1/control = 1.11 vs. 1.75 and T2/control = 1.23 vs. 2.1 for NC and NTV, respectively). The nitrate concentration in the leached water reached up to 400 mg L–1, which implied a risk of groundwater pollution. Phosphorous losses through leaching were very low with concentrations of < 0.15 mg L–1, without any significant differences between treatments. The phosphorous concentrations in the surface horizon increased by 50.8% in T1 and by 66.8% in T2 in the NC soils, compared with increases of 20.3% and 38%, respectively, in the NTV soils. Due to the high infiltration capacity of the study soils, leaching effects must be considered in order to prevent groundwater pollution.

Sabbatical stay at CREVER, University Rovira i Virgili

A three-year research proposal of international impact and quality was developed between the author and CREVER researchers, taking into account the infrastructure and research lines already being carried out at CREVER. The project is related to the study of new mixtures in thermal activated systems, by the addition of a third component to help the heat transfer processes. The project proposes the use of water and lithium nitrate as absorbents in ternary ammonia mixtures, varying the concentration with the objective of optimising the mixture for solar air conditioning purposes. Also, the research proposal will promote an intensive collaboration in the following years between CREVER and The Centro de Investigación en Energía-UNAM, Mexico.

Pla de gestió i conservació dels Estanyets de Pals i les Closes Fondes (Pals, Baix Empordà)

Es destaca la presència de tres espècies bioinvasores, tals com la gambúsia(Gambusiaaffinis), la canya (Arundodonax) i el cranc vermell americà (Procambarusclarkii). S’ha detectat que la qualitat de l’aigua ha disminuït en alguns paràmetres, especialment en l’Estanyet del Safareig. En els tres estanyets els sòlids dissolts totalsa TSD) estan al voltant del límit màxim recomanat per la EPA (Agència de Protecció Ambiental d’Estats Units). S’ha observat que la Cladophora, indicadora de concentracions elevades de nitrogen a l’aigua, és un cloròfit molt abundant. S’han identificat dos hàbitats d’interès comunitari no prioritari, segons la Directiva Hàbitats: les closes i les freixenedes termòfiles de Fraxinusangustifolia. En funció dels resultats obtinguts s’han elaborat les propostes de gestió i conservació per aquest espai.

Balanç de nitrogen i anàlisi del consum d'aigua al Baix Empordà

El present treball pretén avaluar l’impacte de les activitats agràries sobre les aigües subterrànies, al Baix Empordà. La ramaderia intensiva genera uns residus que l’agricultura no és capaç d’assumir. Els excedents generats s’infiltren al subsòl, generalment en forma de nitrats (NO3-), provocant la contaminació de les aigües subterrànies. Aquesta pot provocar greus problemes ecològics en els sistemes aquàtics, i afectar a la salut humana. S’ha realitzat un balanç de nitrogen per a les zones agrícoles de l’àrea d’estudi, avaluant els diversos processos que incorporen o extreuen nitrogen al sòl. Paral·lelament, s’ha estudiat el consum d’aigua provocat pel diversos sectors presents a la zona d’estudi, per tal d’avaluar quantitativament la pressió que provoquen sobre els aqüífers. Els resultats obtinguts mostren que la majoria de municipis estudiats generen excedents de nitrogen, justificant la presència de nitrats al subsòl.

Eliminació simultània de fòsfor i nitrogen en aigües residuals, utilitzant microorganismes DPAO en un reactor discontinu seqüencial (SBR)

En aquest estudi es realitzà eliminació biològica simultània de fòsfor i nitrogen en un Reactor Discontinu Seqüencial (SBR), el qual conté una biomassa enriquida amb Organismes Desnitrificadors Acumuladors de Fòsfor (DPAO) que utilitzen com a única font de carboni l’àcid propiònic i com acceptors d’electrons: nitrit en la fase anòxica i oxigen en l’aeròbica. L’SBR opera amb cicle de 8 h alternant fase anaeròbica, anòxica i aeròbica. El seguiment del sistema es realitzà mitjançant mesures on-line (titrimetria) i off-line (quantificació d’àcid propiònic, nitrit i fòsfor), utilitzant l’HPLC per quantificar l’àcid propiònic i cromatografia iònica per les mesures de nitrit i fòsfor. Amb aquest sistema es pretén augmentar la captació de fòsfor en la fase anòxica fet que s’aconseguí realitzant diferents canvis al reactor per tal de maximitzar el consum de nitrit en aquesta fase, ja fos allargant el temps de fase o augmentant la concentració de biomassa. Aquest experiment ha suposat un augment de la captació de fòsfor (33 mg P-PO4 3-/L), de l’eliminació neta de fòsfor (17 mg P-PO4 3-/L) i de consum de nitrit (27 mg N-NO2-). Per altra banda, es pretenia veure els efectes a curt termini de l’eliminació de la fase aeròbica a partir del seguiment de 2 cicle puntuals i d’un cicle de 32 h sense fase aeròbica. En ambdós casos s’aconseguí una eliminació neta de fòsfor.

Influencia de la altura, la distancia de los tubos a la calle, la anchura de la calle, el tráfico y la densidad de vehículos sobre la concentración de NO2

Durante las primeras décadas del s. XX se contempló un importante aumento de las enfermedades coronarias, este hecho estimuló la investigación sobre las causas de dichas enfermedades. En 1978, y para investigar este fenómeno se inició el estudio REGICOR en el Hospital Josep Trueta de Girona. En el s. XX también se contempló un creciente problema de contaminación de las atmósferas urbanas, esto hizo que diferentes científicos estudiaran las relaciones entre las enfermedades coronarias y la contaminación atmosférica en áreas urbanas (Godish, 1997; Krupa & Legge, 2000; Brook et al., 2004 y Krewski et al., 2004). El proyecto realizado está situado en el contexto del primer estudio realizado en España que investiga los efectos sobre la salud de la contaminación atmosférica (REGICOR 2000-AIR). En el proyecto se pretende investigar la influencia de diferentes factores (distancia de los tubos a la calle, altura de los tubos, anchura de la calle, tráfico y densidad de tráfico) sobre la contaminación atmosférica de las ciudades de Girona y Salt, con el fin de poder caracterizar lo mejor posible la exposición a contaminación atmosférica. Para este fin se utilizará el NO2 como marcador de contaminación atmosférica y se seleccionaran varios puntos de muestreo en las dos ciudades dónde se pondrán captadores de NO2 para la medición de dicha contaminación. Después, y mediante un análisis estadístico, se podrá determinar la influencia de los factores en la variación de concentración de NO2 en el área seleccionada.

Blow-up, concentration phenomenon and global existence for the Keller-Segel model in high dimension

"Vegeu el resum a l'inici del document del fitxer adjunt."

Marbofloxacin achieves high concentration in pig tonsils according to a dose dependent fashion

The penetration of marbofloxacin into tonsils was assessed in fattening pigs. Two different dosages were used to treat the animals: 2 mg/kg b.w. every 24 hours during 3 days (P1 group) and 4 mg/kg b.w. every 48 hours two times (P2 group. A ratio between the mean tonsillar concentration of marbofloxacin for both doses 24 hours after the last administration (0.5 and 0.7 µgr/mL) and its MIC90 for APP (0.03 µgr/mL) was calculated. These Ratio values were 16.6 and 23.3 for P1 and P2 group.

Eliminació autotròfica de nitrogen en una pila biològica (microbial fuel cells )

L’aigua i l’energia formen un binomi indissociable. En relació al cicle de l’aigua, des de fa varies dècades s’han desenvolupat diferents formes per recuperar part de l’energia relacionada amb l’aigua, per exemple a partir de centrals hidroelèctriques. No obstant, l’ús d’aquesta aigua també porta associat un gran consum energètic, relacionat sobretot amb el transport, la distribució, la depuració, etc... La depuració d’aigües residuals porta associada una elevada demanda energètica (Obis et al.,2009). En termes energètics, tot i que la despesa elèctrica d’una EDAR varia en funció de diferents paràmetres com la configuració i la capacitat de la planta, la càrrega a tractar, etc... es podria considerar que el rati mig seria d’ aproximadament 0.5 KWh•m-3.Els principals costos d’explotació estan relacionats tant amb la gestió de fangs (28%) com amb el consum elèctric (25%) (50% tractament biològic). Tot i que moltes investigacions relacionades amb el tractament d’aigua residual estan encaminades en disminuir els costos d’operació, des de fa poques dècades s’està investigant la viabilitat de que l’aigua residual fins i tot sigui una font d’energia, canviant la perspectiva, i començant a veure l’aigua residual no com a una problemàtica sinó com a un recurs. Concretament s’estima que l’aigua domèstica conté 9.3 vegades més energia que la necessària per el seu tractament mitjançant processos aerobis (Shizas et al., 2004). Un dels processos més desenvolupats relacionats amb el tractament d’aigües residuals i la producció energètica és la digestió anaeròbia. No obstant, aquesta tecnologia permet el tractament d’altes càrregues de matèria orgànica generant un efluent ric en nitrogen que s’haurà de tractar amb altres tecnologies. Per altre banda, recentment s’està investigant una nova tecnologia relacionada amb el tractament d’aigües residuals i la producció energètica: les piles biològiques (microbial fuel cells, MFC). Aquesta tecnologia permet obtenir directament energia elèctrica a partir de la degradació de substrats biodegradables (Rabaey et al., 2005). Les piles biològiques, més conegudes com a Microbial Fuel Cells (acrònim en anglès, MFC), són una emergent tecnologia que està centrant moltes mirades en el camp de l’ investigació, i que es basa en la producció d’energia elèctrica a partir de substrats biodegradables presents en l’aigua residual (Logan., 2008). Els fonaments de les piles biològiques és molt semblant al funcionament d’una pila Daniell, en la qual es separa en dos compartiments la reacció d’oxidació (compartiment anòdic) i la de reducció (compartiment catòdic) amb l’objectiu de generar un determinat corrent elèctric. En aquest estudi, bàsicament es mostra la posada en marxa d'una pila biològica per a l'eliminació de matèria orgànica i nitrogen de les aigües residuals.

Thermodynamics and log–contrast analysis in fluid geochemistry

There are two principal chemical concepts that are important for studying the naturalenvironment. The first one is thermodynamics, which describes whether a system is atequilibrium or can spontaneously change by chemical reactions. The second main conceptis how fast chemical reactions (kinetics or rate of chemical change) take place wheneverthey start. In this work we examine a natural system in which both thermodynamics andkinetic factors are important in determining the abundance of NH+4 , NO−2 and NO−3 insuperficial waters. Samples were collected in the Arno Basin (Tuscany, Italy), a system inwhich natural and antrophic effects both contribute to highly modify the chemical compositionof water. Thermodynamical modelling based on the reduction-oxidation reactionsinvolving the passage NH+4 -& NO−2 -& NO−3 in equilibrium conditions has allowed todetermine the Eh redox potential values able to characterise the state of each sample and,consequently, of the fluid environment from which it was drawn. Just as pH expressesthe concentration of H+ in solution, redox potential is used to express the tendency of anenvironment to receive or supply electrons. In this context, oxic environments, as thoseof river systems, are said to have a high redox potential because O2 is available as anelectron acceptor.Principles of thermodynamics and chemical kinetics allow to obtain a model that oftendoes not completely describe the reality of natural systems. Chemical reactions may indeedfail to achieve equilibrium because the products escape from the site of the rectionor because reactions involving the trasformation are very slow, so that non-equilibriumconditions exist for long periods. Moreover, reaction rates can be sensitive to poorly understoodcatalytic effects or to surface effects, while variables as concentration (a largenumber of chemical species can coexist and interact concurrently), temperature and pressurecan have large gradients in natural systems. By taking into account this, data of 91water samples have been modelled by using statistical methodologies for compositionaldata. The application of log–contrast analysis has allowed to obtain statistical parametersto be correlated with the calculated Eh values. In this way, natural conditions in whichchemical equilibrium is hypothesised, as well as underlying fast reactions, are comparedwith those described by a stochastic approach

Anàlisi comparativa dels processos emergents sharon i anammox per al tractament d’aigües amb una alta càrrega de nitrogen

Estudi de tractaments innovadors en aigües residuals amb elevada concentració de nitrogen mitjançant la tecnologia ANAMMOX (Anaerobic Ammonium Oxidation) i SHARON i posterior anàlisi teòrica de la gestió dels fangs residuals d’una EDAR