In Situ Evaluation of Tensile Properties of Heat-Affected Zones From Welded Steel Pipes Castelluccio, G. M.; Yawny, Alejandro Andres; Perez Ipiña, Juan Elias; Ernst, H. A. Currently, measuring the local tensile strength in inhomogeneous materials is not standardised, nor accepted techniques are available despite such technique would be beneficial in a variety of technological applications. Thus, this work introduces an innovative method for assessing stress-strain properties at a sub-millimeter scale and illustrates the potential of the technique by evaluating the strength of a sub-region in the HAZ from welded steels pipes. The method employs a fully instrumented stage inside a scanning electron microscope that stretches small tensile specimens (2.0 mm × 0.5 mm cross-section, 12.5 mm gage length) while registering detailed images of the deformed region. The specimens, cut from full-scale welds, include in their gage length weld metal, base metal and HAZ and have an 85 Îm period grid of evaporated lead on their surface to visualise the deformation. Upon straining, local strain is determined by correlating sequential images of the specimen surface with an open source code for particle image velocimetry. The calculated local strain within the HAZ and the load values recorded during testing are converted into a local stress-strain response. The results for two different heat inputs agree with usual, but indirect and less accurate assessments procedures, including local hardness measurements and notched bar testing.

Environmental effects of ozone depletion and its interactions with climate change: Progress report, 2011 Andrady, A. L.; Aucamp, P. J.; Austin, Amy Theresa; Bais, A. F.; Ballaré, C. L.; Björn, L. O.; Bornman, J. F.; Caldwell, M.; Cullen, A. P.; Erickson, D. J.; de Gruijl, F. R.; Häder, D. P.; Helbling, Eduardo Walter; Ilyas, M.; Longstreth, J.; Lucas, R; Mckenzie, L.; Madronich, S.; Norval, N.; Paul, N. D.; Redhwi, H. H.; Robinson, S.; Shao, M.; Solomon, K. R.; Sulzberger, B.; Takizawa, Y.; Tang, X.; Torikai, A.; van der Leun, J. C.; Williamson, C. E.; Wilson, S. R.; Worrest , R. C.; Zepp, R. G. The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with two focal issues. The first focus is the effects of increased UV radiation on human health, animals, plants, biogeochemistry, air quality, and materials. The second focus is on interactions between UV radiation and global climate change and how these may affect humans and the environment. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was published in 2010 (Photochem. Photobiol. Sci., 2011, 10, 173-300). In the years in between, the EEAP produces less detailed and shorter progress reports, which highlight and assess the significance of developments in key areas of importance to the parties. The next full quadrennial report will be published in 2014-2015.

Sunflower root growth regulation: the role of jasmonic acid and its relation with auxins Corti Monzón, Georgina de la Paz; Pinedo, Marcela Lilian; Lamattina, Lorenzo; de la Canal, Laura Jasmonates are lipid-derived hormones that act as signal molecules in abiotic and biotic stresses and influence several aspects of plant growth and development. In this work we have investigated the effect of jasmonic acid (JA) on the root architecture of Helianthus annuus seedlings and if JA and auxins interact to modulate the growth of the primary root (PR) and lateral roots (LR). The addition of lM concentrations of JA to the growing medium of sunflower seedlings decreased the growth of the PR and LR, and also reduced the number of LR. Moreover, treatment with ibuprofen, an inhibitor of JA synthesis, increased PR and LR root length causing a deep effect on root architecture. Hence, not only exogenous but also the endogenous JA regulates sunflower root growth. Microscopic analysis showed that the application of JA reduces the cortex cell length and the estimated cell production rate in root meristem while ibuprofen only affects the cell elongation. A possible interaction between JA and auxins to regulate root growth was further analyzed. We show that JA produced its phenotype even in the presence of reduced levels of auxin generated by treatment with an auxin transport inhibitor. Besides, the auxin produced its phenotype even when ibuprofen was applied. In conclusion, JA may induce primary and lateral root growth inhibition in sunflower by an auxin-independent pathway.

Short term impact of artisanal dredges in a Patagonian mussel fishery: Comparisons with commercial diving and control sites Narvarte, Maite Andrea; González, Raul Alberto Candido; Medina, Alonso Ismael; Avaca, Maria Soledad; Ginsberg, Silvia Susana; Aliotta, Salvador Mussels in the San Matías Gulf fishery are targeted using artisanal dredges and diving. The main objective of this study was to assess the direct impact of artisanal dredging on the biota and sediments, and to compare the composition of the catches and the individual damage induced by fishing between dredging and commercial diving. The experimental design included samplings from dredge catches, dredge tracks, control sites and commercial diving. According to their damage level, individuals were scored as undamaged, lightly damaged and severely damaged. Sediment characteristics were analyzed using coring samples and traps. Damage of mussels, mostly corresponding to the severely damaged category, was less than 5% both in samples from dredging and diving. Conversely, mean damage of the main bycatch species (sea urchins and ophiuroids) was 75 and 65% in samples from dredging and diving respectively, being most of the individuals lightly damaged. Considering also the catch sample composition of both fishing methods, dredging affected relatively more individuals than diving. Although sediment removal in dredged areas was three times higher than that in non-dredged ones, mean grain size and gravel percentage of sea floor sediments showed subtle differences between them.

Efecto de los metales sobre microcrustáceos de agua dulce. Avances metodológicos y potencialidad de cladóceros y copépodos como organismos test; Effects of metals on freshwater microcrustaceans. Metodological advances and potentiality of cladocerans and copepods as test organisms Gutierrez, Marìa Florencia; Gagneten, Ana María El incremento de los metales en los cuerpos de agua dulce a causa de las actividades antropogénicas genera importantes alteraciones sobre la biota. Esta revisión analiza los efectos adversos de varios metales de relevancia ecotoxicológica sobre los microcrustáceos zooplanctónicos (cladóceros y copépodos), los avances experimentales en esta línea y las ventajas de cada grupo como organismos test. En general, la necesidad de obtener indicadores más sensibles y representativos que los tradicionales, promovió lineamientos hacia estudios subcrónicos, interspecíficos y multigeneracionales. Por otra parte, la tendencia actual hacia el estudio de mezclas de sustancias y los efectos indirectos permite adquirir una visión más integral del problema. El impacto sobre las poblaciones es muy variable, dependiendo de la naturaleza del metal, las características del medio, el tiempo de exposición, las condiciones de cultivo y aspectos genéticos. Sin embargo, la mayoría de los trabajos se centran en pocas especies, dejando vacancias en el conocimiento de las representantes de cada región particular. Si bien algunos atributos de los cladóceros y copépodos como el tamaño, la morfología y el rol ecológico los tornan buenos indicadores, las diferencias en el desarrollo, reproducción y estrategias de perpetuación confieren ventajas a un grupo sobre otro.; The increase of metals in fresh water systems due to anthropogenic activities cause important alterations on the biota. The present review analyze the adverse effects of various metals of ecotoxicological relevance on microcrustaceans zooplankton species (cladocerans and copepods), the experimental advances and the advantages of each group as test organisms. In general, the need to obtain more sensitive and representative indicators than the tradicional ones leads to subchronic, interespecific and multigenerational studies. Additionally, the analysis of mixtures as well as their indirect effects allows to acquire more integral knowledges of the impact of contaminants. The toxic effects are different, depending on the nature of metals, the physicochemical characteristics of the water, exposutre time and genetic traits. However, most works are focused on few species, leading vacant areas on the knowledge of the representatives of every particular region. Despite some cladocerans and copepods atributes make them good bioindicators (size, morphology and ecological role), differences of development, reproduction and perpetuation strategies bring advantages to one group on another.

Natural polyphenols may ameliorate damage induced by copper overload Arnal, Nathalie; Tacconi, Maria Josefa; Marra, Carlos Alberto The effect of the simultaneous exposure to transition metals and natural antioxidants frequently present in food is a question that needs further investigation. We aimed to explore the possible use of the natural polyphenols caffeic acid (CA), resveratrol (RES) and curcumin (CUR) to prevent damages induced by copper-overload on cellular molecules in HepG2 and A-549 human cells in culture. Exposure to 100 μM/24. h copper (Cu) caused extensive pro-oxidative damage evidenced by increased TBARS, protein carbonyls and nitrite productions in both cell types. Damage was aggravated by simultaneous incubation with 100 μM of CA or RES, and it was also reflected in a decrease on cellular viability explored by trypan blue dye exclusion test and LDH leakage. Co-incubation with CUR produced opposite effects demonstrating a protective action which restored the level of biomarkers and cellular viability almost to control values. Thus, while CA and RES might aggravate the oxidative/nitrative damage of Cu, CUR should be considered as a putative protective agent. These results could stimulate further research on the possible use of natural polyphenols as neutralizing substances against the transition metal over-exposure in specific populations such as professional agrochemical sprayers and women using Cu-intrauterine devices.

Adjusting to trade policy: Evidence from U.S. antidumping duties on Vietnamese catfish Brambilla, María Irene; Porto, Guido Gustavo; Tarozzi, Alessandro In 2003, after claims of dumping, the United States imposed heavy tariffs on Vietnamese catfish, which led to a collapse of imports. We use panel data to explore household responses in the catfish-producing Mekong delta between 2002 and 2004 and find that income growth was significantly slower among households relatively more involved in catfish farming in 2002. This is explained by a relative decline in both catfish income and revenues from other miscellaneous farm activities. Labor supply did not adjust, most likely because of off-farm employment limitations. Households more exposed to the shock reduced the share of investment assigned to catfish while substituting into agriculture.

Determination of enantiomeric composition of ibuprofen in pharmaceutical formulations by partial least-squares regression of strongly overlapped chromatographic profiles Osorio Grisales, Jaiver; Arancibia, Juan Alberto; Castells, Cecilia Beatriz Marta; Olivieri, Alejandro Cesar In this report, we demonstrate how chiral liquid chromatography combined with multivariate chemometric techniques, specifically unfolded-partial least-squares regression (U-PLS), provides a powerful analytical methodology. Using U-PLS, strongly overlapped enantiomer profiles in a sample could be successfully processed and enantiomeric purity could be accurately determined without requiring baseline enantioresolution between peaks. The samples were partially enantioseparated with a permethyl-β-cyclodextrin chiral column under reversed-phase conditions. Signals detected with a diode-array detector within a wavelength range from 198 to 241nm were recorded, and the data were processed by a second-order multivariate algorithm to decrease detection limits. The R-(-)-enantiomer of ibuprofen in tablet formulation samples could be determined at the level of 0.5mgL-1 in the presence of 99.9% of the S-(+)-enantiomorph with relative prediction error within ±3%.

Breeding biology of the White-rumped Swallow (Tachycineta leucorrhoa; Hirundinidae) in a wetland: A comparative approach Lorenzón, Rodrigo Ezequiel; Quiroga, Martin Anibal We studied the reproductive biology of the White-rumped Swallow (Tachycineta leucorrhoa) in a colony of 50 nests boxes located in a wetland of the Paraná River, Santa Fe, Argentina between 2004 and 2006. The nest boxes were checked regularly and reproductive parameters, as well as morphological data of eggs and nestlings, were recorded. The species had an average clutch size of 4.7 eggs whose volumes and weight means were 2.04 cm 3 and 2.17 g. respectively. The incubation period averaged 15.9 days and decreased with the clutch size. The mean nestling period was 23.8 days. Clutch size, number of nestlings per nest and the nestling period decreased with the advance of the breeding seasons, while the incubation time increased. Breeding parameters showed a similarity with those reported for the population from Chascomús site, although the eggs were 5% heavier, the incubation period took one more day and the reproductive success was also higher. With the closely related species Tachycineta meyeni, the studied species showed a lower clutch size. Finally, considering another closely related species Tachycineta bicolor, the White-rumped Swallow showed the reproductive life history traits characteristic of species in the southern hemisphere. We provide new information for this species nesting on wetlands, a fact that contributes to the understanding of changes in the life history of the Tachycineta genus along the American continent.

PFT1, the MED25 subunit of the plant Mediator complex, promotes flowering through CONSTANS dependent and independent mechanisms in Arabidopsis Iñigo, Sabrina; Alvarez, Mariano J.; Strasser, Bárbara; Califano, Andrea; Cerdan, Pablo Diego Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far-red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post-translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light-quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO-dependent and -independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO-dependent and -independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO-independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid-dependent defences.

Sylvester's double sums: an inductive proof of the general case Krick, Teresa Elena Genoveva; Szanto, Agnes In 1853, Sylvester introduced a family of double sum expressions for two finite sets of indeterminates and showed that some members of the family are essentially the polynomial subresultants of the monic polynomials associated with these sets. In 2009, in a joint work with C. D’Andrea and H. Hong we gave the complete description of all the members of the family as expressions in the coefficients of these polynomials. More recently, M.-F. Roy and A. Szpirglas presented a new and natural inductive proof for the cases considered by Sylvester. Here we show how induction also allows to obtain the full description of Sylvester’s double-sums.

Dispositivo interactivo luminoso como recurso didáctico para la mejor comprensión del concepto acido-base en química general; Interactive Lighting Device as a Teaching Resource for the Better Comprehension of the Acid-Base Concept in General Chemistry Matkovic, Silvana Raquel; Briand, Laura Estefania El presente trabajo aborda la creación de un recurso didáctico que consiste en un dispositivo interactivo luminoso, de sencilla construcción, que complementará a una parte experimental. Se propone utilizarlo para ayudar al alumno a correlacionar su funcionamiento con el proceso de cambio de color observado al interaccionar un indicador ácido- base con una sustancia ácida o alcalina, y utilizarlo para introducir el modelo experto con el cual se enseña en el ámbito académico dicha interacción. Este dispositivo, consta de dos partes que al ponerse en contacto cierran un circuito que enciende una luz que a su vez produce una modificación en el color del recipiente que la contiene. En definitiva esta propuesta involucra una parte experimental que utiliza sustancias naturales y de uso diario junto al uso de un dispositivo luminoso, de tipo interactivo para modelar la interacción molecular característica de un indicador ácido-base.; A teaching resource is constructed with the aim of helping student to better comprehend the acid-base concept in general chemistry, in particular the process of color change that is observed when an acid-base indicator reacts with acid or basic species. The proposal involves an interactive lighting device easy to build. The device lights when its two parts are in contact closing an electric circuit. Therefore it has a certain color when both parts are in contact that differs from the color of the when they are apart. Additionally, the contact of natural dyes with everyday domestic substances is described as a complementary experimental section. The interactive lighting device is a teaching resource that allows correlating the interaction of a chemical species with the change of color of an acid-base indicator.

Renormalization: The observable-state model Ardenghi, Juan Sebastian; Castagnino, Mario Alberto G. J. The usual mathematical formalism of quantum field theory is not rigorous because it contains divergences that can only be renormalized by nonrigorous mathematical methods. So we present a method of subtraction of divergences using the formalism of decoherence. This is achieved by replacing the standard renormalization method by a projector on a well defined Hilbert subspace. In this way a list of problems of the standard formalism disappears while the physical results of quantum field theory remain valid. From its own nature, this formalism can be also used in nonrenormalizable theories.

Die besetzten Fabriken in Argentinien: Wege der Arbeiterkontrolle in der Krise Kabat, Marina En el texto se analiza la organización del trabajo en fábricas ocupadas y el desenvolvimiento económico de las mismas en medio del contexto de crisis económico. Se analizan en particular firmas relacionadas con la industria del cuero y se las compara con la situación vigente en el resto de las fábricas ocupadas. Una particularidad que encontramos es que, mientras que en otras ramas, las fábricas ocupadas relacionadas con la cadena del cuero pertenecen a las firmas más pequeñas del sector, lo contrario ocurre en este caso, donde muchas de los establecimientos que quiebran y son recuperados por sus trabajadores corresponden a firmas importantes del sector. Dentro de los cambios y continuidades en la organización del trabajo desde la formación de las cooperativas, prestamos especial atención al desarrollo de la polifuncionalidad, los cambios en la distribución de tareas y la tercerización del trabajo.

Phytochemical profile and anti-lipoxygenase activity of alcoholic extracts of plant species from asteraceae family Torres Carro, Romina; Alberto, Maria Rosa; Isla, Maria Ines Usage of medicinal plants with curative purpose is an ancient and common practice still in use now a day. On physiopathology of sicknesses that develop an inflammatory and allergic process, lipoxygenase (LOX) has an important role being the enzymes responsible of the biosynthesis of inflammatory mediators. We evaluated the anti-LOX capacity of alcoholic extracts of nine plant species (B. boliviensis, B. incarum, Ch. keidelii, C. atacamensis, N. armatum, P. lepidophylla, P. lucida, P. phyliciformis, T. absinthioides) belonging to Asteraceae family and its relation to its phytochemical profile. Tinctures of plants collected in Argentine Puna were analyzed. Total polyphenols content vary between 64-160 µg Gallic Acid Equivalents, GAE/mg, phenolics non flavonoids vary between 53- 153 µg GAE/mg, flavones/flavonols between 6- 28 µg Quercetin Equivalents/mg and flavonones/dihidroflavonones between 24 and 51 µg Naringenin Equivalents/mg. Species from genus Parastrephia presented the highest inhibitory activity over LOX with IC50 values between 219 and 253 µg/ml, being P. lepidophylla the most active one. This could be related to the higher levels of total phenolics and flavones/flavonols measured in this species. The results indicate the potential use of Parastrephia extracts as natural anti-inflammatory.

Valorización de un fruto nativo del monte argentino (Geoffroea Decorticans "Chañar") y sus productos derivados (Arrope de Chañar) Costamagna, Milena Soledad; Isla, Maria Ines; Ordóñez, Roxana Mabel En el Noroeste Argentino existe una extraordinaria biodiversidad vegetal con numerosos frutos autóctonos que constituyen una importante alternativa productiva en la economía del NOA. Sin embargo, no existe información nutricional ni funcional de estos frutos en las bases de datos de composición de alimentos latinoamericanas ni del Reino Unido o Estados Unidos de América. Hace relativamente poco tiempo comenzamos un proyecto tendiente a la valorización de estos frutos en los que se incluyen al algarrobo, mistol, chañar, entre muchos otros. Los frutos del chañar, Geoffroea decorticans (Gill. Ex Hook.et Arn) Burkart junto al mistol y al algarrobo son alimentos importantes en la dieta de comunidades aborígenes del monte desertico argentino (Tobas y Wichis) desde tiempos ancestrales. Tradicionalmente los frutos del chañar son consumidos en añapa, en bollitos con grasa de pescado y en arropes con y sin azúcar. Las semillas son consumidas despues de tostar como un agente saborizante por su sabor a almendras y su alto contenido de aceites (principalmente acidos oleicos y linoleicos). Estudios recientes indicarían que el biodiesel de semillas de chañar (recuperación de 87% de metil esteres) cumpliría con los estandares internacionales. El objetivo del presente trabajo fue determinar las propiedades nutricionales y funcionales de frutos maduros y arrope de chañar. Materiales y Métodos: Se realizó la cuantificación de compuestos de valor nutricional (grasas, proteínas y azúcares) y compuestos con valor funcional (compuestos fenólicos totales, flavonoides, taninos condensados, taninos hidrolizables, entre otros) mediante métodos espectrofotométricos. En cada caso se realizaron extracciones específicas para cada grupo de metabolítos. Con el propósito de analizar la termoestabilidad de los compuestos funcionales se realizaron extracciones acuosas y alcohólicas de frutos maduros y arrope elaborado artesanalmente con y sin el agregado de azúcar y arrope comercial. Resultados: Se demostró que los frutos maduros de chañar contienen compuestos fenólicos (6,09 mg EAG/g) principalmente taninos condensados (419 mg PrCB/g). Los preparados de arrope con y sin el agregado de azúcar disminuyen notablemente el contenido de fenólicos y taninos probablemente por acción del calor. Tanto las extracciones acuosas como alcohólicas de frutos y de arrope presentaron actividad antioxidante con valores de CD50 frente a DPPH entre 18 y 48 µg EAG/ml para las preparaciones alcoholicas y entre 50 y 246 µg EAG/ml para las extracciones acuosas. Mayor actividad antioxidante fue demostrada frente al radical ABTS con valores de CD50 entre 7 y 18 µg EAG/ml para las preparaciones acuosas y entre 2 y 12 µg EAG/ml para las preparaciones alcohólicas. Conclusión: Los resultados obtenidos contribuyen a la formulación de bases de datos nutricionales nacionales e internacionales. A su vez la determinación de las actividades biológicas de estos frutos considerados exóticos, favorecen la promoción de su consumo y producción a mayor escala por parte de la industria local, lográndose de esta manera, la diversificación de los usos de los frutos regionales y sus derivados dando mayor valor agregado a los mismos.

Evaluación del efecto genotóxico-antigenotóxico de frutos de 8 especies del género Solanum Arenas Espinoza, J. F.; Zampini, Iris Catiana; Isla, Maria Ines Introducción: El cáncer se ha convertido en una de las primeras causas de muerte en el mundo. Algunas sustancias presentes en las plantas podrían servir para proteger al ADN del daño producido por compuestos mutagénicos que actúan como iniciadores del proceso de carcinogénesis. Se ha demostrado que muchos compuestos presentes en plantas medicinales o alimenticias poseen actividad antimutagénica y anticarcinogénica. El objetivo del presente trabajo fue evaluar en un modelo de laboratorio in vitro la capacidad mutagénica/antimutagénica de frutos de ocho especies del género Solanum que crecen en Tucumán. Materiales y Métodos: Se prepararon extractos acuosos de ocho especies del género Solanum (S. abutiloides, S. argentinum, S. claviceps, S. consimile, S. chaetophorum, S. lorentzii, S. riparium y S. tucumanense). Se evaluó el potencial mutagénico y antimutagénico de los extractos mediante el Test de Ames sobre dos cepas de Salmonella typhimurium, TA98 y TA100. Como agente xenobiótico se utilizó 4-nitro-O-fenilendiamina (NPD). Resultados: Ningún fruto mostró efecto mutagénico en las concentraciones ensayadas. S. claviceps y S. chaetophorum, manifestaron un efecto antimutagénico frente al xenobiótico de entre 30 y 40%, respecto al control positivo. En trabajos previos demostramos que estas dos especies fueron las más activas como antioxidantes, lo que estaría relacionado con el efecto observado. S. consimile y S. tucumanense junto al xenobiótico produjeron un aumento en el número de revertantes/placa, es decir que podrían potenciar el efecto mutagénico de NPD. Los otros extractos no fueron capaces de inhibir el efecto mutagénico aún a la más alta concentración ensayada. Conclusiones: Los resultados de este trabajo demuestran que los frutos de dos de las especies estudiadas podrían proteger al ADN del daño producido por mutágenos y resulta interesante profundizar en el estudio de los mismos.

Disminución del área foliar de cebolla (Allium cepa L.) var. Valcatorce INTA y su efecto sobre el rendimiento Orioli, Gustavo Adolfo; Siliquini, O. A. La relación entre el área foliar (AF) y el rendimiento biológico o el económico (Re) de una planta aumenta hasta llegar a un óptimo. Por su parte la relación entre el índice de área foliar (IAF) y el Re es específica y llega a un máximo que se mantiene para densidades de plantas entre un valor mínimo y uno máximo, fuera de los cuales el Re disminuye. El desarrollo del AF sigue una curva sigmoidea cuyo valor máximo dependerá del medio ambiente y la densidad del cultivo, valor que puede disminuir a causa de patologías, herbivoría o contingencias climáticas como el granizo. A los efectos de determinar como la intensidad y la etapa de desarrollo en que se produce la disminución afectan el Re, las plantas de un cultivo de cebolla cultivada bajo riego, fertilización y a una densidad de 500.000 plantas·ha-1, fueron sometidas a defoliaciones de 20, 40 o 60 % del control en tres etapas de desarrollo: comienzo de bulbificación y 30 y 45 días después. Los resultados muestran que defoliaciones del 40 y 60 % en bulbificación y del 60 % a los 30 y 45 días después redujeron significativamente el peso del bulbo. En los otros tratamientos el ritmo de recuperación del AF entre la época de defoliación y la entrega fue tal que el AF llegó a valores que no difirieron significativamente del control. Como consecuencia de ello el peso del bulbo y porcentaje de bulbos medianos también fueron similares al control.

Effects of Abiotic Factors on the Geographic Distribution of Body Size Variation and Chromosomal Polymorphisms in Two Neotropical Grasshopper Species ( Dichroplus : Melanoplinae: Acrididae) Bidau, Claudio Juan; Miño, Carolina Isabel; Castillo, Elio Rodrigo Daniel; Marti, Dardo Andrea We review the effects of abiotic factors on body size in two grasshopper species with large geographical distributions: Dichroplus pratensis and D. vittatus, inhabiting Argentina in diverse natural habitats. Geographical spans for both species provide an opportunity to study the effects of changes in abiotic factors on body size. The analyses of body size distribution in both species revealed a converse Bergmannian pattern: body size is positively correlated with latitude, altitude, and seasonality that influences time available for development and growth. Allen?s rule is also inverted. Morphological variability increases towards the ends of the Bergmannian clines and, in D. pratensis, is related with a central-marginal distribution of chromosomal variants that influence recombination. The converse Bergmannian patterns influence sexual size dimorphism in both species but in different fashions. Body size variation at a microspatial scale in D. pratensis is extremely sensitive to microclimatic clines. We finally compare our results with those for other Orthopteran species.

Influencia freática en maíz : interacciones con la fecha de siembra y las condiciones hídricas Florio, Eva Laura; Nosetto, Marcelo Daniel En gran parte de la Región Pampeana la napa suele encontrarse cercana a la superficie afectando la productividad de los cultivos. Esos efectos dependen en especial de la profundidad de la napa y de las características meteorológicas de la campaña. En este trabajo evaluamos la influencia de la profundidad de napa sobre el rendimiento y la radiación interceptada en lotes de maíz de siembra temprana y tardía y su interacción con las condiciones hídricas del ciclo. Para esto analizamos la relación entre profundidad de napa y rendimiento (n = 35) en 13 lotes ubicados al sur de Córdoba durante 7 campañas (2004-2011). Además, se utilizó el índice EVI del sensor MODIS como indicador de la radiación interceptada por el cultivo. Se observó que las áreas con napa entre 1,5-2,5 m de profundidad tuvieron rendimientos máximos (11 t/ha), no siendo afectados por la fecha de siembra ni las condiciones hídricas de la campaña. Con napas más profundas se registró una caída en el rendimiento que fue significativamente superior en maíces tempranos en campañas secas (3, 7 t/m de descenso de napa). Con napas por debajo de 4, 2 m los rendimientos se estabilizaron en 1, 8 t/ha en maíces tempranos en campañas secas y en 6, 5 t/ha en maíces tempranos de campañas húmedas y en tardíos. En maíces tardíos de campañas secas y húmedas se observaron valores significativamente menores de EVI en situaciones de napa profunda (EVI = 0,42) en comparación con áreas de napa más superficial (EVI = 0,46). Por otro lado, dentro de los maíces tempranos, las campañas húmedas presentaron mayores valores de EVI que las campañas secas (0,43 vs. 0,40), independientemente de la posición de la napa freática. Este estudio devela nuevos aspectos sobre la influencia freática sobre el maíz y aporta nuevas herramientas para un manejo más eficiente del cultivo y de los recursos hídricos.