Atributos fisiológicos de Brachiaria SPP: en la adaptación a suelos inundados

Como consecuencia del calentamiento global, en algunas regiones del mundo se prevén aumentos en las precipitaciones. Los pastos de Brachiaria son los forrajes tropicales mas sembrados para la producción de ganado, estos pastos continuamente experimentan condiciones de inundación durante las épocas lluviosas. La inundación del suelo reduce la disponibilidad de oxígeno para la planta y afecta su desarrollo radical, su crecimiento y su metabolismo. En este trabajo evaluamos las diferentes respuestas morfológicas y fisiológicas de la planta entera que presentan en el cultivar sensible Ruzi (Brachiaria ruziziensis Germ) y el tolerante Tully (Brachiaria humidicola (Rendle) Schwickerdt) después de ser sometidas 15 días a condiciones de inundación. El tratamiento control equivale al 80% de la capacidad de campo. El tratamiento de inundación reduce la clorofila (SPAD) y la eficiencia fotosintética (fv’/fm’) en B. ruziziensis pero no en B. humidicola. Cuando el tratamiento de inundación fue combinado con baja fertilidad, B. ruziziensis reduce su biomasa aérea en mayor proporción que su contenido de clorofila y su eficiencia fotosintética. Los contenidos de antocianinas y malondialdehido aumentaron cuando las plantas estuvieron sometidas a inundación, pero solo fue significativo en B. humidicola. En los contenidos de carotenoides y clorofilas totales no se observaron cambios significativos entre los tratamientos inundación y control. En B. humidicola, las antocianinas se depositan en la epidermis foliar, posiblemente sirviendo como mecanismo de fotoprotección. El principal cambio morfológico en condiciones de inundación es la formación de aerénquima. La longitud radical total disminuye cuando las plantas están sometidas a inundación, en contraste el diámetro promedio de las raíces no varía significativamente. El porcentaje de aerénquima aumenta considerablemente cuando las plantas se someten a inundación. Encontramos que la formación de aerénquima en B. humidicola es un rasgo constitutivo (expresado en control e inundación), mientras que en B. ruziziensis es un rasgo inducible. Adicionalmente a la formación de aerénquima, B. humidicola presenta deposición de suberina en las partes externas de la raíz (OPR por sus siglas en inglés) formando bandas tangenciales cubriendo alrededor de 80% de las células. Por otra parte, en B. ruziziensis solo se observan deposiciones parciales de suberina en la OPR (50%). Nuestros resultados indican que el gran nivel de tolerancia a inundación exhibido por B. humidicola es asociado con incrementos en la formación de aerénquima en la raíz, aumentos en las deposiciones de suberina en la OPR y a la inducción de mecanismos de fotoprotección en hojas.Abstract. Due to climate change, it is expected that total rainfall will increase in some regions around the world. Brachiaria grasses are the most widely sown tropical forages for livestock production and these grasses experience waterlogged conditions during the rainy season. Waterlogging conditions in soil reduce the availability of oxygen and affects root development, plant growth and metabolism. We evaluated the differences in root and shoot morphological and physiological responses of waterlogging-sensitive ruzigrass (Brachiaria ruziziensis Germ) and waterlogging-tolerant korniviagrass (Brachiaria humidicola (Rendle) Schwickerdt) that were subjected to waterlogged conditions for 15 days. We used a control treatment with 80% of field capacity for comparison. Waterlogging treatment reduced the chlorophyll content (SPAD) and the photosynthetic efficiency (fv’/fm’) in waterlogging-sensitive B. ruziziensis but not in waterlogging-tolerant B. humidicola. When waterlogging stress was combined with low soil fertility stress, B. ruziziensis reduced its shoot biomass production more markedly than its leaf chlorophyll content and photosynthetic efficiency. The contents of anthocyanins and maldialdehyde increased when the plants were under waterlogging but this increase was significant in B. humidicola. No significant differences were observed in the content of carotenoids or total chlorophyll between waterlogging and control treatments. In B. humidicola, the anthocyanins were deposited in the leaf epidermal layer that could possibly serve as a photo-protection mechanisms. Waterlogging induced major changes in root morphological and anatomical characteristics. A major root morphological change that occurred under waterlogged conditions was the formation of aerenchyma. Total root length decreased when the plants were under waterlogged conditions. However, the root diameter did not vary significantly. The aerenchyma percentage increased considerably when the plants were subjected to waterlogging. We found that the aerenchyma formation in B. humidicola was a constitutive trait (expressed under both control and waterlogged conditions) while it was an inducible trait for B. ruziziensis. In addition to aerenchyma formation, B. humidicola also showed suberin deposition in the root exodermis, forming tangential bands covering nearly 80% of the cells. However, B. ruziziensis showed partial suberin deposition in cells. Our results indicate that the higher level of waterlogging tolerance exhibited by B. humidicola was associated with increase in root aerenchyma formation, increased suberin deposition root exodermis, and induction of photoprotection mechanisms in leaves.Maestrí

Post-Franco Theatre

In the multiple realms and layers that comprise the contemporary Spanish theatrical landscape, “crisis” would seem to be the word that most often lingers in the air, as though it were a common mantra, ready to roll off the tongue of so many theatre professionals with such enormous ease, and even enthusiasm, that one is prompted to wonder whether it might indeed be a miracle that the contemporary technological revolution – coupled with perpetual quandaries concerning public and private funding for the arts – had not by now brought an end to the evolution of the oldest of live arts, or, at the very least, an end to drama as we know it

The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l’Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

Root-zone hypoxia reduces growth of the tropical forage grass Urochloa humidicola in high-nutrient but not low-nutrient conditions

Abstract Background and Aims The perennial C4 grass Urochloa humidicola is widely planted on infertile acidic and waterlogging-prone soils of tropical America. Waterlogging results in soil anoxia, and O2 deficiency can reduce nutrient uptake by roots. Interestingly, both nutrient deficiencies and soil waterlogging can enhance root cortical cell senescence, and the increased gas-filled porosity facilitates internal aeration of roots. We tested the influence of nutrient supply and root-zone O2 on root traits, leaf nutrient concentrations and growth of U. humidicola. Methods Plants were grown in pots in a completely randomized design under aerated or stagnant deoxygenated hydroponic conditions and six nutrient regimes, with low to high concentrations of all essential elements, for 28 d in a controlled-temperature greenhouse. The standard acid solution (SAS) used was previously designed based on infertile acidic soils of the tropical America savannas, and step increases in the concentration of SAS were used in aerated or deoxygenated 0.1 % agar solution, which mimics changes in gas composition in waterlogged soils. Measurements included shoot and root growth, root porosity, root anatomy, radial O2 loss, and leaf tissue nutrient concentrations. Key Results Shoot dry mass was reduced for plants in stagnant compared with aerated conditions at high, but not at low, levels of mineral nutrition. In low-nutrition stagnant solution, roots were shorter, of greater porosity and had smaller radial thickness of the stele. Suberized lamellae and lignified sclerenchyma, as well as a strong barrier to radial O2 loss, were documented for roots from all treatments. Leaf nutrient concentrations of K, Mg and Ca (but not N, P and S) were higher in aerated than in stagnant conditions. Conclusions Under low-nutrient conditions, plant growth in stagnant solution was equal to that in aerated solution, whereas under higher-nutrient regimes growth increased but dry mass in stagnant solution was less than in aerated solution. Slow growth in low-nutrient conditions limited any further response to the low O2 treatment, and greater porosity and smaller stele size in roots would enhance internal O2 movement within roots in the nutrient-limited stagnant conditions. A constitutive barrier to radial O2 loss and aerenchyma facilitates O2 movement to the tips of roots, which presumably contributes to maintaining nutrient uptake and the tolerance of U. humidicola to low O2 in the root-zone

Salinity tolerance in chickpea is associated with the ability to ‘exclude’ Na from leaf mesophyll cells

Salinity tolerance is associated with Na ‘exclusion’ from, or ‘tissue tolerance’ in, leaves. We investigated whether two contrasting chickpea genotypes, salt-tolerant Genesis836 and salt-sensitive Rupali, differ in leaf tissue tolerance to NaCl. We used X-ray microanalysis to evaluate cellular Na, Cl, and K concentrations in various cell types within leaflets and also in secretory trichomes of the two chickpea genotypes in relation to photosynthesis in control and saline conditions. TEM was used to assess the effects of salinity on the ultrastructure of chloroplasts. Genesis836 maintained net photosynthetic rates (A) for the 21 d of salinity treatment (60 mM NaCl), whereas A in Rupali substantially decreased after 11 d. Leaflet tissue [Na] was low in Genesis836 but had increased markedly in Rupali. In Genesis836, Na was accumulated in epidermal cells but was low in mesophyll cells, whereas in Rupali cellular [Na] was high in both cell types. The excessive accumulation of Na in mesophyll cells of Rupali corresponded to structural damage to the chloroplasts. Maintenance of photosynthesis and thus salinity tolerance in Genesis836 was associated with an ability to ‘exclude’ Na from leaflets and in particular from the photosynthetically active mesophyll cells, and to compartmentalize Na in epidermal cells

Influence of soil fertility on waterlogging tolerance of two Brachiaria grasses = Influencia de la fertilidad del suelo en la tolerancia a inundación en dos pastos de Brachiaria

As a consequence of global warming, rainfall is expected to increase in several regions around the world. This, together with poor soil drainage, will result in waterlogged soil conditions. Brachiaria grasses are widely sown in the tropics and, these grasses confront seasonal waterlogged conditions. Several studies have indicated that an increase in nutrient availability could reduce the negative impact of waterlogging. Therefore, an outdoor study was conducted to evaluate the responses of two Brachiaria sp. grasses with contrasting tolerances to waterlogging, B. ruziziensis (sensitive) and B. humidicola (tolerant), with two soil fertility levels. The genotypes were grown with two different soil fertilization levels (high and low) and under well-drained or waterlogged soil conditions for 15 days. The biomass production, chlorophyll content, photosynthetic efficiency, and macro- (N, P, K, Ca, Mg and S) and micronutrient (Fe, Mn, Cu, Zn and B) contents in the shoot tissue were determined. Significant differences in the nutrient content of the genotypes and treatments were found. An increase of redoximorphic elements (Fe and Mn) in the soil solution occurred with the waterlogging. The greater tolerance of B. humidicola to waterlogged conditions might be due to an efficient root system that is able to acquire nutrients (N, P, K) and potentially exclude phytotoxic elements (Fe and Mn) under waterlogged conditions.  A high nutrient availability in the waterlogged soils did not result in an improved tolerance for B. ruziziensis. The greater growth impairment seen in the B. ruziziensis with high soil fertility and waterlogging (as opposed to low soil fertility and waterlogging) was possibly due to an increased concentration of redoximorphic elements under these conditions