Interacción Rhizobium leguminosarum bv trifolii y hongos micorrícicos en un Andisol con diferentes niveles de saturación de aluminio

Aluminium phytotoxicity is a serious limitation of the productivity of prairies growing on volcanic soil by affecting nodulation and effectiveness of Rhizobium. The aim of this study was to select Rhizobium strains to determine the effect as inoculant on Trifolium repens cropped in an Andisol with different aluminium saturation levels. Acidity tolerance (pH 4.5 and 6.0) of twelve Rhizobium strains of collection at three Al levels (100, 200, 300 μM) was evaluated in mineral nutritive medium vitro. Simultaneously, in a greenhouse trial, strains effectivity were tested by inoculation of Trifolium pratense growing in an acidic Andisol and compared with dry matter accumulation produced by native strains. According to the results of this two trials, three Rhizobium strains (R-109, R-113 and R-115) were selected to study the effect of their inoculation on Trifolium repens growth cropped in an Andisol at four Al saturation levels (SAl1 to SAl4). In addition, the effect on arbuscular mycorrhizal propagules was also studied. Plants showed different capacity for association with the inoculated strains giving the best response R-113 at SAl1 level with positive synergism expressed by microbiological parameters such as high nodulation (16 nodules pot-1), AMF spore number (384 spores 100 g-1), root colonization percentage (45%), together with agronomical variables with an increase of aerial phytomass (93,5%) in comparison with the control. Higher Al levels had an deleterious effect on the inoculation of collection strains; therefore, with R-109 strain inoculation the smallest root growth and nodulation were observed in comparison with soil with native strains whereas R-113 was the more effective one.La fitotoxicidad por Al es una seria limitante de la productividad de praderas crecidas sobre suelos volcánicos afectando la nodulación y efectividad de los Rhizobium. El objetivo del estudio consistió en seleccionar cepas de Rhizobium de colección para estudiar su efectividad en Trifolium repens crecido en un Andisol con cepas nativas y distinta saturación de Al. Para ello se evaluó previamente en caldo nutritivo la tolerancia a la acidez y toxicidad por Al de 12 cepas de colección mediante control de curvas de crecimiento. Paralelamente, se inocularon los Rhizobium en un Andisol para evaluar su efectividad mediante rendimiento de Trifolium pratense. Se seleccionaron las cepas R-109, R-113 y R-115 para inocularlas en el Andisol utilizando cuatro tratamientos: suelo adicionado de 2 Mg CaCO3 ha-1 (SAl1), un testigo (SAl2) y suelo adicionado de dos niveles de saturación Al (SAl1, SAl4) utilizando Trifolium repens como hospedero. Las plantas mostraron capacidad para asociarse con las especies inoculadas presentando mayor efectividad R-113-SAl1 sinergismo positivo expresado en variables microbiológicas como nodulación (16 nódulos maceta-1), esporas de hongos micorrícicos arbusculares, HMA (384 esporas 100g-1), colonización HMA (45%) junto con variables agronómicas alcanzándose un incremento de biomasa foliar (93,5%) frente al testigo. Niveles más elevados de Al afectaron la inoculación con cepas de colección; así, con R-109 se obtuvo el menor crecimiento radical y nodulación respecto al suelo natural mientras que R-113 fue la cepa más efectiva

Hyperfine Structure of S-States in Muonic Helium Ion

Corrections of orders alpha^5 and alpha^6 are calculated in the hyperfine splittings of 1S and 2S - energy levels in the ion of muonic helium. The electron vacuum polarization effects, the nuclear structure corrections and recoil corrections are taken into account. The obtained numerical values of the hyperfine splittings -1334.56 meV (1S state), -166.62 meV (2S state) can be considered as a reliable estimate for the comparison with the future experimental data. The hyperfine splitting interval Delta_{12}=(8 Delta E^{hfs}(2S)- Delta E^{hfs}(1S)) = 1.64 meV can be used for the check of quantum electrodynamics.Comment: 14 pages, 5 figure

Efecto de cultivos hospederos y no hospederos sobre propágulos micorrícicos arbusculares

Recent field studies have shown that fungal spores decrease when non host plants are used as a pre-culture. The objective of this study was to evaluate how host plant like oats (Avena sativa L.), and non host, as lupine (Lupinus albus L.), and rapeseed (Brassica napus L.) can influence on arbuscular mycorrhizal fungi (AMF) propagules diversity and phosphatase activity when growing in an Andisol and an Inceptisol. The trial was conducted from September 2006 through March 2007 in greenhouse conditions using 5 kg pots with in a completely randomized design with four replicates. The number of AMF spores was higher in the Andisol than the Inceptisol and highest when using oats than lupine or raps as plant host. Oats also showed a large enrichment of morphotypes, whereas lupine and raps were poor. The phosphatase activity (P-ase) in Inceptisol was lower than in Andisol and between crops increased in the order oats < rapeseed < lupine; while significant differences between lupines with other crops were registred. Again, our results reinforce the hypothesis that the mycorrhizae and phosphatase activity are complementary mechanisms developed by plants for a better P acquisition.Estudios recientes en campo han demostrado que las esporas fúngicas disminuyen cuando se utilizan como pre-cultivo no hospederos. El objetivo de este trabajo fue estudiar la influencia de un cultivo hospedero, avena (Avena sativa L.) y cultivos no hospederos, como lupino (Lupinus albus L.) y raps (Brassica napus L.) sobre los propágulos de hongos micorrícicos arbusculares (HMA) y diversidad fúngica junto con la actividad fosfatásica en un Andisol serie Temuco e Inceptisol serie Lumaco. El ensayo se realizó en condiciones de invernadero, desde septiembre de 2006 hasta marzo de 2007, utilizándose macetas de 5 kg con un diseño experimental completamente al azar con cuatro repeticiones. El número de esporas HMA fue mayor en el Andisol que en el Inceptisol y mayor cuando se usó avena como planta hospedera que lupino y raps. La avena también mostró una gran riqueza de morfotipos mientras que, en lupino y raps fue baja. La actividad fosfatásica en el Inceptisol fue menor que en el Andisol y entre cultivos aumentó en orden avena < raps < lupino; mientras que, se encontraron diferencias significativas entre lupino con los otros cultivos. Nuevamente, nuestros resultados refuerzan la hipótesis que las micorrizas y actividad fosfatásica son mecanismos complementarios que utiliza la planta para una mejor captación de fósfor

Dimuon production by laser-wakefield accelerated electrons

We analyze $\mu^+\mu^-$ pair production generated by high-energy electrons emerging from a laser-wakefield accelerator. The $\mu^+\mu^-$ pairs are created in a solid thick high-$Z$ target, following the electron accelerating plasma region. Numerical estimates are presented for electron beams obtained presently in the LBL TW laser experiment \cite{C2} and possible future developments. Reactions induced by the secondary bremsstrahlung photons dominate the dimuon production. According to our estimates, a 20 pC electron bunch with energy of 1 (10) GeV may create about 200 (6000) muon pairs. The produced $\mu^\pm$ can be used in studying various aspects of muon-related physics in table top installations. This may be considered as an important step towards the investigation of more complicated elementary processes induced by laser driven electrons.Comment: 14 pages, 5 figure

Ionization Potential of the Helium Atom

Ground state ionization potential of the He^4 atom is evaluated to be 5 945 204 221 (42) MHz. Along with lower order contributions, this result includes all effects of the relative orders alpha^4, alpha^3*m_e/m_alpha and alpha^5*ln^2(alpha).Comment: 4 page

Efecto de los hongos micorrícicos arbusculares en un cultivo ecológico de ají (Capsicum annuum L.) cacho de cabra

Mapuche farmers in southern Chile have been cultivating local ecotypes of chili pepper (Capsicum annuum L.), called locally "Cacho de cabra", for many decades. It is used to make "merkén", a condiment that is consumed locally and exported. This vegetable requires a nursery stage and can obtain nutritional benefits from symbiotic associations such as mycorrhizal fungi, achieving a better adaptation to transplanting. Arbuscular mycorrhizal fungi (AMF) are obligate biotrophes appearing in abundance in agroecosystems with conservation management. The aim of this study was to compare effectiveness of two AMF, a commercial mycorrhizal inoculant (IC, Glomus intraradices) and another native (IN, Glomus claroideum) with a control without inoculation (-I) on the production and quality of "Cacho de cabra". At 45 days after sowing (DAS) transplanting was carried out and at 90 and 216 DAS fruit quality, fungal and edaphic parameters were evaluated. The harvest was at four stages. With IN inoculation plants and with greater foliar area were obtained. Also, precocity of fruit production was observed. The harvest started 49 days earlier and fresh weight was 177% higher than that of the control. Root colonization was low, showing significant differences between IN and IC, while a large number of spores was produced in the substrate. It was concluded that inoculation with native fungi decreased transplanting stress thus accelerating the maturation stage of plants and resulting in higher and better yield quality

Hadronic Vacuum Polarization and the Lamb Shift

Recent improvements in the determination of the running of the fine-structure constant also allow an update of the hadronic vacuum-polarization contribution to the Lamb shift. We find a shift of -3.40(7) kHz to the 1S level of hydrogen. We also comment on the contribution of this effect to the determination by elastic electron scattering of the r.m.s. radii of nuclei.Comment: 7 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty require