El comportamiento de las semillas de Sorghum halepense (L.) Pers. en relación con la población de rizomas

p.227-231Se estudió el comportamiento de las semillas de sorgo de Alepo caídas naturalmente en un área que previamente había sido cultivada con trigo y que poseía alta infestación de dicha maleza, con el objeto de investigar una posible inhibición de germinación por acción de los rizomas existentes en el suelo. Los resultados indican que no hay una relación de tendencia definida, entre la germinación de las semillas y el peso seco de rizomas presentes en el perfil del suelo. Lo mismo vale para la mortandad de las semillas, aunque este carácter muestra una tendencia creciente con el aumento del peso seco de rizomas en el suelo. De la información aquí presentada no se concluye la existencia de algún mecanismo de inhibición que pudiera asociarse a una táctica particular, dentro de las estrategias reproductivas de esta especie. Para las condiciones del estudio efectuado, es probable que la competencia por nutrientes, luz, etc., sea la que regula el establecimiento de plántulas de sorgo de Alepo en la comunidad vegetal. Sin embargo, el efecto de los rizomas sobre la germinación de las semillas podría adquirir importancia en casos en que la biomasa de rizomas fuera muy elevada (más de 4 g-1.700 g de suelo), siendo ésta una situación poco frecuente en los campos de cultivo estudiados

Genetic diversity of terricolous Peltigera cyanolichen communities in different conservation states of native forest from southern Chile

Decreasing quality of forest habitats is among the major factors leading to a loss of epiphytic lichen diversity. However, there is little information about how this factor influences the diversity of terricolous lichens, which do not grow over living trees and could be less susceptible to such disturbances. In this work we describe the genetic diversity of Peltigera terricolous cyanolichens and their cyanobiont (Nostoc) from three habitats at the Karukinka Natural Park (Tierra del Fuego, southern Chile), which represent different conservation states: native mature-forest (low disturbance intensity), native youngforest (medium disturbance intensity) and grassland (high disturbance intensity). In both forest contexts, a higher diversity and a higher number of unique OTUs (operational taxonomic units) were found. In contrast, in the grassland, the diversity was lower and the Peltigera species were mostly cosmopolitan. The presence of unique OTUs and the higher diversity of lichens in native forest areas highlight the importance of their preservation, indicating that decreasing forest quality also has a negative impact on terricolous lichens diversity. [Int Microbiol 2013; 16(4):243-252]Keywords: Peltigera · Nostoc · lichens · genetic diversity · Karukinka Natural Park · southern Chil

Growth and development patterns of two sweet potato (Ipomoea batatas L.) cultivares in Alajuela

Los análisis de crecimiento son básicos para fundamentar las diferentes prácticas agronómicas en un cultivar. En el presente trabajo se determinó el patrón de crecimiento y desarrollo de los cultivares de camote C-79 y C-82. El crecimiento de camote expresado como peso seco total, se dividió en dos partes: a) de la siembra hasta la máxima biomesa aérea; en esta fase el cv. C-82 a pesar de tener un bajo desarrollo aéreo presentó el mayor desarrollo radical, mientras tanto en el cv. C-79 se dió lo inverso. b) de la máxima biomasa aérea a la cosecha; al cesar el crecimiento de la parte aérea en el C-79 se logra el mayor índice de tuberización, mientras que en el C-82 este proceso se ve disminuido. En el cv. C-79 el follaje, principalmente los tallos, al inicio actúan como un sumidero de asimilados que luego son translocados, mientras que en el C-82 la parte aérea es más eficiente para producir y translocar carbohidratos hacia las raíces tuberosas desde el principio y cuando ésta desciende baja también la capacidad de tuberización. La mayor eficiencia del cv. C-82 se expresa también en la mayor área foliar, razón de área foliar, razón de peso radical y en las relaciones de peso más equilibradas entre hojas-parte aérea y raíces-parte aérea.Growth studies are basic to implement the different agronomic practices of any particular crop. In this work, growth and development patterns of the sweet potato cultivars C-79 and C-82 were determined. The sweet potato growth expressed as total dry weight was divided as follows: a) from planting to maximum aerial biomass, on this stage cv. C-82, although having a low aerial development had the highest root debelopment, while C-79 had a reverse pattern. b) from maximum aerial biomass to harvest, on C-79 the highest tuberization ratio was accomplished when the vegetative growth declined, while on C-82 this ratio declined during this stage. On C-79 foliage, mainly the stems, act as temporary carbohydrates sink, whereas on C-82 the aerial portion is more efficient in producing and translocating carbohydrates to the tuberous roots. The higher efficiency of the cv. C-82 is also evident on the higher leaf area, leaf-area ratio, root weight ratio and the better balanced leafaerial portion and root-aerial parts relationships.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM

Influenced but not determined by historical events: genetic, demographic and morphological differentiation in Heleobia ascotanensis from the Chilean Altiplano

In the present study, we focus on the phylogeographic pattern, demographic history and morphological differentiation of Heleobia ascotanensis, a freshwater gastropod restricted to the Ascotán saltpan in the Chilean Altiplano. The current distribution of the species is limited to twelve isolated or partially isolated springs that were affected by transitions between humid and arid periods during last glaciations. The genetic analysis of 322 specimens showed that H. ascotanensis is subdivided into three genetically divergent populations, with low and moderate degrees of historical gene flow among them and incipient morphological differentiation as a consequence of genetic and geographical isolation. Molecular analyses revealed different demographic histories among populations which seem to respond independently to climatic events, probably due to an environmental imposition and idiosyncratic strategies developed to cope with water availability. The results of this study and co-distributed taxa support the hypothesis that contemporary and historical events have influenced microevolutionary differentiation of these snails, although there is a need to complement further information to predict genetic or morphological divergence at microgeographic scale

Two-Dimensional Time-Domain Antenna Arrays for Optimum Steerable Energy Pattern with Low Side Lobes

This document presents the synthesis of different two-dimensional time-domain antenna arrays for steerable energy patterns with side lobe levels. The research is focused on the uniform and nonuniform distributions of true-time exciting delays and positions of antenna elements. The uniform square array, random array, uniform concentric ring array, and rotated nonuniform concentric ring array geometries are particularly studied. These geometries are synthesized by using the well-known sequential quadratic programming. The synthesis regards the optimal true-time exciting delays and optimal positions of pulsed antenna elements. The results show the capabilities of the different antenna arrays to steer the beam in their energy pattern in time domain and how their performance is in frequency domain after the synthesis in time domain

The influence of binarity on dust obscuration events in the planetary nebula M 2-29 and its analogues

The central star of the planetary nebula (CSPN) M 2-29 shows an extraordinary R Coronae Borealis-like fading event in its optical lightcurve. The only other CSPN to show these events are CPD-568032 (Hen 3-1333) and V651 Mon (NGC 2346). Dust cloud formation in the line of sight appears responsible but the exact triggering mechanism is not well understood. Understanding how planetary nebulae (PNe) trigger dust obscuration events may help understand the same process in a wide range of objects including Population-I WC9 stars, symbiotic stars and perhaps Asymptotic Giant Branch (AGB) stars with long secondary periods (LSPs). A binary scenario involving an eccentric, wide companion that triggers dust formation via interaction at periastron is a potential explanation that has been suggested for LSP variables. Model fits to the lightcurves of CPD-568032 and M 2-29 show the dust forms in excess of 70 AU at the inner edge of a dust disk. In the case of CPD-568032 this radius is far too large to coincide with a binary companion trigger, although a binary may have been responsible for the formation of the dust disk. We find no direct evidence to support previous claims of binarity in M 2-29 either from the OGLE lightcurve or deep medium-resolution VLT FLAMES spectroscopy of the CSPN. We classify the CSPN as Of(H) with T_eff=50+-10 kK and log g=4.0+-0.3. We find a mean distance of 7.4+-1.8 kpc to M 2-29 at which the M_V=-0.9 mag CSPN could potentially hide a subgiant luminosity or fainter companion. A companion would help explain the multiple similarities with D'-type symbiotic stars whose outer nebulae are thought to be bona-fide PNe. The 7.4 kpc distance, oxygen abundance of 8.3 dex and Galactic coordinates (l=4.0, b=-3.0) prove that M 2-29 is a Galactic Bulge PN and not a Halo PN as commonly misconceived.Comment: 15 pages, 14 figures, 7 tables. Accepted for publication in A\&

Soft–bottom sipunculans from San Pedro del Pinatar (Western Mediterranean): influence of anthropogenic impacts and sediment characteristics on their distribution

We analysed the distribution of soft bottom sipunculans from San Pedro del Pinatar (Western Mediterranean). This study was carried out from December 2005 to June 2010, sampling with biannual periodicity (June and December). Physical and chemical parameters of the sediment were analysed (granulometry, organic matter content, pH, bottom salinity and shelter availability). Nine different species and subspecies were identified, belonging to five families. Aspidosiphon muelleri muelleri was the dominant species, accumulating 89.06% of the total abundance of sipunculans. Higher sipunculan abundances were correlated with stations of higher percentage of coarse sand, empty mollusc shells and empty tubes of the serpulid polychaete Ditrupa arietina, where some of the recorded species live. Sediment characteristics played the main role controlling the sipunculans distribution. Anthropogenic impacts could be indirectly affecting their distribution, changing the sediment characteristics. Key words: Sipuncula, Aspidosiphon muelleri, Mediterranean, Anthropogenic impact, Soft–bottom.Se analizó la distribución de los sipuncúlidos de fondos blandos de San Pedro del Pinatar (Mediterráneo occidental). Este estudio se llevó a cabo entre diciembre de 2005 y junio de 2010, muestreando con periodicidad semestral (junio y diciembre). Se analizaron parámetros físicos y químicos del sedimento (granulometría, contenido de materia orgánica, pH, salinidad de fondo y disponibilidad de refugio). Nueve especies y subespecies diferentes fueron identificadas, pertenecientes a cinco familias. Aspidosiphon muelleri muelleri fue la especie dominante, acumulando el 89,06% de la abundancia total de sipuncúlidos. Las mayores abundancias de sipuncúlidos se correlacionaron con las estaciones con mayores porcentajes de arena gruesa, conchas de moluscos vacías y tubos vacíos del poliqueto serpúlido Ditrupa arietina, donde viven algunas de las especies registradas. Las características del sedimento jugaron el papel principal en el control de la distribución de sipuncúlidos. Los impactos antropogénicos podrían estar afectando indirectamente su distribución, cambiando las características del sedimento. Palabras clave: Sipuncúlidos, Aspidosiphon muelleri, Mediterráneo, Impacto antropogénico, Fondos blandos.We analysed the distribution of soft bottom sipunculans from San Pedro del Pinatar (Western Mediterranean). This study was carried out from December 2005 to June 2010, sampling with biannual periodicity (June and December). Physical and chemical parameters of the sediment were analysed (granulometry, organic matter content, pH, bottom salinity and shelter availability). Nine different species and subspecies were identified, belonging to five families. Aspidosiphon muelleri muelleri was the dominant species, accumulating 89.06% of the total abundance of sipunculans. Higher sipunculan abundances were correlated with stations of higher percentage of coarse sand, empty mollusc shells and empty tubes of the serpulid polychaete Ditrupa arietina, where some of the recorded species live. Sediment characteristics played the main role controlling the sipunculans distribution. Anthropogenic impacts could be indirectly affecting their distribution, changing the sediment characteristics. Key words: Sipuncula, Aspidosiphon muelleri, Mediterranean, Anthropogenic impact, Soft–bottom