31 research outputs found
A New Extrafloral Nectary-Bearing Plant Species in the Brazilian Savanna and its Associated Ant Community: Nectary Structure, Nectar Production and Ecological Interactions
Brazilian Savanna stands out for the large number of species with extrafloral nectaries (EFNs) with high morphological diversity. In Smilax polyantha (Smilacaceae), the base of the petiole showed a slight secretion and great visitation by ants suggesting the presence of an EFN. In this way, we aimed to determine the ant community associated with this plant, as well as to identify and characterize this unsuspected structure and determine the phenology and liquid production of this tissue. The study was carried out in a Cerrado area, in UberlĂąndia, Brazil. Ten individuals were used for the anatomical analysis and histochemical tests and the EFNs secretory activity was monitored, being categorized into active and non-active EFN. In addition, the volume and sucrose concentration were determined from three nectaries of ten individuals, and individuals of ants found foraging on these nectary were collected, day and night. Results showed a large amount of extrafloral nectar secretion and the EFN tissue is composed of a few cell layers that showed positive reactions for proteins and reducing sugars. We recorded a significantly correlation between percentage of EFNs activity and abundance of ants. The secretory activity is concentrated in September and ten ant species, of five subfamilies, were identified foraging on the EFNs
Negative effects of ant-plant interaction on pollination: costs of a mutualism
The mutualism of ants and extrafloral nectary (EFN)-bearing plants is known to reduce rates of herbivory. However, ants may have negative impacts on other mutualisms such as pollination, constituting an indirect cost of a facultative mutualism. For instance, when foraging on or close to reproductive plant parts ants might attack pollinators or inhibit their visits. We tested the hypothesis that ants on EFN-bearing plants may negatively influence pollinator behavior, ultimately reducing plant fitness (fruit set). The study was done in a reserve at Brazilian savannah using the EFN-bearing plant Banisteriopsis malifolia (Malpighiaceae). The experimental manipulation was carried out with four groups: control (free visitation of ants), without ants (ant-free branches), artificial ants (isolated branches with artificial ants on flowers) and plastic circles (isolated branches with plastic circles on flowers). We made observations on flower visitors and their interactions, and measured fruit formation as a proxy for plant fitness. Our results showed that pollinators hesitated to visit flowers with artificial ants, negatively affecting pollination, but did not hesitate to visit flowers with plastic circles, suggesting that they recognize the specific morphology of the ants. Pollinators spent more time per flower on the ant-free branches, and the fruiting rate was lower in the group with artificial ants. Our results confirm an indirect cost in this facultative mutualism, where the balance between these negative and positive effects of ants on EFN-bearing plants are not well known
Trabalho, terra e geração de renda em trĂȘs dĂ©cadas de reflorestamentos no alto Jequitinhonha.
A partir dos anos 1970, as chapadas do Alto Jequitinhonha, localizadas no nordeste de Minas Gerais, atĂ© entĂŁo ĂĄreas de uso comum de agricultores familiares, foram plantadas com eucaliptos. O objetivo deste artigo Ă© comparar os efeitos do reflorestamento sobre a estrutura fundiĂĄria, valor da produção agrĂcola e ocupação rural com os efeitos da produção agrĂcola familiar sobre essas mesmas variĂĄveis na microrregiĂŁo homogĂȘnea de Capelinha, no Alto Jequitinhonha. Tal microrregiĂŁo foi escolhida para o estudo por ser a ĂĄrea de maior concentração de eucaliptais da regiĂŁo. Foram utilizados dados secundĂĄrios dos Censos do IBGE para os anos de 1970, 1980, 1985 e 1996, alĂ©m de dados secundĂĄrios de pesquisas realizadas sobre a regiĂŁo em questĂŁo, incluindo entrevistas com dirigentes de empresas e lideranças sindicais. O artigo conclui que, em trinta anos, o reflorestamento concentrou terras e criou um nĂșmero reduzido de empregos; a agricultura familiar, ao contrĂĄrio, teve suas ĂĄreas de terras comprimidas e super-exploradas em decorrĂȘncia da perda das chapadas, mas continuou sendo a principal responsĂĄvel pela geração de ocupaçÔes e rendas na regiĂŁo
AtRTD - a comprehensive reference transcript dataset resource for accurate quantification of transcript - specific expression in <i>Arabidopsis thaliana</i>
RNA-sequencing (RNA-seq) allows global gene expression analysis at the individual transcript level. Accurate quantification of transcript variants generated by alternative splicing (AS) remains a challenge. We have developed a comprehensive, nonredundant Arabidopsis reference transcript dataset (AtRTD) containing over 74 000 transcripts for use with algorithms to quantify AS transcript isoforms in RNA-seq. The AtRTD was formed by merging transcripts from TAIR10 and novel transcripts identified in an AS discovery project. We have estimated transcript abundance in RNA-seq data using the transcriptome-based alignment-free programmes Sailfish and Salmon and have validated quantification of splicing ratios from RNA-seq by high resolution reverse transcription polymerase chain reaction (HR RT-PCR). Good correlations between splicing ratios from RNA-seq and HR RT-PCR were obtained demonstrating the accuracy of abundances calculated for individual transcripts in RNA-seq. The AtRTD is a resource that will have immediate utility in analysing Arabidopsis RNA-seq data to quantify differential transcript abundance and expression.</p
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Applications of the hexanic fraction of Agave sisalana Perrine ex Engelm (Asparagaceae): control of inflammation and pain screening
Typology of Pure Deodar Forests Driven by VegetationâEnvironment Relations in Manoor Valley, Northwestern Himalaya
The current research was carried out to characterize the phytosociology of the forests of one of Pakistanâs most valuable tree species (Deodar) across its native range. In this context, our main hypothesis was that, along the altitudinal gradient, we would find different plant communities that would be driven by different environmental variables (climatic, edaphic, and physiographic). Therefore, to assess the vegetation structure of the pure Deodar forests of the unexplored Manoor Valley (Northwestern Himalaya), Pakistan, frequent field visits were carried out during different seasons of 2015â2018. Ecological methods: Line transects sampling (23 stands) and phytosociological attributes were evaluated in relation to geographical and environmental variables. Various statistical software applications (i.e., PCORD, RStudio 4.0, and R 3.6.1) were used to examine all of the gathered data of plant species and environmental variables. A total of three different plant communities (CedrusâIsodonâCynodon, CedrusâCynodonâDryopteris, and SambucusâCedrusâDesmodium) were identified by grouping 162 species and 23 stands in pure Deodar forests under the influence of geographic, slope, edaphic, and climatic variables, ranging from 1580.8 to 2373.8 m. The altitude (1936â2373 m), slope angle (25â85°), sandy (29â48%) and loamy soil texture, wind speed (1.45 msâ1), and temperature (25.8 °C) all had a strong influence on the SambucusâCedrusâDesmodium community. In contrast with this, the CedrusâCynodonâDryopteris community showed a positively significant relationship with the northeastern slope, silty (32â58%) and sandy (15.8â55%) loamy soil texture, and barometric pressure (814.3 pa). Nonetheless, the CedrusâIsodonâCynodon community revealed a significant positive association with the northeastern to southwestern slope, pH (6.3), wet bulb (19.7), and dew point (17.7). We found significant differences (p SambucusâCedrusâDesmodium community has the maximum number of plants (129 species), Shannonâs diversity (Hâ = 3.7), and Simpsonâs dominance (0.98) values among the recorded communities. The Pielouâs evenness index value was led by the CedrusâIsodonâCynodon community (0.97). Beta diversity showed a dissimilarity lower than 50% among the three communities. Simple term effects in the canonical correspondence analysis model revealed significant (p < 0.05) differences in altitude, slope angle, slope (southeastern), and wind speed variables. The present investigation sheds light on vegetation pattern and species contribution as a function of environmental gradients and provides a baseline for future studies
Could Lower Testosterone in Older Men Explain Higher COVID-19 Morbidity and Mortalities?
The health scourge imposed on humanity by the COVID-19 pandemic seems not to recede. This fact warrants refined and novel ideas analyzing different aspects of the illness. One such aspect is related to the observation that most COVID-19 casualties were older males, a tendency also noticed in the epidemics of SARS-CoV in 2003 and the Middle East respiratory syndrome in 2012. This gender-related difference in the COVID-19 death toll might be directly involved with testosterone (TEST) and its plasmatic concentration in men. TEST has been demonstrated to provide men with anti-inflammatory and immunological advantages. As the plasmatic concentration of this androgen decreases with age, the health benefit it confers also diminishes. Low plasmatic levels of TEST can be determinant in the infection’s outcome and might be related to a dysfunctional cell Ca2+ homeostasis. Not only does TEST modulate the activity of diverse proteins that regulate cellular calcium concentrations, but these proteins have also been proven to be necessary for the replication of many viruses. Therefore, we discuss herein how TEST regulates different Ca2+-handling proteins in healthy tissues and propose how low TEST concentrations might facilitate the replication of the SARS-CoV-2 virus through the lack of modulation of the mechanisms that regulate intracellular Ca2+ concentrations