The Plant Growth-Promoting Potential of Halotolerant Bacteria Is Not Phylogenetically Determined: Evidence from Two Bacillus megaterium Strains Isolated from Saline Soils Used to Grow Wheat.

(1) Background: Increasing salinity, further potentiated by climate change and soil degradation, will jeopardize food security even more. Therefore, there is an urgent need for sustainable agricultural practices capable of maintaining high crop yields despite adverse conditions. Here, we tested if wheat, a salt-sensitive crop, could be a good reservoir for halotolerant bacteria with plant growth-promoting (PGP) capabilities. (2) Methods: We used two agricultural soils from Algeria, which differ in salinity but are both used to grow wheat. Soil halotolerant bacterial strains were isolated and screened for 12 PGP traits related to phytohormone production, improved nitrogen and phosphorus availability, nutrient cycling, and plant defence. The four 'most promising' halotolerant PGPB strains were tested hydroponically on wheat by measuring their effect on germination, survival, and biomass along a salinity gradient. (3) Results: Two halotolerant bacterial strains with PGP traits were isolated from the non-saline soil and were identified as Bacillus subtilis and Pseudomonas fluorescens, and another two halotolerant bacterial strains with PGP traits were isolated from the saline soil and identified as B. megaterium. When grown under 250 mM of NaCl, only the inoculated wheat seedlings survived. The halotolerant bacterial strain that displayed all 12 PGP traits and promoted seed germination and plant growth the most was one of the B. megaterium strains isolated from the saline soil. Although they both belonged to the B. megaterium clade and displayed a remarkable halotolerance, the two bacterial strains isolated from the saline soil differed in two PGP traits and had different effects on plant performance, which clearly shows that PGP potential is not phylogenetically determined. (4) Conclusions: Our data highlight that salt-sensitive plants and non-saline soils can be reservoirs for halotolerant microbes with the potential to become effective and sustainable strategies to improve plant tolerance to salinity. However, these strains need to be tested under field conditions and with more crops before being considered biofertilizer candidates.

Effect of Biochar Type, Concentration and Washing Conditions on the Germination Parameters of Three Model Crops.

Biochar has been recognized as a promising and efficient material for soil amendment. However, its effects on seed germination are variable due to its alkaline pH and/or the presence of phytotoxic substances. In this study, two types of biochar (B1 and B2) were mixed with soil at different concentrations (0%, 5%, 10%, 25%, 50% and 100%, w:w), and both the solid and liquid fractions of these mixtures were tested on the germination of basil, lettuce and tomato seeds. Furthermore, solid fractions subjected to a pre-washing treatment (B1W and B2W) were also investigated for their effects on seed germination. Three germination parameters were then measured: seed germination number (GN), radicle length (RL) and germination index (GI). Biochar B2W at 10% increased both RL and GI in basil by 50% and 70%, respectively, while B1 at 25% increased these parameters in tomato by 25%. No effects or negative effects were recorded for lettuce. Liquid fractions (L1 and L2) generally hampered seed germination, suggesting the presence of potentially water-soluble phytotoxic compounds in biochar. These results point to biochar as a suitable component for germination substrates and highlight that germination tests are critical to select the best performing biochar according to the target crop.

The Early Oxidative Stress Induced by Mercury and Cadmium Is Modulated by Ethylene in Medicago sativa Seedlings.

Cadmium (Cd) and mercury (Hg) are ubiquitous soil pollutants that promote the accumulation of reactive oxygen species, causing oxidative stress. Tolerance depends on signalling processes that activate different defence barriers, such as accumulation of small heat sock proteins (sHSPs), activation of antioxidant enzymes, and the synthesis of phytochelatins (PCs) from the fundamental antioxidant peptide glutathione (GSH), which is probably modulated by ethylene. We studied the early responses of alfalfa seedlings after short exposure (3, 6, and 24 h) to moderate to severe concentration of Cd and Hg (ranging from 3 to 30 µM), to characterize in detail several oxidative stress parameters and biothiol (i.e., GSH and PCs) accumulation, in combination with the ethylene signalling blocker 1-methylcyclopropene (1-MCP). Most changes occurred in roots of alfalfa, with strong induction of cellular oxidative stress, H2O2 generation, and a quick accumulation of sHSPs 17.6 and 17.7. Mercury caused the specific inhibition of glutathione reductase activity, while both metals led to the accumulation of PCs. These responses were attenuated in seedlings incubated with 1-MCP. Interestingly, 1-MCP also decreased the amount of PCs and homophytochelatins generated under metal stress, implying that the overall early response to metals was controlled at least partially by ethylene.

Validation of the Activities' Scale in Higher Education Students' Personal Learning Environments.

BACKGROUND: Personal learning environments are the networks of tools, activities, and connections that each person uses for their learning. Although there have been increasing numbers of studies, measurement instruments in this regard are still limited. The aim of this study is to construct and validate a scale to assess the activities that make up Personal Learning Environments. METHOD: The sample comprised 1,187 students in their final year of undergraduate degrees. 64% were women and 36% men, with a mean age of 24 and a standard deviation of 4.21 years. RESULTS: The scale consists of 27 Likert-type items responding to three factors according to the theoretical construct reviewed, and produced high coefficients in internal consistency tests. CONCLUSIONS: The analyses demonstrate a valid instrument with solid psychometric properties. More specifically, the results indicate suitable content validity. Exploratory and confirmatory factor analyses indicate appropriate construct validation, with consistency between the theoretical and factorial model.

Modulation of the Wheat Seed-Borne Bacterial Community by Herbaspirillum seropedicae RAM10 and Its Potential Effects for Tryptophan Metabolism in the Root Endosphere.

Plants and their associated microbiota share ecological and evolutionary traits that are considered to be inseparably woven. Their coexistence foresees the use of similar metabolic pathways, leading to the generation of molecules that can cross-regulate each other's metabolism and ultimately influence plant phenotype. However, the extent to which the microbiota contributes to the overall plant metabolic landscape remains largely unexplored. Due to their early presence in the seed, seed-borne endophytic bacteria can intimately colonize the plant's endosphere while conferring a series of phytobeneficial services to their host. Understanding the dynamics of these endophytic communities is a crucial step toward the formulation of microbial inoculants that can modulate the functionality of the plant-associated microbiota for improved plant fitness. In this work, wheat (Triticum aestivum) roots non-inoculated and inoculated with the bacterium Herbaspirillum seropedicae strain RAM10 were analyzed to explore the impact of inoculant-endophyte-wheat interrelationships on the regulation of tryptophan (Trp) metabolism in the endosphere environment. Root inoculation with H. seropedicae led to phylum-specific changes in the cultivable seed-borne endophytic community. This modulation shifted the metabolic potential of the community in light of its capacity to modulate the levels of key Trp-related metabolites involved in both indole-3-acetic acid (IAA) biosynthesis and in the kynurenine pathway. Our results support a mode of action of H. seropedicae relying on a shift in both the composition and functionality of the seed-borne endophytic community, which may govern important processes such as root growth. We finally provide a conceptual framework illustrating that interactions among roots, inoculants, and seed-borne endophytes are critical to fine-tuning the levels of IAA in the endosphere. Understanding the outcomes of these interactions is a crucial step toward the formulation of microbial inoculants based on their joint action with seed-borne endophytic communities to promote crop growth and health in a sustainable manner.

Validation of the Activities’ Scale in Higher Education Students’ Personal Learning Environments / Validación de la Escala de Actividades en los Entornos Personales de Aprendizaje de Estudiantes de Educación Superior

Background: Personal learning environments are the networks of tools, activities, and connections that each person uses for their learning. Although there have been increasing numbers of studies, measurement instruments in this regard are still limited. The aim of this study is to construct and validate a scale to assess the activities that make up Personal Learning Environments. Method: The sample comprised 1,187 students in their final year of undergraduate degrees. 64% were women and 36% men, with a mean age of 24 and a standard deviation of 4.21 years. Results: the scale consists of 27 Likert-type items responding to three factors according to the theoretical construct reviewed, and produced high coefficients in internal consistency tests. Conclusions: the analyses demonstrate a valid instrument with solid psychometric properties. More specifically, the results indicate suitable content validity. Exploratory and confirmatory factor analyses indicate appropriate construct validation, with consistency between the theoretical and factorial model. (AU)

Antecedentes: los entornos personales de aprendizaje se definen como el entramado de herramientas, actividades y conexiones que cada persona utiliza para su aprendizaje. Los estudios sobre el tema han ido en aumento, sin embargo, son todavía escasos los instrumentos de medición al respecto. El objetivo de este trabajo es construir y validar una escala para evaluar las actividades que integran los Entornos Personales de Aprendizaje. Método: la muestra estaba formada por 1.187 estudiantes universitarios de último año de carrera. Un 64% eran mujeres y un 36% hombres, con una edad media de 24 años y una desviación típica de 4.21. Resultados: la escala queda formada por 27 ítems tipo Likert respondiendo a tres factores de acuerdo con el constructo teórico revisado, obteniendo coeficientes elevados en las pruebas de consistencia interna. Conclusiones: los análisis realizados muestran un instrumento válido y con propiedades psicométricas sólidas. Concretamente, los resultados arrojan una adecuada validez de contenido. Los análisis factoriales exploratorio y confirmatorio indican una pertinente validación de constructo, existiendo coherencia entre el modelo teórico y factorial. (AU)

An Optimized in situ Quantification Method of Leaf H2O2 Unveils Interaction Dynamics of Pathogenic and Beneficial Bacteria in Wheat.

Hydrogen peroxide (H2O2) functions as an important signaling molecule in plants during biotic interactions. However, the extent to which H2O2 accumulates during these interactions and its implications in the development of disease symptoms is unclear. In this work, we provide a step-by-step optimized protocol for in situ quantification of relative H2O2 concentrations in wheat leaves infected with the pathogenic bacterium Pseudomonas syringae pv. atrofaciens (Psa), either alone or in the presence of the beneficial bacterium Herbaspirillum seropedicae (RAM10). This protocol involved the use of 3-3'diaminobenzidine (DAB) staining method combined with image processing to conduct deconvolution and downstream analysis of the digitalized leaf image. The application of a linear regression model allowed to relate the intensity of the pixels resulting from DAB staining with a given concentration of H2O2. Decreasing H2O2 accumulation patterns were detected at increasing distances from the site of pathogen infection, and H2O2 concentrations were different depending on the bacterial combinations tested. Notably, Psa-challenged plants in presence of RAM10 accumulated less H2O2 in the leaf and showed reduced necrotic symptoms, pointing to a potential role of RAM10 in reducing pathogen-triggered H2O2 levels in young wheat plants.

Factors which motivate the use of social networks by students / Factores que motivan el uso de las redes sociales por los estudiantes

BACKGROUND: The aim of this research was to identify those factors which motivate the use of social networks by 4th year students in Secondary Education between the ages of 15 and 18. METHOD: 1,144 students from 29 public and private schools took part. The data were analysed using Partial Least Squares Structural Equation Modelling technique. RESULTS: Versatility was confirmed to be the variable which most influences the motivation of students in their use of social networks. The positive relationship between versatility in the use of social networks and educational uses was also significant. CONCLUSIONS: The characteristics of social networks are analysed according to their versatility and how this aspect makes them attractive to students. The positive effects of social networks are discussed in terms of educational uses and their contribution to school learning. There is also a warning about the risks associated with misuse of social networks, and finally, the characteristics and conditions for the development of good educational practice through social networks are identified

ANTECEDENTES: el objetivo de esta investigación fue identificar aquellos factores que motivan el uso de redes sociales por parte del alumnado de 4º curso de Educación Secundaria Obligatoria con edades entre los 15 y 18 años. MÉTODO: participaron 1.144 estudiantes de 29 centros educativos públicos, privados y concertados. Se utilizó un método de encuesta y los datos fueron analizados en base a la técnica de ecuaciones estructurales «Partial Least Squares» RESULTADOS: se constata que la versatilidad es la variable que más influye en la motivación de uso de las redes sociales por parte de los estudiantes. También resulta significativa la relación positiva entre la versatilidad en el uso de las redes sociales respecto a la utilidad educativa. CONCLUSIONES: se analizan las características de las redes sociales en cuanto a su versatilidad y cómo ello las hace atractivas a los estudiantes. Se discuten los efectos positivos de las redes sociales en cuanto a su utilidad educativa y su contribución al aprendizaje escolar. Se alerta sobre los peligros que pueden derivarse de un empleo inadecuado de las redes sociales y se identifican los rasgos y condiciones para el desarrollo de buenas prácticas educativas mediante redes sociales

Factors which motivate the use of social networks by students.

BACKGROUND: The aim of this research was to identify those factors which motivate the use of social networks by 4th year students in Secondary Education between the ages of 15 and 18. METHOD: 1,144 students from 29 public and private schools took part. The data were analysed using Partial Least Squares Structural Equation Modelling technique. RESULTS: Versatility was confirmed to be the variable which most influences the motivation of students in their use of social networks. The positive relationship between versatility in the use of social networks and educational uses was also significant. CONCLUSIONS: The characteristics of social networks are analysed according to their versatility and how this aspect makes them attractive to students. The positive effects of social networks are discussed in terms of educational uses and their contribution to school learning. There is also a warning about the risks associated with misuse of social networks, and finally, the characteristics and conditions for the development of good educational practice through social networks are identified.