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

Bullying : sentimientos y sensaciones

El bullying es un fenómeno mundial, conocer sus diferentes formas puede contribuir a su mitigación en espacios escolares. El texto aborda de manera conceptual este fenómeno y explica como algunas prácticas en el hogar y el espacio escolar contribuyen a la formación de victimarios de Bullying

Role of serotiny on Pinus pinaster Aiton germination and its relation to mother plant age and fire severity

erotiny degree may hypothetically depend on mother plant age and fire severity, and fire severity can strongly affect the regeneration of Pinus pinaster Aiton, which is an obligate seeder species with aerial seed banks stocked in cones showing a certain degree of serotiny. The main objective of this study was to evaluate the effect of serotiny and mother plant age on seed germination of P. pinaster in relation to fire severity. For this purpose, cones were collected in two stands from mother trees of different ages. Serotinous cones were opened in oven at increasing temperatures to determine the number of seeds released. The length of cones and the number and weight of seeds were measured. Seeds from both classes of mother plant age were subjected to 34 different treatments simulating different fire severity levels, and their germination was recorded. The results showed that serotiny was significantly higher in cones from young mother trees. Seed germination in the control groups from serotinous cones was always higher than that from non-serotinous cones without thermal shock. Fire severity decreased seed germination as fire severity increases in both mother age classes. Mother plant age was related to the serotiny level, which was higher in young than in old trees, suggesting a strong selection in the population due to a recent fire.This work is part of the research projects AGL2013-48189-C2-2-R (Ministerio de Economía y Competividad, Madrid, Spain, and ERDF founding), AGL2017-86075-C2-2-R (Ministerio de Ciencia, Educación y Universidades, Madrid, Spain, and ERDF founding), LE001P17 (Junta de Castilla y León, Valladolid, Spain), ED431C2019/07 and ED431E 2018/09 (Xunta de Galicia, Santiago de Compostela, Spain)S

Impact of COVID-19 on University Students: An Analysis of Its Influence on Psychological and Academic Factors

The irruption of COVID-19 has had different consequences on mental health in the youth population. Specifically, the sector made up of university students has suffered an abrupt change of teaching modality because of the pandemic. As such, this paper aims to analyze the impact that COVID-19 has had on different personal factors of students: (i) satisfaction with life; (ii) lived uncertainty; (iii) depression, anxiety, and stress, as well as factors related to academic development; (iv) motivation and the creation of teaching and learning strategies during this period; and (v) the perception of the degree of adaptability to the new scenario brought about by the university system. For this purpose, a cross-sectional quantitative design was advocated through the elaboration of an SEM model, which included 1873 university students from Andalusian Universities (Spain). The results reflected the strong negative impact that the pandemic had, especially on the levels of life satisfaction and the indices of depression, anxiety, and stress of the students. Likewise, the findings reflected the relevance of the correct adaptability on the part of the university to these new circumstances. It is necessary for university institutions to focus their efforts on quality attention to students, in order to establish fluid communication with them and to adapt to their academic and personal needs.Direccion General de Investigacion y Transferencia del Conocimiento de la Junta de Andalucia (Spain)European FEDER public funds (Project I+D+i) CV20-0124

Respuesta de las plantas a estrés por inundación. Una revisión

La inundación tiene un efecto negativo sobre la mayoría de plantas terrestres debido a que reduce su crecimiento e induce la senescencia. La deficiencia de oxígeno, efecto principal de la inundación, cambia el metabolismo de la planta induciendo la vía anaeróbica o fermentativa como mecanismo alterno, aunque poco eficiente para la producción de energía. Igualmente el déficit de oxígeno aumenta la producción de especies reactivas de oxígeno (ROS), tanto en la mitocondria como en el cloroplasto. Como respuesta al incremento de ROS hay un aumento en el sistema de defensa antioxidante de la planta, el cual es considerado, junto con la inducción de la vía fermentativa, como una respuesta a corto plazo. Cuando la planta está sometida a largos periodos de inundación se presentan, adicionalmente, cambios morfológicos, como la formación de aerénquima, los cuales son considerados respuestas a largo plazo. En este artículo se revisan las respuestas, tanto a corto como a largo plazo, de las plantas a la condición de estrés hídrico por inundación

Fire effects on germination response of the native species Daucus carota and the invasive alien species Helichrysum foetidum and Oenothera glazioviana

Fire is an ecological factor that affects ecosystem structure and functioning and determines later recovery of the ecosystem through the modification of biological processes, such as seed germination and seedling establishment. Another factor that modifies ecosystems is the presence of invasive alien species, which easily colonize new habitats after disturbances such as forest fires. Within this research, we analysed the germination response to fire of three species that share a habitat, one native species (Daucus carota L.) and two invasive alien species (Helichrysum foetidum (L.) Moench and Oenothera glazioviana Micheli) to identify and compare the effects of fire on the germination of these three species. For this purpose, germination tests were performed by using seeds treated with heat, smoke, charcoal and ash, simulating conditions of forest fires. The three species showed slightly different responses to fire factors. At high levels, heat and ash prevented the germination of the three species. In contrast, intermediate heat shocks and some smoke treatments stimulated O. glazioviana germination, while the other species remained unaffected. H. foetidum presented high germination success for most treatments. The difference in the germination response of the three species can change the current balance among three species in natural fire-prone ecosystems, contributing to the spread of O. glazioviana and H. foetidum to new areas and potentially reducing native D. carota populations.This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness, the Spanish Ministry of Science, Innovation and Universities, the Castilla y León Regional Government, the Galicia Regional Government and the European Regional Development Fund (ERDF) in the framework of the GESFIRE (AGL2013-48189-C2-2-R), FIRESEVES (AGL2017-86075-C2-2-R) and SEFIRECYL (LE001PE17) projects, the Competitive Reference Group BIOAPLIC (ED431C2019/07) and the Strategic Researcher Cluster BioReDeS (ED431E 2018/09)S