Xylem is a complex tissue that forms the bulk of tree bodies and has several functions, including to conduct water, store water and nutrients, and biomechanically support the plant body. We examined how xylem functional traits varied at different positions within Populus balsamifera spp. trichocarpa (Black Cottonwood). Whole trees were excavated, and xylem samples were collected at 1m increments along the main root-to-shoot axis of six trees, from root tip to shoot tip. We examined biomechanical and water storage traits of the xylem, including using a non-invasive imaging technique to examine water content within long, intact branches (high resolution computed tomography; microCT). Xylem density, strength, and stiffness were higher in shoots than roots. Along the main root-to-shoot axis, xylem strength and stiffness were greatest at shoot tips and tissue became linearly weaker and less stiff down the plant and through the root. Roots had greater water storage with reduced biomechanical support, and shoots had biomechanically stronger and stiffer xylem with reduced water storage. These findings support trade-offs among xylem functions between roots and shoots. Understanding how xylem functions differ throughout tree bodies is important in understanding whole-tree function and how terrestrial plants endure numerous environmental challenges over decades of growth.
Las emociones cumplen un papel fundamental en la capacidad de acción de los seres humanos, razón por la cual es indispensable estudiarlas para entender los fenómenos sociales contemporáneos en los que participan los adolescentes. Esta investigación tiene como objetivo comprender las experiencias de la compasión, los celos y la envidia de los adolescentes implicados en situaciones de cyberbullying en los roles de espectadores y agresores. Se trata de una investigación con diseño cualitativo en la que se entrevistó a 31 adolescentes entre los 12 y 17 años (M=15,23, DS=1,6) que participaron de situaciones de cyberbullying como espectadores y/o agresores. Los resultados indican que la compasión adquiere la forma de tristeza y rabia, especialmente entre los espectadores de cyberbullying. Por otra parte, los celos son un motivo que justifica la agresión a otros a través de Internet, y una forma de gestionar las tensiones en los vínculos sexo-afectivos. El uso de redes sociales digitales y la participación en escenarios presenciales en los que se disputan posiciones a nivel académico favorece el proceso de comparación social vinculado a la envidia que está en la base del cyberbullying. Finalmente, este estudio es una invitación para padres, docentes e institucionales estatales a que acompañen a los adolescentes a gestionar sus conflictos sin que las agresiones presenciales y online medien en sus interacciones.
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