Foliar plasticity related to gradients of heat and drought stress across crown orientations in three Mediterranean Quercus species

[EN]Studies on plasticity at the level of a single individual plant provide indispensable information to predict leaf responses to climate change, because they allow better identification of the environmental factors that determine differences in leaf traits in the absence of genetic differences. Most of these studies have focused on the responses of leaf traits to variations in the light environment along vertical gradients, thus paying less attention to possible differences in the intensity of water stress among canopy orientations. In this paper, we analyzed the differences in leaf traits traditionally associated with changes in the intensity of water stress between east and west crown orientations in three Quercus species. The leaves facing west experienced similar solar radiation levels but higher maximum temperatures and lower daily minimum water potentials than those of the east orientation. In response to these differences, the leaves of the west orientation showed smaller size and less chlorophyll concentration, higher percentage of palisade tissue and higher density of stomata and trichomes. These responses would confirm the role of such traits in the tolerance to water stress and control of water losses by transpiration. For all traits, the species with the longest leaf life span exhibited the greatest plasticity between orientations. By contrast, no differences between canopy positions were observed for leaf thickness, leaf mass per unit area and venation patterns

Análisis de diferentes variables Bioquímicas y Fisiológicas en las prácticas del master universitario en Agrobiotecnología mediantes técnicas de cultivo hidropónico

Memoria ID10/114. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2010-2011.El objetivo concreto que se proponía en la Memoria presentada era la adquisición, por parte de los alumnos matriculados en el Master, de una formación práctica en agrobiotecnología y en algunas metodologías utilizadas, en este caso, en la obtención de plantas por técnicas de cultivo hidropónico o cultivo de plantas sin suelo. Los alumnos realizaron diferentes experiencias con plantas de tomate, establecieron el cultivo hidropónico, sembrando primero las semillas en bandejas-semillero, transplantaron las plántulas a macetas con vermiculita (sustrato inerte para la sujeción de la planta) y pasaron las plántulas a una cámara Fitotron con distintos fotoperíodos, aplicando las soluciones nutritivas necesarias

Foliar plasticity related to gradients of heat and drought stress across crown orientations in three Mediterranean Quercus species.

Studies on plasticity at the level of a single individual plant provide indispensable information to predict leaf responses to climate change, because they allow better identification of the environmental factors that determine differences in leaf traits in the absence of genetic differences. Most of these studies have focused on the responses of leaf traits to variations in the light environment along vertical gradients, thus paying less attention to possible differences in the intensity of water stress among canopy orientations. In this paper, we analyzed the differences in leaf traits traditionally associated with changes in the intensity of water stress between east and west crown orientations in three Quercus species. The leaves facing west experienced similar solar radiation levels but higher maximum temperatures and lower daily minimum water potentials than those of the east orientation. In response to these differences, the leaves of the west orientation showed smaller size and less chlorophyll concentration, higher percentage of palisade tissue and higher density of stomata and trichomes. These responses would confirm the role of such traits in the tolerance to water stress and control of water losses by transpiration. For all traits, the species with the longest leaf life span exhibited the greatest plasticity between orientations. By contrast, no differences between canopy positions were observed for leaf thickness, leaf mass per unit area and venation patterns

Costs of leaf reinforcement in response to winter cold in evergreen species

The competitive equilibrium between deciduous and evergreen plant species to a large extent depends on the intensity of the reduction in carbon gain undergone by evergreen leaves, associated with the leaf traits that confer resistance to stressful conditions during the unfavourable part of the year. This study explores the effects of winter harshness on the resistance traits of evergreen leaves. Leaf mass per unit area (LMA), leaf thickness and the concentrations of fibre, nitrogen (N), phosphorus (P), soluble protein, chlorophyll and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined in three evergreen and two deciduous species along a winter temperature gradient. In the evergreen species, LMA, thickness, and P and structural carbohydrate concentrations increased with the decrease in winter temperatures. Nitrogen and lignin concentrations did not show definite patterns in this regard. Chlorophyll, soluble proteins and Rubisco decreased with the increase in winter harshness. Our results suggest that an increase in LMA and in the concentration of structural carbohydrates would be a requirement for the leaves to cope with low winter temperatures. The evergreen habit would be associated with higher costs at cooler sites, because the cold resistance traits imply additional maintenance costs and reduced N allocation to the photosynthetic machinery, associated with structural reinforcement at colder sites.This article has received financial support from the Spanish Ministerio de Ciencia e Innovación—EU-FEDER (Projects No. CGL2006-04281 and CGL2010-21187), the Regional Government of Castilla-León (Project No. SA126A08) and the Miguel Casado S José Foundation

Unidad didáctica. Conocemos la Siberia

Unidad didáctica orientada a los alumnos del tercer ciclo de primaria. Su objetivo primordial es el acercamiento físico e intelectual a la comarca de la Siberia, en la cual viven los alumnos. Comarca desconocida, en gran parte por las malas comunicaciones de la zona.ExtremaduraES