Willow clones : fiber longitude in the wood

En la madera de clones de sauce (Salix spp.) la longitud de fibra, que está asociada con su aptitud papelera, varía ampliamente en el mismo árbol. En algunas especies se ha comprobado diferencias entre la médula y el exterior -a lo largo de ejes radiales (variación radial)- y longitudinales, entre la base del tronco y la parte superior (variación axial). La determinación de dichas diferencias permitiría localizar muestras útiles para evaluar la calidad de árboles completos, utilizables en la industria celulósica. Por tal motivo se han estudiado en 8 clones de sauces de 13 años extrayendo material a 3 distintas alturas en el fuste: 1,3; 4,3 y 6,5 m. En cada una de ellas se tomaron muestras de 3 posiciones radiales correspondientes a las edades, en años: 3-4 (interna), 6-7 (media) y 10-11 (externa). Se midió el largo de 30 fibras por posición sobre material disociado. En el sentido radial se verificó -en todos los clones y a todas las alturas- un aumento de la longitud de fibra desde el interior hacia el exterior. Para la variación axial se registró una tendencia general de disminución desde las secciones inferiores a las superiores.Fiber longitude is a property of the willow (Salix spp.) wood, associated to its paper aptitude and it can vary significantly within the same tree. In several species, these variations were noticied between the pit and the exterior along the radial axes (radial variation) and longitudinal axes between the botton of the trunck and the upper part (axial variation). Acknowledging that these variations would facilitate the location of useful samples for quality evaluation of all the clones, used for paper industry. The aim of this work was to study axial and radial variations of fiber longitude in 8 clone stems of 13 year old willows. Material from 3 different stem heigths was taken from each clone at 1,3; 4,3 and 6,5 m. For each of these heigths, samples of 3 radial positions corresponding to the ages, in years: 3-4 (internal), 6-7 (medium) and 10-11 (external) were obtained. The length of 30 fibers was measured againts dissociated material. As regards the radial aspect, an increase in fiber longitude from the inside to the outside was noticed in all the clones and at all heigths. For axial variation a general decreasing tendency from lower sections towards the upper ones was recorded.Fil: Marlats, Raúl M..Fil: Senisterra, Gabriela E..Fil: Marquina, Jorge L..Fil: Monteoliva, Silvia.Fil: Ciocchini, Gabriel R.

Dry weight partitioning and hydraulic traits in young <i>Pinus taeda</i> trees fertilized with nitrogen and phosphorus in a subtropical area

Plants of Pinus taeda L. from each of four families were fertilized with N, P or N+P at planting. The H family had the highest growth in dry mass while the L family had the lowest growth. Measurements of plant hydraulic architecture traits were performed during the first year after planting. Stomatal conductance (gs), water potential at predawn (Ψpredawn) and at midday (Ψmidday), branch hydraulic conductivity (ks and kl) and shoot hydraulic conductance (K) were measured. One year after planting, dry weight partitioning of all aboveground organs was performed. P fertilization increased growth in all four families, while N fertilization had a negative effect on growth. L family plants were more negatively affected than H family plants. This negative effect was not due to limitations in N or P uptake because plants from all the families and treatments had the same N and P concentration in the needles. P fertilization changed some hydraulic parameters, but those changes did not affect growth. However, the negative effect of N can be explained by changes in hydraulic traits. L family plants had a high leaf dry weight per branch, which was increased by N fertilization. This change occurred together with a decrease in shoot conductance. Therefore, the reduction in gs was not enough to avoid the drop in Ψmidday. Consequently, stomatal closure and the deficient water status of the needles resulted in a reduction in growth. In H family plants, the increase in number of needles per branch due to N fertilization was counteracted by a reduction in gs and also by a reduction in tracheid lumen size and length. Because of these two changes, Ψmidday did not drop and water availability in the needles was adequate for sustained growth. In conclusion, fertilization affects the hydraulic architecture of plants, and different families develop different strategies. Some of the hydraulic changes can explain the negative effect of N fertilization on growth.Instituto de Fisiología Vegetal (INFIVE

Quantum effects after decoherence in a quenched phase transition

We study a quantum mechanical toy model that mimics some features of a quenched phase transition. Both by virtue of a time-dependent Hamiltonian or by changing the temperature of the bath we are able to show that even after classicalization has been reached, the system may display quantum behaviour again. We explain this behaviour in terms of simple non-linear analysis and estimate relevant time scales that match the results of numerical simulations of the master-equation. This opens new possibilities both in the study of quantum effects in non-equilibrium phase transitions and in general time-dependent problems where quantum effects may be relevant even after decoherence has been completed.Comment: 7 pages, 7 figures, revtex, important revisions made. To be published in Phys. Rev.

Dry weight partitioning and hydraulic traits in young <i>Pinus taeda</i> trees fertilized with nitrogen and phosphorus in a subtropical area

Plants of Pinus taeda L. from each of four families were fertilized with N, P or N+P at planting. The H family had the highest growth in dry mass while the L family had the lowest growth. Measurements of plant hydraulic architecture traits were performed during the first year after planting. Stomatal conductance (gs), water potential at predawn (Ψpredawn) and at midday (Ψmidday), branch hydraulic conductivity (ks and kl) and shoot hydraulic conductance (K) were measured. One year after planting, dry weight partitioning of all aboveground organs was performed. P fertilization increased growth in all four families, while N fertilization had a negative effect on growth. L family plants were more negatively affected than H family plants. This negative effect was not due to limitations in N or P uptake because plants from all the families and treatments had the same N and P concentration in the needles. P fertilization changed some hydraulic parameters, but those changes did not affect growth. However, the negative effect of N can be explained by changes in hydraulic traits. L family plants had a high leaf dry weight per branch, which was increased by N fertilization. This change occurred together with a decrease in shoot conductance. Therefore, the reduction in gs was not enough to avoid the drop in Ψmidday. Consequently, stomatal closure and the deficient water status of the needles resulted in a reduction in growth. In H family plants, the increase in number of needles per branch due to N fertilization was counteracted by a reduction in gs and also by a reduction in tracheid lumen size and length. Because of these two changes, Ψmidday did not drop and water availability in the needles was adequate for sustained growth. In conclusion, fertilization affects the hydraulic architecture of plants, and different families develop different strategies. Some of the hydraulic changes can explain the negative effect of N fertilization on growth.Instituto de Fisiología Vegetal (INFIVE

Candida albicans Hyphal Extracellular Vesicles Are Different from Yeast Ones, Carrying an Active Proteasome Complex and Showing a Different Role in Host Immune Response.

Candida albicans is the principal causative agent of lethal fungal infections, predominantly in immunocompromised hosts. Extracellular vesicles (EVs) have been described as crucial in the interaction of microorganisms with their host. Since the yeast-to-hypha transition is an important virulence trait with great impact in invasive candidiasis (IC), we have addressed the characterization of EVs secreted by hyphal cells (HEVs) from C. albicans, comparing them to yeast EVs (YEVs). YEVs comprised a larger population of bigger EVs with mainly cell wall proteins, while HEVs were smaller, in general, and had a much higher protein diversity. YEVs were able to rescue the sensitivity of a cell wall mutant against calcofluor white, presumably due to the larger amount of cell wall proteins they contained. On the other hand, HEVs also contained many cytoplasmic proteins related to protein metabolism and intracellular protein transport and the endosomal sorting complexes required for transport (ESCRT) pathway related to exosome biogenesis, pointing to an intracellular origin of HEVs. Interestingly, an active 20S proteasome complex was secreted exclusively in HEVs. Moreover, HEVs contained a greater number of virulence-related proteins. As for their immunogenic role, both types of EV presented immune reactivity with human sera from patients suffering invasive candidiasis; however, under our conditions, only HEVs showed a cytotoxic effect on human macrophages and could elicit the release of tumor necrosis factor alpha (TNF-α) by these macrophages. IMPORTANCE This first analysis of HEVs of C. albicans has shown clear differences between them and the YEVs of C. albicans, showing their relevance and possible use in the discovery of new diagnostic markers and treatment targets against C. albicans infections. The data obtained point to different mechanisms of biogenesis of YEVs and HEVs, as well as different involvements in cell biology and host interaction. YEVs played a more relevant role in cell wall maintenance, while HEVs were more closely related to virulence, as they had greater effects on human immune cells. Importantly, an active 20S proteosome complex was described as a fungal-EV cargo. A deeper study of its role and those of many other proteins exclusively detected in HEVs and involved in different relevant biological processes of this fungus could open up interesting new areas of research in the battle against C. albicans

Influencia del anticoagulante, temperatura y pH sobre la actividad colinesterasa de ganado vacuno y poricno

Using the pH-stat system, a volumetric-potenciometric technique, the cholinesterases activities of erythrocytes and serum from cattle and pig were studied. The analysis of different anticoagulants effect reveals that EDTA and heparin are the preferred anticoagulants for belong studies of those enzymes. A 37ºC temperature and pH=8,0 are the optimal values for "in vitro" acetylcholinesterase activity measurement. At acidic pH a strong de crease of the enzyme activity is detected. The activity value is zero when the pH is about 5,0.Utilizando el sistema pH-stat, tecnica volumétrica-potenciométrica, se han determinado las actividades colinesterasas de eritrocitos y plasma de ganado vacuno y porcino. Al estimar la influencia del anticoagulante se concluye que EDTA y heparina son los anticoagulantes idóneos para posteriores estudios de dichos enzimas. Se establece en 37ºC y pH 8,0, la temperatura y pH óptimos de medida de actividad "in vitro" del enzima acetilcolinesterasa. A pH acidos se observa un descenso brusco de la actividad enzimática, haciendose nula a pH próximo a 5,0

Influencia del anticoagulante, temperatura y pH sobre la actividad colinesterasa de ganado vacuno y porcino

Utilizando el sistema pH-stat, tecnica volumétrica-potenciométrica, se han determinado las actividades colinesterasas de eritrocitos y plasma de ganado vacuno y porcino. Al estimar la influencia del anticoagulante se concluye que EDTA y heparina son los anticoagulantes idóneos para posteriores estudios de dichos enzimas. Se establece en 37ºC y pH 8,0, la temperatura y pH óptimos de medida de actividad "in vitro" del enzima acetilcolinesterasa. A pH acidos se observa un descenso brusco de la actividad enzimática, haciendose nula a pH próximo a 5,0.Using the pH-stat system, a volumetric-potenciometric technique, the chollnesterases activities of erythrocytes and serum from cattle and pig were studied. The analysis of different anticoagulants effect reveals that EDT A and heparin are the preferred anticoagulants for belong studies of those enzymes. A 370C temperature and pH=8,0 are the optimal values for "in vitro" acetylcholinesterase acti vity measurement. A t acidic pH a strong de crease of the enzyme activity is detected. The activity value is zero when the pH is about 5,0

Decoherence and the rate of entropy production in chaotic quantum systems

We show that for an open quantum system which is classically chaotic (a quartic double well with harmonic driving coupled to a sea of harmonic oscillators) the rate of entropy production has, as a function of time, two relevant regimes: For short times it is proportional to the diffusion coefficient (fixed by the system--environment coupling strength). For longer times (but before equilibration) there is a regime where the entropy production rate is fixed by the Lyapunov exponent. The nature of the transition time between both regimes is investigated.Comment: Revtex, 4 pages, 3 figures include

Dry weight partitioning and hydraulic traits in young <i>Pinus taeda</i> trees fertilized with nitrogen and phosphorus in a subtropical area

Plants of Pinus taeda L. from each of four families were fertilized with N, P or N+P at planting. The H family had the highest growth in dry mass while the L family had the lowest growth. Measurements of plant hydraulic architecture traits were performed during the first year after planting. Stomatal conductance (gs), water potential at predawn (Ψpredawn) and at midday (Ψmidday), branch hydraulic conductivity (ks and kl) and shoot hydraulic conductance (K) were measured. One year after planting, dry weight partitioning of all aboveground organs was performed. P fertilization increased growth in all four families, while N fertilization had a negative effect on growth. L family plants were more negatively affected than H family plants. This negative effect was not due to limitations in N or P uptake because plants from all the families and treatments had the same N and P concentration in the needles. P fertilization changed some hydraulic parameters, but those changes did not affect growth. However, the negative effect of N can be explained by changes in hydraulic traits. L family plants had a high leaf dry weight per branch, which was increased by N fertilization. This change occurred together with a decrease in shoot conductance. Therefore, the reduction in gs was not enough to avoid the drop in Ψmidday. Consequently, stomatal closure and the deficient water status of the needles resulted in a reduction in growth. In H family plants, the increase in number of needles per branch due to N fertilization was counteracted by a reduction in gs and also by a reduction in tracheid lumen size and length. Because of these two changes, Ψmidday did not drop and water availability in the needles was adequate for sustained growth. In conclusion, fertilization affects the hydraulic architecture of plants, and different families develop different strategies. Some of the hydraulic changes can explain the negative effect of N fertilization on growth.Instituto de Fisiología Vegetal (INFIVE