leonardo piazza

The distribution and ultrastructure of capitate glandular trichomes (GTs) in Flourensia species (Asteraceae) have been recently elucidated, but their metabolic activity and potential biological function remain unexplored. Selective nonvolatile metabolites from isolated GTs were strikingly similar to those found on leaf surfaces. The phytotoxic allelochemical sesquiterpene (-)-hamanasic acid A ((-)HAA) was the major constituent (ca. 40%) in GTs. Although GTs are quaternary ammonium compounds (QACs)-accumulating species, glycine betaine was not found in GTs; it was only present in the leaf mesophyll. Two (-)HAA accompanying surface secreted products: compounds (1) 4-hydroxyacetophenone (piceol) and (2) 2-hydroxy-5-methoxyacetophenone, which were isolated and fully characterized (GC-MS, NMR), were present in the volatiles found in GTs. The essential oils of fresh leaves revealed ca. 33% monoterpenes, 26% hydrocarbon- and 30% oxygenated sesquiterpenes, most of them related to cadinene and bisabolene derivatives. Present results suggest a main role of GTs in determining the volatile and nonvolatile composition of F. campestris leaves. Based on the known activities of the compounds identified, it can be suggested that GTs in F. campestris would play key ecological functions in plant-pathogen and plant-plant interactions. In addition, the strikingly high contribution of compounds derived from cadinene and bisabolene pathways, highlights the potential of this species as a source of high-valued bioproducts. This article is protected by copyright. All rights reserved.

Sucesivas investigaciones abordadas desde nuestra Institucion, develaron la problematica de la escasa aplicacion de estrategias procedimentales (experiencias de laboratorio, salidas de campo) en la ensenanza de la Biologia, por parte de los docentes en escuelas secundarias de Punilla. En base a esto se indago acerca de las concepciones que los docentes construyen, a partir de su formacion inicial y su practica docente, sobre la ensenanza y el aprendizaje de la Biologia, y las estrategias didactico-metodologicas que despliegan en sus propias practicas. La mayoria de los docentes opinaron que las experiencias de laboratorio son muy importantes, positivas y enriquecedoras para los alumnos. Su baja frecuencia es atribuida a factores contextuales tales como alto numero de alumnos, falta de ayudantes, entre otras. De los once docentes encuestados, siete identificaron en mayor porcentaje una concepcion constructivista y cuatro una concepcion activa, seguidas por las concepciones tecnica, t...

Durante el ciclo 2011 se identificaron las problematicas que deben afrontar los docentes en sus primeras experiencias de insercion laboral: a) Reclaman que no recibieron suficiente preparacion/formacion en el profesorado con respecto a cuestiones de indole administrativas y normativo-legales. b) Con respecto a lo netamente aulico y conceptual, remiten a: la ausencia de elementos relacionados con lo pedagogico, entre ellos, algunos contenidos disciplinares especificos y la internalizacion de estrategias didacticas para abordar ciertas tematicas; las dificultades para la gestion del grupo-clase a su cargo. Los docentes noveles expresan que estas falencias, limitaciones y obstaculos se pusieron en evidencia a la hora de su practica docente. Reconocen que la/s escuela/s en donde ejercen se transforma en un ambito de formacion, en la medida que les implica socializarse en pautas, reglas y formas de “ser y estar” privativas del/los ambito/s escolar/es en que les toca desenvolverse. Rescat...

Las Experiencias de Laboratorio (trabajos en laboratorio, salidas de campo, etc.) son eficaces instrumentos de ensenanza. El docente debe poseer un buen manejo de la metodologia, la interpretacion de los resultados y los contenidos que le permitiran abordar. Como alumnos de 4o ano del Profesorado de Biologia, el objetivo fue evaluar el potencial de la realizacion de un trabajo de investigacion en problematicas ambientales para el desarrollo de Experiencias de Laboratorio en el nivel medio. Especificamente, se investigo la posible contaminacion del agua del rio Dolores por su cercania al basural de la ciudad de Capilla del Monte. Se realizaron analisis fisico-quimicos (propiedades organolepticas, pH, conductividad, solidos totales disueltos) y biologicos (bacterias coliformes fecales). Una vez finalizado, a modo de autoevaluacion, se planifico una Experiencia de Laboratorio en temas ambientales, analizando las factibilidades de su adecuacion (materiales, procedimientos, salidas de ca...

The distribution and ultrastructure of capitate glandular trichomes (GTs) in Flourensia species (Asteraceae) have been recently elucidated, but their metabolic activity and potential biological function remain unexplored. Selective nonvolatile metabolites from isolated GTs were strikingly similar to those found on leaf surfaces. The phytotoxic allelochemical sesquiterpene (-)-hamanasic acid A ((-)HAA) was the major constituent (ca. 40%) in GTs. Although GTs are quaternary ammonium compounds (QACs)-accumulating species, glycine betaine was not found in GTs; it was only present in the leaf mesophyll. Two (-)HAA accompanying surface secreted products: compounds (1) 4-hydroxyacetophenone (piceol) and (2) 2-hydroxy-5-methoxyacetophenone, which were isolated and fully characterized (GC-MS, NMR), were present in the volatiles found in GTs. The essential oils of fresh leaves revealed ca. 33% monoterpenes, 26% hydrocarbon- and 30% oxygenated sesquiterpenes, most of them related to cadinene a...

In this work, the localization, density, morphology and ultrastructure of secretory structures in aerial organs of Flourensia campestris (FC) and F. oolepis (FO) (Asteraceae) by means of a combination of light, fluorescence, transmission (TEM) and scanning electron microscopy (SEM) were examined. The possible role of secretory structures in the production and secretion of the phyto-toxic sesquiterpene (-)-hamanasic acid A ((-)HAA) in both species was also assessed. Capitate glandular trichomes were found in all reproductive organs of FC and FO, and were being reported for the first time. These glandular trichomes, typically associated to edges and veins, were of the same type as those already described for vegetative organs, and were abundant in involucral bracts and corolla of tubulose and ligulate flowers. Their density in reproductive organs of both species was similar (ca. 30/mm 2) and lower than that found in leaves (ca. 100/mm 2) and stems (ca. 160/mm 2 in FC, and up to 650/mm...

We have assessed the effects of stretch or endothelin-1 (ET-1) on atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) secretion and gene expression using a new model of isolated right atria from the rat. This model allows for comparatively long-term in vitro study of adult tissue while retaining the anatomic conformation of the atrium. Stretch and ET-1 resulted in a transient stimulation of ANF and BNP secretion, with an initially larger proportional increase in ANF release. Stretch and ET-1 induced a marked increase in BNP gene expression after 1.5 and 4 h, respectively; the increase in BNP mRNA levels was maintained throughout the 8-h experimental period. Stretch and ET-1 also stimulated c-myc and Egr-1 mRNA levels, two markers of mechanical and receptor-mediated transcriptional activation. The selective response of BNP gene to stretch and ET-1 and the distinct responses of ANF and BNP secretion indicate that the atrial cardiocytes have the capability to individual...

The presence of the phytotoxic sesquiterpene (-)-hamanasic acid A {(-)HAA; 7-carboxy-8-hydroxy-1(2), 12(13)-dien-bisabolene} isolated from Flourensia campestris (FC), was investigated in the South American species of the genus, together with the evaluation of the phytotoxic activity of their leaf aqueous extracts. (-)HAA was identified and isolated from F. fiebrigii (FF) and F. oolepis (FO), being chemically (GC-MS, NMR, [a]) and biologically (bioassayed on lettuce) indistinguishable from that of FC, while no (-)HAA was found in F. hirta (FH), F. riparia (FR) and F. niederleinii (FN). Its leaf content in FF was similar to that found in FC (ca. 15 mg g-1 WT) and significantly higher than in FO (0.8 mg g-1 WT). The screening for the presence of (-)HAA in other species of Flourensia communities showed that its natural occurrence is restricted only to Flourensia species. No (-)HAA could be detected in any of the 37 -most representative- species of these communities (26 natives, 11 exoti...

An aqueous extract from Flourensia campestris (Asteraceae) dry aerial parts showed strong inhibition on the germination and growth of Lactuca sativa. Based on bio-guided chromatographic fractionation of aq. extracts from dry and fresh leaves and spectroscopic means, (-)-hamanasic acid A (7-carboxy-8-hydroxy-1(2), 12(13)-dien-bisabolene (1)) was isolated as the most inhibitory active principle on germination (ECg(50)=2.9 mM) and on root (ECr(50)=1.5 mM)/shoot (ECs(50)=2.0 mM) growth. As measured by GC, and correlated with a simple designed 2D-TLC, compound 1 was distributed throughout the plant, with a remarkably high concentration (1.6%) in the leaves and the inflorescences. At least a quarter of the amount of 1 was found in aqueous extracts suggesting that leaching would be a key route for its release into the environment. By contrast, leaf essential oils (HD) between 0.5 and 1.5 μl ml(-1) did not show herbicidal effects and 1 was not found in them (TLC) nor among volatiles (HS-SPME). Volatile compositions were assessed by GC-FID and GC-MS and led to the identification of 23 compounds (4 monoterpenes and 19 sesquiterpenes) with a wide seasonal (spring-summer%) variation, represented principally by bicyclo-germacrene (37-6%), spathulenol (4-32%), globulol (20-0%), beta-caryophyllene (15-6%), caryophyllene oxide (1-13%) and bicycloelemene (10-1%), respectively. The high amount of 1 in F. campestris together with its feasibility of being extracted with water suggest that (-)-hamanasic acid A is an allelochemical in this species. Species-specific studies must be carried out to evaluate the potential of 1 as a natural herbicidal compound.