Papers by Juan Pablo Segura
HortScience, 1995
The effects of stage of microspore development, cold pretreatment, and growth regulators on the e... more The effects of stage of microspore development, cold pretreatment, and growth regulators on the embryogenic response of anthers from service tree (Sorbus domestica L.) are reported. Callus proliferation required the presence of growth regulators in the culture medium, best results being obtained with combinations of auxins and BA. Microspore embryogenesis was only induced when anthers containing tetrads or uninucleate pollen were cultured on BA-supplemented media containing IBA or IAA. A cold pretreatment before anther culture elicited a significant decrease in callus formation and inhibited embryogenesis. Chemical names used: benzyladenine (BA), indole-3-butyric acid (IBA), indole-3-acetic acid (IAA).
HortScience, 2010
Successful propagation of Nerium oleander L. (oleander) was achieved by in vitro methods. Shoot c... more Successful propagation of Nerium oleander L. (oleander) was achieved by in vitro methods. Shoot cultures were initiated from seedlings of wild-growing plants and from shoot apices of adult plants belonging to the commercial cultivars Splendens Giganteum, Revanche, and Alsace. Axillary shoot breaking from shoot tips excised from these cultures required the presence of either 6-benzylaminopurine (BA) or thidiazuron (TDZ). The higher number of axillary shoots from juvenile material was obtained by culturing shoot tips from BA-pretreated material derived from seedlings on a modified Schenk and Hildebrandt medium (SHM) supplemented with BA or TDZ (average of 3.9 shoots per explant with a mean length of 10.4 mm) and when the media were supplemented with 8.8 μM TDZ (average of 3.5 shoots per explant with a mean length of 7.3 mm) or 4.4 μM BA (average of 3.3 shoots per explant with a mean length of 12.3 mm). Among cultivars, cv. Revanche showed best shoot proliferation rates, especially whe...
Journal of the American Society for Horticultural Science, 1992
A protocol for in vitro propagation in flowering ash (Fraxinus ornus L.) has been developed. Shoo... more A protocol for in vitro propagation in flowering ash (Fraxinus ornus L.) has been developed. Shoot apices or nodal segments from aseptically grown seedings or shoot apices from adult trees were used as initial explants. Highest shoot multiplication rates were obtained when the explants were cultured for 30 days in liquid Rugini induction medium supplemented with BA followed by 30 days on solidified Rugini multiplication medium without growth regulators. Regenerated shoots were rooted on Heller medium containing auxins alone or in combination with BA. Rooting percentages up to 71% (juvenile material) or 50% (adult material) were obtained in the presence of NAA and BA, and were not improved by treating the basal end of the shoots with concentrated NAA solutions. Following conventional procedures, regenerated plants were transferred to soil with more than 80% success. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); 1-naphthaleneacetic acid (NAA).
Tree Physiology, 2005
We developed procedures for in vitro cloning of Cedrus atlantica Manetti and C. libani A. Rich ex... more We developed procedures for in vitro cloning of Cedrus atlantica Manetti and C. libani A. Rich explants from juvenile and mature plants. Explant size was one determinant of the frequency of axillary bud break in both species. Shoot tips and nodal explants mainly developed calli, whereas bud sprouting occurred in defoliated microcuttings cultured on a modified Murashige and Skoog medium without growth regulators. Isolation and continuous subculture of sprouted buds on the same medium allowed cloning of microcuttings from C. atlantica and C. libani seedlings and bicentennial C. libani trees, thus providing a desirable alternative for multiplying mature trees that have demonstrated superior characteristics. We also report adventitious bud differentiation from isolated embryos of C. atlantica. Neither auxin treatments nor other methods tested, including infection with Agrobacterium rhizogenes, were effective in inducing root initiation.
Plant Physiology, 2006
Spike lavender (Lavandula latifolia) is an aromatic shrub cultivated worldwide for the production... more Spike lavender (Lavandula latifolia) is an aromatic shrub cultivated worldwide for the production of essential oils. The major constituents of these oils are monoterpenes, which are obtained from isopentenyl diphosphate and dimethylallyl diphosphate precursors through the plastidial methylerythritol phosphate (MEP) pathway and/or the cytosolic mevalonate pathway. 1-Deoxy-d-xylulose-5-P synthase (DXS) catalyzes the first step of the MEP pathway. A cDNA coding for the Arabidopsis (Arabidopsis thaliana) DXS was constitutively expressed in spike lavender. Gas chromatography/mass spectrometry analyses revealed that transgenic plants accumulated significantly more essential oils compared to controls (from 101.5% to 359.0% and from 12.2% to 74.1% yield increase compared to controls in leaves and flowers, respectively). T0 transgenic plants were grown for 2 years, self-pollinated, and the T1 seeds obtained. The inheritance of the DXS transgene was studied in the T1 generation. The increased...
Plant Physiology, 2009
Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the pla... more Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD+ to NADH. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described. However, the in vivo functions of the plastidial isoforms remain unresolved. In this work, we have identified two Arabidopsis (Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. We demonstrate that GAPCps are important for the synthesis of serine in roots. Serine supplement...
American Journal of Botany, 2005
Panicum virgatum L. (switchgrass) is an obligate outcrossing C 4 perennial prairie grass currentl... more Panicum virgatum L. (switchgrass) is an obligate outcrossing C 4 perennial prairie grass currently being pursued for the production of lignocellulosic ethanol. Commercial production of switchgrass for bioenergy has increased substantially in the United States. Understanding the degree of native genetic diversity within and among switchgrass populations will facilitate effective germplasm improvement, conservation, and management programs. In this study, the genetic diversity and differentiation among natural and agronomic switchgrass populations were analyzed at the molecular level by using random amplified polymorphic (RAPD) DNA markers. The mean genetic diversity among populations ranged from 0.051 ± 0.136 to 0.243 ± 0.214 and the mean genetic similarity among all the switchgrass populations was 0.775. The clustering pattern of switchgrass populations grouped the individuals based on their sites of origin, with agronomic cultivars predominantly separated into distinct clusters. The grouping of individuals within and across the populations was corroborated by principal component analysis. These results are consistent with previous reports for switchgrass accessions. RAPD DNA markers were suitable for quickly estimating the genetic diversity of native and agronomic switchgrass populations, and suggest that introgression of agronomic genes into natural switchgrass populations and subsequent changes in genetic structure may be detectable.
Archivos de Medicina (Manizales), 2009
Introducción. Las estadísticas de morbi-mortalidad del departamento de Caldas(Colombia) muestran ... more Introducción. Las estadísticas de morbi-mortalidad del departamento de Caldas(Colombia) muestran el infarto de miocardio en los primeros lugares, por ello surge elinterés de investigar el grado de conocimiento en la interpretación del patrón electrocardiográficoen los estudiantes de Medicina de la Universidad de Manizales.Materiales y Métodos. Un estudio descriptivo correlacional, en el cual se evalúa elconocimiento del patrón electrocardiográfico en 99 estudiantes de Medicina de laUniversidad de Manizales. Se diseñó un cuestionario para evaluar el conocimiento delpatrón electrocardiográfico que consta de preguntas de selección múltiple con únicarespuesta, preguntas falso-verdadero y una evaluación práctica.Resultados. Se observa que los semestres noveno y décimo muestran una calificaciónpromedio significativamente mayor que octavo; y una tendencia a que los estudiantescon promedios más altos logren mejores puntuaciones en el cuestionario. Lacalificación promedio fue de 1,82. No se ...
En aplicaciones a elevadas temperaturas como por ejemplo en cámaras de combustión y toberas de ve... more En aplicaciones a elevadas temperaturas como por ejemplo en cámaras de combustión y toberas de vehículos aeroespaciales se requiere el uso de aleaciones que permitan una elevada extracción de calor y buenas propiedades mecánicas. A lo largo de los años se han estudiados varias aleaciones base cobre que cumplen con estos requisitos, entre ellas: Cu-Cr, Cu-Ag, Cu-Zr, Cu-Cr-Zr, Cu-Ag-Zr, Cu-Cr-Nb, Cu-Al2O3, entre otras. En lo que respecta a la fabricación a nivel industrial de cámaras de combustión y toberas surge el interrogante acerca del método de producción a utilizar. Por un lado se propone la realización de las piezas mediante el método de fusión y colado en molde de arena, mientras que por otro lado se sugiere utilizar un proceso de conformado plástico en caliente como por ejemplo el de forja con la finalidad de romper la estructura de colada, homogeneizar las propiedades del material y soldar posibles defectos provenientes de la fusión y colada. En este trabajo se presenta una comparación entre las propiedades mecánicas a partir de ensayos de tracción a temperatura ambiente y en caliente en aleaciones Cu-Ag-Zr en la condición de cómo colado y forjado. Los resultados obtenidos sugieren que el material que posee un proceso de conformado plásticoen caliente posee mejores propiedades mecánicas que aquel en condición de cómo colado a temperatura ambiente. Evidentemente, la ruptura de la estructura de colada, la eliminación de posibles defectos y el refinamiento de grano producido por el forjado permite mejoras en las propiedades mecánicas del material, así como también, una mejor respuesta a los tratamientos térmicos de envejecido a los que se somete a esta aleación. Por otro lado, a elevadas temperaturas la muestra fundida presenta mayor tensión de fluencia y resistencia a la tracción que la forjada, lo que podría explicarse con el cambio del mecanismo de ruptura por encima de la temperatura equicohesiva.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí
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... | Ayuda. Los mapas de riesgo de crecidas en España. Algunas feflexiones sobre 25 años crucial... more ... | Ayuda. Los mapas de riesgo de crecidas en España. Algunas feflexiones sobre 25 años cruciales. Autores: JB Marco Segura; Localización: Mapas de peligrosidad de avenidas e inundaciones: métodos, experiencias y aplicación / coord. ...
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Papers by Juan Pablo Segura