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Search Results: 1 - 10 of 597059 matches for " León A. Bravo "
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Effect of Photon Flux Density and Exogenous Sucrose on the Photosynthetic Performance during In Vitro Culture of Castanea sativa  [PDF]
Patricia L. Sáez, León A. Bravo, Manuel Sánchez-Olate, Paulina B. Bravo, Darcy G. Ríos
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.714187
Abstract: The low photon flux density (PFD) under in vitro conditions and sucrose added to the culture medium negatively limits the photochemical activity and photoprotective mechanisms of microshoots. In this work we hypothesize that decreasing sucrose in the culture medium in combination with increasing irradiance, could improve the photosynthesis and consequently the in vitro growth. We evaluated the effect of exogenous sucrose (30 and 5 g·L-1, HS and LS, respectively), under different PFD (50 and 150 μmol photons m-2·s-1, LL and HL, respectively) on the photosynthetic performance and growth of Castanea sativa microshoots. Decreasing sucrose negatively affected the physiological attributes evaluated. Only chloroplast ultrastructure was improved by LS; however this did not lead to an improved in photosynthesis or growth. HL HS produced an increase in photosynthetic activity and chlorophyll contents, reaching under these conditions a higher proliferation rate and biomass production. Additionally, the photochemical activity (electron transport rate and non-photochemical quenching) was improved by HL. Thus, our results suggest that, at least for C. sativa HL is beneficial during the in vitro culture, improving photosynthetic performance as well as growth, but this is only possible in the presence of moderate concentrations of sucrose added to the culture medium.
Photochemical Efficiency during the Establishment and Consolidation Phases of in Vitro Pinus radiata Micrograft Made from Scions of Different Ontogenetic Age  [PDF]
María E. Materán, Patricia L. Sáez, Manuel Sánchez-Olate, León A. Bravo, Roberto Rodríguez, Darcy Ríos, Rafael E. Coopman
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.61026
Abstract: The aim of the present study was to evaluate the applicability of maximal photochemical efficiency of photosystem II (Fv/Fm) as an early estimate of P. radiata micrografts viability coming from different position (basal vs. apical) in the ortets. We hypothesize that Fv/Fm variation is a good indicator of micrograft’s viability and phenological stage during micrograft development. The micrografts were established in QL medium supplemented whit 0.1 mg·L-1 IBA and 1 mg·L-1 BAP and cultured at 25°C ± 2°C and 80 μmol photons m-2s-1 of photosynthetic active radiation by 16 h per day. During the establishment and consolidation phase, we found significant differences in Fv/Fm with respect to time and buds positions provenience. During establishment, basal shoot tips have lower Fv/Fm than apical shoot tips, which agrees with the lowest viability (35%). However, during the consolidation phase, the trend changed and basal shoot tips presented higher Fv/Fm than apical shoot tips and showed an increase in ETR and NPQ, with respect to apical shoots and ortet. Although the measurement of fluorescence parameters implies the insertion of the fluorometer sonde in vitro, this implies aseptic considerations, but always conveies a contamination risk. We conclude that fluorescence (Fv/Fm, ETR, NPQ) can be indicators of the micrograft’s development according to the shoot tips position in the ortet and can be useful early-indicators of the scions’ physiological condition during micrograft transition from establishment to consolidation.
Seasonal Induction of Cluster Roots in Embothrium coccineum J.R. Forst. & G. Forst. in the Field: Factors that Regulate their Development
Donoso-?anculao,Gabriel; Castro,Mauricio; Navarrete,Darío; Bravo,León A; Corcuera,Luis J;
Chilean journal of agricultural research , 2010, DOI: 10.4067/S0718-58392010000400005
Abstract: embothrium coccineum j.r. forst. & g. forst. (proteaceae) is a tree that grows successfully in nutrient poor soils of southern chile at full sunlight. under these conditions it develops cluster roots (cr).however, the induction of cr on this species has not been studied completely. the aim of this work was to study the effect of seasonality, soil and weeds in the development of cr in e. coccineum. the present study was performed in los lagos region (41o72? s lat), chile. plants of e. coccineum were grown in sandy soils in presence or absence of weeds, using two concentrations of organic matter. the number of cr per plant, cr mass and p concentration in leaves was measured during the four seasons in e. coccineum plants. the cr development in the soil with high organic matter concentration and without weeds was observed in autumn, spring and summer, and in the soil with low organic matter concentration was observed in autumn, winter and spring. not found related of this result with the foliar p concentration in e. coccineum. the results suggest a strong seasonal and weeds effect on cr development in e. coccineum under field conditions.
Leaf seasonal accumulation of a 47-kDa dehydrin and changes in its cryoprotective activity in Nothofagus dombeyi (Mirb.) Blume Acumulación estacional de una deshidrina de 47-kDa en hojas y cambios en su actividad crioprotectora en Nothofagus dombeyi (Mirb.) Blume
Jorge Gallardo-Cerda,León A Bravo,Luis J Corcuera
Gayana. Botanica , 2012,
Abstract: Nothofagus dombeyi (Mirb.) Blume is an evergreen tree, pioneer in habitats subject to unfavorable environmental conditions as nighttime freezing temperatures and low water content. It inhabits zones characterized by cold Winter with freezing temperature and Spring frosts reaching to -5°C. Furthermore, it has the capacity to maintain a functional photosynthetic apparatus at low temperatures. We postulated that N. dombeyi is capable to accumulate dehydrins in leaves in response to cold. Seasonal variation in dehydrins, soluble total proteins, and cryoprotective activity in vitro of protein extracts of N. dombeyi leaves were analyzed during the years 2004 and 2005. A dehydrin-like protein of 47-kDa was immunologically identified; this protein was present only in Winter and Spring. The highest accumulation of this protein and the maximal in vitro cryoprotective activity was found during Spring. The leaf total protein extract of this season preserved the 100% of lactate dehydrogenase (LDH) enzyme activity after 5 freeze/thaw cycles in liquid nitrogen adding 10 μg/ml of total proteins extract. The soluble protein concentration increased from 1.8 mg/g in Summer to 4.8 mg/g in Fall on base of fresh weight, and declined through Winter and Spring. The 47-kDa dehydrin may be related to cold hardiness of leaf tissue in overwintering N. dombeyi. We conclude that cell dehydration caused by freezing is the main factor involved in the triggering of 47-kDa dehydrin accumulation in leaves of N. dombeyi. The accumulation of reactive oxygen species (ROS) by oxidative stress product of high irradiance and frosts during Spring, and their role in the triggering of the 47-kDa dehydrin accumulation in leaves of N. dombeyi is discussed. Nothofagus dombeyi (Mirb.) Blume es un árbol siempreverde, pionero en sitios con condiciones ambientales desfavorables como baja temperatura nocturna y baja disponibilidad hídrica. Habita en zonas caracterizadas por inviernos fríos con temperaturas congelantes y heladas de primavera que pueden llegar a los -5°C. Además tiene la capacidad de mantener su aparato fotosintético funcional en condiciones de baja temperatura. Postulamos que N. dombeyi es capaz de acumular deshidrinas en sus hojas en respuesta a baja temperatura. Se analizó la variación estacional de deshidrinas, proteínas solubles totales y la actividad crioprotectora in vitro de extractos proteicos de hojas de N. dombeyi durante los a os 2004 y 2005. Una proteína con características de deshidrina de 47 kDa de peso molecular fue identificada inmunológicamente en hojas, la que estuvo pres
Seasonal Induction of Cluster Roots in Embothrium coccineum J.R. Forst. & G. Forst. in the Field: Factors that Regulate their Development Inducción Estacional de Raíces Proteoideas en Embothrium coccineum J.R. Forst. & G. Forst. en el Campo: Factores que Regulan su Desarrollo
Gabriel Donoso-?anculao,Mauricio Castro,Darío Navarrete,León A Bravo
Chilean Journal of Agricultural Research , 2010,
Abstract: Embothrium coccineum J.R. Forst. & G. Forst. (Proteaceae) is a tree that grows successfully in nutrient poor soils of southern Chile at full sunlight. Under these conditions it develops cluster roots (CR).However, the induction of CR on this species has not been studied completely. The aim of this work was to study the effect of seasonality, soil and weeds in the development of CR in E. coccineum. The present study was performed in Los Lagos Region (41o72’ S lat), Chile. Plants of E. coccineum were grown in sandy soils in presence or absence of weeds, using two concentrations of organic matter. The number of CR per plant, CR mass and P concentration in leaves was measured during the four seasons in E. coccineum plants. The CR development in the soil with high organic matter concentration and without weeds was observed in autumn, spring and summer, and in the soil with low organic matter concentration was observed in autumn, winter and spring. Not found related of this result with the foliar P concentration in E. coccineum. The results suggest a strong seasonal and weeds effect on CR development in E. coccineum under field conditions. Embothrium coccineum J.R. Forst. & G. Forst.(Proteaceae) es un árbol que crece en suelos pobres en nutrientes del sur de Chile a pleno sol. En estas condiciones desarrolla raíces proteoideas. Sin embargo, la inducción de raíces proteoideas en esta especie no ha sido estudiada completamente. El objetivo de este trabajo fue estudiar el efecto de la estacionalidad, suelo y malezas en el desarrollo de las raíces proteoideas en E. coccineum. El presente estudio fue desarrollado en la Región de Los Lagos (41o72' lat. S), Chile. Las plantas se cultivaron en suelo arenoso en presencia o ausencia de malezas, utilizando dos concentraciones de materia orgánica. El número de raíces proteoideas por planta, el peso de las raíces proteoideas y la concentración de P foliar, se midieron durante las cuatro estaciones en plantas de E. coccineum. El desarrollo de las raíces proteoideas en el suelo con alta concentración de materia orgánica y sin malezas fue observado en oto o, primavera y verano y en el suelo con baja concentración de materia orgánica fue observado en oto o, invierno y primavera. No se encontró relación de este resultado con la concentración de P foliar en E. coccineum. Los resultados sugieren un fuerte efecto estacional y de las malezas en el desarrollo de las raíces proteoideas en E. coccineum en condiciones de campo.
Prevalencia y factores relacionados con la presencia de manifestaciones orales en pacientes con VIH/SIDA, Cali, Colombia
Pinzón,Elisa María; Bravo,Sonia Marlene; Méndez,Fabián; Clavijo,Gail Mildred; León,Miguel Evelio;
Colombia Médica , 2008,
Abstract: aim: to determine the prevalence and factors related with the presence of oral manifestations in hiv/aids patients who attended health institutions in cali-colombia. materials and methods: a cross-sectional descriptive study was made in 319 patients who attended four health institutions in the city of cali. the inclusion criteria were: being hiv positive patients, being over 18 years old, attending medical checkups and accepting participation. pregnant women and inmates were excluded. results: the general prevalence of oral manifestations was 77.1% (ci 95%: 72.4-81.7). the most frequent oral manifestation was xerostomia with 41.1% (ci 95%: 35.5-46.6), followed by the manifestations from mycotic origin [(35.7% (ci 95% 30.4-41)] bacterial [34.2% (ci 95%: 28.9-39.4)] virals [16.6 (ci 95% 12.5-20.7)], oral ulcers [7.5 (ci 95%: 4.6-10.4)] and neoplastics [3.8 (ci95% 1.6-5.8)]. the population studied did not show non-hodgkin's lymphoma. in the multivariate analysis, the presence of oral injuries was associated with time of hiv/aids diagnosis during the previous 12 months, detectable viral load, and presence of removable dental prosthesis and self-report of dry mouth. conclusions: the prevalence of oral manifestations registered in this population is high compared with those reported world-wide. considering the association found, our results suggest that oral injuries are initial clinic characteristics of the disease and may be useful to predict treatment failure and progression from hiv infection to aids.
Cold-acclimation limits low temperature induced photoinhibition by promoting a higher photochemical quantum yield and a more effective PSII restoration in darkness in the Antarctic rather than the Andean ecotype of Colobanthus quitensis Kunt Bartl (Cariophyllaceae)
Luisa Bascu?án-Godoy, Carolina Sanhueza, Marely Cuba, Gustavo E Zu?iga, Luis J Corcuera, León A Bravo
BMC Plant Biology , 2012, DOI: 10.1186/1471-2229-12-114
Abstract: The same reduction (25%) in maximum PSII efficiency (Fv/Fm) was observed in both cold-acclimated (CA) and non-acclimated (NA) plants under PhT. A full recovery was observed in CA plants of both ecotypes under dark conditions, but CA Antarctic plants recover faster than the Andean ecotype.Under PhT, CA plants maintain their quantum yield of PSII, while NA plants reduced it strongly (50% and 73% for Andean and Antarctic plants respectively). Cold acclimation induced the maintenance of PsaA and Cyt b6/f and reduced a 41% the excitation pressure in Antarctic plants, exhibiting the lowest level under PhT. xCold acclimation decreased significantly NPQs in both ecotypes, and reduced chlorophylls and D1 degradation in Andean plants under PhT.NA and CA plants were able to fully restore their normal photosynthesis, while CA Antarctic plants reached 50% higher photosynthetic rates after recovery, which was associated to electron fluxes maintenance under photoinhibitory conditions.Cold acclimation has a greater importance on the recovery process than on limiting photodamage. Cold acclimation determined the kinetic and extent of recovery process under darkness in both C. quitensis ecotypes. The greater recovery of PSII at low temperature in the Antarctic ecotype was related with its ability to maintain PsaA, Cyt b6/f and D1 protein after photoinhibitory conditions. This is probably due to either a higher stability of these polypeptides or to the maintenance of their turnover upon cold acclimation. In both cases, it is associated to the maintenance of electron drainage from the intersystem pool, which maintains QA more oxidized and may allow the synthesis of ATP and NADPH necessaries for the regeneration of ribulose 1,5-bisphosphate in the Calvin Cycle. This could be a key factor for C. quitensis success under the harsh conditions and the short growing period in the Maritime Antarctic.The balance between absorbed and photochemically converted energy for metabolism is critical in
Photosynthetic responses to temperature and light of Antarctic and Andean populations of Colobanthus quitensis (Caryophyllaceae)
Revista chilena de historia natural , 2007, DOI: 10.4067/S0716-078X2007000300007
Abstract: colobanthus quitensis (kunth, 1831) bartling (caryophyllaceae) is characterized by a wide latitudinal distribution, ranging between the tropical high andes and the antarctic peninsula. although both habitat types are characterized by cold and freezing temperatures, important microclimatic differences exist during the growing season. hence, important differences in the response of the photosynthetic apparatus to abiotic factors could be expected between antarctic and andean populations of c. quitensis. we studied the relationship between net photosynthesis, leaf temperature and light intensity in two populations of c. quitensis, one from la parva in the andes of central chile and the other from king george island, in the maritime antarctic. plants from both populations were grown in the laboratory at 15 °c under 250 μmol photons m-2 s-1, with a 16/8 h light/dark photoperiod. twenty plants (about two months old) of each population were transferred to a 4 °c chamber with the same light and photoperiod conditions as above to assess the photosynthetic acclimation capacity. at 15 °c, populations differed in their optimum leaf temperature for photosynthesis, being 24.0 °c in individuals from the andes and 18.6 °c in individuals from the antarctic. in contrast, antarctic individuals showed the highest net photosynthesis rate under both temperature treatments, with the lowest light compensation and saturation points. antarctic individuals had higher photosynthetic activity at lower temperatures compared to individuals from the andes. our results suggest that c. quitensis has adapted photosynthetic performance of individuals growing in different localities to the prevailing climatic conditions. differences in photosynthetic responses to temperature and light are discussed in relation to ecotypic differentiation between two populations studied
Photosynthetic performance of Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae) in a high-elevation site of the Andes of central Chile
Revista chilena de historia natural , 2006, DOI: 10.4067/S0716-078X2006000100004
Abstract: photosynthesis of colobanthus quitensis and mesoclimatic conditions of air temperature and light intensity during the growing season were investigated at 2,650 m in the central chilean andes. on three typical days of the growing period (january, march and may), co2 exchange and chlorophyll fluorescence were measured. in addition, a series of fluorescence response curves with increasing light intensity at different temperatures were performed to estimate the propensity of andean c. quitensis populations to be photoinhibited. net photosynthesis (pn) was low (ca. 2.0 mmol co2 m-2s-1) during the morning and noon in days with high photosynthetic active radiation (par, above 1,800 mmol photons m-2s-1). pn increased in the afternoon (3.5-4.8 mmol co2 m-2s-1) when par decreased to ca. 1,400 mmol photons m-2s-1 and leaf temperature were ca. 20 °c. fv/fm in the diurnal periods was between 0.7-0.75 without evidence of photoinhibition. leaves at 15 and 22 °c exhibited a slow decrease of fpsii with the increase in actinic light intensity, although the fraction of reaction centers open (expressed by qp) remained higher at 22 °c. npq was saturated at light intensities close to 500 mmol photons m-2s-1 in leaves at 22 °c and at higher intensities at 15 °c, suggesting that npq could be a mechanism of energy dissipation at high light intensity and high leaf temperature in the field. our results indicated that c. quitensis is not photodamaged during the diurnal cycle and that the low pn registered during some diurnal periods are likely to be related with photorespiration, which has been suggested as an efficient protective mechanism for photoinhibition in alpine plants. our results are also compared with the photosynthetic performance of c. quitensis populations from the maritime antarctic
Cloning and constitutive expression of Deschampsia antarctica Cu/Zn superoxide dismutase in Pichia pastoris
Jaime R Sánchez-Venegas, Alejandro Navarrete, Jorge Dinamarca, León A Bravo Ramírez, Ana Moraga, Manuel Gidekel
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-207
Abstract: The Copper/Zinc superoxide dismutase (Cu/ZnSOD) gene, SOD gene, was isolated from a D. antarctica by cDNA library screening. This SOD gene was cloned in the expression vector pGAPZαA and successfully integrated into the genome of the yeast P. pastoris SMD1168H. A constitutive expression system for the expression of the recombinant SOD protein was used. The recombinant protein was secreted into the YPD culture medium as a glycosylated protein with a 32 mg/l expression yield. The purified recombinant protein possesses a specific activity of 440 U/mg.D. antarctica Cu/ZnSOD recombinant protein was expressed in a constitutive system, and purified in a single step by means of an affinity column. The recombinant SOD was secreted to the culture medium as a glycoprotein, corresponding to approximately 13% of the total secreted protein. The recombinant protein Cu/ZnSOD maintains 60% of its activity after incubation at 40°C for 30 minutes and it is stable (80% of activity) between -20°C and 20°C. The recombinant SOD described in this study can be used in various biotechnological applications.The hairgrass Deschampsia antarctica Desv. is one of the two vascular plants that have adapted to the extreme climate of the Maritime Antarctic [1]. It is tolerant to low temperatures, usually between -2°C and 6°C in summer and freezing in winter [2]. Episodes of high light intensity and increased UV radiation due to the thinning of the ozone layer during spring are frequent in Antarctic [3]. Because of the extreme conditions in which this plant lives, it has attracted the interest of plant physiologists, biochemists and molecular biologists, who are trying to discover the mechanisms that enable it to colonize the Antarctic environment [4-6].It has been determined that the combination of low temperature, high light and UV radiation leads to an increase in the production of reactive oxygen species, such as the superoxide anion, hydrogen peroxide and the hydroxyl radical [7]. The accumulatio
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