Publications (13)33.89 Total impact
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Article: Influence of canopy position, needle age and season on the foliar gas exchange of Pinus canariensis
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ABSTRACT: We investigated the seasonal variation in the gas exchange of current and 1-year-old needles in the upper sun and lower shade crown of adult Pinus canariensis trees. In general, current year needles displayed lower gas exchange rates than the 1-year-old needles. In both needle age classes, gas exchange was significantly lower in the shade than in the sun crown. However irrespective of crown position and needle age, maximum daily net photosynthesis, transpiration, and stomatal conductance for water vapour were generally higher during the wet and cold winter as compared to the dry and hot summer. These higher gas exchange values obtained during the cold and wet season can mainly be explained by higher soil-water availability and lower evaporative demand as compared to the warm and dry seaon. In addition, we also observed a displacement in the temperature optimum of net photosynthesis towards lower temperatures during the cold and wet season as compared to the warm and dry season. The observed gas exchange characteristics indicate a conservative water saving strategy and thus allowing P. canariensis needles to maintain a positive carbon gain even at periods of high evaporative demand and low soil-water availability.European Journal of Forest Research 04/2012; 127(4):293-299. · 1.98 Impact Factor -
Article: Short- and long-term modulation of the lutein epoxide and violaxanthin cycles in two species of the Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana Mill.).
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ABSTRACT: Short- and long-term responses of the violaxanthin (V) and lutein epoxide (Lx) cycles were studied in two species of Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana L.). The Lx content exceeded the V content in shade leaves of both species. Both Lx and V were de-epoxidised on illumination, but only V was fully restored by epoxidation in low light. Violaxanthin was preferentially de-epoxidised in low light in L. nobilis. This suggests that Lx accumulates with leaf ageing, partly because its conversion to lutein is limited in shade. After exposure to strong light, shade leaves of avocado readjusted the total pools of alpha- and beta-xanthophyll cycles by de novo synthesis of antheraxanthin, zeaxanthin and lutein. This occurred in parallel with a sustained depression of F(v)/F(m). In Persea indica, a closely related but low Lx species, F(v)/F(m) recovered faster after a similar light treatment, suggesting the involvement of the Lx cycle in sustained energy dissipation. Furthermore, the seasonal correlation between non-reversible Lx and V photoconversions and pre-dawn F(v)/F(m) in sun leaves of sweet bay supported the conclusion that the Lx cycle is involved in a slowly reversible downregulation of photosynthesis analogous to the V cycle.Plant Biology 06/2008; 10(3):288-97. · 2.39 Impact Factor -
Article: Comparison of GenoType MTBC with RFLP-PCR and multiplex PCR to identify Mycobacterium tuberculosis complex species.
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ABSTRACT: The aims of the work presented here were to evaluate a commercial system based on DNA hybridization technology on nitrocellulose strips (GenoType MTBC; Hain Diagnostika, Nehren, Germany) for identifying Mycobacterium tuberculosis complex isolates to the species level and to compare the results with those obtained using the RFLP-PCR and multiplex PCR molecular techniques, biochemical tests and susceptibility testing. The commercial system correctly identified 102 of 103 (99.03%) strains studied, indicating it is capable of discriminating among the tuberculosis complex species.European Journal of Clinical Microbiology 02/2007; 26(1):63-6. · 2.86 Impact Factor -
Article: Usefulness of E-test strips for testing susceptibility of Mycobacterium tuberculosis complex strains.
European Journal of Clinical Microbiology 01/2006; 24(12):856-7. · 2.86 Impact Factor -
Article: Systematic molecular characterization of multidrug-resistant Mycobacterium tuberculosis complex isolates from Spain.
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ABSTRACT: We used spoligotyping and restriction fragment length polymorphism (RFLP) of the IS6110-insertion sequence to study the molecular epidemiology of multidrug-resistant (MDR) tuberculosis in Spain. We analyzed 180 Mycobacterium tuberculosis complex isolates collected between January 1998 and December 2000. Consecutive isolates from the same patients (n = 23) always had identical genotypes, meaning that no cases of reinfection occurred. A total of 105 isolates (58.3%) had unique RFLP patterns, whereas 75 isolates (41.7%) were in 20 different RFLP clusters. Characterization of the katG and rpoB genes showed that 14 strains included in the RFLP clusters did not actually cluster. Only 33.8% of the strains isolated were suggestive of MDR transmission, a frequency lower than that for susceptible strains in Spain (46.6%). We found that the Beijing/W genotype, which is prevalent worldwide, was significantly associated with immigrants. The 22 isolates in the largest cluster corresponded to the Mycobacterium bovis strain responsible for two nosocomial MDR outbreaks in Spain.Journal of Clinical Microbiology 04/2005; 43(3):1220-7. · 4.15 Impact Factor -
Article: Leaf Gas Exchange Characteristics in Relation to Leaf Canopy Position of Myrica faya in its Native Environment (Tenerife, Canary Islands)
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ABSTRACT: Diurnal courses of gas exchange were measured throughout one year in fully expanded current-year leaves in the uppermost canopy (sun leaves, 18 m above ground) and in the lower canopy (shade leaves, 12 m above ground) of Myrica faya Ait., a dominant component of the Canarian laurel forest in Tenerife, Canary Islands, Spain.M. faya showed large differences between sun and shade leaves in gas exchange characteristics (about 50 % of maximum carbon assimilation rate (Amax) reduction in shade leaves, but this reduction can be higher on specific days) that were modulated by strong light attenuation and high leaf area index (LAI) of the stand. This species presented low Amax, about 10 μmol m-2 s-1, high maximum transpiration (E, 8 mmol m-2 s-1) and stomatal conductance (gs, 750 mmol m-2 s-1) and very low instantaneous water use efficiency (WUE, mean maximum 1.1 mmol mol-1) and A/gs (mean maximum 23.5 μmol mol-1). M. faya responded to high air vapour pressure deficit (VPD), decreasing its gs but maintaining relatively high values of A and E during the studied period. Stomatal response to VPD showed a higher sensitivity than its congeners, M. cerifera, and Laurus azorica, tree species co-occurring in the Canarian laurel forest. In general, all these gas exchange characteristics lead us to consider this species more similar to subtropical plants of humid regions than to species of the Mediterranean region.Plant Biology 08/2002; 4(5):576 - 583. · 2.39 Impact Factor -
Article: Three‐Dimensional Reconstruction of the Stomatal Complex in Pinus canariensis Needles Using Serial Sections
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ABSTRACT: The three-dimensional (3D) morphology of the stomata in leaves of Pinus canariensis is described with respect to the spatial arrangement of guard cells, subsidiary cells, polar and lateral cells. Serial semi-thin sections of the stomatal apparatus were digitally reconstructed and analysed with regard to the position, shape and size of the cell types involved. The stomatal complex consists of 16 cells with uniquely shaped polar and lateral cells. The polar cells form a kind of roof above the epistomatal chamber thereby reducing the surface aperture. The structural features of the stomatal complex differ from other Pinus species and are presumed to be an adaptation to extreme environmental conditions.Plant Biology 12/2001; 4(1):70 - 76. · 2.39 Impact Factor -
Article: Gas exchange characteristics of a Canarian laurel forest tree species (Laurus azorica) in relation to environmental conditions and leaf canopy position.
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ABSTRACT: Diurnal courses of gas exchange were measured over a 1-year period in fully expanded current-year leaves in the upper (sun-exposed, 18 m above ground) and the lower (shaded, 12 m above ground) canopy of Laurus azorica (Seub.) Franco, a major canopy species of the Canarian laurel forest in Tenerife, Canary Islands, Spain. Laurus azorica exhibited high leaf plasticity in gas exchange characteristics, with a maximum carbon assimilation rate (Amax) of shade leaves about 50% that of sun leaves. This difference reflects the high leaf area index (LAI) of the stand and the correspondingly sharp light attenuation with increasing canopy depth. In sun leaves, Amax peaked at about 11 micromol m-2 s-1 and maximum transpiration (E) was about 8 mmol m-2 s-1, which corresponded with a maximum stomatal conductance (gs) of about 650 mmol m-2 s-1. Mean maximum instantaneous water-use efficiency (WUE) was 1.5 mmol mol-1 and the mean maximum A/gs was 20-35 micromol mol-1. Mean minimum internal CO2 concentration (Ci) was 225 micromol mol-1. Although high air vapor pressure deficit (VPD) caused a small decrease in gs, it remained high enough to maintain relatively high A and E. These gas exchange characteristics indicate a non-conservative use of water, which is appropriate for a species subject to droughts that are mild or of short duration. In this respect, Laurus azorica differs from its congener, L. nobilis L., of the Mediterranean region and other shrubs growing in Mediterranean-type climates in California and Chile that have to withstand more severe or more prolonged droughts.Tree Physiology 10/2001; 21(14):1039-45. · 2.88 Impact Factor -
Article: In vitro susceptibilities of rapidly growing mycobacteria to telithromycin (HMR 3647) and seven other antimicrobials.
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ABSTRACT: The antimicrobial activities of telithromycin (HMR 3647) and seven other antimicrobials against 94 strains of rapidly growing mycobacteria were determined. Telithromycin at a concentration of 1 microg/ml inhibited Mycobacterium peregrinum (100%), Mycobacterium chelonae (80%), Mycobacterium abscessus-Mycobacterium mucogenicum (44.4%), and Mycobacterium fortuitum (2.1%). All or most strains of M. peregrinum, M. fortuitum, and M. mucogenicum were inhibited by 2 microg of quinolones per ml.Antimicrobial Agents and Chemotherapy 02/2000; 44(1):181-2. · 4.84 Impact Factor -
Article: Identification by spoligotyping of a caprine genotype in Mycobacterium bovis strains causing human tuberculosis.
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ABSTRACT: We have used spoligotyping to characterize 18 Mycobacterium bovis strains isolated from cattle and 23 M. bovis strains isolated from goats. The spoligotypes revealed that caprine strains form a separate and well-differentiated group that we refer to hereafter in this abstract as the caprine genotype. To evaluate the importance of this genotype as a cause of tuberculosis in other animal species, including humans, we applied the spoligotyping method to 112 strains, including to all isolates identified as M. bovis by a Mycobacterial National Reference Laboratory (Majadahonda, Madrid) from 1994 to 1996. Eighty-three of these strains were identified in human isolates. In addition to being identified in three goat isolates and two sheep isolates, the caprine genotype was also found in three isolates causing human tuberculosis. Evidence to support the argument that there is a zoonotic risk of caprine tuberculosis was presented by the identification of the caprine genotype in an isolate from a veterinary worker with a recent history of contact with tuberculous goats.Journal of Clinical Microbiology 01/1998; 35(12):3328-30. · 4.15 Impact Factor -
Article: Canopy transpiration of a Canary Islands pine forest
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ABSTRACT: Canopy transpiration (Ec) of a 50-year old Pinus canariensis Chr. Sm. Ex DC. stand in Tenerife, Canary Islands was estimated continuously throughout 1 year from August 2000 to July 2001 by means of xylem sap flow measurements. Although there was pronounced seasonal trend in soil water availability and evaporative demand, Ec did not show any clear seasonal trend and averaged 0.80 during the cold-wet and 0.82 mm day−1 during the warm-dry period. This is, because summer drought is often mitigated by a high relative humidity of the air and a high frequency of clouds due to the north-east trade winds. However, at a given solar radiation and vapour pressure deficit Ec was significantly lower during the warm and dry season than at other times during the year. The annual total of Ec was 252.3 mm, which is significantly below the values estimated for other Mediterranean forest ecosystems and thus shows a strong adaptation to low soil water availability during periods of great evaporative demand.Agricultural and Forest Meteorology. -
Article: Physiological responses of tagasaste to a progressive drought in its native environment on the Canary Islands
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ABSTRACT: Diurnal courses of gas exchange, chlorophyll fluorescence, shoot water potential (Ψ) and leaf relative water content (RWCleaf) were recorded in Chamaecytisus proliferus (L. fil.) Link ssp. proliferus var. palmensis (Christ) (tagasaste) growing in natural conditions in the North-West slope of Tenerife, Canary Islands. During the studied period (April–July 2000), the soil relative water content (RWCsoil) progressively decreased, while the air vapour pressure deficit increased. As a consequence a decrease in Ψ and RWCleaf took place as well as a decrease in stomatal conductance (gs) and CO2 assimilation rate (A). These characteristics, typical of an anisohydric plant, allowed this species to endure a mild drought.Photochemical efficiency of PSII (φPSII) followed the inverse pattern to that observed for the photosynthetic photon flux density (PPFD), decreasing at midday and recovering during the late afternoon. This recovering at the end of each day, and the constant values of the maximum quantum yield of PSII photochemistry (Fv/Fm) during the studied period, indicate that there was no permanent damage to the photosynthetic apparatus due to mild water stress.Environmental and Experimental Botany 53(2):195-204. · 2.98 Impact Factor -
Article: The measurement and modelling of the variation of stemflow in a laurel forest in Tenerife, Canary Islands
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ABSTRACT: The stemflow of 30 sample trees belonging to six different species was quantified in the laurel forest of Agua Garcı́a, Tenerife, Canary Islands, during a complete year. Different methods described in the literature, for scaling up the stemflow values from tree level to stand level were applied. The best for this type of forest is based on the application of annual regressions between basal area and stemflow in each species, giving a total annual stand stemflow of 42.86 l m−2. This represents 6.85% of annual gross precipitation. This is not a very high value but important to be taken into account in the determination of the water balance of the forest. An antecedent precipitation of 2 mm was necessary for the initiation of the stand stemflow. Stemflow attained 10% of gross precipitation during big rain events, being positively correlated with the mean hourly rain intensity.Differences among trees and species were also studied resulting that trees with the biggest crown area, not dominated by their neighbours, and with the smoothest bark collected the largest volumes of stemflow in the stand. Bark roughness, divergence angle of the branches with respect to the trunk and also the size of the leaves, were responsible for the differences between species.As a consequence of the stemflow the rain can be concentrated up to 12.8 times in the infiltration areas of the trees which could produce better soil conditions for tree growth. The results obtained in the Agua Garcı́a laurel forest stand are the first stemflow data obtained for the Canarian laurel forest and they are in the range found in other types of forests.Journal of Hydrology. 221:161-175.
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Institutions
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2001–2012
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Universidad de La Laguna
- Facultad de Farmacia
La Laguna, Canary Islands, Spain
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2006
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Fundación Jiménez Díaz
Madrid, Madrid, Spain
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