Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Quercus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed2006

Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland.

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.

Age Factors↗
PubMed2004

Antibacterial and xanthine oxidase inhibitory cerebrosides from Fusarium sp. IFB-121, an endophytic fungus in Quercus variabilis.

Two antibacterial and xanthine oxidase inhibitory cerebrosides, one of which is chemically new, were characterized from the chloroform-methanol (1:1) extract of Fusarium sp. IFB-121, an endophytic fungus in Quercus variabilis. By means of chemical and spectral methods [IR, electrospray ionization MS (ESI-MS), tandem ESI-MS, 1H and 13C NMR, distortionless enhancement by polarization transfer, COSY, heteronuclear multiple-quantum coherence, heteronuclear multiple-bond correlation, and 2-D nuclear Overhauser effect correlation spectroscopy], the structure of the new metabolite named fusaruside was established as (2S,2'R,3R,3'E,4E,8E,10E)-1-O-beta-D-glucopyranosyl-2-N-(2'-hydroxy-3'-octadecenoyl)-3-hydroxy-9-methyl-4,8,10-sphingatrienine, and the structure of the other was identified as (2S,2'R,3R,3'E,4E,8E)-1-O-beta-D-glucopyranosyl-2-N-(2'-hydroxy-3'-octadecenoyl)-3-hydroxy-9-methyl-4,8-sphingadienine. Both new and known cerebrosides, although inactive to Trichophyton rubrum and Candida albicans, showed strong antibacterial activities against Bacillus subtilis, Escherichia coli, and Pseudomonas fluorescens, with their minimum inhibitory concentrations being 3.9, 3.9, and 1.9 microg/mL, and 7.8, 3.9, and 7.8 microg/mL, respectively. Furthermore, both metabolites were inhibitory to xanthine oxidase, with the IC50 value of fusaruside being 43.8 +/- 3.6 microM and the known cerebroside being 55.5 +/- 1.8 microM.

Anti-Bacterial Agents↗
PubMed2005

Molecular cloning and characterization of calmodulin genes in young oak seedlings (Quercus petraea L.) during early flooding stress.

As part of an integrated study on the molecular response of woody plants to flooding, three CaM genes were isolated from oak seedlings (Quercus petraea Liebl.) and characterized. QpCaM-1 was almost exclusively expressed in roots, whereas QpCaM-2 and -3 were more evenly distributed throughout the plant. The present paper documents the differential expression of these genes during hypoxia.

Amino Acid Sequence↗
PubMed2005

Temporal variations in PAH concentrations in Quercus ilex L. (holm oak) leaves in an urban area.

Temporal variations of polycyclic aromatic hydrocarbon (PAH) concentrations in leaves of a Mediterranean evergreen oak, Quercus ilex L., were investigated in order to assess the suitability of this species to biomonitor PAH air contamination. Leaf samples were collected at six sites of the urban area of Naples (Italy) and at a control site in the Vesuvius National Park, in May and September 2001, and in January and May 2002. PAH extraction was conducted by sonication in dichloromethane-acetone and quantification by GC-MS. In winter, leaf total PAH concentrations showed, at all the urban sites, values 2-fold higher than in all the other samplings, reflecting the temporal trend reported for PAH air contamination in the Naples urban area. Moreover, leaf PAH concentrations showed, at all the urban sites, a decrease in May 2002 after the winter accumulation. At the control site leaf PAH concentrations showed lower values and smaller temporal variations than at the urban sites. The findings support the suitability of Q. ilex leaves to monitor temporal variations in PAH contamination. The highest winter concentrations of total PAHs were due to the medium molecular weight PAHs that increased with respect to both low and high molecular weight PAHs. The medium molecular weight PAHs showed the same temporal trend both at the urban and remote sites.

Cities↗
PubMed2006

Phragmites australis and Quercus robur leaf extracts affect antioxidative system and photosynthesis of Ceratophyllum demersum.

During senescence, leaves are deposited on aquatic bodies and decay under water releasing chemical substances that might exert physiological stress to aquatic organisms. Leaf litter alone contributes 30% of the total dissolved organic carbon (DOC) in streams. We investigated the impact of leaves extract from Phragmites australis and Quercus robur on the antioxidative system and photosynthetic rate of the aquatic macrophyte Ceratophyllum demersum exposed for 24h. Rate of photosynthetic oxygen release and antioxidant enzyme activity (glutathione S-transferases, glutathione reductases and peroxidases) as well as lipid peroxidation in C. demersum were measured. Significant (P<0.01) elevations of antioxidative enzyme activity in C. demersum which tends to plateau at high DOC concentrations were observed. There was no detectable effect on lipid peroxidation. A significant dose-dependent reduction in photosynthetic oxygen production was measured.

Antioxidants↗
PubMed2005

Impact of short-term and long-term elevated CO2 on emission of carbonyls from adult Quercus petraea and Carpinus betulus trees.

The study aimed to elucidate the effect of elevated CO2 in short- and long-term experiments on the emission potential of carbonyls from mature oak (Quercus petraea) and hornbeam (Carpinus betulus). The trees were investigated using a canopy crane established in a mixed forest in Switzerland. Short-term CO2 experiments were performed on single leaves with a gas exchange measuring unit by increasing CO2 in the enclosure before and during the measurements. Long-term CO2 fumigation was performed for one vegetation period by a webFACE design. Short-term as well as long-term exposure of leaves resulted in no significant changes in carbonyl exchange in neither Q. petraea nor C. betulus. Carbonyl emission was not affected by stomatal closure under elevated CO2 levels. In contrast to the emission of isoprenoids from vegetation which is thought to be reduced at elevated atmospheric CO2, the exchange of carbonyls seems to be generally unaffected under these conditions.

Acetaldehyde↗
PubMed2006

Photosynthetic responses to elevated CO(2) and O(3) in Quercus ilex leaves at a natural CO(2) spring.

Photosynthetic stimulation and stomatal conductance (Gs) depression in Quercus ilex leaves at a CO(2) spring suggested no down-regulation. The insensitivity of Gs to a CO(2) increase (from ambient 1500 to 2000 micromol mol(-1)) suggested stomatal acclimation. Both responses are likely adaptations to the special environment of CO(2) springs. At the CO(2)-enriched site, not at the control site, photosynthesis decreased 9% in leaves exposed to 2x ambient O(3) concentrations in branch enclosures, compared to controls in charcoal-filtered air. The stomatal density reduction at high CO(2) was one-third lower than the concomitant Gs reduction, so that the O(3) uptake per single stoma was lower than at ambient CO(2). No significant variation in monoterpene emission was measured. Higher trichome and mesophyll density were recorded at the CO(2)-enriched site, accounting for lower O(3) sensitivity. A long-term exposure to H(2)S, reflected by higher foliar S-content, and CO(2) might depress the antioxidant capacity of leaves close to the vent and increase their O(3) sensitivity.

Adaptation, Physiological↗
PubMed2006

Drought changes the dynamics of trace element accumulation in a Mediterranean Quercus ilex forest.

We conducted a field drought manipulation experiment in an evergreen oak Mediterranean forest from 1999 to 2005 to investigate the effects of the increased drought predicted for the next decades on the accumulation of trace elements that can be toxic for animals, in stand biomass, litter and soil. Drought increased concentrations of As, Cd, Ni, Pb and Cr in roots of the dominant tree species, Quercus ilex, and leaf Cd concentrations in Arbutus unedo and of Phillyrea latifolia codominant shrubs. The increased concentration of As and Cd can aggravate the toxic capacity of those two elements, which are already next or within the levels that have been shown to be toxic for herbivores. The study also showed a great reduction in Pb biomass content (100-135 gha(-1)) during the studied period (1999-2005) showing the effectiveness of the law that prohibited leaded fuel after 2001. The results also indicate that drought increases the exportation of some trace elements to continental waters.

Arsenic↗
PubMed2004

Antimicrobial and antioxidative enrichment of oak (Quercus robur) bark by rotation planar extraction using ExtraChrom.

The multifunctional ExtraChrom instrument was used in the extraction of antimicrobial and radical scavenging components from oak (Quercus robur L.) bark. Milled and sieved oak bark was extracted with 80% (v/v) methanol solution in water on the ExtraChrom instrument using step-gradient in the preparative separation. Extracts were tested using agar diffusion method on Staphylococcus aureus, Enterobacter aerogenes and Candida albicans. Some extracts showed moderate bactericidal, fungicidal, bacteriostatic and fungistatic activity. The composition related to activity of the fractions and extracts was screened simultaneously by thin-layer chromatography (TLC) detected by UV and by spraying the plate with radical scavenging reagent 1,1-diphenyl-2-picrylhydrazyl (DPPH) to detect antioxidant activity. Thus, we could demonstrate the antiradical and antimicrobial activity of oak beneficial in the storage of wine against the oxidation and human microbial exposure.

Bacteria↗
PubMed2004

Antiinflammatory evaluation of alcoholic extract of galls of Quercus infectoria.

Galls of Quercus infectoria Olivier (Fagaceae) possess pleiotropic therapeutic activities, with particular efficacy against inflammatory diseases. The present study was undertaken to evaluate the effect of alcoholic extract of Q. infectoria galls on various in vivo and in vitro experimental models of inflammation. Oral administration of gall extract significantly inhibited carrageenan, histamine, serotonin and prostaglandin E2 (PGE2) induced paw oedemas, while topical application of gall extract inhibited phorbol-12-myristate-13-acetate (PMA) induced ear inflammation. The extract also inhibited various functions of macrophages and neutrophils relevant to the inflammatory response. In vitro exposure of rat peritoneal macrophages to gall extract ameliorated lipopolysaccharide (LPS) stimulated PGE2 and nitric oxide (NO) production and PMA stimulated superoxide (O2*-) production in a dose dependent manner. Gall extract also scavenged NO and O2*-. Probing into mechanism of NO inhibition in macrophages revealed gall extract to ameliorate the induction of inducible NO synthase (iNOS), respectively without any inhibitory effect on its catalytic activities even at higher concentrations. Gall extract also significantly inhibited formyl-Met-Leu-Phe (fMLP) stimulated degranulation in neutrophils. These results suggest that alcoholic extract of galls of Q. infectoria exerts in vivo antiinflammatory activity after oral or topical administration and also has the ability to prevent the production of some inflammatory mediators.

Animals↗
PubMed2005

Nitrogen transport in the xylem sap of Quercus ilex: the role of ornithine.

The storage and remobilization of nitrogen in deciduous and evergreen species is a major source of N, supporting the seasonal growth of trees. In evergreens, in addition to wood and roots, older leaves are important reservoirs of N used in the growth of new foliage. Just before bud burst, when transpiration is inactive or low, and when uptake of nitrogen by the roots may be restricted due to low temperatures, levels of organic N in the xylem are high. Amino acids usually comprise the bulk of this organic N. Changes in amino acid concentrations in early spring are thought to result mainly from hydrolysis of N reserves, and not from current N uptake. The seasonal profiles of amino acids in the xylem sap of Quercus ilex, an evergreen Mediterranean tree, were investigated. The first amino acid detected in the xylem sap before spring was ornithine, which may result from the breakdown of arginine present in storage proteins. Arginine is one of the main amino acids present in storage proteins because each arginine molecule has four nitrogen atoms. When protein degradation increases the free arginine pool, the arginase activity is enhanced and, consequently, the conversion of arginine to ornithine. It seems that ornithine has an important role in N transport early in the growth season of Q. ilex.

Biological Transport, Active↗
PubMed2003

Cryopreservation of embryogenic cultures of Quercus robur using desiccation and vitrification procedures.

Oak embryogenic cultures are generally maintained by repetitive embryogenesis. To facilitate management of embryogenic lines and limit the risks of somaclonal variation and contamination a cryopreservation protocol should be developed. In this work we investigated the ability of several pre-treatments to enable 4-6mg clumps (1.0-1.5mm) of globular-heart stage somatic embryos of Quercus robur to withstand freezing in liquid nitrogen. In the best of the two embryogenic culture lines used, 56% of clumps resumed embryogenesis after cooling when they had been pre-treated by successive pre-culture on 0.3 and 0.7M sucrose supplemented media followed by desiccation in the air flow of a laminar flow cabinet to water contents of 24-34%. In both lines, embryogenesis resumption rates of about 70% were achieved by pre-culture on 0.3M sucrose medium followed by application of a vitrification solution (PVS2) for 60-90min prior to rapid plunging in liquid nitrogen.

Cell Line↗
PubMed2003

Rotation planar extraction and rotation planar chromatography of oak (Quercus robur L.) bark.

The versatile novel instrument for rotation planar extraction and rotation planar chromatography was exploited for the investigation of oak bark (Quercus robur L.). The same instrument enabled extraction of the bark, analytical proof of (+)-catechin directly in the crude extract and also its fractionation. Additionally, epimeric flavan-3-ols, (+)-catechin and (-)-epicatechin were separated by analytical ultra-micro rotation planar chromatography on cellulose plates with pure water as developing solvent. A comparison of the extraction of oak bark with 80% aqueous methanol by rotation planar extraction and medium pressure solid-liquid extraction was carried out and both techniques were shown to be suitable for the efficient extraction of oak bark. The raw extracts and fractions on thin-layer chromatography showed many compounds that possessed antioxidant activity after spraying with 1,1-diphenyl-2-picrylhydrazyl. Rotation planar fractionation of 840 mg of crude oak bark extract on silica gel gave 6.7 mg of pure (+)-catechin in one run.

Chromatography, Liquid↗
PubMed2002

Evaluation of the historical records of lead pollution in the annual growth rings and bark pockets of a 250-year-old Quercus crispula in Nikko, Japan.

The annual growth rings and bark pockets of a 250-year-old Japanese oak (Quercus crispula), collected from the Nikko National Park, Japan in 2000 AD, were analysed by ICP mass spectrometry. The annual rings, sampled in 5-year increments, recorded Pb concentrations from 0.01 to 0.1 mg kg(-1) and there was no significant change in concentration with time. In contrast, bark pocket samples dating from 1875 to the present showed a progressive increase in Pb concentration with time, from approximately 0.1 to 10 mg kg(-1). Shoots of epiphytic moss growing on the tree trunk contained 17 mg kg(-1) Pb. The bark pockets recorded historical increases in airborne Pb pollution accompanying the industrialisation of Japan, which was initiated by the opening of Japan's borders from 1854. This increase was not reflected by the annual rings. The 206Pb/207Pb isotope ratio of the bark pockets decreased from approximately 1.18 to 1.16 from 1964 to the present, indicating changes in the sources of Pb pollution. The 206Pb/207Pb isotope ratio of the moss shoots was similar to the current bark (1.16). The data showed bark pockets to be more effective than annual rings for recording historical change in airborne lead pollution.

Air Pollutants↗
PubMed2001

Foliar antioxidant status of adult Mediterranean oak species (Quercus ilex L. and Q. pubescens Willd.) exposed to permanent CO2-enrichment and to seasonal water stress.

Foliar antioxidants were measured in adult individuals of holm oak (Quercus ilex L.) and white oak (Q. pubescens Willd.) growing in the field either within the vicinity of natural CO2 springs or at a nearby control site under ambient CO2, which had been previously exposed to either daily irrigation or no irrigation. In oak trees permanently exposed to elevated CO2 the activities of antioxidant enzymes tended to be lower and the ascorbate pool was larger and more in reduced form, suggesting an attenuation of the oxidative risk in the CO2-enriched trees. In the enriched individuals of both species. the imposition of water shortage significantly increased the size of the glutathione pool and the total superoxide dismutase activity in a species-specific manner. Moreover, water-stressed trees exposed to elevated CO2 tended to have higher catalase and ascorbate peroxidase activities than water-stressed control trees. Such changes may reflect the need for an enhanced compensatory effort when trees acclimated to elevated CO2 are exposed to oxidative stress-promoting environmental factors, such as water shortage.

Acclimatization↗
PubMed2003

Response of Quercus pubescens leaves exposed to geothermal pollutant input in southern Tuscany (Italy).

The paper reports a case of evident and widespread leaf damage on trees in southern Tuscany (Central Italy) attributed to the input of pollutants produced in a geothermal area. The main potentially phytotoxic substances are boron and hydrogen sulphide. Trees affected are conifers as well as both evergreen and deciduous broadleaves. In the present study the possible impact of geothermal pollutants on Quercus pubescens leaves has been considered. Leaf samples coming from three sampling locations (S1 inside the geothermal area; S2 on the margins; S3 outside) and three consecutive dates (June, July and August) were analyzed for the following parameters: sulphur and boron concentration; leaf area; leaf mass per area; chlorophyll fluorescence (Fv/Fm); chlorophyll a, chlorophyll b and carotenoid concentrations. Anatomical and ultrastructural observations were also performed. In all sampling location sulphur and boron concentrations are greater than the background values recorded in southern Tuscany in a previous survey. The sulphur concentration in leaves was higher in S1 than S2 and S3, but did not increase throughout the survey period. Boron reached the greatest concentrations in S2 and showed a continuous increase over the study period. Leaves subjected to a higher load of pollutants were smaller in size (in terms of leaf area), but were more sclerophyllous. Damaged chloroplasts and reduced Fv/Fm values were observed at S1 and S2, but chlorophyll concentration values were higher at S1. Such an apparent anomaly can possibly be explained by the onset of compensation and recovery mechanisms. Foliar injuries appeared to be related to boron concentration.

Boron↗
PubMed2002

Larvicidal activity of extracts from Quercus lusitania var. infectoria galls (Oliv.).

The present study indicates the efficacy of extracts and fractions of Quercus lusitania var. infectoria galls (Oliv.) as larvicidal agents and their possible use in biological control of Culex pipiens, the urban nuisance mosquito. Extracts and fractions were tested against second and fourth instar larvae. The LC(50) values of gallotannins were 335 and 373 ppm, respectively for the 2nd and 4th instar period. The most interesting value of LC(50) (24 h) is obtained with the fraction F(2) (60 ppm).

Animals↗
PubMed2003

Biodegradation of oak (Quercus alba) wood during growth of the shiitake mushroom (Lentinula edodes): a molecular approach.

The chemical transformations that occur during growth of the shiitake mushroom (Lentinula edodes) on oak (Quercus alba) were investigated to improve mushroom cultivation and utilization of the spent substrate. Oak logs were decayed by L. edodes over 8 years, during which time they were sampled at six intervals (30, 40, 66, 76, 77, and 101 months). Fresh and decayed oak samples were analyzed using solid-state (13)C NMR and pyrolysis-gas chromatography-mass spectrometry as well as off-line thermochemolysis with tetramethylammonium hydroxide. Degraded oak exhibited lower carbon contents and increased oxygen content compared to the control. Solid-state (13)C NMR analysis revealed that polysaccharides were the major component of both fresh and decayed oak but that L. edodes mediated the preferential loss of cellulose and xylans as compared to lignin, which remained in an altered form. Several trends point toward the degradation of lignin, including a decrease in the proportion of syringyl units as compared to guaiacyl units and a reduction in side-chain length. An increase in guaiacyl and syringyl acid-to-aldehyde ratios occurred with growth, which suggested that the fungus had caused oxidation of Calpha-Cbeta bonds. The overall effect of L. edodes on oak is similar to that of many white-rot fungi, which simultaneously degrade all cell wall components.

Carbon↗