A possible early eighteenth century record of introgression in oaks.
Explore the source record for details and available documents.
Genetics↗
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.
Measurement carbon dioxide concentration does not affect root respiration of nine tree species in the field.
Inhibition of respiration has been reported as a short-term response of tree roots to elevated measurement CO2 concentration ([CO2]), calling into question the validity of root respiration rates determined at CO2 concentrations that differ from the soil [CO2] in the rooting zone. Our objectives were to validate previous observations of a direct CO2 effect on root respiration in sugar maple (Acer saccharum Marsh.) and to determine if high [CO2] also inhibited root respiration in other tree species. Root respiration rates for nine common North American tree species were measured in the field at ambient soil temperature at both 350 and 1000 microl CO2 l-1. No evidence of direct inhibition of root respiration by elevated measurement [CO2] was found for any of the species tested. The ratio of respiration rates at 1000 and 350 microl CO2 l-1 ranged from 0.97 to 1.07, and the 95% confidence intervals for this ratio included unity for all species tested. Tests of a respiration cuvette used in earlier experiments suggested that gas leakage from the cuvette/IRGA system created an apparent direct CO2 effect on respiration of sugar maple roots when none actually existed. Small sample masses used in those experiments exacerbated the error. Careful attention to the possibility of gas leaks and the avoidance of small sample masses should produce data that will allow researchers to accurately assess whether direct effects of measurement [CO2] exist. Our findings of no direct CO2 effect on respiration of roots of a wide variety of species suggest that such effects may be less common than previously thought for tree roots.
Carbon Dioxide↗
Microelectrode technique for in situ measurement of carbon dioxide concentrations in xylem sap of trees.
We developed a new microelectrode technique for measuring CO2 concentration ([CO2]) in xylem sap of trees. This technique enabled us to make rapid and continuous measurements of xylem sap [CO2] in situ. In this report, we discuss the methodology and establish the feasibility of the technique. We also describe calibration procedures, temperature sensitivity, field use and other characteristics of the microelectrodes. An example of data collected in the field is provided. Microelectrode calibration was accomplished at constant temperature in air of known [CO2]. When sampling temperature differed from calibration temperature, correction was necessary. We developed an equation to correct for temperatures between 15 and 35 degrees C when calibration was conducted at 25 degrees C. Equations based on Henry's Law were used to convert measured gas phase [CO2] (%) to concentration of all products of CO2 dissolved in sap (mmol l(-1)). We inserted microelectrodes into stems of three tree species to measure diurnal changes in [CO2] in the xylem sap. A diurnal pattern with depression during the day and elevation at night was observed. Mean daily [CO2] ranged from 1.6 to 10.3 mmol l(-1). Microelectrodes were suitable for making diurnal measurements for up to 7 days without recalibration. We also used the microelectrodes to measure [CO2] of soil in situ. Soil [CO2] ranged from 1 to 4% (gas phase), with little diurnal variation.
Calibration↗
Variations in transpiration rate and leaf cell turgor maintenance in saplings of deciduous broad-leaved tree species common in cool temperate forests in Japan.
To clarify mechanisms underlying variation in transpiration rate among deciduous broad-leaved tree species, we measured diurnal changes in stomatal conductance (gs) and leaf water potential, and calculated the maximum transpiration rate (Emax), leaf-specific hydraulic conductance (K(s-l)) and difference between the soil water potential and the daily minimum leaf water potential (Psis - Psi(l,min)). Pressure-volume (P-V) measurements were made on leaves. Saplings of eight broad-leaved tree species that are common in Japanese cool temperate forests were studied. Maximum transpiration rate varied significantly among species. There was a statistically significant difference in Psis - Psi(l,min), but not in K(s-l). Species with large Emax also had large Psis - Psi(l,min) and gs. The results of the P-V analyses showed that species with a large Psis - Psi(l,min) maintained turgor even at low leaf water potentials. The similar daily minimum leaf pressure potentials (Psip) across all eight species indicate that Psip values below this minimum are critical. Based on these results, we suggest that the leaf cell capacity for turgor maintenance strongly affects Psis - Psi(l,min) and consequently Emax via stomatal regulation.
Betula↗
In situ measurement of water absorption by fine roots of three temperate trees: species differences and differential activity of superficial and deep roots.
The spatial heterogeneity of water uptake by fine roots under field conditions was analyzed in situ with miniature sap flow gauges in a mature beech-oak-spruce mixed stand. Sap flow rate (J), sap flow density (Jd), and root surface-area-specific flow rate (uptake rate, Js) were measured for eight to 10 small-diameter roots (3-4 mm) per species in the organic layer (superficial roots) and in the mineral soil (30-80 cm, deep roots) during four months in summer 1999. We calculated Js by relating J to the surface area of the section of the fine root system distal to the position of the gauge on the root. When measured synchronously, roots of the three species did not differ significantly in mean Js, although oak roots tended to have lower rates. However, Jd decreased in the sequence spruce > beech > oak in most measurement periods. Microscopic investigation revealed differences in fine root anatomy that may partly explain the species differences in Jd and Js. Oak fine roots had a thicker periderm than beech and spruce roots of similar diameter and spruce roots had fewer fine branch rootlets than the other species. Synchronously recorded Jd and Js of nearby roots of the same tree species showed large differences in flow with coefficients of variation from 25 to 150% that could not be explained by patchy distribution of soil water. We hypothesize that the main cause of the large spatial heterogeneity in root water uptake is associated with differences between individual roots in morphology and ultrastructure of the root cortex that affect root radial and root-soil interface conductivities. The high intraspecific variation in Js may mask species differences in root water uptake. Superficial roots of all species typically had about five times higher Jd than deep roots of the same species. However, Js values were similar for superficial and deep roots in beech and spruce because small diameter roots of both species were more branched in the organic layer than in mineral soil. In oak, deep roots had lower Js (maximum of 100 g m(-2) day(-1)) than superficial roots (about 1000 g m(-2) day(-1)). We conclude that temperate tree species in mixed stands have different water uptake capacities. Water flow in the rhizosphere of forests appears to be a highly heterogeneous process that is influenced by both tree species and differences in uptake rates of individual roots within a species.
Fagus↗
Assessing forest structure and function from spectral transmittance measurements: a case study in a Mediterranean holm oak forest.
Annual changes in structural attributes and seasonal dynamics in water content, photosynthetic rate and light-use efficiency (LUE) were assessed by spectral transmittance for 4 years (1999-2003) in six stands of a Mediterranean holm oak forest. Green biomass, total biomass and leaf area index (LAI) were determined. In 1999, seasonal dynamics of net carbon dioxide (CO2) exchange and water content were measured. We recorded photosynthetically active radiation (PAR) transmittance and hyperspectral transmittance in the 400-1100 nm region and derived reflectance-based vegetation indices. Transmittance over the PAR region derived from either ceptometer or spectroradiometer measurements (PART and TPAR, respectively) was related to green and total biomass. Both PART and TPAR were also related to LAI (r=0.79 and r=0.70, respectively, P <0.001) and were appropriate for comparison among stands, whereas subtle changes in LAI within a stand were better assessed by the transmittance amplitude in the red edge region (TRE) (within a stand, r=0.77-0.99, P <0.001). Spectral transmittance-based indices successfully captured physiological processes that occurred on temporal (seasonal) and spatial scales. The transmittance-based water index (TWI) was related to both foliage and canopy water content (r=0.69, P <0.001). Estimates of foliage and canopy water content improved in dense (closed) stands (r=0.84 and r=0.87, respectively, P <0.001) compared with low-density stands. Under non-drought conditions, transmittance-based photochemical reflectance index (TPRI) was related to LUE (r=0.58, P <0.05) and net CO2 exchange (r=0.72, P <0.01), and the combined TPAR x TPRI index greatly improved these relationships (r=0.93 and r=0.84, respectively, P <0.01), indicating that both structural and physiological adjustments modified CO2 fixation capacity in these forest stands. Our novel approach to the study of transmitted radiation provides a tool for estimating structural and functional variables such as LAI, LUE and water content, which are key determinants of terrestrial productivity.
Biomass↗
Refined pipe theory for mechanistic modeling of wood development.
We present a mechanistic model of wood tissue development in response to changes in competition, management and climate. The model is based on a refinement of the pipe theory, where the constant ratio between sapwood and leaf area (pipe theory) is replaced by a ratio between pipe conductivity and leaf area. Simulated pipe conductivity changes with age, stand density and climate in response to changes in allocation or pipe radius, or both. The central equation of the model, which calculates the ratio of carbon (C) allocated to leaves and pipes, can be parameterized to describe the contrasting stem conductivity behavior of different tree species: from constant stem conductivity (functional homeostasis hypothesis) to height-related reduction in stem conductivity with age (hydraulic limitation hypothesis). The model simulates the daily growth of pipes (vessels or tracheids), fibers and parenchyma as well as vessel size and simulates the wood density profile and the earlywood to latewood ratio from these data. Initial runs indicate the model yields realistic seasonal changes in pipe radius (decreasing pipe radius from spring to autumn) and wood density, as well as realistic differences associated with the competitive status of trees (denser wood in suppressed trees).
Computer Simulation↗
Electrical measurement of tree root absorbing surfaces by the earth impedance method: 2. Verification based on allometric relationships and root severing experiments.
We validated, by means of allometric relationships and root severing experiments, the modified earth impedance method developed for measuring absorbing root surfaces. For the allometric studies, a series of 350 small and large trees of six broadleaf and coniferous species in several experimental sites was examined. We found a good linear ln-ln fit between absorbing root surface area and basal area (or stem cross-sectional area at the root collar in seedlings) over a range of stem diameters from 0.5-55 cm. The absorbing root surface area also changed consistently with crown projected area and the root-accessed area (territory) of the tree. At the whole-tree level, absorbing root surface area reached about 70 times that of basal area and 40% of crown projected area, or roughly 1/3 of the root-accessed area in Norway spruce (in this species, the ratio was relatively larger in small trees and smaller in large trees). The absorbing root surfaces of mechanically severed parts of Norway spruce root systems changed in about the same proportions as the geometrically determined parts of the severed root systems. These results are promising and support field applications of the method in biological and ecological studies.
Absorption↗
No evidence of fine-scale local adaptation of winter moths to variable tree phenology.
Spatial variation in plant phenology can impose strong selective pressures on herbivorous insects whose fitness relies on synchrony with host plants, promoting local adaptation to host timing. Winter moths (Operophtera brumata) have been shown to synchronize egg hatching with host budburst, but whether this reflects local adaptation remains unclear. We used three complementary approaches to assess small-scale local adaptation of winter moths to oak phenology in Wytham Woods, UK, a 385-hectare woodland with repeatable variation in individual oak budburst phenology. We experimentally investigated whether host tree phenology predicts hatch timing using common gardens across multiple temperatures, evaluated fitness benefits of synchrony using translocations, and assessed population structure and gene-environment associations using whole-genome sequencing. We found no support for local adaptation to individual trees. Common garden experiments revealed systematic differences in hatch timing which were unrelated to host budburst, while translocations indicated no fitness consequences of asynchrony. Genetic analyses showed no detectable population structure or association with budburst timing. Local adaptation to host phenology therefore appears not to arise on individual trees but may instead occur at broader spatial scales. Understanding the scale of local adaptation is essential for predicting how insect-plant synchrony will respond to environmental change across heterogeneous landscapes.
Animals↗
Description of Komagataella phaffii sp. nov. and the transfer of Pichia pseudopastoris to the methylotrophic yeast genus Komagataella.
The new methanol-assimilating yeast species Komagataella phaffii Kurtzman sp. nov. (type strain NRRL Y-7556(T)=CBS 2612(T)) is described. Of the four known strains of this species, two were isolated from black oak trees in California, USA, one from an Emory oak in Arizona, USA, and one from an unidentified source in Mexico. The species forms hat-shaped ascospores in deliquescent asci and appears to be homothallic. Analysis of nucleotide sequences from domains D1/D2 of large-subunit (26S) rDNA separates the new species from Komagataella pastoris, the type species of the genus, and from Pichia pseudopastoris, which is here renamed Komagataella pseudopastoris (Dlauchy, Tornai-Lehoczki, Fulop & Peter) Kurtzman comb. nov. (type strain NRRL Y-27603(T)=CBS 9187(T)=NCAIM Y 01541(T)). On the basis of D1/D2 26S rDNA sequence analysis, the three species now assigned to the genus Komagataella represent a clade that is phylogenetically isolated from other ascomycetous yeast genera.
DNA, Fungal↗
Chloroatranol, an extremely potent allergen hidden in perfumes: a dose-response elicitation study.
Oak moss absolute is a long-known, popular natural extract widely used in perfumes. It is reported as the cause of allergic reactions in a significant number of those with perfume allergy. Oak moss absolute has been the target of recent research to identify its allergenic components. Recently, chloroatranol, a hitherto unknown fragrance allergen, was identified in oak moss absolute. The objective was to assess the clinical importance of chloroatranol as a fragrance allergen by characterizing its elicitation profile. 13 patients previously showing a positive patch test to oak moss absolute and chloroatranol were included, together with a control group of 10 patients without sensitization to either of the 2 materials. A serial dilution patch test was performed on the upper back with concentrations ranging from 200 to 0.0063 p.p.m. of chloroatranol in ethanol. Simultaneously, the participant performed an open test simulating the use of perfumes on the volar aspect of the forearms in a randomized and double-blinded design. A solution with 5 p.p.m. chloroatranol was used for 14 days, and, in case of no reaction, the applications were continued for another 14 days with a solution containing 25 p.p.m. All test subjects (13/13) developed an allergic reaction at the site of application of the solution containing chloroatranol. Among them, 12/13 (92%) gave a positive reaction to the 5 p.p.m. solution and 1 to 25 p.p.m. None of the controls reacted (P < 0.001). The use test was terminated at median day 4. The dose eliciting a reaction in 50% of the test subjects at patch testing was 0.2 p.p.m. In conclusion, the hidden exposure to a potent allergen widely used in perfumes has caused a highly sensitized cohort of individuals. Judged from the elicitation profile, chloroatranol is the most potent allergen present in consumer products today.
Adult↗
Contact allergy to fragrances: frequencies of sensitization from 1996 to 2002. Results of the IVDK*.
Increasing frequencies of sensitization to the fragrance mix (FM) have been acknowledged as a serious problem for many years. It is well known that the single compounds (SCs) of the FM contribute differently to the FM patch rest reactions. In this study, we were interested in the time trends of the FM, the SCs, Myroxylon pereirae resin (MP; balsam of Peru) and oil of turpentine (OT) as possible further indicators of perfume allergy and analysed the data collected by the Information Network of Departments of Dermatology multicentre project from 1996 to 2002. During the study period (1996-2002), the FM [8% petrolatum (pet.)], MP (25% pet.) and OT (1% pet.) were tested in 59,298, 59,334 and 59,478 patients, respectively. SCs were tested in a selected group of patients, ranging from n = 1083 to n = 1924 per year. A significant increase in the proportions of patients with positive reactions to FM, MP and OT between 1996 and 1998 is noted, and a significant decline from 1999 to 2002 (Cochrane Armitage trend test, P < 0.0001). The highest frequency of sensitization to the FM was 13.1% in 1999, and the lowest 7.8% in 2002. The number of concomitant reactions to OT, a surrogate marker for terpenes, in FM-positive patients was significantly increased between 1997 and 1999. Reactions to SCs in FM-positive patients were observed in 29.9% (oak moss absolute) to 5.9% (geraniol). There was no time trend in reactions to SCs, although the relative share was increased for isoeugenol, cinnamic aldehyde and geraniol in 1999. In summary, we report for the first time, a significant decline in sensitization to the FM, very probably due to a reduced exposure (less potent allergens used in fine fragrances, possibly less use of natural ingredient-based cosmetics and lowered use concentration of important fragrance allergens). The differences in ranking of SCs could stimulate (a) a redefinition of the FM and (b) a differentiated preventive and regulatory approach, with oak moss and isoeugenol being regulated strictly by prohibition, concentration limits further reconsidered and/or health warnings and clearly less noxious substances like geraniol treated less restrictively.
Bryophyta↗
Milia as sequelae to allergic contact dermatitis.
Explore the source record for details and available documents.
Bryophyta↗
The oak processionary caterpillar as the cause of an epidemic airborne disease: survey and analysis.
BACKGROUND: Thaumetopoea processionea L. (order Lepidoptera), the oak processionary moth, is found in oak forests in most European countries. Its third to sixth larval instars are armed with poisonous hairs (setae) containing an urticating toxin (thaumetopoein) potentially harmful to humans. Because T. processionea infests trees at the edges of forests or standing alone people frequently come into contact with its setae. In the woodland bordering on the western suburbs of Vienna conditions favouring its increase have led to frequent outbreaks of lepidopterism. OBJECTIVES: To determine the incidence of lepidopterism in a suburban environment with three separate caterpillar-infested oak trees and to ascertain the frequency of the various symptoms of lepidopterism and the manner of contact with setae. METHODS: We conducted a telephone survey of all the households/institutions located within 500 m of the infested trees. To gain more information on patients' symptoms and on situations likely to lead to increased contact with setae we asked those who reported cutaneous reactions to complete a questionnaire. As part of the environmental study we described the outbreak site, examined patients and, with tape-strip samples taken from the surface of the soil, looked for setae persisting in the environment. RESULTS: Of 1025 people surveyed 57 (5.6%) reported one or more symptoms of lepidopterism: 55 (96%) reported pruritus, 54 (95%) dermatitis, eight (14%) conjunctivitis, eight (14%) pharyngitis and two (4%) respiratory distress. The questionnaire was returned by 37 (69%) of the individuals with dermatitis. Of those, 16% had reacted with weal formation, 49% with papular rash and 22% with toxic irritant dermatitis. In 13% of respondents it was not possible to define the reaction. The risk factor analysis showed that airborne contamination was the most important cause: 97% of people had frequently passed an infested tree, 57% lived near a tree (in a neighbouring garden) and 32% had a tree in their own garden. Direct contact with larvae was of minor importance (38%). In four of the tape-strip samples intact setae were identified 1 year after the infestation. CONCLUSIONS: Lepidopterism caused by T. processionea is a public health problem of increasing significance. In years with outbreaks of the pest it can reach epidemic proportions in communities located near infested trees. Contact with airborne setae was mainly responsible for the occurrence of the disease.
Adolescent↗
Strong fungal specificity and selectivity for algal symbionts in Florida scrub Cladonia lichens.
Symbiosis is a major theme in the history of life and can be an important force driving evolution. However, across symbioses, it is difficult to tease apart the mechanisms that structure the interactions among potential partners. We used genetic similarity and frequency-based methods to qualitatively and quantitatively examine the patterns of association among several co-occurring Cladonia lichen fungi and their algal photobionts in six disjunct Florida scrub sites. The patterns of association were described by the degree of specificity, i.e. the phylogenetic range of associated partners, and of selectivity, i.e. the frequency of association among partners. Six fungal species associated with only one algal internal transcribed spacer clade, with the remaining two fungi being associated with two algal clades. In all cases, the fungi associated in unequal frequencies with the observed algal photobiont genotypes within those clades--suggesting that both specificity and selectivity were higher than expected. Fungal species can be grouped into three significantly different specificity classes: photobiont specialists, intermediates and generalists. In contrast to the pronounced specificity for photobionts among fungal species, the different Florida scrub sites do not harbour distinct photobiont pools, and differential photobiont availability cannot explain the patterning of lichen associations at this spatial scale. Therefore, we conclude that fungal specificity and selectivity for algal photobionts are major factors in determining the local composition of symbiotic partnerships.
Biological Evolution↗
Shared alleles in sympatric oaks: recurrent gene flow is a more parsimonious explanation than ancestral polymorphism.
Explore the source record for details and available documents.
Alleles↗
Anaphylaxis by fruits of the Fagaceae family: acorn and chestnut.
Explore the source record for details and available documents.
Anaphylaxis↗
Tuber magnatum Pico, a species of limited geographical distribution: its genetic diversity inside and outside a truffle ground.
The aim of this work was to clarify the genetic structure of the ectomycorrhizal fungus, Tuber magnatum Pico, in a natural truffle ground located in north Italy. Ascomata of this population of T. magnatum were collected over a period of up to 5 years. For comparative analysis, T. magnatum fruit bodies of different geographical origin were also considered. We used single locus markers, such as the variable region of ribosomal genes (ITS), the beta-tubulin gene and sequence-characterized amplified regions (SCAR), as tools to identify single-nucleotide polymorphisms (SNPs). On the basis of the molecular results, which were indirectly supported by a karyological analysis, a self-fertilization mechanism is suggested. A SCAR region was polymorphic within the samples of the truffle ground, leading to the identification of two genotypes. In addition, both the SCAR and the ITS proved to be polymorphic among samples coming from different geographical regions, revealing a genetic differentiation in T. magnatum.
Ascomycota↗