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At least 109 records · Page 6Linked to original sources
PubMed2000

Leaf photosynthetic characteristics of beech (Fagus sylvatica) saplings during three years of exposure to elevated CO(2) concentration.

Beech (Fagus sylvatica L.) seedlings were cultivated from seeds sown in pots or directly in the ground in outdoor chambers that were transparent to solar radiation, and provided either ambient air or CO(2)-enriched air (ambient + 350 &mgr;mol mol(-1)). The rooting volume was high in all experiments. In the short-term experiment, potted plants were assigned to a factorial CO(2) x nutrient treatment (optimal nutrient supply and severe nutrient shortage) for 1 year. In the long-term experiment, plants were grown directly in the ground and received an optimal supply of water and nutrients in both CO(2) treatments for 3 years. Nutrient stress caused carboxylation capacity (V(m)) to decrease in the potted seedlings exposed to CO(2)-enriched air during their first growing season. In the long-term experiment with optimal nutrient supply, CO(2)-enriched air did not affect V(m), but caused an upward acclimation of maximum electron transport rate (J(m)). Consequently, there was a 14% increase in the J(m)/V(m) ratio, indicating nitrogen reallocation to maintain an equilibrium between RuBP consumption and RuBP regeneration. Both V(m) and J(m) decreased during the growing season in both CO(2) treatments. Although upward acclimation of J(m) was no longer apparent at the end of the third growing season, plants in CO(2)-enriched air maintained a higher J(m)/V(m) ratio than plants in ambient air, indicating that photosynthetic acclimation always occurred. Second flush leaves appeared during each growing season. When expressed on the basis of foliar nitrogen concentration, their photosynthetic characteristics (V(m) and J(m)) were enhanced compared with other leaves. Because the number of second flush leaves was also increased in the elevated CO(2) treatment, this response should be taken into account when modeling the effects of elevated CO(2) concentration on canopy photosynthesis. Stomatal conductance decreased in response to atmospheric CO(2) enrichment; however, the stomatal response to irradiance followed a single relationship based on two stomatal conductance models.

Journal Article↗
PubMed2000

Genetic diversity and bark physiology of the European beech (Fagus sylvatica): a coevolutionary relationship with the beech scale (Cryptococcus fagisuga).

In 1994 and 1995, the degree of infestation by the beech scale (Cryptococcus fagisuga Lind.) was recorded on 120 beech trees (Fagus sylvatica L.) in the Pless Forest near Göttingen, Germany. Simultaneously, the trees were characterized genetically and compounds of primary and secondary metabolism of beech bark were analyzed. A correlation was established between beech scale infestation and the genotype of the host trees, based on gene locus A of isocitrate dehydrogenase (IDH-A). The fraction of infested beech trees was higher in the heterozygous genotype A2A3 group than in the homozygous genotype A2A2 and A3A3 groups, whereas the fraction of beech trees with decreasing infestation from one year to the next was lower in the heterozygous genotype A2A3 group than in the homozygous genotype A2A2 and A3A3 groups. Concentrations of soluble carbohydrates, protein amino acids and proanthocyanidins were determined in the inner and outer bark of trees with differing degrees of infestation. The results indicate that the defense reaction of beech against infestation by beech scale comprises multiple processes in which nutrient availability to the beech scale is reduced by concentration shifts and by the formation of inhibiting compounds.

Journal Article↗
PubMed2001

Mechanisms of xylem recovery from winter embolism in Fagus sylvatica.

Hydraulic conductivity in the terminal branches of mature beech trees (Fagus sylvatica L.) decreased progressively during winter and recovered in the spring. The objective of this study was to determine the mechanisms involved in recovery. Two periods of recovery were identified. The first recovery of hydraulic conductivity occurred early in the spring, before bud break, and was correlated with the occurrence of positive xylem pressure at the base of the tree trunk. Active refilling of the embolized vessels caused the recovery. The second recovery of hydraulic conductivity occurred after bud break and was correlated with the onset of cambial activity. Formation of new functional vessels, leading to an increase in xylem diameter, was largely responsible for the increase in xylem conductivity. The two mechanisms were complementary: active refilling of embolized vessels occurred mostly in the root and the trunk, whereas formation of new functional vessels occurred mainly in young terminal shoots.

Plant Diseases↗
PubMed1988

Sensitivity of red oak (Quercus rubra L.) and American beech (Fagus grandifolia Ehrh.) seedlings to sodium salts in solution culture.

Sodium salt sensitivity of red oak (Quercus rubra L.) and American beech (Fagus grandifolia Ehrh.) was evaluated in solution culture. Both species showed symptoms of salt injury when grown in the presence of less than 10 mM Na. In red oak, leaf symptoms first appeared at a sodium concentration of 6.0 mM and leaf weight was significantly reduced at 7.5 mM Na. Leaf, stem and root dry weights of American beech were significantly reduced in the presence of 4.0 mM sodium. In both species, browning of leaf margins and necrosis were evident in the Na-treated plants. The observed symptoms were associated with high concentrations of sodium in the tissues. Neither species appears to have control over sodium uptake and translocation.

Journal Article↗
PubMed1989

Mineral nutrients, carbohydrates and phenolic compounds in leaves of beech (Fagus sylvatica L.) in southern Sweden as related to environmental factors.

Concentrations of major elements, trace elements, starch, total sugars and phenols were measured in leaves of beech (Fagus sylvatica L.) trees located at 89 sites in the province of Scania, southern Sweden. Concentrations of elements had only a weak relationship to soil variables, but leaf N increased with distance from sources of industrial air pollution. Within-site variation in concentrations of most elements was smaller than variation among sites and was lowest for N, P, K and Cu and highest for Mn. Most trees had optimal or superoptimal concentrations of leaf N, whereas leaf concentrations of K, Mg and P were near or below the concentrations needed for normal growth. Several nutrients were negatively correlated with leaf color, total sugars and phenols, whereas insect damage was not related to any of the measured parameters.

Journal Article↗
PubMed1990

Bud dormancy in beech (Fagus sylvatica L.). Effect of chilling and photoperiod on dormancy release of beech seedlings.

Two-year-old Fagus sylvatica L. seedlings were subjected to natural winter chilling or were overwintered in a heated greenhouse. Plants were then grown in controlled environment chambers with photoperiods of 9 or 13 h. Renewal of bud growth was found to be mainly determined by winter chilling. There was a slight interaction between chilling and photoperiod. Sprouting of apical buds took two to three times as long in unchilled plants as in chilled plants. Shoot elongation was influenced by chilling and was also greater in the 13-h photoperiod than in the 9-h photoperiod, but this may have been due at least in part to the higher irradiance. Chilling resulted in rapid dormancy loss and changed the growth pattern from basitonal to acrotonal.

Journal Article↗
PubMed1990

Formation of cis-coniferin in cell-free extracts of Fagus grandifolia Ehrh bark.

American beech (Fagus grandifolia Ehrh) bark exclusively accumulates cis-monolignols and their glucosidic conjugates; no evidence for the accumulation of trans-monolignols has been found. The glucosyltransferase from this source exhibits a very unusual substrate specificity for cis, and not trans, monolignols. This is further evidence that cis monolignols are involved in lignin formation in these plant tissues. Preliminary evidence for the existence of a novel trans-cis monolignol isomerase was obtained, in agreement with our contention that this isomerization is not photochemically mediated.

Cell Wall↗
PubMed2004

Evidence of a cross-talk regulation of a GA 20-oxidase (FsGA20ox1) by gibberellins and ethylene during the breaking of dormancy in Fagus sylvatica seeds.

Gibberellin 20-oxidase (GA 20-oxidase) is an enzyme that catalyses the last three steps in the synthesis of active GAs and is a potential control point in the regulation of GA biosynthesis. Reverse transcriptase-polymerase chain reaction with degenerated oligonucleotides conserved among GA 20-oxidases was used to isolate a cDNA clone for this enzyme in Fagus sylvatica L. seeds. This clone contains all the features and exhibits homology to GA 20 oxidases from several plant species. Expression of this clone, named FsGA20ox1, as a fusion protein expressed in Escherichia coli confirmed that it was able to metabolize [(14)C]GA(12) to [(14)C]GA(9) and [(14)C]GA(53) to [(14)C]GA(20). Analysis of FsGA20ox1 transcript levels showed similar low expression during stratification at 4 degrees C and in the presence of gibberellic acid or ethephon (compound that releases ethylene in solution), treatments proved to be efficient in breaking the dormancy of beech seeds. However, there was a drastic increase of FsGA20ox1 transcript levels in the presence of paclobutrazol (PCB), a well-known GAs biosynthesis inhibitor, or of 2-aminoxyacetic acid (AOA), an inhibitor of ethylene biosynthesis. Furthermore, the effect of AOA was reversed by the addition of GA(3) and that of PCB by ethephon. This indicates that the gene product is subjected to down-regulation by GA and ethylene, and further suggests a cross-talk gene regulation by these two hormones during the transition from seed dormancy to germination.

Journal Article↗
PubMed1984

Hydroxyproline-Rich Protein Material in Wood and Lignin of Fagus sylvatica.

The nitrogen content, distribution, and amino acid composition of protein material were determined in wood and lignin of Fagus sylvatica. The data indicated that the nitrogen originated from hydroxyproline-rich cell wall glycoprotein, about half of which may be bound to the lignin polymer. The implications for lignocellulose biodegradation are discussed.

Journal Article↗
PubMed2004

Assessing the use of delta(13)C natural abundance in separation of root and microbial respiration in a Danish beech (Fagus sylvatica L.) forest.

Our understanding of forest biosphere-atmosphere interactions is fundamental for predicting forest ecosystem responses to climatic changes. Currently, however, our knowledge is incomplete partly due to inability to separate the major components of soil CO(2) effluxes, viz. root respiration, microbial decomposition of soil organic matter and microbial decomposition of litter material. In this study we examined whether the delta(13)C characteristics of solid organic matter and respired CO(2) from different soil-C components and root respiration in a Danish beech forest were useful to provide information on the root respiration contribution to total CO(2) effluxes. The delta(13)C isotopic analyses of CO(2) were performed using a FinniganMAT Delta(PLUS) isotope-ratio mass spectrometer coupled in continuous flow mode to a trace gas preparation-concentration unit (PreCon). Gas samples in 2-mL crimp seal vials were analysed in a fully automatic mode with an experimental standard error +/-0.11 per thousand. We observed that the CO(2) derived from root-free mineral soil horizons (A, B(W)) was more enriched in (13)C (delta(13)C range -21.6 to -21.2 per thousand ) compared with CO(2) derived from root-free humus layers (delta(13)C range -23.6 to -23.4 per thousand ). The CO(2) evolved from root respiration in isolated young beech plants revealed a value intermediate between those for the soil humus and mineral horizons, delta(13)C(root) = -22.2 per thousand, but was associated with great variability (SE +/- 1.0 per thousand ) due to plant-specific differences. delta(13)C of CO(2) from in situ below-ground respiration averaged -22.8 per thousand, intermediate between the values for the humus layer and root respiration, but variability was great (SE +/- 0.4 per thousand ) due to pronounced spatial patterns. Overall, we were unable to statistically separate the CO(2) of root respiration vs. soil organic matter decomposition based solely on delta(13)C signatures, yet the trend in the data suggests that root respiration contributed approximately 43% to total respiration. The vertical gradient in delta(13)C, however, might be a useful tool in partitioning respiration in different soil layers. The experiment also showed an unexpected (13)C-enrichment of CO(2) (>3.5 per thousand ) compared with the total-C signatures in the individual soil-C components. This may suggest that analyses of bulk samples are not representative for the C-pools actively undergoing decomposition.

Biomass↗
PubMed2005

Comparison of ozone uptake and sensitivity between a phytotron study with young beech and a field experiment with adult beech (Fagus sylvatica).

Chamber experiments on juvenile trees have resulted in severe injury and accelerated loss of leaves along with reduced biomass production under chronically enhanced O3 levels. In contrast, the few studies conducted on adult forest trees in the field have reported low O3 sensitivity. In the present study, young beech in phytotrons was more sensitive to O3 than adult beech in the field, although employed O3 regimes were similar. The hypotheses tested were that: (1) differences in O3 uptake were caused by the ontogenetically higher stomatal conductance of young compared to adult trees, (2) the experimental settings in the phytotrons enhanced O3 uptake compared to field conditions, and (3) a low detoxification capacity contributes to the higher O3 sensitivity of the young trees. The higher O3 sensitivity of juvenile beech in the phytotrons is demonstrated to relate to both the experimental conditions and the physiological responsiveness inherent to tree age.

Air Pollutants↗
PubMed2006

Effects of simultaneous ozone exposure and nitrogen loads on carbohydrate concentrations, biomass, growth, and nutrient concentrations of young beech trees (Fagus sylvatica).

Beech seedlings were grown under different nitrogen fertilisation regimes (0, 20, 40, and 80 kg Nha(-1)yr(-1)) for three years and were fumigated with either charcoal-filtered (F) or ambient air (O3). Nitrogen fertilisation increased leaf necroses, aphid infestations, and nutrient ratios in the leaves (N:P and N:K), as a result of decreased phosphorus and potassium concentrations. For plant growth, biomass accumulation, and starch concentrations, a positive nitrogen effect was found, but only for fertilisations of up to 40 kg Nha(-1) yr(-1). The highest nitrogen load, however, reduced leaf area, leaf water content, growth, biomass accumulation, and starch concentrations, whereas soluble carbohydrate concentrations were enhanced. The ozone fumigation resulted in reduced leaf area, leaf water content, shoot growth, root biomass accumulation, and decreased starch, phosphorus, and potassium concentrations, increasing the N:P and N:K ratios. A combined effect of the two pollutants was detected for the leaf area and the shoot elongation, where ozone fumigation amplified the nitrogen effects.

Air Pollution↗
PubMed2006

Ozone exposure, defoliation of beech (Fagus sylvatica L.) and visible foliar symptoms on native plants in selected plots of South-Western Europe.

The relationships between crown defoliation of beech, visible foliar symptoms on native vegetation and ozone exposure were investigated on permanent monitoring sites in South-Western Europe in the years 2000-2002. Relationships between defoliation of beech and O3 (seasonal mean, 2-week maximum, AOT40) were investigated by means of multiple regression models (11 plots, 1-3 years of data each) and a model based on temporal autocorrelation of defoliation data (14 plots, 1-3 years of data each). Different multiple regression techniques were used. The four models generated (R2=0.71-0.85, explained variance in cross-validation 61-78%) identified several significant predictors of defoliation, with AOT40 (p=0.008) and foliar content of phosphorous (p=0.0002-0.0004) being common to all models. The autocorrelation model (R2=0.55; p<0.0001) was used to calculate expected defoliation on the basis of the previous year's defoliation, and model predictions were used as an estimate of expected defoliation under constant site and environmental condition. Residuals (predicted-measured) plotted against current AOT40 shows that a possible effect of ozone occurs only at very high AOT40 (>35,000 ppbh). O3-like visible foliar symptoms were recorded on 65 species at 47% of the common monitoring sites in 2001 and 38% in 2002. No relationship was found between O3 exposure, frequency of symptomatic sites and frequency of species with symptoms (R2=0.11; p>0.05). A number of questions related to the ecological and methodological basis of the survey were identified. Inherent sampling and non-sampling errors and multicollinearity of the data suggest great caution when examining results obtained from mensurational, correlative studies.

Ecosystem↗
PubMed2002

In situ ageing of fine beech roots (Fagus sylvatica) assessed by transmission electron microscopy and electron energy loss spectroscopy: description of microsites and evolution of polyphenolic substances.

Root biomass is quantitatively and qualitatively important in most ecosystems, but its contribution to the pool of organic matter in the soil is not clear. This work was designed to specify root ageing on an ultrastructural scale by transmission electron microscopy combined with microanalysis by electron energy loss spectroscopy. This approach is very suitable for studying the soil/plant interface, and for semi-quantitative analysis of the evolution of polyphenolic substances during root evolution. Three root segments were studied according to a gradient of root senescence: the apical and basal segments of the mycorrhiza and the mycorrhiza-carrier root. Each segment contained a certain proportion of senescent cells, some of which were of fungal origin, and this proportion increased as the root aged. In the three segments, the soil/plant interfaces were differentiated, and the micro-organisms observed in situ were described. Senescent root cells contained many polyphenolic substances and our results showed that these substances were, according to the root segment, differently associated with Ca, N and Si. When all these ultrastructural data are correlated with more global data, they can be usefully applied to root cell physiology, microbiology and pedology. This approach makes it possible to specify the evolution of organic matter in situ in soils whatever its origin.

Cellular Senescence↗
PubMed2002

Decline in diversity and abundance of endophytic fungi in twigs of Fagus sylvatica L. after experimental long-term exposure to sodium dodecylbenzene sulphonate (SDBS) aerosol.

Sodium dodecylbenzene sulphonate (SDBS) is an anionic synthetic detergent found in polluted sea aerosol and is known for its harmful effects on leaf surface ultrastructure on conifers and broadleaved trees. Four-year-old saplings of European beech were sprayed weekly for three consecutive growing seasons with either a 50 mg l(-1) solution of SDBS in deionized water or with pure deionized water (control). Two- to three- year-old twigs were collected from SDBS-treated and control plants during the growing season one year after the last treatment to isolate endophytic fungi. The frequency of colonization by endophytic fungi was significantly lower on SDBS-treated plants (63.8%) than on control plants (85.4%). Multiple colonization of twigs occurred more frequently and diversity of endophyte species was higher in control plants than in SDBS-treated plants. Thirty-six fungal species were isolated from 360 twigs. Cladosporium cladosporioides, Coryneum compactum, Phialocephala dimorphospora, and a species each of Mycosphaerella and Phomopsis were the most abundant endophytes with frequencies of colonization of more than 5%. The abundance of the Phomopsis species proved to be significantly reduced by the SDBS treatment. Within the limits of the indoor experimental conditions, the obtained results suggest that long-term exposure of aerial parts of beech to SDBS can affect the amount and composition of endophytic fungal communities of lignified twigs. Degradation of the leaf epicuticular wax layer and changes of the assimilation capacity and leaf water content (transpiration) of the crowns are presumed to be responsible for the reduction of endophytic fungi detected in twigs of SDBS-treated plants.

Aerosols↗
PubMed2005

Physiological changes of Fagus sylvatica seedlings infected with Phytophthora citricola and the contribution of its elicitin "citricolin" to pathogenesis.

Beech seedlings were infected with the root rot pathogen Phytophthora citricola to study its impact on leaf physiology and water status. Net photosynthesis rate decreased two days after inoculation in infected seedlings. In contrast, electron quantum yield of photosystem II, leaf water potential, and total water consumption were only slightly impaired until 6 dpi. At the same time, wilt symptoms occurred on leaves. These results indicate the involvement of a mobile signal triggering the early changes in leaf physiology by root infection. As the elicitin gene of P. citricola was induced during root infection, we purified and characterised the elicitin protein and tested its ability to change leaf physiological parameters of beech and tobacco plants. P. citricola produced a single acidic elicitin (citricolin), which caused necrosis and decreased gas exchange of tobacco leaves. Furthermore, it induced an oxidative burst in tobacco cell suspension culture. However, none of these effects were observed in beech.

Algal Proteins↗
PubMed2005

Leaf morphology and chemistry in Fagus sylvatica (beech) trees as affected by site factors and ozone: results from CONECOFOR permanent monitoring plots in Italy.

During summer 2001, leaf samples were collected from seven beech stands that are part of the Italian network of permanent monitoring plots (CONECOFOR). In each plot, sun leaves from the upper crown were collected from five trees and subjected to chemical analysis (C, N, P, S, K, Ca and Mg) and morphological analysis (area, dry mass, thickness and thickness of individual tissues). Based on the measurements, nutrient ratios (N/C, N/K, N/P, N/Ca, N/Mg, K/Ca, Mg/Ca), sclerophylly indices (leaf mass per area (LMA) and leaf density (LD)) and nitrogen content per leaf area unit (NLA) were determined. Stomatal density was also measured. Among stands, leaf area was smallest and sclerophylly (indicated as LMA) was greatest in the southernmost stands and under drought conditions. Reduced leaf area and increased LMA also appeared to be strongly related to tropospheric ozone concentrations, whereas crown transparency was related mainly to site factors such as rainfall and temperature and, to a lesser extent, ozone concentration. The southernmost stands had a lower N/C ratio than the more northern stands, suggesting that the apoplastic fraction of cells within the leaf played a greater role. In the northern stands (especially at Lombardy and in Piedmont) where ozone concentrations were high, nutrient ratios were unbalanced and the high value of LMA appeared to be related primarily to the contribution of plasmatic components. Overall, leaf morphology was most sensitive to climate stress at the southern plots and to environmental pollution (nitrogen deposition and tropospheric ozone concentration) at some of the northern plots.

Fagus↗