Antioxidants in the apoplast and symplast of beech (Fagus sylvatica L.) leaves: seasonal variations and responses to changing ozone concentrations in air

Concentrations of the antioxidants ascorbate and glutathione were measured in the apoplast of beech (Fagus sylvatica L.) leaves and in leaf tissue. During early leaf development, reduced ascorbate (ASC) was almost absent from the apoplast, whereas levels of oxidized ascorbate (DHA) were high. Less than 20% of the apoplastic ascorbate was reduced. ASC increased towards midsummer, reaching top levels of about 4molm^?3 apoplast volume in July and August. Reduction increased to 60–75% in summer. Neither DHA reductase nor glutathione was detected in the apoplast of beech leaves. Levels of apoplastic ascorbate were compared with ambient concentrations of ozone in air. Statistical analysis indicated a significant interrelation between atmospheric ozone and apoplastic ascorbate. In midsummer of 1993, contents of DHA were increased in the apoplast when ozone concentrations were high. Apoplastic ASC was also positively correlated with ambient ozone concentrations, but with a delay of 3 to 7d. In leaf tissue, levels of ascorbate were between 17 and 21 μmolg^?1 FW in summer. Except for late April and November, more than 95% of the intracellular ascorbate was reduced. Glutathione contents were lowest during the summer. Oxidation was increased in spring and autumn, when apoplastic ascorbate was also largely oxidized. Usually, 80 to 90% of the glutathione was reduced. During the summer, intracellular concentrations of oxidized glutathione (GSSG) were increased, with a delay of about 1d following periods of high ambient ozone concentrations. The transitory accumulation of GSSG may be explained by slow enzymatic regeneration of glutathione.     

Fine root biomass in a beech (Fagus sylvatica L.) stand on Paiko Mountain,NW Greece

Abstract

Fine roots represent a small proportion of total plant biomass however they represent the most dynamic component of the root systems of woody plants. There is limited information on the beech fine root production in Mediterranean ecosystems and especially in Greece. We measured live, dead and total fine root biomass (d<2 mm) (LFRB, DFRB and TFRB, respectively) over a growing season in a beech (Fagus sylvatica L.) stand on Paiko mountain, NW Greece, in order to contribute to the generally scarce knowledge of the fine root biomass of beech stands. It was found that TFRB and LFRB increased from May to July and then decreased. LFRB decreased with soil depth while there was no pattern at the change of DFRB with soil depth.     

Influence of aluminium on biomass, nutrients, soluble carbohydrates and phenols in beech (Fagus sylvatica)

The effects of aluminium on biomass, nutrients and soluble carbohydrates and phenols were studied in beech ( Fagus sylvatica L.) seedlings. After germination, seedlings with cotyledons and the buds of the first leaf-pair developed, were preconditioned for two weeks and then grown for 31 days in nutrient solutions containing 0.1, 0.5, 1.0 or 2.0 m M A1C1₃. Aluminium did not affect the dry weights of roots but at Al concentrations ≥ 1.0 m M the development of the terminal shoot above the first leaf pair, was reduced by 80% or more. The concentrations of most nutrients (P, Ca, Mg, Zn, Cu) in the plant tissues decreased strongly even at the lowest Al levels, but K increased in the shoots. The tissue concentration of N was not affected of Al. but the distribution between the organs was changed to a higher content of N in the roots. At ≥1.0 m M Al the concentrations of starch in both the shoots and the roots were significantly increased, and at ≥ 0.5 m M the roots contained more of total phenols than untreated seedlings. The elevated concentrations and contents of starch and phenols in the seedlings may partly be related to the reduced shoot growth. The observed effects of Al were marked already at Al levels found in soil waters from beech forests in southern Sweden.     

Carbon and nitrogen dynamics in acid detergent fibre lignins of beech (Fagus sylvatica L.) during the growth phase

To study the incorporation of carbon and nitrogen in different plant fractions, 3‐year‐old‐beech (Fagus sylvatica L.) seedlings were exposed in microcosms to a dual‐labelling experiment employing ¹³C and ¹⁵N throughout one season. Leaves, stems, coarse and fine roots were harvested 6, 12 and 18 weeks after bud break (June to September) and used to isolate acid‐detergent fibre lignins (ADF lignin) for the determination of carbon and nitrogen and their isotope ratios. Lignin concentrations were also determined with the thioglycolic acid method. The highest lignin concentrations were found in fine roots. ADF lignins of all tissues analysed, especially those of leaves, also contained significant concentrations of nitrogen. This suggests that lignin‐bound proteins constitute an important cell wall fraction and shows that the ADF method is not suitable to determine genuine lignin. ADF lignin should be re‐named as ligno‐protein fraction. Whole‐leaf biomass was composed of 50 to 70% newly assimilated carbon and about 7% newly assimilated nitrogen; net changes in the isotope ratios were not observed during the experimental period. In the other tissues analysed, the fraction of new carbon and nitrogen was initially low and increased significantly during the time‐course of the experiment, whereas the total tissue concentrations of carbon remained almost unaffected and nitrogen declined. At the end of the experiment, the whole‐tissue biomass and ADF lignins of fine roots contained about 65 and 50% new carbon and about 50 and 40% new nitrogen, respectively. These results indicate that significant metabolic activity was related to the formation of structural biopolymers after leaf growth, especially below‐ground and that this activity also led to a substantial binding of nitrogen to structural compounds.     

The effect of shoot architecture on hydraulic conductance in beech (Fagus sylvatica L.)

 Shoot hydraulic conductance was measured in beech (Fagus sylvatica L.) that had previously been exposed to high levels of nitrogen input. Whole-shoot hydraulic conductance, conductance per unit pressure gradient and leaf specific conductance were negatively correlated with the number of bud scars per unit length, a morphological parameter of tree decline. We propose a negative feedback mechanism by which stress induced alterations in shoot morphology can cause a lasting reduction of tree vigour. Received: 2 July 1997 / Accepted: 25 June 1998     

Gene Flow in European Beech (Fagus sylvatica L.)

Three relatively isolated stands were used to study gene flow in European beech (Fagus sylvatica L.) in Northern Germany. Nine allozyme loci (Got-B, Idh-A, Lap-A, Mdh-B, Mdh-C, Mnr-A, 6-pgdh-A, Pgi-B and Pgm-A) were utilized for multilocus-genotyping adult trees and seeds. Expected heterozygosity (He) ranged from 0.325 to 0.351 for the three stands. F(ST) revealed that there was small differentiation among stands (mean F(ST) = 0.013). The indirect estimates of gene flow (Nm) based on the mean F(ST) were high and the average Nm was 19.14. External gene flow by pollen ranged from 0.7 to 1.2% inferred from new alleles in seed samples. Moreover, paternity analysis was used to assess effective pollen dispersal by inferring paternity of offspring. The weighted mean distances of pollen dispersal for these three stands were 36.8 and 37.1 m based on simple exclusion procedure and most-likely method, respectively. Two of the trees in one stand had rare allozyme alleles (Lap-A1 and Idh-A4, respectively), which were used to directly measure pollen movement away from those trees. The frequency of the rare Lap and Idh alleles in seeds declines as the distance from the source tree increases. The weighted mean distance of pollen dispersal with rare allele Lap-A1 or Idh-A4 was 26.3 m.     

Phosphate and calcium uptake in beech (Fagus sylvatica) in the presence of aluminium and natural fulvic acids

In the present study we examine the effects of Al on the uptake of Ca²⁺ and H₂PO^-₄ in beech (Fagus sylvatica L.) grown in inorganic nutrient solutions and nutrient solutions supplied with natural fulvic acids (FA). All the solutions used were chemically well characterized. The uptake of Al by roots of intact plants exposed to solutions containing 0, 0.15 or 0.3 mM AlCl₃ for 24 h, was significantly less if FA (300 mg l⁻¹) were also present in the solutions. The Ca²⁺(⁴⁵Ca²⁺) uptake was less affected by Al in solutions supplied with FA than in solutions without FA. There was a strong negative correlation between the Al and Ca²⁺ uptake (r²=0.98). When the Al and Ca²⁺ (⁴⁵Ca²⁺) uptake were plotted as a function of the Al³⁺ activity (or concentration of inorganic mononuclear Al), almost the same response curves were obtained for the -FA and +FA treatments. We conclude that FA-complexed Al was not available for root uptake and therefore could not affect the Ca²⁺ uptake. The competitive effect of Al on the Ca²⁺ uptake was also shown in a 5-week cultivation experiment, where the Ca concentration in shoots decreased at an AlCl₃ concentration of 0.3 mM. The effect of Al on H₂PO⁻₄ uptake was more complex. The P content in roots and shoots was not significantly affected, compared with the control, by cultivation for 5 weeks in a solution supplied with 0.3 mM AlCl₃, despite a reduction of the H₂PO⁻₄ concentration in the nutrient solution to about one-tenth. At this concentration Al obviously had a positive effect on H₂PO⁻₄ uptake. The presence of FA decreased ³²P-phosphate uptake by more than 60% during 24 h, and the addition of 0.15 or 0.3 mM AlCl₃ to these solutions did not alter the uptake of ³²P-phosphate.     

Patterns of post-glacial spread and the extent of glacial refugia of European beech (Fagus sylvatica)

Aim  Establishing possible relationships between the magnitudes of the glacial distribution of the European beech, Fagus sylvatica L., and its post-glacial spread.
Location  Europe.
Methods  A database of over 400 pollen records has been used to locate Fagus populations at the end of the last glacial and during the post-glacial in Europe and to assess the areal extent of their past distribution.
Results  The rate of late-glacial and post-glacial increase in the number of pollen sites where Fagus was locally present conforms well to a logistic model of population growth. This suggests that the area occupied by beech populations expanded exponentially from the glacial refugia for a duration of over 10,000 years, until about 3500 yr bp . In the past three millennia beech populations increased at a slower rate, tending towards an equilibrium value.
Main conclusions  The conformity of the increase in beech distribution to the classical logistic model of population growth indicates that: (1) a multiplicative biological process was the main factor shaping the pattern of the post-glacial expansion of F. sylvatica in Europe, (2) climate conditions, human activity and competition may have influenced its rate of spread, and (3) beech populations did not expand with a moving closed front, but with a diffuse spread from scattered nuclei. The distribution of Fagus in Europe at the end of the last glacial appears to have been of two orders of magnitude less extensive than at present. Pleistocene refugia were likely to have been a mosaic of sparse stands of small populations scattered in multiple regions. Fagus populations appear to have increased very slowly and to a moderate extent in southern Europe, where they are now declining slightly. The central European populations increased quickly and extensively, reaching northern Europe, and are now approaching their carrying capacity.     

Influence of aluminium on phosphorus and calcium localization in roots of beech (Fagus sylvatica)

Beech plants ( Fagus sylvatica L. provenance Maramures) were grown in nutrient solution at low pH (4.2) and exposed to different concentrations of AlCl₃. Uptake and leakage of Ca²⁺(⁴⁵Ca²⁺) and H²PO₄-(³²P) were studied. A high external aluminium concentration (1.0m M ) reduced the uptake and export to the shoot of both calcium and phosphate, while 0.1 m M Al increased the phosphorus level in the roots. To determine the impact of aluminium on the localization of calcium and phosphate, leakage of the elements from both intact plants and plants frozen prior to the leakage experiment was studied. The leakage of Ca²⁺ from intact plants was not affected by prior exposure to 0.1 m M Al. Freezing of the beech plants before the leakage experiment increased leakage of calcium slightly more from roots of control plants than for roots exposed to 0.1 m M Al, indicating that even low concentrations of alminium may impede the influx of calcium across the plasma membrane in the roots. The patterns of Ca²⁺ leakage from roots previously exposed to 1.0 m M Al indicated that very little Ca²⁺ was located extracellularly. The extracellular fraction of phosphate increased with increasing Al concentration in the nutrient solution. Low Al concentration (0.1 m M ) only reduced the intracellular phosphate concentration to a minor extent, while 1.0 m M Al profoundly decreased it. It is concluded that 0.1 m M AlCl₃ has a limited effect upon the localization of Ca²⁺ and phosphate in the roots. At higher levels of Al, 0.1–1.0 m M , there is a more dramatic change in nutrient localization in the free space and uptake over the plasma membrane.     

Seasonal variation of calcium,magnesium, potassium,and manganese contents in xylem sap of beech(Fagus sylvatica L.) in a 35-year-old limestone beech forest stand

Summary In a 35-year-old calcareous beech forest stand five beech trees (Fagus sylvatica L.) were felled every 2 weeks, and xylem sap was obtained by means of water displacement from the lowest trunk sections, each 100 cm in length. From mid-October 1988 to mid-October 1989 a total of 130 trees were investigated. The seasonal variations of the Ca, Mg, K and Mn contents, as well as those of pH, show four characteristic phases. Additionally, distribution of the mineral contents along the trunk was studied in four trees. The seasonal increase and decrease of xylem sap mineral contents along the trunk is shown for the characteristic phenophases. The Ca, Mg, K, and Mn contents of xylem saps were determined by means of atomicabsorptionspectrophotometry.     

Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses

Sclerophylly and synthesis of phenolic compounds are active responses of plants subjected to environmental stress (drought, low nutrient supply, u.v.-B radiation, ozone). Here we describe the morphological and histochemical alterations occurring in field-grown leaves of Fagus sylvatica L. from three sites located along an ecological gradient: from a site in cool and protected conditions to one located on a mountain ridge, where the trees grow on a thin layer of soil and are exposed to the wind and to intense solar radiation in summer. The morphological data show that, as the ecological conditions of the stand worsen, individual leaf surface decreases, while the thickness of the leaves and their specific d. wt (i.e. d. wt per unit leaf area) increases. Histochemical and ultrastructural tests show a marked increase of phenolics during the course of the year. These substances, present primarily in the leaves of trees growing in stress conditions, have been identified mainly as tannins. They accumulate in the vacuoles, especially those of the upper epidermal layer and the palisade mesophyll; at a later stage they appear to be solubilized in the cytoplasm and retranslocated, eventually impregnating the outer wall of the epidermal cells amidst the cellulose fibrils, where they cluster together and form an electron-opaque layer between the wall and the cuticle. Observation of the epidermal cells also reveals that the outer cell wall is thicker. The paper discusses the roles of secondary metabolites in protection and detoxification processes; the possible ecological significance of these alterations in the ecophysiology of beech trees.     

Is the spatial distribution of European beech (Fagus sylvatica L.) limited by its potential height growth?

Aim To improve our understanding of species range limits by studying how height growth, a trait related to plant survival, varies throughout the geographic range of Fagus sylvatica L. in France. Location The geographic range of beech in France, representing the western area of its European distribution, within which this species exhibits range distribution limits in both plains and mountainous areas. Methods A generalized linear regression model was used to link beech growth performance to environmental variables using data from 819 plots of the French National Forest Inventory (IFN) database. This model was applied to predict potential growth on 97,281 IFN plots covering the geographic range of beech in France. A kriging technique was used to interpolate estimated growth potential. Finally, the performance of plot‐based predictions of potential growth from the map (i.e. map quality) was evaluated against an independent data set. Results The beech growth performance model highlighted the major impact of climate on potential tree growth at a broad spatial scale. The relevant climatic factors were related mainly to spring cold, summer heat, and winter temperatures and rainfall. The study also revealed the predictive power of soil parameters, which explained a large proportion of the variation in potential beech growth (c. 30%). Analyses of height growth patterns near the boundary of the species range in France showed that the limit only partly coincides with the growth decline caused by climatic and soil factors. Along parts of the range limit, the predicted potential for growth was high, suggesting that in these areas the limit of the range could be explained by other factors, such as competition or constraints on reproduction. Main conclusions The spatial variation in the potential height growth of Fagus sylvatica can be explained by environmental factors and is partly correlated with its regional range limits. By identifying areas where growth potential constrains the geographic range of species, environmental growth models can help to improve our knowledge of the spatial drivers of species geographic range limits and shed light on their response to future environmental changes.     

Factors toxic to beech (Fagus sylvatica L.) seedlings in acid soils

The effects of highly and moderately acid soils on total biomass, biomass partitioning, fine root characteristics and nutritional status of beech seedlings (Fagus sylvatica L.) were studied in a growth chamber experiment. In Haplic Arenosols seedlings grew slowly but equally well without damage symptoms in a highly acid and a moderately acid soil horizon. The moderately acid A_h+B_w-horizon of a Eutric Cambisol was favourable to seedling growth. The fine root development was reduced in the highly acid A+B_w-horizon of a Dystric Cambisol and in the A_h+E-horizon of a Haplic Podzol, the latter of which also caused increased mortality. Seedling growth in the B₂-horizon of the Haplic Podzol was vigorous, in spite of a higher level of extractable Al and lower base saturation as compared with the A_h+E-horizon. These results are interpreted in relation to soil acidity, soil Al and nutritional status of the seedlings. We conclude that neither Al-toxicity nor nutrient deficiency cause the damage symptoms observed in the A_h+E-horizon of a Haplic Podzol and the fine root reduction in the A+B_w-horizon of a Dystric Cambisol. The damage symptoms of the PZh_A treatment seems to be more the result of H-toxicity or H-related factors other than nutrient shortage or Al-toxicity. Other pH-related toxic factors are discussed.