The abundance, identities, and degradation abilities of indigenous polychlorinated biphenyl (PCB)-degrading bacteria associated with five species of mature trees growing naturally in a contaminated ...site were investigated to identify plants that enhance the microbial PCB degradation potential in soil. Culturable PCB degraders were associated with every plant species examined in both the rhizosphere and root zone, which was defined as the bulk soil in which the plant was rooted. Significantly higher numbers of PCB degraders (2.7- to 56.7-fold-higher means) were detected in the root zones of Austrian pine (Pinus nigra) and goat willow (Salix caprea) than in the root zones of other plants or non-root-containing soil in certain seasons and at certain soil depths. The majority of culturable PCB degraders throughout the site and the majority of culturable PCB degraders associated with plants were identified as members of the genus Rhodococcus by 16S rRNA gene sequence analysis. Other taxa of PCB-degrading bacteria included members of the genera Luteibacter and Williamsia, which have not previously been shown to include PCB degraders. PCB degradation assays revealed that some isolates from the site have broad congener specificities; these isolates included one Rhodococcus strain that exhibited degradation abilities similar to those of Burkholderia xenovorans LB400. Isolates with broad congener specificity were widespread at the site, including in the biostimulated root zone of willow. The apparent association of certain plant species with increased abundance of indigenous PCB degraders, including organisms with outstanding degradation abilities, throughout the root zone supports the notion that biostimulation through rhizoremediation is a promising strategy for enhancing PCB degradation in situ.
The arbuscular mycorrhizal (AM) grass
Calamagrostis epigejos
and predominantly ectomycorrhizal (EcM) tree
Salix caprea
co-occur at post-mining sites spontaneously colonized by vegetation. During ...succession, AM herbaceous vegetation is replaced by predominantly EcM woody species. To better understand the interaction of AM and EcM plants during vegetation transition, we studied the reciprocal effects of these species’ coexistence on their root-associated fungi (RAF). We collected root and soil samples from three different microenvironments: stand of
C. epigejos
, under
S. caprea
canopy, and contact zone where roots of the two species interacted. RAF communities and mycorrhizal colonization were determined in sampled roots, and the soil was tested for EcM and AM inoculation potentials. Although the microenvironment significantly affected composition of the RAF communities in both plant species, the effect was greater in the case of
C. epigejos
RAF communities than in that of
S. caprea
RAF communities. The presence of
S. caprea
also significantly decreased AM fungal abundance in soil as well as AM colonization and richness of AM fungi in
C. epigejos
roots. Changes observed in the abundance and community composition of AM fungi might constitute an important factor in transition from AM-dominated to EcM-dominated vegetation during succession.
► In this study we assess the effect of different rhizosphere microbes on the phytoextraction efficiency of
Salix caprea. ► The different inocula have significantly influenced the root biomass and ...the accumulation of zinc, cadmium, and potassium. ► Higher concentrations of Zn and Cd in leaves were associated with increased accumulation of K. ► Rhizosphere microbes may enhance the phytoextraction capacity also on moderately polluted soils.
Although the beneficial effects on growth and trace element accumulation in
Salix spp. inoculated with microbes are well known, little information is available on the interactions among trace elements and macronutrients. The main purpose of this study was to assess the effect of phytoaugmentation with the rhizobacteria
Agromyces sp.,
Streptomyces sp
., and the combination of each of them with the fungus
Cadophora finlandica on biomass production and the accumulation of selected trace elements (Zn, Cd, Fe) and macronutrients (Ca, K, P and Mg) in
Salix caprea grown on a moderately polluted soil. Dry matter production was significantly enhanced only upon inoculation with
Agromyces sp. Regarding the phytoextraction of Cd and Zn, shoot concentrations were mostly increased after inoculation with
Streptomyces sp. and
Agromyces sp. +
C. finlandica. These two treatments also showed higher translocation factors from roots to the leaves for both Cd and Zn. The accumulation of Cd and Zn in shoots was related to increased concentrations of K. This suggests that microorganisms that contribute to enhanced phytoextraction of Cd and Zn affect also the solubility and thus phytoavailability of K. This study suggests that the phytoextraction of Zn and Cd can be improved by inoculation with selected microbial strains.
Studying regeneration processes in oak-dominated forests requires a multi-faceted approach that considers local factors, disturbances, management actions, and tree responses. Our aims were to ...quantify the carbon and water-use responses of saplings and evaluate ecological consequences at the early tree regeneration phase of a pedunculate oak-hornbeam forest. We measured plant eco-physiological parameters using an open-chamber IRGA equipment in large experimental canopy gaps (instantaneous field data) and greenhouse (climate-controlled reference data) conditions. We used the non-parametric Kruskal–Wallis ANOVA test to analyze differences and similarities in the gas-exchange response. Functional fingerprints indicated shared resource use and efficiency functions at species-specific performance levels with temporal variations. Medium-level and seasonally balanced carbon uptake and water-use functions characterized pedunculate oak (Quercus robur L.) and European hornbeam (Carpinus betulus L.). In contrast, the response patterns in wild cherry (Prunus avium (L.) L.) and green ash (Fraxinus pennsylvanica Marshall) were dominated by water use. Goat willow (Salix caprea L.) had consistently elevated gas-exchange levels with the largest seasonal variation among the study species. We found that trees could be ranked on a relative isohydric-to-anisohydric scale regarding their species–environment interaction. According to the carbon-gain response pattern coupling with a non-structural carbohydrate exchange scheme, we were able to classify tree species as having medium- and long-term carbon resource management. In conclusion, spatially heterogeneous and temporally balanced canopy gaps facilitate tree species’ development and mixed-stand regeneration by providing a functionally diversifying recruiting environment.
Considering the surface of individual tree compartments, it is obvious that the main portion of bark, i.e., the largest area and the greatest bulk mass, is located on the stem. We focused on basic ...bark properties, specifically thickness, surface area, biomass, and specific surface mass (expressed as dry weight per square unit) on stems of four broadleaved species: common aspen (
L.), goat willow (
L.), rowan (
L.), and sycamore (
L.). Based on the previous work from mature forests, we hypothesize that bark properties of young trees are also species-specific and change along the stem profile. Thus, across the regions of Slovakia, we selected 27 forest stands composed of one of the target broadleaved species with ages up to 12 years. From the selected forests, 600 sample trees were felled and stem bark properties were determined by measuring bark thickness, weighing bark mass after its separation from the stem, and drying to achieve a constant weight. Since the bark originated from trees of varying stem diameters and from different places along the stem (sections from the stem base 0-50, 51-100, 101-150, 151-200, and 201-250 cm), we could create regression models of stem characteristics based on the two mentioned variables. Our results confirmed that bark thickness, thus also specific surface mass, increased with stem diameter and decreased with distance from the stem base. While common aspen had the thickest stem bark (4.5 mm on the stem base of the largest trees) the thinnest bark from the analyzed species was found for sycamore (nearly three times thinner than the bark of aspen). Since all four tree species are very attractive to large wild herbivores as forage, besides other uses, we might consider our bark mass models also in terms of estimating forage potential and quantity of bark mass consumed by the herbivory.
In the European boreal forest, early successional tree species in the genera
Salix and
Populus are among the most favoured by browsers, often causing poor regeneration. It is frequently assumed that ...the fast height growth rate of these species on favourable sites can increase their chances to outgrow browsers. Spatial or temporal variation in browsing pressure could be important mechanisms for escape too, but there are few examples of this. In 1999 a large area of old-growth mixed
Pinus sylvestris L. and
Picea abies L. Karst. forest burned in Tyresta National Park in central Sweden. In the following year, an abundance of
Populus tremula L. and
Salix caprea L. seedlings regenerated naturally. Four years later we analyzed seedling height and browsing history for the tallest seedlings inside and outside natural aggregations of dead wood formed by windthrow of fire-killed trees. All seedlings outside the aggregations had been browsed (on average three times) and average height was 60
±
9
cm for
P. tremula and 54
±
12
cm for
S. caprea. Inside aggregations, only 33% of the tallest seedlings had any evidence of browsing, and in most cases only from one episode. Average height for
P. tremula was 153
±
41
cm and for
S. caprea 167
±
27
cm. Stem base diameter was also wider for seedlings growing in dead wood aggregations than in open areas. Droppings of moose, roe deer, and hare were abundant in the area, but judging from bite marks, most browsing damage was due to the ungulates. For seedlings inside dead wood aggregations, backward regression analysis showed that both the structure of the aggregations and the spatial position of seedlings influenced seedling height: for
P. tremula seedlings, there was a significant association with increasing height of the dead wood aggregation, increasing distance to the edge of the aggregation, and decreasing distance to the nearest dead wood stem. For
S. caprea seedlings there was a significant association only with the height of the aggregation. The results show that the legacy of the pre-fire tree stand can allow seedlings of palatable early successional trees to escape browsers. The effectiveness of this mechanism depends on both the quality of the pre-fire stand and on the fire behaviour generating the dead wood. A fire regime of long fire-intervals (allowing for wide-crowned trees to develop) followed by a stand-replacing fire (allowing for large aggregates of dead wood) would be optimal.
—The purpose of the study was to test the hypothesis that
Acer negundo
, an alien (invasive) tree species in Eurasia, has allelopathic activity. Using the method of roll culture, two experiments were ...performed to estimate the effect of water extracts from summer (green) and autumn (colored) leaves of
A. negundo,
compared to native woody species
Sorbus aucuparia
,
Prunus padus,
and
Salix caprea,
on the early development of
Festuca rubra
,
Sinapis alba,
and
Trifolium repens.
The results failed to prove conclusively that
A. negundo
leaf extract affects the early development of test plants: its effect was similarly strong as those of extracts from the leaves of native
P. padus
and
S. caprea,
while the leaf extract of the native shrub
S. aucuparia
proved to have a distinct inhibitory effect. On the whole, no evidence was obtained that allelopathic influences of compounds leached from
A. negundo
leaves may be the actual mechanism accounting for the ecological success of this species in its secondary range.
A Gram-reaction-positive, motile, yellow-pigmented and rod-shaped bacterial strain, designated AR33T, was isolated from the rhizosphere of Salix caprea L. growing in a former zinc/lead mining and ...processing site in Austria. A polyphasic approach was applied to determine its taxonomic position. 16S rRNA gene sequence analysis, and morphological and chemotaxonomic properties showed that strain AR33T belongs to the genus Agromyces. Strain AR33T had peptidoglycan type B2γ and the major menaquinones were MK-11, MK-10 and MK-12. The main branched-chain fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. Strain AR33T showed catalase and oxidase activity and multiple heavy metal resistances to zinc, lead and cadmium. The DNA G+C content was 70.1 mol%. Levels of 16S rRNA gene sequence similarity with closely related recognized species of the genus Agromyces ranged between 98 and 99 %. However, DNA-DNA hybridization between strain AR33T and the type strains of three Agromyces species showed values lower than 42 % relatedness. Therefore, differential phenotypic characteristics together with DNA-DNA relatedness suggested that strain AR33T can be recognized as representing a distinct Agromyces species, for which the name Agromyces aureus sp. nov. is proposed. The type strain is AR33T (=DSM 101731T=LMG 29235T).
Salix caprea L. is an ornamental plant with prominent antioxidant activity. In the last decades Salix caprea bud extracts (SCBEs) have been used for the treatment of oxidative stress related ...disorders.
A large part of cellular functions depends on the amount of intracellular Ca2+ concentration which in turn is mainly determined by Ca2+ ions movements across plasma membrane as well as by Ca2+ released from the stores. For better evaluating the mechanism of action of SCBEs, we focused on the effect of SCBEs on voltage gated Ca2+ channels (VGCCs) functioning and related catecholamines secretion in mouse chromaffin cells (MCCs). These latter are neuroendocrine cells that share a wide variety of functions with neurons. They are particularly interesting for studying the relationship between VGCCs activation and catecholamines secretion both in control and under stressful conditions.
We focused on the effect of SCBEs on VGCCs being these latter considered one of the main pathway of Ca2+ influx across plasma membrane. Ca2+ currents and capacitance changes were measured in patch clamp experiments performed in voltage clamp configuration.
We show that SCBEs inhibited VGCCs in a dose dependent manner. On average, the saturating concentration of SCBEs (SCBEsmax) is able to block 36% of the maximum Ca2+ current amplitude (ICa) without selectivity for L (ICa, L) or non-L type (ICa, non-L) Ca2+ channels. Furthermore, ICa inhibition is not followed by alteration of VGCCs gating kinetics, but is responsible for a marked decrease of Ca2+ dependent catecholamines secretion.
We conclude that the ability of SCBEs to inhibit VGCCs function, known to be potentiated during oxidative stress, could contribute to the already known antioxidant properties of Salix caprea L. We finally suggest that the inhibitory effect of SCBEs on catecholamines secretion may contribute to treat stress dependent cellular dysfunctions.
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