Salicaceae Family Research Articles

Apriona cinerea

<i>Apriona cinerea</i>

Anti-inflammatory effects of ethanol extracts of Chinese propolis and buds from poplar (Populus×canadensis)

Ethnopharmacological relevancePropolis is used widely in a number of cultures as a folk medicine and is gaining wider recognition for its potential therapeutic use, due to its wide range of biological properties and pharmacological activities, especially its anti-inflammatory effects. Despite an increasing number of studies focused on the biological activities of propolis together with its botanical sources, studies on Chinese propolis are insufficient. This study was designed to investigate the anti-inflammatory properties of ethanol extracts from Chinese propolis (EECP) and poplar buds (EEPB) from Populus×canadensis Moench (Salicaceae family). Materials and methodsPhytochemical analysis of EECP and EEPB was performed via total phenolic and flavonoid content measurements followed by high-performance liquid chromatography (HPLC) analysis. DPPH and ABTS free-radical scavenging methods were used to evaluate their anti-oxidant properties. The anti-inflammatory effects of EECP and EEPB were investigated in vitro by evaluating their modulating effects on the key inflammatory cytokines and mediators in LPS/IFN-γ co-stimulated RAW 264.7 cells and by measuring nuclear factor (NF)-κB activation in TNF-α or IL-1β stimulation HEK 293 cells using reporter gene assays. Their effects on acute inflammatory symptoms (LPS-induced endotoxemia and acute pulmonary damage) were also examined in mice. ResultsEECP and EEPB exhibited strong free-radical scavenging activity and significant in vitro anti-inflammatory effects by modulating key inflammatory mediators of mRNA transcription, inhibiting the production of specific inflammatory cytokines, and blocking the activation of nuclear factor (NF)-κB. The administration of EECP and EEPB (25 and 100mg/kg) provided significant protective effects by attenuating lung histopathological changes and suppressing the secretion of LPS-stimulated inflammatory cytokines, such as interleukin-6 (IL-6), IL-10, MCP-1, TNF-α and IL-12p70 production in endotoxemic mice. ConclusionsThe results presented here reveal the potent anti-inflammatory properties of Chinese propolis and poplar buds, and provide biological information for developing suitable substitute(s) for propolis in the prevention and treatment of inflammatory diseases.

Anti-inflammatory and analgesic activity of aqueous extract of Flos populi

Ethnopharmacological relevanceFlos populi is an important traditional Chinese medicine prepared from the male inflorescence of Populus tomentosa Carr. or Populus canadensis Moench (Salicaceae family). Flos populi is mainly used for the treatment of various inflammatory diseases and anti diarrhea in East Asian countries. The objective of this study was to investigate the anti-inflammatory and analgesic properties of the aqueous extract of Flos populi (FPAE). Materials and methodsCotton pellets-induced granuloma, carrageenan-induced paw oedema, arachidonic acid-induced right ear oedema and xylene-induced ear oedema were used to assess anti-inflammatory activity of FPAE and analgesic activity was evaluated by hot plate test, acetic acid-induced abdominal writhing test and formalin test. ResultsFPAE produced significant dose–response anti-inflammatory activity against cotton pellets-induced granuloma. FPAE at dosages of 50, 100 and 200mg/kgbw. significantly reduced carrageenan-induced paw edema by 48.84% (P<0.05), 54.95% (P<0.05), and 62.05% (P<0.05) at 5h after carrageenan injection, respectively. FPAE significantly (P<0.05) reduced the ear oedema induced by arachidonic acid and peaked at the dose of 200mg/kgbw. (40.78%). A significant (P<0.05) dose dependent inhibition of xylene-induced oedema was produced by FPAE and peaked at the highest dose of 200mg/kgbw. (23.95%). FPAE (50, 100 and 200mg/kgbw.) produced significant dose–response analgesic activity in the hot-plate test. However, the low percentage inhibition (<50%) suggests that it is not a centrally acting analgesic. Extract at dosages of 50, 100 and 200mg/kgbw., p.o. significantly reduced acetic acid-induced writhing by 39.6% (P<0.05), 45.4% (P<0.05), and 51.8% (P<0.05), respectively. The extract also caused marked dose-dependent inhibition of formalin-induced pain in the second phase (P<0.05). ConclusionThe findings in this study suggest that the aqueous extract of Flos populi possesses anti-inflammatory and analgesic activities. These results may support the fact that this plant is used traditionally to cure inflammatory diseases.

Phenological cues drive an apparent trade‐off between freezing tolerance and growth in the family Salicaceae

With increasing concern about the ecological consequences of global climate change, there has been renewed interest in understanding the processes that determine species range limits. We tested a long-hypothesized trade-off between freezing tolerance and growth rate that is often used to explain species range limits. We grew 24 willow and poplar species (family Salicaceae) collected from across North America in a greenhouse common garden under two climate treatments. Maximum entropy models were used to describe species distributions and to estimate species-specific climate parameters. A range of traits related to freezing tolerance, including senescence, budburst, and susceptibility to different temperature minima during and after acclimation were measured. As predicted, species from colder climates exhibited higher freezing tolerance and slower growth rates than species from warmer climates under certain environmental conditions. However, the average relative growth rate (millimeters per meter per day) of northern species markedly increased when a subset of species was grown under a long summer day length (20.5 h), indicating that genetically based day-length cues are required for growth regulation in these species. We conclude that the observed relationship between freezing tolerance and growth rate is not driven by differences in species' intrinsic growth capacity but by differences in the environmental cues that trigger growth. We propose that the coordinated evolution of freezing tolerance and growth phenology could be important in circumscribing willow and poplar range limits and may have important implications for species' current and future distributions.

Molecular cytogenetic characterisation of Salix viminalis L. using repetitive DNA sequences

Salix viminalis L. (2n = 38) is a diploid dicot species belonging to the Salix genus of the Salicaceae family. This short-rotation woody crop is one of the most important renewable bioenergy resources worldwide. In breeding for high biomass productivity, limited knowledge is available on the molecular cytogenetics of willow, which could be combined with genetic linkage mapping. The present paper describes the adaptation of a fluorescence in situ hybridisation (FISH) protocol as a new approach to analyse the genomic constitution of Salix viminalis using the heterologous DNA clones pSc119.2, pTa71, pTa794, pAs1, Afa-family, pAl1, HT100.3, ZCF1 and the GAA microsatellite marker. Three of the nine probes showed unambiguous signals on the metaphase chromosomes. FISH analysis with the pTa71 probe detected one major 18S-5.8S-26S rDNA locus on the short arm of one chromosome pair; however, the pTa794 rDNA site was not visible. One chromosome pair showed a distinct signal around the centromeric region after FISH with the telomere-specific DNA clone HT100.3. Two chromosome pairs were found to have pAs1 FISH signals, which represent a D-genome-specific insert from Aegilops tauschii. Based on the FISH study, a set of chromosomes with characteristic patterns is presented, which could be used to establish the karyotype of willow species.

Biodiversità nella dendroflora italiana

In the vascular flora native to Italy,which consists of about 7,000 species, trees include few units. that, between Gymnosperms and Angiosperms, are not more than 188 species and infraspecific taxa.Indeed the Italian tree flora is diversified and enriched by woody polistemmed or shrubby species that, growing old and in special conditions, could reach a tree-likesize. Genetic expressions of classic tree-like species, variously treated from the taxonomical point of view, are also to be added. The tree like flora here taken into account amounts to 53 genera (7 Gymnosperms and 46 Angiosperms) on the whole consisting of 188 specific and infraspecific taxa (21 Gymnosperms and 167 Angiosperms). Several genera (Pinus,Quercus, Salix, Pyrus, Tamarix) are highly diversified. The Rosaceae family, including Crataegus, Malus, Pyrus, Prunus and Sorbus is the richest in genera. In the Fagaceae family, consisting of Castanea, Fagus, and Quercus, the first two genera are monospecific while Quercus is highly diversified from the taxonomical point of view. In the Salicaceae family, the genus Salix alone is taxonomically diversified almost as the whole genus Quercus. Under the the phyto-geographycal aspect, the Italian tree flora is mainly correlated to the European characteristics, rather than the Mediterranean ones; endemism is more remarkable as far as infraspecific taxa are concerned;nevertheless there are also several noteworthy endemic species belonging to the genera Abies, Betula,Malus and Pyrus.

Softwood and Hardwood Lignin Fluorescence Spectra of Wood Cell Walls in Different Mounting Media

Wood cell walls are naturally fluorescent due to the presence of lignin. Autofluorescence offers a more specific method for localising lignin than staining and can potentially be used to assess cell wall modification resulting from a range of biological, chemical and physical treatments. In order to optimise conditions for imaging lignin by autofluorescence and to evaluate possible differences in fluorescence between softwood and hardwood lignin, wood sections of radiata pine and poplar were examined by confocal laser scanning microscopy to measure fluorescence spectra in a range of mounting media. Glycerol/buffer mixtures at three different pH values were compared with immersion oil and thiodiethanol using both UV and visible excitation. Glycerol/buffer at pH9 produced the strongest lignin fluorescence at visible excitation indicating that this is the optimal mounting medium for imaging and spectroscopy. For UV excitation, thiodiethanol gave increased brightness relative to glycerol. Poplar lignin was four times brighter than pine lignin with excitation at 488 nm at pH9, and showed characteristic differences in spectral emission under these conditions. This characteristic fluorescence was localised to the inner secondary wall of fibres, expressed as a gradient from the outer S2 region increasing towards the lumen, as visualised by spectral unmixing. Comparison with sapwood from other hardwood species suggests that this fluorescence emission is characteristic of poplar and willow (Salicaceae). Members of the Salicaceae family are known to contain characteristic syringyl p-hydroxybenzoate lignin and it is likely that this special lignin type is responsible for the characteristic pH dependant fluorescence of poplar fibre walls.

Physical and Mechanical Properties of Four Salix Species

The increasing use of Salix species in the manufacture of various products has been attracting interest towards the Salicaceae family in South America. This paper reports the physical and mechanical parameters of Salix viminalis L. (purple osier) , Salix x rubens Schrank (basket willow) , Salix purpurea Linne (purple willow) and Salix sp ., cultivated in the Canoas River Valley, in the Serra Catarinense region of the state of Santa Catarina, Brazil. The evaluations were conducted with raw material, the most commonly used format in handcrafts, and the results indicate there are differences in physical and mechanical properties among the species. Salix viminalis and Salix purpurea were similar in density and in their modulus of elasticity, and had higher values of tensile and strength modulus than Salix x rubens and Salix sp .

First total chemical synthesis of natural acyl derivatives of some phenolglycosides of the family Salicaceae

The total synthesis of certain natural phenolglycosides of the family Salicaceae, namely: salireposide, populosides A, B, and C and not occurring in plants desoxysalireposide (2-(β-d-glucopyranosyloxy)-benzylbenzoate) and per-acetate of iso-salireposide (2-(β-d-glucopyranosyloxy)-5-benzoyloxy benzyl alcohol), starting from readily available phenols and glucose was accomplished. A simple method for the synthesis of phenolglycosides derivatives of 2-acyloxy salicyl and gentisyl alcohol was developed. The key step of these natural products’ synthesis is a selective removal of acetyl groups in the presence of other acyl groups.

Polymorphism and Divergence in Two Willow Species,Salix viminalisL. andSalix schweriniiE. Wolf

We investigated species divergence, present and past gene flow, levels of nucleotide polymorphism, and linkage disequilibrium in two willows from the plant genus Salix. Salix belongs together with Populus to the Salicaceae family; however, most population genetic studies of Salicaceae have been performed in Populus, the model genus in forest biology. Here we present a study on two closely related willow species Salix viminalis and S. schwerinii, in which we have resequenced 33 and 32 nuclear gene segments representing parts of 18 nuclear loci in 24 individuals for each species. We used coalescent simulations and estimated the split time to around 600,000 years ago and found that there is currently limited gene flow between the species. Mean intronic nucleotide diversity across gene segments was slightly higher in S. schwerinii (πi = 0.00849) than in S. viminalis (πi = 0.00655). Compared with other angiosperm trees, the two willows harbor intermediate levels of silent polymorphisms. The decay of linkage disequilibrium was slower in S. viminalis compared with S. schwerinii, and we speculate that this is due to different demographic histories as S. viminalis has been partly domesticated in Europe.

NMR and MS profiling of chemosystematic markers in triploid Populus tomentosa

Chemosystematics, or chemotaxonomy, is the attempt to classify and identify plants, according to demonstrable differences and similarities in their secondary metabolites. Thus, chemotaxonomic markers are powerful tools for the identification of a wide variety of plants [1]. Chinese forest scientists have been making significant efforts to develop fast-growing trees due to the extreme shortage of wood resources. Triploid Populus tomentosa Carr. (Salicaceae), the cloned hardware poplar species from Populus tomentosa, has been receiving the most attention [2]. However, secondary metabolites of triploid P. tomentosa have never been studied to date, though poplars have been widely used in folk medicines for the treatment of various diseases [3]. This work was carried out to investigate the secondary metabolites and the chemosystematic markers from triploid P. tomentosa. Column chromatographic purification of triploid P. tomentosa extracts resulted in the isolation of twelve phenolics: grandidentatin, isograndidentatin A, isograndidentatin B, caffeic acid, populoside A, salireposide, luteolin, salicortin, apigenin, populoside, ρ-coumaric acid, and 7-O-caffeoylsalirepin. The structures of the isolated secondary metabolites were extensively elucidated and characterized by spectroscopic method, including 1D and 2D NMR, and EI, FAB and MALDI-TOF MS. This was the first investigation of the secondary metabolites of triploid P. tomentosa wood. The isolation of isograndidentatin A, isograndidentatin B, grandidentatin, here in triploid P. tomentosa was interesting and glucosides of 1,2-dihydroxycyclohexane acylated by ρ-coumaric acid (or ρ-coumaric acid derivatives) could be considered as useful chemosystematic marks within the Salicaceae family, which was also well in accord with the our previous conclusion [4].

Comparison of Trichloroethylene Toxicity, Removal, and Degradation by Varieties of Populus and Salix for Improved Phytoremediation Applications

Trichloroethylene (TCE), a chlorinated organic solvent, is one of the three most common and widespread groundwater contaminants worldwide. Exposure to this contaminant has been linked to liver and kidney toxicity and cancer in humans and animals [1]. The Salicaceae family, which includes poplar and willow trees, has been very successful in phytoremediation efforts involving chlorinated solvents including TCE. Previous phytoremediation studies investigated removal of this contaminant using one or two genotypes, but a screening of a large number of genotypes in this family of plants had not yet been conducted. In this study, nine Populus and twelve Salix varieties were chosen for their previous success in phytoremediation efforts or local native significance, and experiments were conducted to compare toxicity, uptake, and degradation of TCE. Results from the toxicity screening demonstrated that hybrid poplar clones Crandon (Populus alba x grandidentata), Nisqually-1 (P. trichocarpa), D.Pa (P. alba) and willow clone S365 (Salix discolor) had the highest mass gain and best health at the highest TCE concentration. Percent removal of TCE in one week ranged from 19.2 to 44.9 with Crandon, P. deltoides hybrid 91x0403, poplar clone H11-11 (P. trichocarpa x deltoides), Salix sitchensis clone B, and Nisqually-1 all removing more than 40 percent of the TCE from hydroponic solution. In terms of TCE degradation, S. sitchensis clone B, poplar hybrid 91x0403, and hybrid poplar H11-11 had the most TCE metabolite, trichloroethanol, per gram of fresh plant weight, with the best performer, S. sitchensis clone B, having eight times the amount than the lowest genotype tested. These results indicated that there are significant differences in the ability of poplar and willow genotypes to remove and degrade TCE, and that many different genotypes could be successfully utilized for phytoremediation of TCE. This data set could be applied toward choosing the appropriate genotypes for the phytoremediation of TCE in a given location and climate.

Talus cone activity recorded by tree-rings of Arctic dwarf shrubs: a study case from SW Spitsbergen, Norway

Dendrochronological methods were used to determine talus cone activity in the Arctic area. Talus cones are one of the most characteristic geomorphological features of the Svalbad Archipelago. Two species of dwarf shrubs, Salix polaris and Salix reticulata, which belong to the Willow family (Salicaceae), were collected from two talus cones located in the SW Spitsbergen Island. Th ese small creeping shrubs (less than 10 cm tall with stem diameters ranging from 0.5 cm to 1.1 cm) have well developed tree-rings which allow them to be used for dendrochronological research. Th e age of the dwarf shrubs showed the minimum time during which the cones were disturbed by mass movements. Observations and material analysis indicate that currently the talus cones are active, but their development through debris fl ow, creep and rock particle slide is observed only episodically. An increased rate of vegetation colonization during the 1980s indi

Differentiation of metallicolous and non-metallicolous Salix caprea populations based on phenotypic characteristics and nuclear microsatellite (SSR) markers.

The Salicaceae family comprises a large number of high-biomass species with remarkable genetic variability and adaptation to ecological niches. Salix caprea survives in heavy metal contaminated areas, translocates and accumulates Zn/Cd in leaves. To reveal potential selective effects of long-term heavy metal contaminations on the genetic structure and Zn/Cd accumulation capacity, 170 S. caprea isolates of four metal-contaminated and three non-contaminated middle European sites were analysed with microsatellite markers using Wright's F statistics. The differentiation of populations North of the Alps are more pronounced compared to the Southern ones. By grouping the isolates based on their contamination status, a weak but significant differentiation was calculated between Northern metallicolous and non-metallicolous populations. To quantify if the contamination and genetic status of the populations correlate with Zn/Cd tolerance and the accumulation capacity, the S. caprea isolates were exposed to elevated Cd/Zn concentrations in perlite-based cultures. Consistent with the genetic data nested anova analyses for the physiological traits find a significant difference in the Cd accumulation capacity between the Northern and Southern populations. Our data suggest that natural populations are a profitable source to uncover genetic mechanisms of heavy metal accumulation and biomass production, traits that are essential for improving phytoextraction strategies.

How do riparian woody seedlings survive seasonal drought?

In semi-arid regions, a major population limitation for riparian trees is seedling desiccation during the dry season that follows annual spring floods. We investigated the stress response of first-year pioneer riparian seedlings to experimental water table declines (0, 1 and 3 cm day(-1)), focusing on the three dominant cottonwood and willows (family Salicaceae) in California's San Joaquin Basin. We analyzed growth and belowground allocation response to water stress, and used logistic regression to determine if these traits had an influence on individual survival. The models indicate that high root growth (>3 mm day(-1)) and low shoot:root ratios (<1.5 g g(-1)) strongly predicted survival, but there was no evidence that plants increased belowground allocation in response to drawdown. Leaf δ(13)C values shifted most for the best-surviving species (net change of +3.5 per mil from -30.0 ± 0.3 control values for Goodding's willow, Salix gooddingii), implying an important role of increased water-use efficiency for surviving water stress. Both S. gooddingii and sandbar willow (S. exigua) reduced leaf size from controls, whereas Fremont cottonwood (Populus fremontii) sustained a 29% reduction in specific leaf area (from 13.4 to 9.6 m(2) kg(-1)). The functional responses exhibited by Goodding's willow, the more drought-tolerant species, may play a role in its greater relative abundance in dry regions such as the San Joaquin Basin. This study highlights the potential for a shift in riparian forest composition. Under a future drier climate regime or under reduced regulated river flows, our results suggest that willow establishment will be favored over cottonwood.

Biosynthesis of Phenolic Glycosides from Phenylpropanoid and Benzenoid Precursors in Populus

Salicylate-containing phenolic glycosides (PGs) are abundant and often play a dominant role in plant-herbivore interactions of Populus and Salix species (family Salicaceae), but the biosynthetic pathway to PGs remains unclear. Cinnamic acid (CA) is thought to be a precursor of the salicyl moiety of PGs. However, the origin of the 6-hydroxy-2-cyclohexen-on-oyl (HCH) moiety found in certain PGs, such as salicortin, is not known. HCH is of interest because it confers toxicity and antifeedant properties against herbivores. We incubated Populus nigra leaf tissue with stable isotope-labeled CA, benzoates, and salicylates, and measured isotopic incorporation levels into both salicin, the simplest PG, and salicortin. Labeling of salicortin from [13C6]-CA provided the first evidence that HCH, like the salicyl moiety, is a phenylpropanoid derivative. Benzoic acid and benzaldehyde also labeled both salicyl and HCH, while benzyl alcohol labeled only the salicyl moiety in salicortin. Co-administration of unlabeled benzoates with [13C6]-CA confirmed their contribution to the biosynthesis of the salicyl but not the HCH moiety of salicortin. These data suggest that benzoate interconversions may modulate partitioning of phenylpropanoids to salicyl and HCH moieties, and hence toxicity of PGs. Surprisingly, labeled salicyl alcohol and salicylaldehyde were readily converted to salicin, but did not result in labeled salicortin. Co-administration of unlabeled salicylates with labeled CA suggested that salicyl alcohol and salicylaldehyde may have inhibited salicortin biosynthesis. A revised metabolic grid model of PG biosynthesis in Populus is proposed, providing a guide for functional genomic analysis of the PG biosynthetic pathway.

High-density linkage mapping and evolution of paralogs and orthologs in Salix and Populus.

BackgroundSalix (willow) and Populus (poplar) are members of the Salicaceae family and they share many ecological as well as genetic and genomic characteristics. The interest of using willow for biomass production is growing, which has resulted in increased pressure on breeding of high yielding and resistant clones adapted to different environments. The main purpose of this work was to develop dense genetic linkage maps for mapping of traits related to yield and resistance in willow. We used the Populus trichocarpa genome to extract evenly spaced markers and mapped the orthologous loci in the willow genome. The marker positions in the two genomes were used to study genome evolution since the divergence of the two lineages some 45 mya.ResultsWe constructed two linkage maps covering the 19 linkage groups in willow. The most detailed consensus map, S1, contains 495 markers with a total genetic distance of 2477 cM and an average distance of 5.0 cM between the markers. The S3 consensus map contains 221 markers and has a total genetic distance of 1793 cM and an average distance of 8.1 cM between the markers. We found high degree of synteny and gene order conservation between willow and poplar. There is however evidence for two major interchromosomal rearrangements involving poplar LG I and XVI and willow LG Ib, suggesting a fission or a fusion in one of the lineages, as well as five intrachromosomal inversions. The number of silent substitutions were three times lower (median: 0.12) between orthologs than between paralogs (median: 0.37 - 0.41).ConclusionsThe relatively slow rates of genomic change between willow and poplar mean that the genomic resources in poplar will be most useful in genomic research in willow, such as identifying genes underlying QTLs of important traits. Our data suggest that the whole-genome duplication occurred long before the divergence of the two genera, events which have until now been regarded as contemporary. Estimated silent substitution rates were 1.28 × 10-9 and 1.68 × 10-9 per site and year, which are close to rates found in other perennials but much lower than rates in annuals.

Identification of a new nucleopolyhedrovirus from naturally-infected Condylorrhiza vestigialis (Guenée) (Lepidoptera: Crambidae) larvae on poplar plantations in South Brazil

A baculovirus was isolated from larvae of Condylorrhiza vestigialis (Guenée) (Lepidoptera: Crambidae), a pest of a forest species known as Poplar (family Salicaceae, genus: Populus) with high economic value. Electron microscopy analysis of the occlusion body obtained from diseased larvae showed polyhedra containing multiple nucleocapsids per envelope. This baculovirus was thus named Condylorrhiza vestigialis multiple nucleopolyhedrovirus (CoveMNPV) and characterized by its DNA restriction endonuclease pattern, polyhedral protein, viral protein synthesis, and infectivity in insect cell lines. Restriction endonuclease profiles of viral DNA digested with five restriction enzymes were obtained and the CoveMNPV genome size was estimated to be 81 ± 2.5 kbp. The isolation of the polyhedra (OBs) was done from the crude extract of infected larvae by ultracentrifugation through sucrose gradients. These viral particles were analyzed by denaturing polyacrylamide gel electrophoresis (SDS–PAGE), which showed a strong band with approximately 33 kDa, corresponding to the main protein of the occlusion bodies (polyhedrin). Also, a similar band was observed for CoveMNPV infected Spodoptera frugiperda cells (SF-21 AE) pulse-labeled with [ 35S] methionine and fractionated by SDS–PAGE. Of the four insect cell lines tested for susceptibility to CoveMNPV infection, the SF-21 AE was the most susceptible with occlusion bodies produced in most of the inoculated cells. This is the first record of an NPV from C. vestigialis.

Metal Accumulation by Woody Species on Contaminated Sites in the North of France

Metal accumulation was investigated in a range of woody species that were planted on Cd-, Zn- and Pb- polluted sites in North of France. The study is unique in that we directly compare a large number of woody species (25). The highest accumulation of Zn and Cd was found in the Salicaceae family members with up to 950 mg Zn kg−1 dry weight (DW) and 44 mg Cd kg−1 DW in leaves of Populus tremula × Populus tremuloides. Zn content was positively correlated with Cd content, both in leaves and stems. Pb concentration was generally low and was species-independent. Oak and birch species accumulated more Mn as compared to other woody species. A seasonal variation in metal accumulation could be found. Although soil compositions and metal bioavailabilities differed amongst the experimental sites chosen in this study, variation of metal concentrations within a given species was small. High bioconcentration factors for poplar and willow suggested the high potential of these species over other woody species for metal accumulation. Taken together, these data suggest that poplar and willow species are good candidates for phytoremediation programmes.

Detoxification of Cyanide by Woody Plants

Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. This paper examines the potential of three woody plants from the Salicaceae family to degrade cyanide. Pre-rooted trees were grown in carefully designed bioreactors with aqueous solution spiked with potassium cyanide at 23.0 +/- 1 degree C for a maximum of 144 h. Cyanide concentrations ranged from 0.95 to 1.15 CN mg/L. Cyanide in water and in plant tissues was analyzed spectrophotometrically. Results from the investigation indicated that significant reduction of aqueous cyanide was found during the presence of plants in all treatments. Little amounts of applied cyanide were detected in the tissues of plants, mainly in roots and bottom stem. Cyanide remaining in tissues varied with the species of plants, despite similar periods of exposure. The data also indicated that photolysis, hydrolysis, and microbial degradation were not occurring and that volatilization was minimal. In conclusion, transport and metabolism of cyanide in plants is most likely.