The Effect of Mycorrhizal Fungi on the Fate of Aldrin: Phytoremediation Potential

The objective of this study was to investigate the phytoremediation potential of mycorrhizal systems for the remediation of aldrin-contaminated soils. Feltleaf willow (Salix alaxensis) and balsam poplar (Populus balsamifera) were grown in soil spiked with 0.8 mg/kg aldrin- (1,2,3,4,10-¹⁴C). Daconil₂₇₈₇® was employed to suppress indigenous mycorrhizal infection. After 100 days of greenhouse incubation, mycorrhizal infection in the fungicide-amended willows was found to be 2.5 fold lower than in controls. Mycorrhizal infection in the poplar systems was unaffected by fungicide addition. Mycorrhizae were correlated with radiolabel uptake in the willow systems (r = 0.79), and not as strongly in the poplar systems (r = 0.58). Most of the radiolabel in the root material was bound product regardless of mycorrhizal infection, but 12 to 21% was found to be extractable dieldrin. Aldrin was not detected in any vegetative matrix. Dieldrin constituted less than 1% of the radiolabel in the willow leaf material, accumulating to approximately 5 μg/kg. Dieldrin was not detected in the poplar leaves (MDL ≈ 1 μg/kg), although the poplars took up approximately the same amount of radiolabel as the willows. Water-soluble transformation products were formed in the vegetated soils (6 to 12%) and nonvegetated controls (1 to 2%).     

Effects of above-ground browsing by mammals on mycorrhizal infection in an early successional taiga ecosystem

Using an exclosure experiment in the willow stage of primary succession on the floodplain of the Tanana River, we tested the hypothesis that browsing can reduce mycorrhizal infection. We measured the effects winter browsing by moose (Alcesalces) and snowshoe hare (Lepusamericanus) had on mycorrhizal infection and fine root biomass of willow (Salix spp.) and balsam poplar (Populusbalsamifera). We found that protection from winter browsing increased ectomycorrhizal infection by 10% in the top 5 cm of the soil profile, by 23% at 5–10 cm, and by 42% at the 10–15 cm depth. Mammal browsing in taiga forests is now recognized as a major cause of the shift from palatable deciduous species such as willow and balsam poplar to less palatable species such as alder and spruce. We suggest that browsing-induced reduction in ectomycorrhizal infection of salicaceous species plays a central role in this shift in plant community composition. Received: 26 March 1996 / Accepted: 26 September 1996     

Natural and induced cadmium-accumulation in poplar and willow: Implications for phytoremediation

Potentially poplars and willows may be used for the in situ decontamination of soils polluted with Cd, such as pasturelands fertilised with Cd-rich superphosphate fertiliser. Poplar (Kawa and Argyle) and willow (Tangoio) clones were grown in soils containing a range (0.6–60.6 μg g⁻¹ dry soil) of Cd concentrations. The willow clone accumulated significantly more Cd (9–167 μg g⁻¹ dry matter) than the two poplar clones (6–75 μg g⁻¹), which themselves were not significantly different. Poplar trees (Beaupré) sampled in situ from a contaminated site near the town of Auby, Northern France, were also found to accumulate significant quantities (up to 209 μg g⁻¹) of Cd. The addition of chelating agents (0.5 and 2 g kg⁻¹ EDTA, 0.5 g kg⁻¹ DTPA and 0.5 g kg⁻¹NTA) to poplar (Kawa) clones caused a temporary increase in uptake of Cd. However, two of the chelating agents (2 g kg⁻¹ EDTA and 0.5 g kg⁻¹ NTA) also resulted in a significant reduction in growth, as well as abscission of leaves. If the results obtained in these pot experiments can be realised in the field, then a single crop of willows could remove over 100 years worth of fertiliser-induced Cd contamination from pasturelands. This revised version was published online in June 2006 with corrections to the Cover Date.     

Alignment of a <Emphasis Type="Italic">Salix</Emphasis> linkage map to the <Emphasis Type="Italic">Populus</Emphasis> genomic sequence reveals macrosynteny between willow and poplar genomes

Poplars (genus Populus) and willows (genus Salix) are members of the Salicaceae, a family of catkin-bearing trees, shrubs and sub-shrubs. Poplar is considered the model system for biological studies in trees and considerable genetic and genomic resources have become available in recent years. The transfer of information to research studies in willow, for which fewer resources are currently available, would be highly beneficial. However, the extent of conservation between poplar and willow genomes has not yet been extensively studied. To address this, we have constructed a linkage map of willow based on a large mapping population derived from a cross between two Salix viminalis × (S. viminalis × S. schwerinii) hybrid sibs, and aligned this to the publicly available poplar genome sequence. A set of genome-wide, expressed poplar sequences was selected and used to design primer sets that efficiently amplified homeologous regions in willow. Direct sequencing of the willow products confirmed homology with the poplar target in the majority of instances and allowed identification of single nucleotide polymorphisms (SNPs) that were used to map these loci. In total, 202 amplified fragment length polymorphisms (AFLPs), 75 microsatellites and 79 SNPs were used to construct a willow consensus map that spanned 1,856.7 cM with an average interval between markers of 6.3 cM. Poplar sequences homologous to those of the mapped willow microsatellite loci were identified and used in addition to the SNP markers to putatively align all but two minor linkage groups to the poplar genome sequence. A high degree of macrosynteny was revealed.     

Inhibition of mycorrhizal symbiosis in Leucaena leucocephala by chlorothalonil

The effect of the fungicide, chlorothalonil, on vesicular-arbuscular mycorrhizal (VAM) symbiosis was studied in a greenhouse using Leucaena leucocephala as test plant. Chlorothalonil was applied to soil at 0, 50, 100 and 200 μg g⁻¹. The initial soil solution P levels were 0.003 μg mL⁻¹ (sub-optimal) and 0.026 μg mL⁻¹ (optimal). After 4 weeks, the sub-optimal P level was raised to 0.6 μg mL⁻¹ (high). The soil was either uninoculated or inoculated with the VAM fungus, Glomus aggregatum. The fungicide reduced mycorrhizal colonization of roots, development of mycorrhizal effectiveness, shoot P concentration and uptake and dry matter yields at all concentrations tested, although the highest inhibitory effect was noted as the concentration of the fungicide was increased from 50 to 100 μg g⁻¹. Phosphorus applied after four weeks tended to partially offset the deleterious effects of chlorothalonil in plants grown in the inoculated and uninoculated soil which suggests that the fungicide was interfering with plant P uptake. The results suggest that the use of chlorothalonil should be restricted to levels below 50 μg g⁻¹ if the benefits of mycorrhizal symbiosis are to be expected. Contribution from Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3464. Contribution from Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3464.     

Influence of the fungicide pentachloronitrobenzene on VA-mycorrhizal and total root length and phosphorus uptake of oats (Avena sativa)

The effect of application of the fungicide pentachloronitrobenzene (PCNB) at levels between 2 and 50 mg kg^–1 soil on root growth, mycorrhizal infection and P uptake was studied in pot culture with oats (Avena sativa cv. Alfred) growing in a rendzina soil low in available P. The soil had been partially sterilized by X-ray, and half of the pots were inoculated with spores of the VAM-fungusGlomus mosseae (indigenous species).Soil irradiation (0.5 Mrad) did not decrease the levels of infection by VAM. Application of PCNB decreased the VAM-infected root length, at 50 mg PCNB kg^–1 soil VAM-infected root length was about 12% of the controls. Total root length, however, increased to about 126% of control values at PCNB rates up to 20 mg kg^–1 soil, but decreased to 89% of the controls at 50 mg kg^–1 soil. Total P-uptake decreased with increasing levels of PCNB and was linearly correlated with infected root length (r=0.92).The stimulation of root growth by PCNB at rates up to 20 mg kg^–1 soil is regarded as an indirect effect, brought about by suboptimal P-supply due to inhibition of VA-mycorrhiza. Conversely, the reduction of total root length at 50 mg PCNB kg^–1 soil is most likely a direct effect. Due to the phytotoxicity of the fungicide, the contribution of the indigenous VA-mycorrhiza to plant P uptake under field conditions cannot be determined by soil application of PCNB at rates sufficient for complete inhibition of VAM.As inhibition or absence of VAM may lead to compensatory root growth, mycorrhizal dependency ought to be calculated from the amounts of P taken up per unit root length in mycorrhizal and nonmycorrhizal plants, respectively.     

The giant willow aphid (Tuberolachnus salignus) and its effects on the survival and growth of willows

1. The giant willow aphid (Tuberolachnus salignus) is an invasive pest that can attain large populations on willows (Salix spp.). This has the potential to have a negative impact on the extensive use of willows for soil conservation, and as a source of pollen and nectar for honey bees in New Zealand.
2. A willow nursery field trial was established to evaluate the aphid populations, and the survival and growth of young plants of several willow species and hybrids, during two growing seasons from planting.
3. The willow species and hybrids varied widely in their susceptibility to the aphid, with large aphid populations and plant mortality in the most susceptible willows, and reductions in plant growth in all but aphid-resistant willows. The effects on the plants were not seen in the first season, but occurred during the second season.
4. The aphid can be expected to have some negative impacts in New Zealand, with reductions in growth of some willows commonly used for soil conservation, and for pollen and nectar for honey bees.

     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

The effects of vesicular-arbuscular mycorrhizal (VAM) colonisation on phosphorus (P) uptake and growth of clover (Trifolium subterraneum L.) in response to soil compaction were studied in three pot experiments. P uptake and growth of the plants decreased as the bulk density of the soil increased from 1.0 to 1.6 Mg m^-3. The strongest effects of soil compaction on P uptake and plant growth were observed at the highest P application (60 mg kg^-1 soil). The main observation of this study was that at low P application (15 mg kg^-1 soil), P uptake and shoot dry weight of the plants colonised by Glomus intraradices were greater than those of non-mycorrhizal plants at similar levels of compaction of the soil. However, the mycorrhizal growth response decreased proportionately as soil compaction was increased. Decreased total P uptake and shoot dry weight of mycorrhizal clover in compacted soil were attributed to the reduction in the root length. Soil compaction had no significant effect on the percentage of root length colonised. However, total root length colonised was lower (6.6 m pot^-1) in highly compacted soil than in slightly compacted soil (27.8 m pot^-1). The oxygen content of the soil atmosphere measured shortly before the plants were harvested varied from 0.18 m³m^-3 in slightly compacted soil (1.0 Mg m^-3) to 0.10 m³m^-3 in highly compacted soil (1.6 Mg m^-3).     

Soil trace element changes during a phytoremediation trial with willows in southern Québec,Canada

This study determined the changes in trace elements (TE) (As, Cd, Cu, Ni, Pb, Zn) chemistry in the soils of a willow (“Fish Creek” – Salix purpurea, SV1 – Salix x dasyclados and SX67 – Salix miyabeana) plantation growing under a cold climate during a three-year trial. The soil HNO₃-extractable and H₂O-soluble TE concentrations and pools significantly decreased under most cultivars (Fish, SX67). Yet, TE changes showed inconsistent patterns and localized soil TE increases (Ni, Pb) were measured. Temporal changes in soil TE were also detected in control plots and sometimes exceeded changes in planted plots. Discrepancies existed between the amount of soil TE change and the amount of TE uptake by willows, except for Cd and Zn. Phytoremediation with willows could reduce soil Cd and Zn within a decadal timeframe indicating that they can be remediated by willows in moderately contaminated soils. However, the time needed to reduce soil As, Cu, Ni and Pb was too long to be efficient. We submit that soil leaching contributed to the TE decrease in controls and the TE discrepancies, and that the plantation could have secondary effects such as the accelerated leaching of soil TE.     

Growth response and phosphorus uptake of rye with long and short root hairs: Interactions with mycorrhizal infection

Plant growth and phosphorus (P) uptake of two selections of rye (Secale cereale L.) differing in length of root hairs, in response to mycorrhizal infection were investigated. Rye plants with short root hairs (SRH) had a greater length of root infected by Glomus intraradices (up to 32 m pot^–1) than those with long root hairs (LRH) (up to 10 m pot^–1). Application of P decreased the percentage of root length infected in both selections. In low-P soil, mycorrhizal infection increased shoot and root P concentration, especially in LRH plants. Generally, LRH had higher shoot dry weight than SRH plants. P uptake was increased both by LRH and by mycorrhizal infection. Differences in specific P uptake and P utilization efficiency between SRH and LRH plants were observed in non-mycorrhizal plants. With low P supply, P utilization efficiency (dry matter yield per unit of P taken up) of LRH plants increased with time. However, mycorrhizal infection reduced P utilization efficiency, particularly of SRH plants. SRH plants, which were agronomically less efficient (i.e. low dry matter yield at low P supply) were more responsive to either mycorrhizal infection or P addition than the LRH plants. No interaction was observed between mycorrhizal infection and root hair length.     

Effects of Propagule Phenology (Non-Dormant Versus Dormant) and Planting System (Vertical Versus Horizontal) on Growth Performance of Willow Clones Grown Under Different Weeding Regimes

To assess the effects of propagule phenology and planting system on growth performance of three willow clones grown under different weeding regimes, a field experiment was performed in central Sweden 2014–2016. Freshly harvested (non-dormant) and cold-stored (dormant) cuttings (planted vertically) and billets (planted horizontally) from willow clones Tordis, Tora, and Jorr were planted in weeded and in unweeded plots. Sprouting was significantly higher for willows grown from non-dormant (74%) than dormant (58%) propagules and for cuttings (84%) compared with billets (42%). Survival was higher for willows from non-dormant propagules in weeded (71%) compared with unweeded (63%) plots, willows from dormant propagules in weeded (72%) compared with unweeded (60%) plots, and for willows from cuttings (93%) compared with billets (39%). During 2014–2016, aboveground biomass production was significantly higher for willows from cuttings (11.71 t DW ha^?1) than from billets (6.13 t DW ha^?1), grown in weeded (15.29 t DW ha^?1) than in unweeded (2.55 t DW ha^?1) plots, and differed significantly among willow clones (11.48, 9.27, and 6.01 t DW ha^?1 for Tordis, Tora, and Jorr, respectively). In this study, (i) planting with cold-stored and freshly harvested willow propagules was equally successful and therefore cold storage could be potentially avoided and replaced with planting of freshly harvested propagules in early spring; however, (ii) in terms of measured growth performance parameters, willows grown from cuttings performed better than grown from billets; and (iii) weed competition significantly reduced survival and aboveground biomass production, confirming that weed control during establishment of willow is crucial.     

Are Vegetative Reproduction Capacities the Cause of Widespread Invasion of Eurasian Salicaceae in Patagonian River Landscapes?

In recent decades, invasive willows and poplars (Salicaceae) have built dense floodplain forests along most of the rivers in Patagonia, Argentina. These invasion processes may affect Salix humboldtiana as the only native floodplain tree species in this region. It is assumed, that the property to reproduce vegetatively can play an important role in the establishment of invasive species in their new range. Thus, in order to contribute to a better understanding of willow and poplar invasions in riparian systems and to assess the potential impacts on S. humboldtiana the vegetative reproduction capacities of native and invasive Salicaceae were analysed. In a greenhouse experiment, we studied cutting survival and growth performance of the three most dominant invasive Salicaceae of the Patagonian Río Negro region (two Salix hybrids and Populus spec.), as well as S. humboldtiana, taking into account three different moisture and two different soil conditions. In a subsequent experiment, the shoot and root biomass of cuttings from the former experiment were removed and the bare cuttings were replanted to test their ability to re-sprout. The two invasive willow hybrids performed much better than S. humboldtiana and Populus spec. under all treatment combinations and tended to re-sprout more successfully after repeated biomass loss. Taking into account the ecology of vegetative and generative recruits of floodplain willows, the results indicate that the more vigorous vegetative reproduction capacity can be a crucial property for the success of invasive willow hybrids in Patagonia being a potential threat for S. humboldtiana.     

Effects of Salmon-Borne Nutrients on Riparian Soils and Vegetation in Southwest Alaska

Spawning Pacific salmon (Oncorhynchus spp.) contribute marine-derived nutrients to riparian ecosystems, potentially affecting characteristics of the associated soils and vegetation. We quantified these effects by comparing soil and vegetative characteristics upstream and downstream of natural migratory barriers on ten spawning streams in southwest Alaska. Mean δ¹⁵N values—indicative of salmon-borne nutrients—were significantly higher in the O horizon and surface mineral soils downstream of barriers (near spawning reaches) than in soils upstream of barriers (near non-spawning reaches). However, the mean total N concentration in surface mineral soil was lower downstream than upstream. Mean foliar δ¹⁵N values were higher downstream for three plant species (Picea glauca, Salix alaxensis and Arctagrostis latifolia) with contrasting physiognomies. Mean overstory stem density was 100% higher downstream, primarily due to a fivefold difference in the density of large-diameter willows (Salix spp.). Mean understory stem density was 47% lower downstream, also driven by a difference in willow density. Mean ground layer non-vascular and dwarf shrub species covers were 28% and 73% lower downstream, respectively. Of the ten soil and vegetative characteristics that differed upstream to downstream, two (O horizon and Picea glauca δ¹⁵N) were correlated with the density of spawning salmon. Collectively, the data suggest that salmon-borne nutrients alter riparian soils and vegetation, while factors unrelated to salmon are responsible for the ultimate expression of many community characteristics.     

METAL UPTAKE AND ALLOCATION IN TREES GROWN ON CONTAMINATED LAND: IMPLICATIONS FOR BIOMASS PRODUCTION

Phytostabilization aims to reduce environmental and health risks arising from contaminated soil. To be economically attractive, plants used for phytostabilization should produce valuable biomass. This study investigated the biomass production and metal allocation to foliage and wood of willow (Salix viminalis L.), poplar (Populus monviso), birch (Betula pendula), and oak (Quercus robur) on five different soils contaminated with trace elements (TE), with varying high concentrations of Cu, Zn, Cd, and Pb as well as an uncontaminated control soil. In the treatment soils, the biomass was reduced in all species except oak. There was a significant negative correlation between biomass and foliar Cd and Zn concentrations, reaching up to 15 mg Cd kg^?1 and 2000 mg Zn kg ^?1 in willow leaves. Lead was the only TE with higher wood than foliage concentrations. The highest Pb accumulation occurred in birch with up to 135 mg kg ^?1 in wood and 78 mg kg ^?1 in foliage. Birch could be suitable for phytostabilization of soils with high Cd and Zn but low Pb concentrations, while poplars and willows could be used to stabilise soils with high Cu and Pb and low Zn and Cd concentrations.     

Development and evaluation of ForestGrowth‐SRC a process‐based model for short rotation coppice yield and spatial supply reveals poplar uses water more efficiently than willow

Woody biomass produced from short rotation coppice (SRC) poplar (Populus spp.) and willow (Salix spp.) is a bioenergy feedstock that can be grown widely across temperate landscapes and its use is likely to increase in future. Process‐based models are therefore required to predict current and future yield potential that are spatially resolved and can consider new genotypes and climates that will influence future yield. The development of a process‐based model for SRC poplar and willow, ForestGrowth‐SRC, is described and the ability of the model to predict SRC yield and water use efficiency (WUE) was evaluated. ForestGrowth‐SRC was parameterized from a process‐based model, ForestGrowth for high forest. The new model predicted annual above ground yield well for poplar (r² = 0.91, RMSE = 1.46 ODT ha^?1 yr^?1) and willow (r² = 0.85, RMSE = 1.53 ODT ha^?1 yr^?1), when compared with measured data from seven sites in contrasting climatic zones across the United Kingdom. Average modelled yields for poplar and willow were 10.3 and 9.0 ODT ha^?1 yr^?1, respectively, and interestingly, the model predicted a higher WUE for poplar than for willow: 9.5 and 5.5 g kg^?1 respectively. Using regional mapped climate and soil inputs, modelled and measured yields for willow compared well (r² = 0.58, RMSE = 1.27 ODT ha^?1 yr^?1), providing the first UK map of SRC yield, from a process‐based model. We suggest that the model can be used for predicting current and future SRC yields at a regional scale, highlighting important species and genotype choices with respect to water use efficiency and yield potential.     

Differences in nitrogen redistribution between early and late plant colonizers through ectomycorrhizal fungi on the volcano Mount Koma

Relationships involving the transfer of nitrogen (N) among Salix reinii (willow), Larix kaempferi (larch), and mycorrhizal fungi were investigated in a ridge and hillslope on the volcano Mount Koma in northern Japan using a two-pool fungal model. This model estimated N transfer among the examined taxa by measuring changes in the stable isotope ratio of N (δ¹⁵N). Although N content in tephra was low at both sites, it was higher on the ridge than on the hillslope, and higher in the willow patch than on bare ground or in the larch understory. The non-mycorrhizal sedge (Carex oxyandra) exhibited non-significant differences between the two sites regarding δ¹⁵N for N obtained from tephra. Larches developed a relationship with larch-specific Suillus mycorrhizal fungal species in the roots, and had a lower foliar δ¹⁵N on the hillslope than on the ridge. The larch δ¹⁵N increased during the growing season, while the willow δ¹⁵N remained stable. The dependence of larch on mycorrhizal fungi for N uptake was 3–5 % on the ridge and 56–76 % on the hillslope in autumn. Therefore, larches exhibited a flexible symbiotic relationship with mycorrhizal fungi for obtaining N. Over 45 % of the N taken up by willow plants was obtained from mycorrhizal fungi at both sites. In conclusion, willow plants promoted N deposition in tephra through the litter supply, and formed a stable relationship with mycorrhizal fungi. This enabled successful revegetation with larch plants, which exhibited flexibility in terms of N uptake (i.e., dependent on mycorrhizae or from tephra).     

Modelling of Cd, Cu, Pb and Zn transport in metal contaminated soil and their uptake by willow (Salix × smithiana) using HYDRUS-2D program

Aims

The main aim of this study was to validate the HYDRUS-2D model for the simulation of Cd, Cu, Pb and Zn transport within a soil column and their accumulation by willows.

Methods

A simulation of metal transport and uptake by willow was implemented using the HYDRUS-2D code. Two scenarios of the column experiment were compared: soil (C) and soil with planted willows (V). Seeping water, soil water content and actual transpiration were measured. Metal contents in soil water and willows were analysed.

Results

The single-porosity model (applied for isotropic soil media) was sufficient for scenario C. The single-porosity (applied for anisotropic soil media) and dual-porosity models (characterizing non-equilibrium water flow) were explored in scenario V. Measured cumulative Cd and Zn uptake showed a 20- and 10-times higher accumulation, respectively, in comparison with the modelled ones. On the other hand, modelled cumulative Pb uptake was reduced by reducing the maximum value of the root uptake concentration c _Root .

Conclusions

The HYDRUS-2D program was usable for modelling of Cd, Cu, Pb and Zn transport and their willow uptake. Additionally, consideration of dual-porosity soil media as well as anisotropy was suitable for the experiment with roots presence in the soil.     

Effects of mycorrhizal infection, soil phosphorus availability and fruit production on the male function in two cultivars of Lycopersicon esculentum

The effects of mycorrhizal infection, soil P availability and fruit production on the male function of reproduction were examined in two cultivars of tomato (Lycopersicon esculentum Mill.). Tomato plants were grown in a greenhouse under three treatment combinations: non‐mycorrhizal, low P (NMPO); non‐mycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). In addition, all treatment combinations were grown both with and without fruit. Fruit production decreased final leaf biomass, flower production and in vitro pollen tube growth rates, often reducing the beneficial effects of increased P uptake. Thus, fruit production diverted resources from subsequent vegetative growth, flower production and pollen development. As the growing season progressed, mean pollen production per flower and in vitro germination and tube growth decreased. Mycorrhizal infection and high soil P conditions increased final leaf biomass, flower production, mean pollen production per flower (in one cultivar) and in vitro pollen tube growth rates. Thus, mycorrhizal infection and high soil P conditions increased pollen quantity and quality, thereby enhancing fitness through the male function. Similar trends in these treatments suggested that mycorrhizal effects on the male function were largely the result of improved P acquisition.     

Variation in the uptake of Arsenic, Cadmium, Lead, and Zinc by different species of willows Salix spp. grown in contaminated soils

The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix ’Pyramidalis’ S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.