Willow Roots Research Articles

Response of ectomycorrhizal fungi to full and selective removal of an invasive tree in riparian woodland

The Brazilian pepper tree (Schinus terebinthifolius) is an invasive species that requires significant disturbance to eradicate. Previous studies have identified associations between the Brazilian pepper tree and ectomycorrhizal fungi (EMF). However, limited research has explored the connection between disturbance from removal and the effect on EMF. This study investigated the sensitivity of EMF and the broader fungal community to the full and selective removal of the Brazilian pepper tree. During the selective removal of Brazilian pepper tree, we examined the mycorrhizal community of the Arroyo willow (Salix lasiolepis) to assess the influence of the restoration disturbance on native species. We used ITS2 sequencing to identify the EMF present during the restoration. Our expectation was that both removal efforts would reduce the presence of EMF. Contrary to our predictions, full removal increased EMF richness and relative abundance in the soil. As anticipated, selective removal reduced the richness and relative abundance of EMF associated with soil. Selective removal led to a decrease in the richness of EMF in arroyo willow roots with no effect on relative abundance. Moreover, fungal community composition in soil and roots shifted significantly during selective and full removal. However, the community composition of EMF, specifically, remained constant across treatment types. During full removal efforts, the application of organic soil amendments may have contributed to the increase in the diversity and relative abundance of EMF. Selective removal will require additional measures, such as soil amendments, to curtail the loss of EMF.

Genomic insight into the insecticidal potential of a new Pseudomonas chlororaphis isolate.

Pseudomonas fluorescens group, such as Pseudomonas protegens and Pseudomonas chlororaphis, can be utilized as insect-killing agents. Most insecticidal Pseudomonas described so far have high toxicity for insects of the order Lepidoptera. In this study, Pseudomonas strain PcR3-3 was isolated from the willow root. It showed a high mortality for the coleopteran species Plagiodera versicolora (Coleoptera: Chrysomelidae), but not for the lepidopteran Helicoverpa armigera. Strain PcR3-3 displayed high colonization ability in the P. versicolora compared with P. chlororaphis PCL1391, indicating that the insecticidal activities correlated with the colonization ability of Pseudomonas strain in the host. Phylogenetic analysis of the genome revealed that PcR3-3 belonged to P. chlororaphis subsp. aureofaciens. Numerous insecticidal protein-encoding genes, typical biosynthetic gene clusters for some insecticidal metabolite and type VI secretion system, known to be involved in insect pathogenicity, were present in the P. chlororaphis PcR3-3 genome. However, the insecticidal toxin Fit-encoding gene which commonly presents in P. chlororaphis, was not found in the P. chlororaphis PcR3-3 genome. Furthermore, there are some divergent insecticidal genes between P. chlororaphis PcR3-3 and P. chlororaphis PCL1391. This finding implies that P. chlororaphis PcR3-3 is a promising biocontrol agent for pest management applications. The P. chlororaphis-P. versicolora association can be used as a model system to study the interaction between Pseudomonas and coleopteran insects.

Impact of roots on the hydrogeological properties of silty soil covers

Mine tailings storage poses significant environmental risks such as the formation of acid mine drainage. Engineered covers offer a solution by controlling water ingress. Their performance is based on specific soil hydrogeological properties (SHPs). They must support vegetation which can impact saturated hydraulic conductivity ( ksat) and water retention curve (WRC). This study assesses the impact of 4-year-old willow root colonization on silty soil covers using flexible wall parameters and water retention tests. The obtained SHPs were compared with root traits. The results suggested that the hydrogeological properties of the studied in situ samples were not significantly affected by roots. The variation of measured and predicted ksat values spanned an order of magnitude, regardless of the root colonization intensity, up to a root length density (RLD) of 2.98 cm/cm3. RLD showed a significant and positive linear relationship with measured ksat values ( R2 = 0.54). However, when root colonization was low (RLD < 1 cm/cm3), RLD was negatively correlated with the nvG ( R2 = 0.44) parameter of the van Genuchten WRC model, while the opposite relationship was observed for samples with RLD > 1 cm/cm3 ( R2 = 0.61). Additionally, RLD and the coarse root (diameter > 1 mm) volume to fine root volume (C/F ratio) influenced WRCs. Over time, coarser roots may have a more pronounced impact on SHPs; further research is needed.

Expression of Sailx suchowensis SsIRT9 enhances cadmium accumulation and alters metal homeostasis in tobacco

Cadmium (Cd) contamination in soils is of great concern for plant growth and human health. Willow (Salix spp.) is a promising phytoextractor because of its high biomass production. However, as a non-hyperaccumulator, willow has a low competitive ability in extraction of Cd. Thus, improving Cd concentrations in developing tissues is one of the primary tasks. Here, our study uncovers a novel SsIRT9 gene from Sailx suchowensis which manipulates plant Cd accumulation. SsIRT9 was more highly expressed in willow roots than other SsIRT genes. As a plasma membrane-localized protein, when expressed in yeast, SsIRT9 retarded cell growth more severely than other SsIRT proteins in the presence of Cd. Furthermore, SsIRT9 was cloned and expressed in tobacco and SsIRT9 did not affect plant growth. In hydroponic experiments, SsIRT9 lines displayed higher Cd in the shoots than the wild type. When grown in Cd-contaminated soils, Cd levels in transgenic tobacco increased by 152–364% in roots and by 135–444% in shoots, demonstrating significant superiority in Cd accumulation over other functional IRT/ZIP transporters. Moreover, expressing SsIRT9 in tobacco altered metal homeostasis, especially manganese and zinc. Taken together, we envision that SsIRT9 expression in plants is a promising strategy for upgrading extraction of Cd from soils.

Manifestation of Triploid Heterosis in the Root System after Crossing Diploid and Autotetraploid Energy Willow Plants.

Successful use of woody species in reducing climatic and environmental risks of energy shortage and spreading pollution requires deeper understanding of the physiological functions controlling biomass productivity and phytoremediation efficiency. Targets in the breeding of energy willow include the size and the functionality of the root system. For the combination of polyploidy and heterosis, we have generated triploid hybrids (THs) of energy willow by crossing autotetraploid willow plants with leading cultivars (Tordis and Inger). These novel Salix genotypes (TH3/12, TH17/17, TH21/2) have provided a unique experimental material for characterization of Mid-Parent Heterosis (MPH) in various root traits. Using a root phenotyping platform, we detected heterosis (TH3/12: MPH 43.99%; TH21/2: MPH 26.93%) in the size of the root system in soil. Triploid heterosis was also recorded in the fresh root weights, but it was less pronounced (MPH%: 9.63-19.31). In agreement with root growth characteristics in soil, the TH3/12 hybrids showed considerable heterosis (MPH: 70.08%) under in vitro conditions. Confocal microscopy-based imaging and quantitative analysis of root parenchyma cells at the division-elongation transition zone showed increased average cell diameter as a sign of cellular heterosis in plants from TH17/17 and TH21/2 triploid lines. Analysis of the hormonal background revealed that the auxin level was seven times higher than the total cytokinin contents in root tips of parental Tordis plants. In triploid hybrids, the auxin-cytokinin ratios were considerably reduced in TH3/12 and TH17/17 roots. In particular, the contents of cytokinin precursor, such as isopentenyl adenosine monophosphate, were elevated in all three triploid hybrids. Heterosis was also recorded in the amounts of active gibberellin precursor, GA19, in roots of TH3/12 plants. The presented experimental findings highlight the physiological basics of triploid heterosis in energy willow roots.

A lab unearthed: Plotting the grounds for future fields

A lab unearthed: Plotting the grounds for future fields

Effects of two categorically differing emergent wetland plants on evapotranspiration

AbstractAlthough wetlands are an important component of many landscapes, emergent plants have had variable impacts on wetland hydrology. In the present study, similar to what others have done with emergent plants, we investigated the impacts of black willow (Salix nigra Marshall) and Pennsylvania smartweed (Persicaria pensylvanica L.) on water loss from standing water relative to water loss with no emergent plants from 2018 to 2020. Pans were established with soil and standing water for three replications of five treatments: open water control, low population density black willow, high density black willow, low density smartweed, and high density smartweed. Each week during the growing season water levels, water temperature, leaf area index, and height were recorded. Pans were then refilled to the standard level. The assumption was that open water was just evaporation and the increase in water loss in the presence of plants was due to transpiration. Thus, we could partition water loss between evaporation and transpiration by calculating the difference between pans without plants and pans with plants. This difference is the transpiration by the plants. Water temperature was measured to check on any possible shading effect. Open water evaporation was lower than black willow and smartweed evapotranspiration. Mean increases in water use relative to the control were 37% for smartweed and 66% for black willow. These differences were even more dramatic when calculated for only the last 2 years. Smartweed increased water use by 40% and black willow by 92%. Because pans with plants had lower maximum daily water temperatures than those of the control in the summer, the increased water loss with plants was largely due to transpiration. Smartweed transpired more than willows. The willow root system and leaf area greatly increased after the first year, resulting in more water loss and lower summer water temperature. Low and high density treatments did not differ significantly for any metrics gathered, with few exceptions. This evapotranspiration information addresses wetland water balance questions and is useful for process‐based models.

Anatomical changes in dwarf shrub roots provide insight into aeolian erosion rates in northeastern Iceland

Iceland is known for having strong aeolian erosion events, as evidenced by erosional escarpments on the soil surface; these are known locally as rofabards. The aim of the study was to estimate aeolian erosion rates at two research plots affected by severe erosion, using anatomic features of the roots of Arctic, woody, dwarf shrubs. Ours is the first study to utilize dendrochronological analyses of exposed roots of dwarf willows (Salix herbacea L.) as an indicator of aeolian erosion. When dwarf shrub roots are exposed to the atmosphere by erosion, cell sizes are reduced by >50 %, with maximum changes in individual plants exceeding 150–200 %. We detected the erosion signal by analyzing changes in cell-size and width of growth rings in the roots. Using this relationship, were able to estimate erosion rates (the retreat of escarpments) since the 1970s for the study area. During the 1970s and 1980s, erosion rates were fairly constant, with retreat ranging from 1.0 to 2.5 cm yr−1. Rapid increases in erosion rates were observed after the late 1990s, occasionally as much as 4.4–5.4 cm yr−1. Increased aeolian erosion rates may be linked to continuous heavy grazing by sheep and climate change, as this period coincides with increased numbers of hot and warm, and dusty days. Our results indicate that dendrochronological methods can be highly useful in determining past geomorphic activity, due to modern environmental changes observed in the Arctic. The methods employed here can be applied even in treeless areas.

The impact of willow brush mattresses on the mechanical filtration stability

Geotextiles or grain filters are frequently used between technical revetment and subsoil at riverbanks on waterways as erosion control from hydraulic loads. Due to the EU Water Framework Directive of the year 2000 (Directive 2000/60/EC) and other EU Directives ecological and near nature hydraulic engineering measures are becoming ever more in demand. That's why more technical-biological bank protection under the use of plants should be applied, for example willow brush mattresses, plant mats, reed gabions.Based on the investigations of the filtration stability of geotextiles used at navigable waterways, a method, and a new test apparatus for verifying the soil retention capability and the mechanical filtration stability of willow brush mattresses and their dense, near-surface root system have been developed.Willow brush mattresses made of white willows (Salix alba L.) or basket willows (Salix viminalis L.) were planted in wooden sample boxes and placed upside down into the test apparatus after a pre-set growing time (0, 1, 3 and 6 months). By flooding and draining the test apparatus water level drawdown has been simulated.The eroded soil material was collected, weighed after drying until weight constancy, and compared with the dry mass of the retained soil material.The results of this new developed mechanical filtration stability tests for willow brush mattresses show that during the initial phase of six months the willow roots reduced soil erosion. Thus, in long-term plant roots can take over mechanical filter function in near nature bank protection. The basket willow led to significant reductions in soil erosion i.e., an increase of the soil retention capability after one month and the white willow after three months of growth.

Root reinforcement: continuum framework for constitutive modelling

The mechanical contribution of plant roots to soil strength has typically been studied at the ultimate limit state only. Since many geotechnical problems are related to serviceability, such as deformation of infrastructure, a new constitutive modelling framework is introduced. The rooted soil is treated as a composite material with separate constitutive relationships for soil and roots, and a comprehensive stress–strain relationship for the root constituent is presented. The model is compared to direct shear experiments on field soil reinforced with gorse, grass and willow roots, as well as an existing root reinforcement model based on the Winkler-spring supported beam theory. The results show that both the newly developed model and the beam-type model yield good predictions for the evolution of root-reinforced shear strength as a function of increasing shear displacements. Both successfully capture the large deformations required to reach peak reinforcement, the reduction in reinforcement due to root breakage and the presence of significant reinforcement even after very large deformations, associated with root slippage. Since both fibre and beam models only require physically meaningful input parameters, they can be useful tools to study the mobilisation of rooted soil strength and simulate the response of rooted soil in continuum-based numerical simulations.

The Absorption and Distribution Characteristics of Willow Clones to Copper and Its Detoxification Mechanism

Phytoremediation technology is a measure to purify pollutants in soil or water through the absorption, volatilization, root filtration, degradation, and stabilization of plants, and its core is to find plants with large biomass and high enrichment. The wild willow tree found in Tonglushan is a fast-growing Euphorbiaceae plant, which has strong tolerance to the heavy metal copper (Cu) and has the characteristics of developed root system, barren resistance, and high economic value. Taking willow as the research object, this paper studied the composition, copper enrichment sites, morphology, subcellular distribution characteristics and absorption, transportation, and enrichment mechanism of willow root exudates under copper stress through hydroponic and pot experiments. By adding phosphate fertilizers, inducers, and other agronomic control measures, the strengthening technology and mechanism of Cu-contaminated soil phytoremediation were studied. The main research contents and results are as follows: the results of hydroponics and pot experiments show that the willow tree has a certain tolerance to Cu, and Cu mainly accumulates in its roots. Oxalic acid, succinic acid, tartaric acid, citric acid, and malic acid are the main organic acids in willow root exudates. Root exudation activity acidified the rhizosphere soil, increased acid exchangeability, and reducible Cu content, while other forms of Cu content decreased. Root exudates affect the uptake and accumulation of copper by willow trees by altering the bioavailability of copper in soil.

Responses of Swamp Cypress (Taxodium distichum) and Chinese Willow (Salix matsudana) Roots to Periodic Submergence in Mega-Reservoir: Changes in Organic Acid Concentration

Organic acids are critical as secondary metabolites for plant adaption in a stressful situation. Oxalic acid, tartaric acid, and malic acid can improve plant tolerance under waterlogged conditions. Two prominent woody species (Taxodium distichum-Swamp cypress and Salix matsudana-Chinese willow) have been experiencing long-term winter submergence and summer drought in the Three Gorges Reservoir. The objectives of the present study were to explore the responses of the roots of two woody species during flooding as reflected by root tissue concentrations of organic acids. Potted sample plants were randomly divided into three treatment groups: control, moderate submergence, and deep submergence. The concentrations of oxalic acid, tartaric acid, and malic acid in the main root and lateral roots of the two species were determined at four stages. The results showed that T. distichum and S. matsudana adapted well to the water regimes of the reservoir, with a survival rate of 100% during the experiment period. After experiencing a cycle of submergence and emergence, the height and base diameter of the two species showed increasing trends. Changes in base diameter showed insignificant differences between submergence treatments, and only height was significant under deep submergence. The concentrations of three organic acids in the roots of two species were influenced by winter submergence. After emergence in spring, two species could adjust their organic acid metabolisms to the normal level. Among three organic acids, tartaric acid showed the most sensitive response to water submergence, which deserved more studies in the future. The exotic species, T. distichum, had a more stable metabolism of organic acids to winter flooding. However, the native species, S. matsudana, responded more actively to long-term winter flooding. Both species can be considered in vegetation restoration, but it needs more observations for planting around 165 m above sea level, where winter submergence is more than 200 days.

Urea-enhanced phytoremediation of cadmium with willow in pyrene and cadmium contaminated soil

The phytoremediation of cadmium (Cd) and pyrene (PYR) in agricultural soil with willow was investigated by carrying out a pot-culture experiment in a greenhouse. The soil was incubated with urea 60 days before it was used for this experiment. The concentrations of Cd and PYR in soil and willow, the bioconcentration and transfer factors, the physiological and biochemical responses, and plant biomass production were determined at the end of the experiment. The phytoremediation with willow based on urea application was effective for enhancing the phytoremediation of Cd and PYR contaminated soil. Urea application did not affect the available Cd but increased the accumulation of soil Cd and the plant biomass of different parts of the willow. The removal rate (77.1–89.5%) of PYR in soil was not significantly affected although urea application decreased the accumulation of PYR in willow root and bark. Urea application significantly promoted the uptake of chlorophyll, carotenoid and malondialdehyde by willow leaves. The results of this study will provide scientific information for the effective phytoremediation of Cd in Cd and PYR contaminated soil.

Assessment of phytostabilization potential of two Salix L. clones based on the effects of heavy metals on the root anatomical traits.

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14mm, length 20cm) exposed to two concentrations (10-4M and 10-5M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl2·H2O, NiSO4·6H2O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637mg/kg (clone '68/53/1') and 6728mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical root's traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured root's traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10-4M of each metal had more negative effects on the roots' anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization.

Including albedo in time‐dependent LCA of bioenergy

AbstractAlbedo change during feedstock production can substantially alter the life cycle climate impact of bioenergy. Life cycle assessment (LCA) studies have compared the effects of albedo and greenhouse gases (GHGs) based on global warming potential (GWP). However, using GWP leads to unequal weighting of climate forcers that act on different timescales. In this study, albedo was included in the time‐dependent LCA, which accounts for the timing of emissions and their impacts. We employed field‐measured albedo and life cycle emissions data along with time‐dependent models of radiative transfer, biogenic carbon fluxes and nitrous oxide emissions from soil. Climate impacts were expressed as global mean surface temperature change over time (∆T) and as GWP. The bioenergy system analysed was heat and power production from short‐rotation willow grown on former fallow land in Sweden. We found a net cooling effect in terms of ∆T per hectare (−3.8 × 10–11 K in year 100) and GWP100 per MJ fuel (−12.2 g CO2e), as a result of soil carbon sequestration via high inputs of carbon from willow roots and litter. Albedo was higher under willow than fallow, contributing to the cooling effect and accounting for 34% of GWP100, 36% of ∆T in year 50 and 6% of ∆T in year 100. Albedo dominated the short‐term temperature response (10–20 years) but became, in relative terms, less important over time, owing to accumulation of soil carbon under sustained production and the longer perturbation lifetime of GHGs. The timing of impacts was explicit with ∆T, which improves the relevance of LCA results to climate targets. Our method can be used to quantify the first‐order radiative effect of albedo change on the global climate and relate it to the climate impact of GHG emissions in LCA of bioenergy, alternative energy sources or land uses.

Ecophysiological Responses of a Willow Cultivar (Salix miyabeana ‘SX67’) Irrigated with Treated Wood Leachate

As wood preservatives leach from exposed treated wood, they contaminate soil and water, creating an environmental problem that needs to be addressed. Treating this contamination is particularly challenging since it includes mixed compounds, such as heavy metals and trace elements, as well as xenobiotic organic pollutants like polychlorinated dibenzo-dioxin/furan congeners (PCDD/Fs) that are very toxic and are under very strict discharge regulations. Cultivating fast-growing willow shrubs, either in soil or in treatment wetlands, offers a flexible and inexpensive treatment option. The main objective of this study was to evaluate the tolerance of a frequently used willow cultivar (Salix miyabeana ‘SX67’) to irrigation with leachate contaminated with pentachlorophenol (PCP) and chromated chromium arsenate (CCA), two important wood preservatives. We designed a mesocosms experiment with willow grown in three different substrates and irrigated over 12 weeks with three different leachate concentrations. Willow proved to be tolerant to irrigation with the raw leachate, with only leaf area decreasing with increasing leachate concentration. However, the type of growing substrate influenced willow ecophysiological responses and overall performance, and seemed to affect contaminant dynamics in the plant-soil system. All contaminants accumulated in willow roots, and Cu and PCDD/Fs were also translocated to aerial parts. Overall, this study suggests that Salix miyabeana ‘SX67’ could be a good candidate for treating water or soil contaminated with wood preservatives.

Tree Willow Root Growth in Sediments Varying in Texture

We investigated the early root development of Salix nigra L. willow grown from cuttings in the different riverbank sediments; silt, sand and stones. Cuttings were grown for 10 weeks in layered sediment types in five large planter boxes, each box having three separate compartments. The boxes differed in the proportion of silt, sand and stones. At 10 weeks, the roots were extracted and sorted into diameter classes (≥2 mm; 1 < 2 mm; <1 mm) according to sediment type and depth. Root length and dry mass were measured and root length density (RLD) and root mass density (RMD) calculated. Root development of S. nigra cuttings varied with the substrate, either silt, sand or stones. Roots initiated from the entire length of the cutting in the substrate but with a concentration of initials located at the bottom and close to the bottom of the cutting. There was substantial root extension into all three substrates and at all depths. Generally, RMD was higher in the stones, influenced by having the bottom of the cuttings in stones for four of the five treatments. RMD was highest for roots <1 mm diameter. RMD of roots <1 mm diameter was least for those roots growing in sand. Whereas RLD for roots >0.5 mm diameter was highest in the sand, RLD of roots with diameter <0.5 mm was lowest in sand. Roots of S. nigra cuttings were least effective in binding sand, primarily because of low RLD of roots <0.5 mm diameter. It is surmised that sand lacks water and nutrients sufficient to sustain growth of fine roots compared with silt and even stones. RLD for roots >0.5 mm diameter was lowest in silt likely due to the greater resistance of the substrate to root penetration, or possibly the greater investment into smaller roots with absorption capability.

Can willow roots oxygenate leachate in vegetation filter beds?¬ a mass spectrometer investigation in Wales

Membrane inlet mass spectrometry (MIMS) was used to monitor dissolved gas concentrationsin-situ in laboratory microcosms and in a constructed willow vegetation filter bed in Walesused to treat leachate. A mini-rhizotron digital camera system was developed for use incombination with MIMS studies of gas dynamics. The major results of the studies are:-• Diurnal cycles in the concentrations of 02, CO2 and C� were shown to occur with arooted willow cutting in a stirred microcosm.• Willow beds show considerable sub-surface spatial diversity. Generally, oxygen decreaseswith depth whereas methane and carbon dioxide increase with depth. Small pockets ofgases were seen. Oxygen occurred throughout the profile.• Microbial processes follow diurnal cycles. Oxygen is released from willow roots duringdaylight. Methane and carbon dioxide accumulate during the dark.• The high degree of mixing distributes oxygenated water throughout the bed. Stopping theflow of leachate allowed conditions to become anaerobic, except in local micro-sites.These techniques appear to offer considerable potential for direct measurement of sub-surfaceenvironments in constructed wetlands, particularly in respect of the microbial processesoccurring in the bed, and the oxygenation capacity of willow vegetation filters.

Soil contamination alters the willow root and rhizosphere metatranscriptome and the root-rhizosphere interactome.

Phytoremediation using willows is thought to be a sustainable alternative to traditional remediation techniques involving excavation, transport, and landfilling. However, the complexity of the interaction between the willow and its associated highly diverse microbial communities makes the optimization of phytoremediation very difficult. Here, we have sequenced the rhizosphere metatranscriptome of four willow species and the plant root metatranscriptome for two willow species growing in petroleum hydrocarbon-contaminated and non-contaminated soils on a former petroleum refinery site. Significant differences in the abundance of transcripts related to different bacterial and fungal taxa were observed between willow species, mostly in contaminated soils. When comparing transcript abundance in contaminated vs. non-contaminated soil for each willow species individually, transcripts for many microbial taxa and functions were significantly more abundant in contaminated rhizosphere soil for Salix eriocephala, S. miyabeana and S. purpurea, in contrast to what was observed in the rhizosphere of S. caprea. This agrees with the previously reported sensitivity of S. caprea to contamination, and the superior tolerance of S. miyabeana and S. purpurea to soil contamination at that site. The root metatranscriptomes of two species were compared and revealed that plants transcripts are mainly influenced by willow species, while microbial transcripts mainly responded to contamination. A comparison of the rhizosphere and root metatranscriptomes in the S. purpurea species revealed a complete reorganization of the linkages between root and rhizosphere pathways when comparing willows growing in contaminated and non-contaminated soils, mainly because of large shifts in the rhizosphere metatranscriptome.

Adsorption Property and Mechanism of Oxytetracycline onto Willow Residues.

To elucidate the adsorption property and the mechanism of plant residues to reduce oxytetracycline (OTC), the adsorption of OTC onto raw willow roots (WR-R), stems (WS-R), leaves (WL-R), and adsorption onto desugared willow roots (WR-D), stems (WS-D), and leaves (WL-D) were investigated. The structural characterization was analyzed by scanning electron microscopy, Fourier-transform infrared spectra, and an elemental analyzer. OTC adsorption onto the different tissues of willow residues was compared and correlated with their structures. The adsorption kinetics of OTC onto willow residues was found to follow the pseudo-first-order model. The isothermal adsorption process of OTC onto the different tissues of willow residues followed the Langmuir and Freundlich model and the process was also a spontaneous endothermic reaction, which was mainly physical adsorption. After the willow residues were desugared, the polarity decreased and the aromaticity increased, which explained why the adsorption amounts of the desugared willow residues were higher than those of the unmodified residues. These observations suggest that the raw and modified willow residues have great potential as adsorbents to remove organic pollutants.