Arbuscular mycorrhizal fungi optimize the acquisition and translocation of Cd and P by cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) plant cultivated on a Cd-contaminated soil

Purpose

Fruiting vegetables are generally considered to be safer than other vegetables for planting on cadmium (Cd)-contaminated farms. However, the risk of transferring Cd that has accumulated in the stems and leaves of fruiting vegetables is a major issue encountered with the usage of such non-edible parts. The objective of this study was to resolve the contribution of arbuscular mycorrhizal (AM) fungi to the production of low-Cd fruiting vegetables (focusing on the non-edible parts) on Cd-contaminated fields.

Materials and methods

An 8-week pot experiment was conducted to investigate the acquisition and translocation of Cd by cucumber (Cucumis sativus L.) plants on an unsterilized Cd-contaminated (1.6 mg kg^?1) soil in response to inoculation with the AM fungus, Funneliformis caledonium (Fc) or Glomus versiforme (Gv). Mycorrhizal colonization rates of cucumber roots were assessed. Dry biomass and Cd and phosphorus (P) concentrations in the cucumber shoots and roots were all measured. Soil pH, EC, total Cd, phytoavailable (DTPA-extractable) Cd, available P, and acid phosphatase activity were also tested.

Results and discussion

Both Fc and Gv significantly increased (P?<?0.05) root mycorrhizal colonization rates and P acquisition efficiencies, and thus the total P acquisition and biomass of cucumber plants, whereas only Fc significantly increased (P?<?0.05) soil acid phosphatase activity and the available P concentration. Both Fc and Gv significantly increased (P?<?0.05) root to shoot P translocation factors, inducing significantly higher (P?<?0.05) shoot P concentrations and shoot/root biomass ratios. In contrast, both Fc and Gv significantly decreased (P?<?0.05) root and shoot Cd concentrations, resulting in significantly increased (P?<?0.05) P/Cd concentration ratios, whereas only Gv significantly decreased (P?<?0.05) the root Cd acquisition efficiency and increased (P?<?0.05) the root to shoot Cd translocation factor. Additionally, AM fungi also tended to decrease soil total and phytoavailable Cd concentrations by elevating plant total Cd acquisition and soil pH, respectively.

Conclusions

Inoculation with AM fungi increased the P acquisition and biomass of cucumber plants, but decreased plant Cd concentrations by reducing the root Cd acquisition efficiency, and resulted in a tendency toward decreases in soil phytoavailable and total Cd concentrations via increases in soil pH and total Cd acquisition by cucumber plants, respectively. These results demonstrate the potential application of AM fungi for the production of fruiting vegetables with non-edible parts that contain low Cd levels on Cd-contaminated soils.

     

Comparison of ammonium fertilizers,EDTA, and NTA on enhancing the uptake of cadmium by an energy plant,Napier grass (<Emphasis Type="Italic">Pennisetum purpureum</Emphasis> Schumach)

Purpose

The aim of this study was to quantify the effect of enhanced agronomic practices on cadmium (Cd) accumulation in the high-biomass energy plant Napier grass (Pennisetum purpureum Schumach).

Materials and methods

Potted-plant experiments were performed to investigate the effects of ammonium fertilizers and chelating agents, alone or in combination, on the growth, accumulation of Cd, and phytoextraction efficiency of P. purpureum on Cd-contaminated soil. The fertilizers included ammonium nitrate, ammonium sulfate, and ammonium chloride. The chelating agents included ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA).

Results and discussion

The addition of ammonium fertilizers and chelating agents generally stimulated growth of P. purpureum, and the shoots accounted for 90.1–94.1% of the total biomass. The concentrations of Cd in different parts of P. purpureum plants were in the order root > leaf > stem. Ammonium chloride alone showed effectiveness in increasing root and shoot Cd concentrations compared to other amendments alone. Both EDTA alone and NTA alone significantly decreased root Cd concentration and increased shoot Cd concentration, while EDTA alone was more efficient on shoot and total Cd accumulation than that by NTA alone. The total accumulation of Cd in P. purpureum ranged from 1.10 to 2.05 mg per plant with 47.3–73.5% of Cd accumulation concentrated in shoots. The results indicate that P. purpureum can remove more Cd through phytoextraction than that by other hyperaccumulators.

Conclusions

Ammonium chloride led to the highest total Cd accumulation. Ammonium chloride applied alone or in combination with either EDTA or NTA resulted in the most effective agronomic approaches for P. purpureum phytoextraction of soil Cd.

     

Metal tolerance in barley and wheat cultivars: physiological screening methods and application in phytoremediation

Purpose

The objective of the study was to evaluate the tolerance of barley (Hordeum vulgare) and wheat (Triticum aestivum) in soil contaminated with different concentrations of Cd and Cr, the effect of these metals on some physiological characteristics and the biomass produced in order to assess their potential application in phytoremediation of contaminated soils.

Materials and methods

A greenhouse experiment using two cultivars of barley, CB502 and Pedrezuela, and one of wheat, Albares, was conducted. The pots were watered with different concentrations of Cd or Cr during the period of plant growth. Cellular membrane damage, content and fluorescence of chlorophyll, and plant biomass were evaluated. After harvesting, the content of metals in the roots, shoots and grains was analysed as well as the available metal concentration in soil samples.

Results and discussion

The results show that the Cd treatments did not significantly affect the growth and physiology of the plants, but they were affected by the Cr treatments. At the highest concentration of Cr, the decrease in chlorophyll content compared to the control was 44, 77 and 83 % for the CB502 and Pedrezuela barleys and the Albares wheat respectively. A reduction in biomass was also observed (74, 81 and 85 % respectively). The amount of Cd and Cr accumulated in the root was higher than that accumulated in the aerial part for the three cultivars. The barleys accumulated the highest amount of metal in the roots. The transfer factor was lower in barley than in the wheat for both metals.

Conclusions

Cadmium treatments do not affect plant development. In the case of Cr, plant development and physiological traits were significantly affected. For the highest concentration of Cr, the CB502 barley had the highest tolerance index, 26 %, and the Albares wheat had the lowest one, 15 %. The two barleys were more effective in phytoremediation of soil contaminated with Cd or Cr than the wheat, presenting a higher tolerance to these metals in the assayed conditions.

     

Effects of red mud addition on cadmium accumulation in cole (<Emphasis Type="Italic">Brassica campestris</Emphasis> L.) under high fertilization conditions

Purpose

Applications of mineral and organic fertilizer increased soil cadmium (Cd) and could enhance Cd concentrations in edible crops, respectively. Although red mud (RMD) effectively decreased metal bioavailability in soil, the influence of RMD addition on vegetable growth and metal accumulation under high fertilization conditions has rarely been addressed. The aim of this study was to investigate the effects of raw RMD addition on cole growth, quality, and nutrition and Cd accumulation under high fertilization conditions.

Materials and methods

Pot experiments with cole (Brassica campestris L.) were carried out in a greenhouse. Three treatments, CK (with no mineral fertilizer and RMD addition), CT (more than 2.5 times conventional level of mineral fertilizer applied without any RMD), and RM (more than 2.5 times conventional level of mineral fertilizer applied with RMD added at 0.4 % w/w), were established. After 40 days, the cole plants and soils of every replicate of all treatments were sampled. The Cd, biomass, vitamin C (VC), and total nitrogen and phosphorus of the cole plant samples and the Cd, pH, nitrate, and phosphorus of the soil samples were determined.

Results and discussion

In contrast to the CT treatment, RM treatment did not significantly influence the biomass and nitrate concentration of the aboveground cole. However, it significantly reduced the Cd content in cole shoots and its bioaccumulation factors by 30.0 and 28.5 %, respectively. The reduction of bioavailable Cd in soil by RMD sorption and the competition with calcium released from RMD led to low Cd assimilation by root. Finally, less Cd was transported to aboveground plant parts in the RM treatment compared with the CT treatment. RMD addition markedly enhanced the total nitrogen in cole shoots by >16.0 %, and the VC by 20.9 %. The promotion of bacterial abundance and soil enzyme activity by RMD addition and calcium release from RMD generated substantial plant available nitrogen.

Conclusions

With large rate of mineral fertilizer application to the soil, RMD (0.4 %, w/w) addition did not significantly influence the biomass, nitrate, and VC of aboveground cole; however, it significantly reduced the Cd and markedly enhanced the total nitrogen in cole shoots. This study provides valuable information for the safe application of RMD in vegetable production.

     

Effect of Cadmium Stress on Growth and Electrical Impedance Spectroscopy Parameters of <Emphasis Type="Italic">Cotinus coggygria</Emphasis> Roots

The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg^?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg^?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance r_e and the intracellular resistance r_i increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the r_e (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg^?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg^?1. The root water content and r_e could reflect the level of Cd tolerance in C. coggygria.     

Exogenously Applied Citric Acid Enhances Antioxidant Defense and Phytoextraction of Cadmium by Willows (<Emphasis Type="Italic">Salix</Emphasis> Spp.)

The effect of exogenously applied citric acid (CA) on phytoextraction and antioxidant defense was analyzed using willow species (Salix viminalis, S. alba, and S. matsudana) grown in soil contaminated with cadmium (Cd). Citric acid has been used as a chelating agent for the purpose of accelerating the solubility of Cd in soil and enhancing the phytoextraction of selected plants. Willows were exposed to 6 mg/kg of Cd, following the same with citric acid (20 mM/kg soil). Results revealed a positive effect of citric acid in mobilization of accumulated Cd from roots to shoots and leaves. The addition of citric acid alleviated Cd toxicity by helping plants to overcome oxidative stress, through CA’s chelating properties and the increased activity of antioxidant enzymes. Different protection strategies were evident through modification of activities of antioxidant enzymes such as catalase (CAT), ascorbate-peroxidase (APx), and guaiacol peroxidase (GPx) in young versus mature leaves in plants exposed to Cd. Furthermore, results revealed that addition of citric acid may be beneficial in the reduction of the negative effect of Cd stress on photosynthesis. The efficiency of coupling phytoextraction with the chelating agents represents a good strategy for decreasing damages caused by cadmium and has good potential in decontamination of a polluted environment.     

Combined bioremediation of soil co-contaminated with cadmium and endosulfan by <Emphasis Type="Italic">Pleurotus eryngii</Emphasis> and <Emphasis Type="Italic">Coprinus comatus</Emphasis>

Purpose

The subjects of this study were to investigate the remediating potential of the co-cultivation of Pleurotus eryngii and Coprinus comatus on soil that is co-contaminated with heavy metal (cadmium (Cd)) and organic pollutant (endosulfan), and the effects of the co-cultivated mushrooms on soil biochemical indicators, such as laccase enzyme activity and bacterial counts.

Materials and methods

A pot experiment was conducted to investigate the combined bioremediation effects on co-contaminated soil. After the mature fruiting bodies were harvested from each pot, the biomass of mushrooms was recorded. In addition, bacterial counts and laccase enzyme activity in soil were determined. The content of Cd in mushrooms and soil was detected by the flame atomic absorption spectrometry (FAAS), and the variations of Cd fractions in soil were determined following the modified BCR sequential extraction procedure. Besides, the residual endosulfan in soil was detected by gas chromatography-mass spectrometry (GC-MS).

Results and discussion

The results indicated that co-cultivation of P. eryngii and C. comatus exerted the best remediation effect on the co-contaminated soil. The biomass of mushroom in the co-cultivated group (T group) was 1.57–13.20 and 19.75–56.64% higher than the group individually cultivated with P. eryngii (P group) or C. comatus (C group), respectively. The concentrations of Cd in the fruiting bodies of mushrooms were 1.83–3.06, 1.04–2.28, and 0.67–2.60 mg/kg in T, P, and C groups, respectively. Besides, the removal rates of endosulfan in all treatments exceeded 87%. The best bioremediation effect in T group might be caused by the mutual promotion of these two kinds of mushrooms.

Conclusions

The biomass of mushroom, laccase activity, bacterial counts, and Cd content in mushrooms were significantly enhanced, and the dissipation effect of endosulfan was slightly higher in the co-cultivated group than in the individually cultivated groups. In this study, the effect of co-cultivated macro fungi P. eryngii and C. comatus on the remediation of Cd and endosulfan co-contaminated soil was firstly reported, and the results are important for a better understanding of the co-remediation for co-contaminated soil.

     

Rhizosphere effects of <Emphasis Type="Italic">Populus euramericana</Emphasis> Dorskamp on the mobility of Zn,Pb and Cd in contaminated technosols

Purpose

This study aimed at investigating the rhizosphere effects of Populus euramericana Dorskamp on the mobility of Zn, Pb and Cd in contaminated technosols from a former smelting site.

Materials and methods

A rhizobox experiment was conducted with poplars, where the plant stem cuttings were grown in contaminated technosols for 2 months under glasshouse conditions. After plant growth, rhizosphere and bulk soil pore water (SPW) were sampled together. SPW properties such as pH, dissolved organic carbon (DOC) and total dissolved concentrations of Zn, Pb and Cd were determined. The concentrations of Zn, Pb and Cd in plant organs were also determined.

Results and discussion

Rhizosphere SPW pH increased for all studied soils by 0.3 to 0.6 units compared to bulk soils. A significant increase was also observed for DOC concentrations regardless of the soil type or total metal concentrations, which might be attributed to the plant root activity. For all studied soils, the rhizosphere SPW metal concentrations decreased significantly after plant growth compared to bulk soils which might be attributed to the increase in pH and effects of root exudates. Zn, Pb and Cd accumulated in plant organs and the higher metal concentrations were found in plant roots compared to plant shoots.

Conclusions

The restricted transfer of the studied metals to the plant shoots confirms the potential role of this species in the immobilization of these metals. Thus, P. euramericana Dorskamp can be used for phytostabilization of technosols.

     

Accumulation and phytoremediation of Pb,Zn, and Ag by plants growing on Koshk lead–zinc mining area,Iran

Purpose

This study investigated the extent of metal accumulation by plants colonizing a mining area in Yazd Province in Central Iran. It also investigated the suitability of these plants for phytoextraction and phytostabilization as two potential phytoremediation strategies.

Materials and methods

Plants with a high bioconcentration factor (BCF) and low translocation factor (TF) have the potential for phytostabilization, whereas plants with both BCFs and TFs >1 may be appropriate for phytoextraction. In this study, both shoots and roots of 40 plant species and associated soil samples were collected and analyzed for total concentrations of trace elements (Pb, Zn, and Ag). BCFs and TFs were calculated for each element.

Results and discussion

Nonnea persica, Achillea wilhelmsii, Erodium cicutarium, and Mentha longifolia were found to be the most suitable species for phytostabilization of Pb and Zn. Colchicum schimperi, Londesia eriantha, Lallemantia royleana, Bromus tectorum, Hordeum glaucum, and Thuspeinantha persica are the most promising species for element phytoextraction in sites slightly enriched by Ag. Ferula assa-foetida is the most suitable species for phytostabilization of the three studied metals. C. schimperi, L. eriantha, L. royleana, B. tectorum, M. longifolia, and T. persica accumulated Ag, albeit at low level.

Conclusions

Our preliminary study shows that some native plant species growing on this contaminated site may have potential for phytoremediation.

     

Grasses and legumes facilitate phytoremediation of metalliferous soils in the vicinity of an abandoned chromite–asbestos mine

Purpose

The present study was carried out in Roro region, Chaibasa, Jharkhand, India, to assess the impact of chromite–asbestos mine waste (CMW) on a nearby agroecosystem. The role of metal-accumulating grass–legume association in facilitating phytoremediation was investigated.

Materials and methods

Soil and plant samples were collected from (i) chromite–asbestos mine waste (CMW) with Cynodon dactylon, Sorghastrum nutans, and Acacia concinna; (ii) contaminated agricultural soil-1 (CAS1) from a foothill with Cajanus cajan; (iii) contaminated agricultural soil-2 (CAS2) distantly located from the hill, cultivated with Oryza sativa and Zea mays; and (iv) unpolluted control soil (CS). Total metal concentrations were quantified in both soils and plants by digesting the samples using HNO₃, HF, HClO₄ (5:1:1; v/v/v), and HNO₃ and HClO₄ (5:1; v/v), respectively, and analyzed under flame atomic absorption spectrophotometry. Metal grouping and site grouping cluster analysis was executed to group the metals and sampling sites. Translocation factor (TF) and bioconcentration factor (BCF) were calculated to determine the phytoremediation efficiency of grasses and legumes.

Results and discussion

Results indicate that total metal concentrations in the CMW were in the order of Cr?>?Ni?>?Mn?>?Cu?>?Pb?>?Co?>?Zn?>?Cd. High concentrations of Cr (1983 mg kg^?1) and Ni (1293 mg kg^?1) with a very strong contamination factor were found in the CAS, which exceeds the soil threshold limits. Further, metal and site grouping cluster analysis also revealed that Cr and Ni were closely linked with each other and the CMW was the main source of contamination. Among all the metals, Cr and Ni were mainly accumulated in grasses (C. dactylon and S. nutans) and legumes (A. concinna and C. cajan) as compared to cereals (Z. mays and O. sativa). The TF of Cr was >1 for grasses. Except for Zn, the BCF for all the metals were <1 in roots and shoots of all the plants and cereals.

Conclusions

The present study revealed that abandoned CMW is the source of contamination for agriculture lands. Phytoremediation relies on suitable plants with metal-scavenging properties. Grass–legume cover (C. dactylon, S. nutans, A. concinna, and C. cajan) has the ability to accumulate metals and act as a potential barrier for metal transport, which facilitate the phytoremediation of the CMW. Possibilities for enhancing the barrier function of the grass–legume cover need to be explored with other low-cost agronomic amendments and the role of rhizospheric organisms.

     

Effects of biochar on Cd and Pb mobility and microbial community composition in a calcareous soil planted with tobacco

An experiment was conducted with tobacco (Nicotiana tabacum L.) grown in a Cd- and Pb-contaminated calcareous soil amended with 0.0, 1.0, 2.5, and 5.0% (w/w) tobacco stalk biochar (BC). The BC amendment significantly increased organic matter, total C, N, P, and K contents of soil, and the C/N ratio. Bioavailable metal concentrations (DTPA extraction) decreased by increasing BC application rate. The 5.0% BC amendment significantly decreased the DTPA-extractable Cd and Pb by 10.4 and 13.6%, respectively. Correspondingly, the bioaccumulation and translocation factors of Cd and Pb also decreased by increasing the BC addition rates and this indicated that BC inhibited the uptake and transfer of both Cd and Pb by tobacco plants. Moreover, high-throughput sequencing revealed that BC increased Chao1 richness, Shannon’s diversity and Simpson’s diversity of bacterial communities of soil. The relative abundance and genera composition of Adhaeribacter, Rhodoplanes, Pseudoxanthomonas, and Candidatus Xiphinematobacter increased under BC treatments, while those of Kaistobacter, Lacibacter, and Pirellula decreased. Overall, BC increased soil nutrients (C, N, P, and K contents), enhanced bacterial diversity indexes and richness, and changed the bacterial community composition, which may all have contributed to reduce the mobility and bioavailability of both Cd and Pb in a calcareous soil.     

Potential bioaccumulation of trace metals in halophytes from salt marshes of a northern Adriatic coastal lagoon

Purpose

The Marano and Grado Lagoon (Italy) has been affected by trace metal(oid) contamination in the last century, especially mercury, from both industrial and long-term mining activities. The uptake and distribution of trace metal(oid)s in halophytes were determined in two selected salt marshes. To evaluate the potential activity of plants as phytoremediation, the bioconcentration and translocation factors (BCF and TF, respectively) were calculated.

Materials and methods

In both salt marshes, individuals of Sarcocornia fruticosa L. and Limonium vulgare L., two of the most abundant halophytes in this environment, were sampled. The aboveground biomass (stems and leaves) was collected and sealed in plastic bags. Once the stems were removed, the belowground biomass and the attached rhizo-sediment were sampled using a single gouge auger sampler. The sediment cores obtained were sectioned on field to a maximum depth of 15 cm. The roots were carefully separated from the rhizo-sediment in the laboratory. The sediment, roots, leaves, and stems were freeze-dried, finely ground, and homogenized. Samples were totally decomposed, using a mixture of mineral acids in a closed microwave system, and analyzed for trace metal(oid) content by ICP-AES. The total Hg content in the solid phase was determined by DMA-80.

Results and discussion

Metal(oid) concentrations in roots were usually up to one or two orders of magnitude higher than in stems and leaves. The exceptions are Cd and Ni, which levels were not detectable, and Cr in stems of both halophytes where the concentration reached up to four times more than in roots. Commonly, trace metal(oid) contents were higher in stems than in leaves, except for Zn. Considering all BCF data, a sequence of metal(oid)s preferentially transferred from sediment to belowground biomass of the two plants is Cd > Mn > As > Pb. This sequence does not coincide for the two salt marshes, except for Cd, probably due to the different source of metal(oid)s in sediments and/or some site-specific lithogenic properties. Metal(oid)s accumulated from rhizo-sediment were largely retained in roots as shown by TF values <1.

Conclusions

The general trend arising from BCF and TF reveals that root tissues accumulate significantly greater amounts of metal(oid)s than the aerial part, thus indicating high plant bioavailability of the substrate metal(oid)s as well as their limited translocation to the aboveground biomass. Our results suggest that both salt marshes investigated act as a sink, and only sporadically as a possible source, for several trace metal(oid)s which are not promptly available for the environment.

     

A Comparative Study on Removal Efficiency of Cr(VI) in Aqueous Solution by <Emphasis Type="Italic">Fusarium</Emphasis> sp. and <Emphasis Type="Italic">Myrothecium</Emphasis> sp.

Environmental pollution with chromium is due to residues of several industrial processes. Bioremediation is an alternative actually considered to remove Cr (VI) from the environment, using adapted organisms that grow in contaminated places. Have been conducted studies with fungi mechanisms of interaction with chromium, most of which have focused on processes biosorption, characterized it by passive binding of metal components of the cell surface, and bioaccumulation, wherein the metal entry to cells occurs with energy expenditure. The paper presents the results of studies carried out on sorption of chromium (VI) ions from aqueous solutions by Fusarium sp. and Myrothecium sp. Both biomasses have the ability to take up hexavalent chromium during the stationary phase of growth and as well inactive conditions. Fusarium sp. showed 26% of biosorption with active biomass and 64% in inactive biomass; meanwhile, Myrothecium sp. obtained 97 and 82%, respectively. Both fungi showed adjust to pseudo-second-order model in active (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.96) and inactive biomass assay (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.99). The data of the active biomass test also confirmed to the intraparticle diffusion model (Fusarium sp. R ² = 0.98; Myrothecium sp. R ² = 0.93). The results obtained through this investigation indicate the possibility of treating waste effluents containing hexavalent chromium using Fusarium sp. and Myrothecium sp.     

Variation in Copper Accumulation at the Tissue Level of Five Hybrid Poplars Subjected to Copper Stress

Heavy metal contamination causes significant environmental problems around the world and poses a threat to human health. Poplar hybrids present features for potential uses in phytoremediation systems in areas with heavy metal contamination. The purpose of this study was to assess the copper (Cu) accumulation level in five poplar inter-species hybrids [(Populus trichocarpa × Populus deltoides) × P. deltoides; P. deltoides × Populus nigra; P. trichocarpa × Populus maximowiczii; P. trichocarpa × P. nigra; and (P. trichocarpa × P. deltoides) × (P. trichocarpa × P. deltoides)] grown in a hydroponic system. The treatments entailed the application of low and high doses of Cu of 8.0 and 16.0 μM, respectively. Cu accumulation was observed in roots, stems, and leaves, which was determined using flame atomic absorption spectroscopy, prior acid digestion of each sample. The methodology was validated according to certified reference material (Cypress BIMEP 432). Significant differences in Cu accumulation were found among genotypes for both roots and leaves, but not for stems. In roots, the genotype P. deltoides × P. nigra had a Cu accumulation level of 169.8% higher than the average accumulation found in the other genotypes. The (P. trichocarpa × P. deltoides) × P. deltoides hybrid showed the least Cu accumulation in leaves. The results of this study can potentially be used for proper crossovers and hybrids selection within the genus Populus for phytoremediation of Cu contaminated land.     

Roots of <Emphasis Type="Italic">Cleistogenes songorica</Emphasis> Improved Soil Aggregate Cohesion and Enhance Soil Water Erosion Resistance in Rainfall Simulation Experiments

Native grasses that have acceptable forage yield and quality can play an important role in the sustainable development and protection of soil ecosystem. In this study, we investigate a native grass of northern China, Cleistogenes songorica, showing promise for erosion control. We used a rainfall simulation method to compare the effects of C. songorica roots and tall fescue roots (Festuca arundinacea) on soil erosion in sandy loam field plots with irrigation during establishment in 2011 and under mild or severe drought treatments in 2012 and 2013. Root length (RL), root diameter (RD), soil bulk density (SBD), soil field capacity (FC), sediment yield (SY), and root biomass (RB) of each soil monolith were sampled in the topsoil layer (0–10 cm) with a rectangular geotome. The proportion of stable aggregates in soil and the soil anti-scouring properties were also evaluated. C. songorica had higher RD than tall fescue throughout the experiment and evolved higher RL and RB by 2013. Both C. songorica and tall fescue enhanced the erosion resistance of soil, but C. songorica stabilized soil more effectively than did tall fescue. The proportion of stable soil aggregates was greater in C. songorica plots than in tall fescue grassland under mild drought. The present study shows that C. songorica has great potential to be one of the biological resources for soil erosion resistance, water and soil conservation in arid and semi-arid areas.     

Humus status of soddy-podzolic soil upon application of different green manures

Results of studying the effect of different plant species on the humus status of loamy sandy soddy-podzolic soil were generalized. It was found that the application of different green manure species (Lupinus luteus L., Trifolium pratense L., and Raphanus sativus L.) and straw from cereal crops (Secale cereale, Hordeum L.) under percolative conditions helped to sustain a stable humus budget in grain agrophytocenoses. A significant change in the fractional composition of HAs and FAs occurred under the effect of green manure. The fractions of free HAs and those bound to clay minerals accumulated with the application of Trifolium pratense and Raphanus sativus biomass and cereal straw. Lower amounts of aggressive and free FAs were formed in the soil with the application of straw and fallow plants. The decomposition of green manure and the formation of humic substances also depended on the hydrothermal conditions during application of manure.     

Assessment of <Emphasis Type="Italic">Koelreuteria paniculata</Emphasis> Seedling for Phytroremediation of Pyrene-Contaminated Soils

Phytoremediation is a cost-effective and environmentally friendly technology using plants for the cleanup of both inorganic and organic contaminated sites. In this study, a pot culture experiment has been conducted for 180 days in a greenhouse to examine the capability of Koelreuteria paniculata on pyrene (Pyr) dissipation in contaminated soil. Three treatments were employed and they were: (1) polluted soil with K. paniculata fine roots addition (T1), (2) polluted soil with planted seedlings (T2), and (3) polluted soil (C). Results showed Pyr concentration in soils was reduced by 21.4, 36.2, and 86.4% by natural losses, fine roots addition, and planted K. paniculata treatments, respectively, meaning plants substantially enhanced the dissipation of Pyr from soil. Cultivated K. paniculata seedlings significantly increased soil total nitrogen (TN), total organic carbon, dissolved organic carbon (DOC), and microbial biomass carbon, but not total phosphorus, when compared to the control. The removal efficiency of Pyr was lower in the adding of fine roots treatment than in the planted K. paniculata treatment. The principal component analysis indicated the promotional dissipation of Pyr in soil by planted K. paniculata was likely attributed to increased microbial quantity and activity, DOC, and TN content in the rhizosphere. Our results suggest that K. paniculata is a suitable plant species used in phytoremediation for Pyr-contaminated soils and the efficiency on the dissipation of Pyr is considerably enhanced using living plants than adding dead organic matters. The study provided a reference for the application of K. paniculata in the remediation of Pyr-contaminated soil.     

Physiological and biochemical responses of <Emphasis Type="Italic">Dolichos lablab</Emphasis> L. to cadmium support its potential as a cadmium phytoremediator

Purpose

This study aims to investigate the response of a high biomass producer non-hyperaccumulator legume plant species, Dolichos lablab L., to cadmium (Cd) stress for phytoremediation process.

Materials and methods

Three individual experiments were carried out to assess physiological and biochemical parameters to support the use of this plant species as a phytoremediator. The first experiment was carried out in Cd-contaminated soil while the second and third experiments were conducted in sand in which Cd was applied to study biochemical responses. Analysis of mineral nutrition, phytoremediation parameters, antioxidant response, and protein identification by gel-based proteomics were performed.

Results and discussion

Good tolerance to Cd under moderate level of contamination was observed. Mineral nutrition was little affected, and phytoremediation index was satisfactory. Additionally, biochemical responses based on antioxidant enzyme analysis were well responsive in roots, reflecting the capacity of Cd stress attenuation in this organ. A proteomic analysis revealed positive regulation of root proteins involved in carbohydrate, amino acids, nitrogen metabolism, and abiotic/biotic stress response, which together may contribute to create a scenario to overcome Cd-induced stress.

Conclusions

Based on the physiological and biochemical results, we concluded that D. lablab L. is suitable for phytoremediation/phytostabilization purposes.

     

Phytoremediation Potential of <Emphasis Type="Italic">Helianthus annuus</Emphasis> and <Emphasis Type="Italic">Hydrangea paniculata</Emphasis> in Copper and Lead-Contaminated Soil

This study was conducted to assess the hyperaccumulation and phytoremediation potential of copper (Cu) and lead (Pb) in Hardy ‘Limelight’ Hydrangea (Hydrangea paniculata) and the common sunflower (Helianthus annuus). The study also investigated the capacity of these two plants to transpire the metals in a temperature-controlled greenhouse. Plants were grown for 4 weeks and periodically watered with known elemental concentrations of copper oxide nanoparticles, copper sulfate, and lead nitrate. Both H. annuus and H. paniculata accumulated significant amounts of Cu and Pb to be classified as hyperaccumulator species. H. annuus took up significant amounts of Cu in the shoots, specifically the leaves (Cu max.?=?1368 ppm), and easily translocated it from stem to leaf (translocation factor (TF) ranged from 2.7 to 81.0). Pb was not as easily taken up and translocated (TF?=?0.6) as Cu was by this species. H. paniculata took up Cu and Pb in high concentrations but preferentially stored more metals in the stems (Cu max.?=?1757 ppm; Pb max.?=?780 ppm) than in the leaves (Cu max.?=?126 ppm; Pb max.?=?35 ppm). The translocation ability of H. paniculata was much lower for both metals compared to H. annuus. Both Cu and Pb transpired from H. annuus at concentrations of 0.04 and 0.005 ppm, respectively.     

Root Porosity Changes in <Emphasis Type="Italic">Salix nigra</Emphasis> Cuttings in Response to Copper and Ultraviolet-B Radiation Exposure

Cuttings of black willow (Salix nigra), a naturally occurring wetland species, are used for restoration and streambank stabilization. As an adaptation to their wetland habitat, this species develops aerenchyma tissue to avoid root anoxia. To determine the effects of combined copper and ultraviolet-B radiation exposure on aerenchyma tissue (measured as root porosity), black willow cuttings were grown hydroponically and exposed to three ultraviolet-B (UV-B) intensities and three Cu concentrations in a completely randomized 3?×?3 factorial design. While both UV-B (F _2,42?=?11.45; p?=?0.0001) and Cu (F _2,42?=?6.14; p?=?0.0046) exposure increased root porosity, total biomass decreased in response to both UV-B (F _2,43?=?3.36; p?=?0.0441) and to Cu (F _2,43?=?4.03; p?=?0.0249). Root biomass decreased only in response to Cu (F _2,41?=?3.41; p?=?0.0427) resulting in a decrease in the root/shoot ratio (F _2,42?=?3.5; p?=?0.0393). Copper exposure also resulted in a decrease in the number of leaves/shoot (F _2,42?=?7.03; P?=?0.0023). No UV-B and Cu interaction was found. While the present research indicates the negative effects of Cu contamination and elevated UV-B intensities on S. nigra, it also points out potential mechanisms that S. nigra uses to alleviate these stresses.