Cd Concentrations In Plants Research Articles

Cadmium transfer between maize and soybean plants via common mycorrhizal networks

More than 80% terrestrial plants establish mutualistic symbiosis with soil-borne arbuscular mycorrhizal fungi (AMF). These fungi not only significantly improve plant nutrient acquisition and stress resistance, but also mitigate heavy metal phytotoxicity, Furthermore, the extraradical mycorrhizal mycelia can form common mycorrhizal networks (CMNs) that link roots of multiple plants in a community. Here we show that the networks mediate migration of heavy metal cadmium (Cd) from maize (Zea mays L.) to soybean (Glycine max (Linn.) Merr.) plants. CMNs between maize and soybean plants were established after inoculation of maize plants with AMF Funneliformis mosseae. Application of CdCl2 in maize plants led to 64.4% increase in the shoots and 48.2% increase in the roots in Cd content in CMNs-connected soybean plants compared to the control without Cd treatment in maize. Meanwhile, although the CMNs-connected soybean plants did not directly receive Cd supply, they upregulated transcriptional levels of Cd transport-related genes HATPase and RSTK 2.13- and 5.96-fold, respectively, induced activities of POD by 44.8% in the leaves, and increased MDA by 146.2% in the roots. Furthermore, Cd addition inhibited maize growth but mycorrhizal colonization improved plant performance in presence of Cd stress. This finding demonstrates that mycorrhizal networks mediate the transfer of Cd between plants of different species, suggesting a potential to use CMNs as a conduit to transfer toxic heavy metals from main food crops to heavy metal hyperaccumulators via intercropping.

Immobilization of cadmium in soil-plant system through soil and foliar applied silicon

We conducted a pot experiment to evaluate the potential for soil- and foliar-applied silicon (Si), alone and in combination, to a Cd-contaminated soil in order to evaluate the effects on such amendments on the Cd translocation from soil to wheat root, shoot and grains. Five treatments were used, T1) control with no external factor added, T2 received only Cd, while T3–T5 treatments received Cd in combination with soil, foliar and soil plus foliar applied Si. Except control (T1), soil was contaminated with Cd at 10 mg kg−1 in all the treatments and 1% solution of Si as an amendment was used for soil and/or foliar application or their combination. Overall, while Si application improved both plant growth and yield in Cd-contaminated soil. Control and combined soil- and foliar-applied Si in Cd contaminated treatments showed equally positive (2.5%) increase in plant height over Cd contaminated treatment. Grain yield was also highest in the treatment receiving Cd plus soil-applied Si (29%) followed by control (26%). It was concluded that Si can alleviate Cd toxicity in wheat irrespective of whether the Si was soil-applied or applied via a foliar method, but soil applied Si proved the best in this regard. Novelty statement Immobilization of metals i.e., cadmium (Cd) with soil-applied amendments like biomaterials and organic manure to decrease Cd concentration in plants have already been widely investigated. Silicon (Si) is a cheap in-organic and readily available element in the nature and also used for the same purpose. It can be applied both in soil as well as by foliar and soil + foliar application to decrease the metals concentration in soil and plants. However, comparative effectiveness of these three methods have not been checked simultaneously. In this study, we have studied the comparative effectiveness of Si application to soil, foliar and their combination (soil + foliar) to decrease Cd concentration during wheat crop.

Effect of EDTA chelate, cow manure, elemental sulfur application and Thiobacillus inoculant on Cd, Zn and Fe phytoremediation efficiency in a Cd-polluted soil

Background and Purpose: Phytoremediation efficiency of heavy metals is one of the important points in environmental studies. This research was conducted to investigate the effect of cow manure, elemental sulfur and EDTA on Cd uptake by Indian mustard in a Cd-polluted soil in the presence of Thiobacillus thiooxidans.
 Materials and Methods: Treatments consisted of applying cow manure (0, 5 and 10 g/kg soil), soil application of elemental sulfur (2 g/kg soil), and Cd-polluted soil (0 and 20 mg Cd/kg soil) with 1.5 mmol EDTA/kg soil in the presence of Thiobacillus spp. After 90 days, Indian mustard plant was harvested and plant Zn, Fe and Cd concentration was measured using atomic absorption spectroscopy. In addition, the soil microbial respiration was measured.
 Results: The use of 2 g/kg soil of elemental sulfur significantly increased the plant Cd concentration in the presence and absence of Thiobacillus by 14.2 and 11.7%, respectively. Adding cow manure to the soil at the rates of 5 and 10 g/kg soil significantly increased the plant Cd concentration by 15.7 and 18.1%, respectively. Also, the application of EDTA chelate at the rate 0f 1.5 mmol/kg soil significantly increased the Cd concentration of the plants grown in the Cd-polluted soil (20 mg Cd/kg soil) by 13.6%.
 Conclusion: The results of the present study showed that using elemental sulfur in the Cdpolluted soil can increase the Cd concentration of the plant which was cultivated in the soil amended with cow manure in the presence of Thiobacillus bacteria. However, the role of soil physic-chemical properties on phytoremediation efficiency cannot be ignored.

The NtNRAMP1 transporter is involved in cadmium and iron transport in tobacco (Nicotiana tabacum)

Plant natural resistance-associated macrophage protein (NRAMP) plays an important role in maintaining intracellular metal homeostasis and coping with environmental heavy metal stress. Until now, studies on NRAMP in tobacco have been limited. In this study, NtNRAMP1 was cloned from tobacco cultivar TN90, and the highest expression level was observed in the roots, which was strongly induced by Fe deficiency. Heterologously expressed NtNRAMP1 significantly increased the Cd sensitivity of the yeast Δycf1 mutant. Three overexpressed NtNRAMP1 lines were generated to reveal the biofunction of NtNRAMP1. In the soil pot experiments under natural conditions, the contents of Fe and total chlorophyll were increased in the leaves of transgenic tobacco compared with the WT. To reveal the characteristics of NtNRAMP1 in metal transport, transgenic plants were cultured in hydroponic solution with 50 μM Cd and 200 μM Fe. Compared with the WT, the Cd concentrations in transgenic plants increased by 1.26–2.02-fold in the roots. Interestingly, the Cd content in the shoots of transgenic plants was slightly reduced compared with that of the WT. Overexpression of NtNRAMP1 did not promote Fe uptake from the external environment into the roots but enhanced the transfer of Fe from the roots to shoots. Additionally, Fe overload in the leaves of transgenic tobacco resulted in increased levels of MDA and H2O2 while Fe toxicity may be relieved by POD. In conclusion, overexpression of NtNRAMP1 in tobacco could promote Cd uptake and Fe transport from the roots to shoots while disturbing Fe homeostasis in the leaves of transgenic tobacco.

Bioaccumulation and Tolerance Indices of Cadmium in Wheat Plants Grown in Cadmium-Spiked Soil: Health Risk Assessment

Farmers use wastewater for irrigation in many developing countries, for example Bangladesh, India, China, Sri Lanka and Vietnam because they have limited access to clean water. This study explored cadmium (Cd) bioaccumulation in two spring wheat cultivars (cv. Mustang and Lancer), which were grown in different concentrations of Cd (0,1, 2, 4, and 8 mg kg−1) in agricultural soils. The half maximum inhibitory concentration (IC50) values were 4.21 ± 0.29 and 4.02 ± 0.95, respectively, whereas the maximum health risk index (HRI) was 3.85 ± 0.049 and 5.33 ± 0.271, respectively, for Mustang and Lancer. In other words, the malondialdehyde content increased significantly in Mustang (around five-fold) and Lancer (around four-fold) compared with the control treatment. Results revealed that Cd content was well above the acceptable limit (HRI >1) in the two cultivars when exposed to different levels of Cd stress. The tolerant cultivar (Mustang) has potential to chelate Cd in the nonedible parts of plants in variable fractions and can be used efficiently to improve growth and macro- and micro-nutrients content while reducing Cd concentration in plants in Cd-contaminated soil. It can also diminish the HRI, which may help to protect humans from Cd risks. The two cultivars’ nutrient availability and sorption capacity significantly shape their survival and adaptability under Cd stress. Based on what is documented in the current study, we can conclude that Mustang is more tolerant and poses fewer health hazards to people than Lancer because of its capacity to maintain grain macro- and micro-nutrients under Cd stress.

Assessing the effects of accumulated Cd(II) on seed germination and root development of Arabidopsis thaliana

In this study, Arabidopsis thaliana was used as a model system to assess the toxic effects of cadmium on plant development and growth. The germination and growth of A. thaliana was inhibited by Cd(II), and the inhibitory effect was dosage-dependent. The significant decrease of germination rates and root growths of A. thaliana were observed from 50 mg/L and 25 mg/L of CdCl2, respectively. Although both shoot and root growths were suppressed by Cd(II), root developments were more sensitive to Cd(II) than shoot developments, as evidenced by shoot growths observed over 50 mg/L of CdCl2. In the concordance to this result, it was also observed that the expression of DR5::VENUS, a visual marker of auxin response, was dependent on the Cd(II) concentration and was strongly reduced from 5 mg/L of CdCl2. In addition, the E. coli-based biosensors were employed to quantify accumulated Cd(II) in plants to understand the correlation between toxic effects and Cd(II) in plants. As a result, it was revealed that 0.012 mg/g and 0.138 mg/g of Cd(II) in dried plants were corresponded to the concentration inhibiting root developments and root growths, respectively. Although it needs further investigations, the findings play a significant role in assessing the toxic effects of Cd(II) based on the relationship between the toxic effects and accumulated Cd(II) concentrations in plants.

Combining mercapto‐functionalized palygorskite with zinc affect cadmium phytoavailability and soil microbial activity in rhizosphere soil

AbstractCadmium (Cd) pollution in soil poses a grave threat to human health. Combining various approaches to reduce Cd accumulation in crops is an active area of research to remediate farmlands with medium‐high levels of Cd contamination. The Mercapto‐functionalized palygorskite (PGS‐SH) and zinc (Zn) application alone or in combination were investigated to explore the reduction of Cd uptake by B. chinensis L and transformation of Cd in soil. The sole application of Zn or PGS‐SH increased the biomass of B. chinensis L. and decreased the concentration of Cd in plants, but more improvements were observed from the combined application of Zn and PGS‐SH. Low concentration of exogenous Zn (50 mg·kg‐1) significantly increased the soil respiration rate (SRR) and the soil dehydrogenase activity (sDHA), while promoted B. chinensis L. growth while inhibiting Cd uptake. However, excessive exogenous Zn (≥ 200 mg·kg‐1) significantly inhibited B. chinensis L. growth and soil microbial activity. The combined application of PGS‐SH and Zn had the highest sDHA (145.59%) and lowest transport factor (TF) (27.59%) compared with the CK. The combination of PGS‐SH and Zn fertilizer is a safe and effective means to reduce the accumulation of Cd in plants and restore microbial activity.

Effect of biosorptive removal of cadmium ions from hydroponic solution containing indigenous garlic peel and mercerized garlic peel on lettuce productivity

One of the most harmful trace elements is cadmium (Cd) because of its persistence and high mobility. As Cd-contamination of soils increases worldwide, techniques to reduce the lettuce plant's Cd accumulation are required. The adverse effects of Cd can be reduced or eliminated using indigenous garlic peel (IGP) and, to a greater extent, mercerized garlic peel (MGP). In addition, the adsorption capacity of garlic peel after mercerization increased compared to indigenous garlic peel. This investigation explored the efficacy of IGP or MGP on the growth characteristics, Cd concentration, and biochemical processes in Cd-stress lettuce plants using a hydroponic growing system. The results demonstrated that IGP or MGP mitigated Cd's toxicity, improving lettuce growth, reducing Cd content, translocation factor, biological accumulation factor, tolerance index, malondialdehyde, and oxidative stress in both leaves and roots. In addition, the application of IGP and MGP significantly increased the non-enzymatic and enzymatic antioxidants in leaves and roots under Cd stress. Furthermore, all treated plants displayed high expression levels of certain regulatory defense genes, UBC21, LOX, and PAL.

Efficiency of a new allylagarose-assembled DGT in measuring Cd, Zn, and Pb bioavailability in sludge-treated soil

The purpose of this study was to assess and validate measures of cadmium (Cd), lead (Pb), and zinc (Zn) bioavailability in a contaminated calcareous soil treated with sewage sludge (0, 10, and 30 g kg −1 ) under peppermint ( Mentha pipertia L.) cultivation using new allylagarose-assembled diffusive gradients in thin-films technique (DGT). To achieve the best gel composition, various diffusive hydrogels were made from different amounts of acrylamide monomer (15, 20, and 25%) and allylagarose cross-linker (0.3, 0.4, and 0.6%). The DGT assembled with 15% acrylamide and 0.3% allylagarose was the best hydrogel based on the obtained swelling rate (3.2) and diffusion coefficients of Cd (5.81 ×10 cm 2 s −1 ), Pb (8.07 cm 2 s −1 ), and Zn (6.13 cm 2 s −1 ). Sewage sludge application increased resupply (R-value) and effective concentration (C E ) of Cd, Pb, and Zn. The highest amounts of C E -Zn (2202 μ g l −1 ), Cd (982.5 μ g l −1 ), and Pb (1847 μ g l −1 ) were observed in soil treated with 30 g kg −1 sewage sludge. Comparison of correlation revealed that 0.3% allylagarose-measured C E -Zn and Pb had a significant logarithmic correlation with the corresponding plant metals concentrations, while C E -Cd was linearly correlated with the plant Cd concentration. These results support the conclusion that the combination of 15% acrylamide and 0.3% allylagarose as a diffusive gel in DGT is a robust gel to predict metal bioavailability and can be reliably used to replace the patented gel cross-linked with agarose. • Increasing percentages of cross-linker led to a reduction in gel pore size. • The high swelling hydrogel facilitated the metals diffusion through the hydrogel. • Increasing sewage sludge level resulted in increasing the re-supply (R) of metals. • 15% acrylamide and 0.3% allylagarose gave the best estimate of bioavailability.

Cadmium Uptake and Translocation By Potato in Acid and Calcareous Soils.

Cadmium contamination of agricultural soils threatens food safety. The bioaccumulation (BAF) of Cd in potato tubers ranged from 0.69 to 1.50 and 0.39 to 0.82 in acidic yellow and alkaline calcareous soils, respectively, when 0.3 to 4.8mg Cd kg-1 was added to the soil. The order of Cd concentration for different organs was root > stem > leaf > tuber. The BAF of Cd decreased with the increase of soil Cd concentration. The effect of pH was important for the transfer and accumulation of Cd for potato. Soil Cd concentration was correlated with the plant Cd concentration and soil pH. Cultivars Hui-2 and Xuanshu 2 accumulated less Cd in six potato cultivars. Logarithmic transformation of the data increased the R2 value from 0.725 to 0.941 in the prediction model of soil Cd concentration. The data are useful in assessing the ecological risk of Cd to potato in Karst area.

Selenium nanoparticles reduced cadmium uptake, regulated nutritional homeostasis and antioxidative system in Coriandrum sativum grown in cadmium toxic conditions

Nanotechnology has become a valuable novel approach to manage several environmental challenges through providing innovative and effective solutions. Heavy metal stress is an important abiotic limiting factor. Seed priming with selenium (Se) alleviates various kinds of environmental stresses; yet, the potential of seed priming with selenium nanoparticles (SeNPs) under cadmium (Cd) stress for coriander crop has never been evaluated. This research work was designed to explore the effects of seed priming with three levels (0, 5, 10 and 15 mg L−1) of SeNPs solution on the physio-biochemical characteristics, nutrition, antioxidative defense system and growth of coriander under Cd stress. Cadmium toxicity reduced chlorophyll content, photosynthetic activity and growth of treated plants. Moreover, Cd stressed plants exhibited modulations in proline level, together with decreased water potential, and leaf osmotic potential. However, SeNPs increased growth attributes, chlorophyll content, total soluble sugars, leaf relative water content, and gas exchange parameters in treated plants which were conversely decreased by Cd toxicity. The seeds priming with SeNPs promoted antioxidant response by increasing catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POX) activity and safeguarding cellular structures through scavenging free radicals and reactive oxygen species. Furthermore, Cd stressed plants displayed an upper level of MDA (1.91 fold) while SeNPs improved membranous integrity through detoxification of hydrogen peroxide. Additionally, SeNPs enhanced nutrients contents (P, K, Ca, Mg, Zn), metal tolerance index and diminished Cd content in plants resulting in the improved growth and development of Cd affected coriander plants.

Effect of Zeolite Application and Seed Priming with Salicylic Acid on Decreasing the Cd Concentration of Inoculated Plant with Piriformospora indica Fungus under Drought Stress

Today, urban management seems necessary to remediate soils contaminated with heavy metals, especially in industrial regions. Thus, this research was done to evaluate the effect of zeolite and seed pre-treatment with salicylic acid on reducing the Cd sorption by ornamental sunflower under drought stress. Treatments (48 treatments) consisted of applying zeolite (0 and 5 % (W/W)) in the Cd (0 and 15 mg Cd (kg soil)-1) polluted soil under cultivation of ornamental sunflower that was inoculated with P.indica in normal and intensive drought stress condition. The plants seeds were pretreated with salicylic acid (0, 0.5 and 1 mM). After 90 days, plants were harvested and atomic absorption spectroscopy (Perkin-Elmer 3030) was used for determining the Pb and Zn concentration. Application of zeolite in the soil significantly decreased and increased the plant Cd and Zn concentration by 11.3 and 14.2%, respectively. Seed priming with salicylic acid at the rate of 1 mM significantly increased the plant Zn and Cd concentration by 12.7 and 14.2%, respectively. In addition, plant inoculation with P.indica significantly decreased the catalase (CAT) and ascorbate peroxidase (APX) enzyme activity which indicate the plant resistance to abiotic stress. However, drought stress had adverse effect on the Cd sorption by plants. Moreover, the CAT and APX enzymes activities were increased. The results of this study showed that applying zeolite and seed priming with salicylic acid had additive effects on decreasing the Cd sorption by ornamental sunflower that was inoculated with P.indica fungus under drought stress.

Influence of Iron Plaque on Accumulation and Translocation of Cadmium by Rice Seedlings

This study investigated the impact of soil type and rice cultivars on variations in the iron plaque formation and cadmium (Cd) accumulation by different portions of rice seedlings under the influence of Fe amendment. The experiments were performed in pots under glasshouse conditions using two typical paddy soils. Rice seedlings were exposed to three concentrations of Cd (0, 1 and 3 mg kg−1 soil) and Fe (0, 1.0 and 2.0 g kg−1 soil). The results revealed that shoot biomass decreased by 12.2–23.2% in Quest and 12.8–30.8% in Langi in the Cd1.0 and Cd3.0 treatments, while shoot biomass increased by 11.2–19.5% in Quest and 26–43.3% in Langi in Fe1.0 and Fe2.0 as compared to the Fe control. The Cd concentration in the roots and shoots of rice seedlings were in the order of Langi cultivar > Quest cultivar, but the Fe concentration in rice tissues showed the reverse order. Fe plaque formations were promoted by Fe application, which was 7.8 and 10.4 times higher at 1 and 2 g kg−1 Fe applications compared to the control Fe treatment. The Quest cultivar exhibited 13% higher iron plaque formation capacity compared to the Langi cultivar in both soil types. These results indicate that enhanced iron plaque formation on the root surface was crucial to reduce the Cd concentration in rice plants, which could be an effective strategy to regulate grain Cd accumulation in rice plants.

The effects of different electrode materials on seed germination of Solanum nigrum L. and its Cd accumulation in soil

The effects of different electrode on Solanum nigrum L. seed germination were determined. The result showed that germination percentage (GP) of seeds in treatment T2 (titanium electrode) was 26.6% higher than in control (CK, without electric field). High potassium and calcium concentrations were beneficial for seed enzymatic activity in treatment T2, which could partly explain the increase in GP. Cd accumulation (μg/pot) in S. nigrum treated with any electric field was significantly higher (p<0.05) than in CK without electric field. Specifically, Cd accumulation under the treatment T3 (stainless steel electrode) was the highest both in roots and shoots; this accumulation in shoots and roots were 74.7 % and 67.4 % higher for stainless steel than in CK. This increase must have been associated with a higher Cd concentration in plants and did not exert a significant effect on the biomass. In particular, Cd concentrations in roots and shoots under stainless steel treatment were both significantly higher than in CK (p<0.05), which had to be related to the higher available Cd concentration in the soil in the middle region. Furthermore, it could be attributed to altered soil pH and other soil properties. Moreover, none of the biomasses were significantly affected (p<0.05) by different electrode materials compared to CK.

Remediation effect of cadmium contaminated soil by the combination of Lactobacillus plantarum and red mud

Bioaugmentation has been receiving much attention recently as an in-situ technology for the remediation of heavy metal polluted soils. To study the effects of the application of different dosages of Lactobacillus plantarum, red mud, and their mixture on cadmium-contaminated soil, the pot experiment was conducted to study the content of cadmium in garlic bolt, plant biomass, soil available Cd concentration, and soil physico-chemical property response. The results showed that: compared with the control, the application of Lactobacillus plantarum resulted in increase of available nitrogen, phosphorus and potassium in soils, while the addition of red mud only increased the content of soil available potassium. However, the biomass of garlic bolt was promoted by the application of Lactobacillus plantarum, red mud and their mixtures to different extend. Lactobacillus plantarum and red mud were applied alone or in combination could effectively reduce the contents of available Cd in the soil and Cd contents in plants, which was32.4%∼ 59.4% and 17.0%∼ 44.3% lower as compared to the control, respectively, the combination of Lactobacillus plantarum and red mud with high dose could obtain best effect on the solidification of cadmium.

Effect of nano-particle compounds and P. indica on bio-degradation of petroleum compounds in the soil contaminated with Cd under cultivation of triticale plant

Background and Purpose: Phytoremediation efficiency of heavy metals is an important factor in environmental studies. This study was conducted to investigate the effect of multi-walled carbon nanotubes (MWCNTs), zeolite, and P.indica on bio-degradation of mazut in a soil treated with Cd and mazut.&#x0D; Materials and Methods: Treatments consisted of applying zeolite (0, 1 and 2% (W/W)), MWCNTs (0, 1 and 2 % (W/W)) in the presence and absence of P.Indica in the Cd (0 , 5 and 10 mg/kg soil) polluted soil that was simultaneously polluted with mazut (0 and 6 % (W/W)). After 70 days, plants were harvested, and plant and soil Cd were measured using AAS. In addition, the degradation percentage of mazut in soil was determined.&#x0D; Results: Addition of 2 % (W/W) MWCNTs and zeolite to the soil polluted with 6 % (W/W) mazut significantly increased the bio-degradation percentage of mazut in the soil by 11.3%. For soil and plant Cd concentration, it was decreased by 10.6 and 12.8%, respectively. In addition, plant inoculation with P.indica significantly increased the bio-degradation of mazut in the Cd polluted soil (10 mg Cd/kg soil) by 14.3%. Increasing soil pollution to mazut from 0 to 6 % (W/W) significantly increased the soil microbial respiration by 14.4%.&#x0D; Conclusion: Based on the results, addition of MWCNs and zeolite in the soil and plant inoculation with P.indica significantly increased the mazut bio-degradation in the soil. However, the amount and type of pollutant had a significant effect on phytoremediation efficiency.

Phytoremediation of cadmium contaminated soils by Amaranthus Hypochondriacus L.: The effects of soil properties highlighting cation exchange capacity

Phytoremediation is a cost-effective method to remedy Cd-contaminated soils. However, it is difficult to predict the performance of a given (hyper)accumulator at different soils due to the divergent plant-soil mutual fitness. Soil properties could be quite influential in determining plant growth and Cd uptake and therefore affect phytoremediation efficiency. To explore the primary soil factors that regulate the efficiency of phytoremediation, a phytoextraction experiment with grain amaranth (Amaranthus Hypochondriacus L.) was conducted in six long-term Cd-contaminated agricultural soils from southern China. The results showed that besides the soil available Cd, the soil cation exchange capacity (CEC) greatly affected plant growth and the amount of total Cd extraction. The deficiency of available Ca and Mg in low CEC soil caused insufficient uptake of Ca and Mg by grain amaranth, which was adverse to plant growth and Cd detoxification. The impaired plant biomass production sharply influenced plant total Cd accumulation, despite the relatively high Cd concentration in plants. While for the grain amaranth grown in soils with higher CEC, the increases in plant Ca and Mg promoted plant photosynthesis and plant tolerance to Cd stress, as indicated by the increase of leaf chlorophyll content and antioxidant enzyme activities, which contributed to the higher plant biomass and phytoremediation efficiency. These findings highlight that maintaining regular plant biomass production is vital to ensure the efficiency of phytoremediation, and low CEC of soil is a substantial barrier that needs to be concerned and further addressed for efficient phytoremediation of Cd-contaminated soils.

The Cd phytoextraction potential of hyperaccumulator Sedum alfredii-oilseed rape intercropping system under different soil types and comprehensive benefits evaluation under field conditions

Soil trace elements (TEs) contamination has become a worldwide problem in arable lands and poses great risk to human health via food chain. Intercropping of hyperaccumulator and cash crops is now proposed as a promising alternative phytoremediation technique to address the issue. However, the effect of intercropping in different soil types and field-scale benefits evaluation are rarely reported. A greenhouse pot experiment and a field trial were therefore designed to explore the effects of intercropping Sedum alfredii (hyperaccumulative population) and oilseed rape on Cd phytoextraction potential, Cd transport and crop production, as well as establishing a feasible assessment framework on the basis of benefits evaluation in contaminated soils. Compared with oilseed rape monoculture, intercropping with S. alfredii significantly and consistently increased biomass, seed yield and Cd accumulation in oilseed rape in five typical soil types. Accumulations of Cd varied with soil types, ranging from 22.8 to 4000 μg pot−1. Stepwise multiple linear regression analysis (SMLRA) showed Cd concentrations in plants were related to available phosphorus (AP), pH, soil organic matter (OM), available potassium (AK), silt and sand; R2 values varied from 0.834 to 0.994 (P < 0.05). A field trial also verified that intercropping could significantly enhance Cd phytoextraction. The highest index for comprehensive benefits evaluation was 0.61 observed in the S. alfredii and oilseed rape intercropping system. This system presented higher Cd phytoextraction potential and comprehensive benefits index whilst allowing ongoing agricultural activities in slightly and moderately Cd-contaminated soils. These results provide a possible technical approach for phytoremediation practice and give new insights into theoretical reference for development of Cd phytoextraction and benefits evaluation.

Biochar improves cd-contaminated soil and lowers Cd accumulation in Chinese flowering cabbage (Brassica parachinensis L.)

Biochar is porous and rich in functional groups on its surface. When applied to Cd-contaminated soils, it can reduce Cd availability and decrease Cd uptake by crops. However, the combined effect of biochar application with vegetables on soil biogeochemistry is often neglected. In the pot experiment of this study, biochar (B) derived from straws of Pennisetum hydridum was applied (2% by weight) to a Cd-contaminated soil planted with two cultivars of Chinese flowering cabbage (Brassica parachinensis L.): Bilvcutai (C+B) and Teqingchixin#4 (T+B). The results showed that in C+B and T+B, soil textures were loam, while CK, C, T were silty loam, and B was sandy loam; soil moisture increased by 19 % and 12 %, respectively; soil pH increased significantly by 0.29 and 0.30 units, respectively; soil organic matter increased by 28 % and 11 %, respectively; soil cation exchange capacity increased by 40 % and 29 %, respectively; Urease, neutral phosphatase, and sucrose activities did not change significantly in C+B, but urease activity increased significantly while phosphatase activity decreased sign ificantly in T+B; Bacterial abundance increased 3.7- and 3.4-fold, and fungal abundance increased 1.2- and 1.7-fold, while actinomycete abundance increased 2.4- and 1.6-fold in C+B and T+B, respectively; soil available nitrogen increased by 38 % and 58 %, respectively; soil available phosphorus increased by 55 % and 66 %, respectively; while soil available Cd was decreased by 30 % and 25 %, respectively. In addition, biochar application improved vegetable gowth, and the plant Cd content in the roots decreased by approximately 18 % and 14 % in C+B and T+B, respectively, and that in the aboveground parts decreased by approximately 10 % in C+B and T+B. Thus, biochar application improved soil fertility and quality while reducing Cd bioavailability and uptake by Chinese flowering cabbage.

Adaptive potential of Typha laxmannii Lepech to a heavy metal contaminated site

To study the adaptive potential of the plant Typha laxmannii Lepech. to heavy metal (HM) stress on the basis of analysis of its morphological and anatomical features under the conditions of an anthropogenically transformed ecosystem of the Don River Delta. The soils on the monitored plots are of the Fluvisol type. The soil characteristics and total concentrations of Mn, Ni, Cd, Cu, Zn, Pb and Cr in soils and cattail plants were analysed. Anatomical-morphological and electron-microscopic examinations revealed the toxic effect of HMs on the roots and leaves of T. laxmannii plants. The studied soils were found to contain high levels of the Zn, Cr, Pb and Cu. It was shown that the sources of Zn, Pb and Cu in the soils were anthropogenic in nature. The high Cr level in soils was due to the natural lithogenic factor. The contents of HM mobile forms in the soils exceeded the maximum permissible concentrations of Cd, Zn, Pb and Ni. An examination of communities of T. laxmannii grown in the impact zone revealed, proliferation anomalies. Ultrastructural studies of plants showed changes in cell membranes, as well as in the main cytoplasmic organelles. The revealed structural changes are assumed to contribute to a slowdown in the ontogenetic development of plants and a decrease in their morphometric parameters under anthropogenic pollution. No significant ultrastructure changes were observed in the roots compared with the leaves, which indicates their high adaptive potential.