Uniconazole (S-3307) strengthens the growth and cadmium accumulation of accumulator plant Malachium aquaticum

The effects of uniconazole (S-3307) application on the growth and cadmium (Cd) accumulation of accumulator plant Malachium aquaticum (L.) Fries. were studied through a pot experiment. The application of S-3307 increased the biomass and photosynthetic pigment content of M. aquaticum in Cd-contaminated soil, and also improved the superoxide dismutase (SOD) and peroxidase (POD) activities in M. aquaticum. Application of S-3307 increased Cd content in shoots and decreased Cd content in roots of M. aquaticum, but the translocation factor (TF) of M. aquaticum increased with the increase of S-3307 concentration. For phytoextraction, the application of S-3307 increased Cd extractions by roots, shoots and whole plants of M. aquaticum, and the maxima were obtained at 75 mg L^?1 S-3307, which increased by 22.07%, 37.79% and 29.07%, respectively, compared with their respective controls. Therefore, S-3307 can be used for enhancing the Cd extraction ability of M. aquaticum, and 75 mg L^?1 S-3307 was the optimal dose.     

Effect of simultaneous establishment of Sedum alfredii and Zea mays on heavy metal accumulation in plants

Land application of biosolids to improve agricultural productivity is a cost-effective approach for resource recovery. Unfortunately, municipal biosolids often contain high concentrations of heavy metals, including zinc and copper. In this study, a co-cropping technique was investigated using a known zinc hyperaccumulator, Sedum alfredii with a grain crop, Zea mays. After a 3-mo growth trial, the results indicate that when Z. mays is co-cropped with S. alfredii, heavy metals accumulated in the grains were significantly reduced when compared to monoculture cropping. Co-cropping improved the growth of both plant species. In addition, the biosolids maintained stable pH, N-P-K concentrations, germination potential, and water content after the plant treatment, regardless of the plant species used in the trial. In conclusion, co-cropping with hyperaccumulators may be an effective approach to reducing the risk of contaminant uptake in edible crops.     

不同性别桑树幼苗对镉与酸雨复合处理的生长响应及镉积累差异

为研究不同性别桑树在镉(Cd)与酸雨(AR)复合处理条件下的生长与镉积累差异,本试验以‘强桑1号’(雌株)和‘农桑14号’(雄株)两种不同性别桑树为材料,研究重金属镉(100 mg·kg^-1干土)和模拟酸雨(pH 3.0)处理下,两者生物量积累和分配、最大净光合速率(A_max)和叶绿素荧光参数,以及Cd积累与分配的差异.试验共设置无Cd和AR(对照)、单独Cd、单独AR、Cd+AR复合4个处理.结果表明:单独Cd处理虽然显著增加了雌株和雄株根茎叶中Cd含量,而且雌株各部分Cd含量显著高于雄株,但是只有雄株根、茎和总生物量、最大净光合速率显著下降,而雌株除了A_max显著下降外,各部分生物量积累下降均不显著,且两者的最大光化学效率(F_v/F_m)、光化学淬灭系数(q_P)和非光化学淬灭系数(q_N)均未发生显著变化.复合处理下,雄株和雌株的总生物量、A_max均显著降低,与单独镉处理相比,雌株根和叶中的Cd含量显著升高,但雄株没有明显变化,两者的F_v/F_m、q_P没有显著变化,但q_N均显著降低.短时间处理下桑树雌株对单独镉胁迫的耐受性高于雄株,但是酸雨的加入会降低雌株对镉的耐受性,可能是因为酸雨促进雌株根系对镉的吸收,并导致叶片积累了更多的镉.     

Magnesium and iron deficiencies alter Cd accumulation in Salix viminalis L.

Evidence exists that Cd and certain nutrient elements, such as Fe and Mg, could share similar mechanisms of plant uptake and accumulation. Here we report that Mg and Fe deficiency in mature plants of Salix viminalis, grown in hydroponic solutions containing 5 µg ml^?1 of Cd, caused a significant increase in Cd accumulation in roots, stems and leaves. Cd (µg g^?1 dry weight) was determined following three treatments: 1) Cd treatment in complete nutrient solution; 2) Cd treatment with Fe deficiency; and 3) Cd treatment with Mg deficiency, yielding, respectively: in young leaves (65.3, 76.1, and 92.2), mature leaves (51.5 to 76.3 and 87.1), upper stems (80.6, 116.8, and 130.6) lower stems (67.2, 119, and 102.3), roots (377.1, 744.8, and 442,5). Our results suggest that Cd utilizes the same uptake and transport pathways as Mg and Fe. Evidence exists that Mg and Fe uptake and translocation could be further facilitated by plants as an adaptive response to deficiency of these elements. Such physiological reaction could additionally stimulate Cd accumulation. Although Cd uptake was mostly confined in roots, high Cd content in aerial plant parts (51.5–130.6 µg g^?1) indicates that the analysed Salix viminalis genotype is suitable for phytoextraction.     

Phytoextraction of HG by parsley (Petroselinum crispum) and its growth responses

The effect of mercury (Hg) on the growth and survival of parsley (Petroselinum crispum) was explored at various treatments. The plants were grown in pots having Hoagland's solution to which various Hg treatments were applied and placed under greenhouse conditions. The treatments were: no metal applied (control) and six doses of Hg as mercuric chloride for 15 days. Linear trend of Hg accumulation was noted in roots, stems, and leaves with increasing Hg treatments. The maximum Hg concentration in root, stem and leaf was 8.92, 8.27, and 7.88 at Hg treatments of 25 mg l^–1, respectively. On the whole, Hg accumulation in different plant parts was in the following order: leaves > stem > roots. Linear trend was also observed for Bioaccumulation Factor (BF) and Translocation Factor (TF) with increasing Hg concentrations in the growth medium. The highest respective BF_Hg and TF_Hg values were 9.32 and 2.02 for the Hg treatments of 25 and 50 mg l^–1. In spite of the reduced growth in the presence of Hg, the plant has phytoremediation potential. It is recommended that parsley should not be cultivated in Hg contaminated sites in order to avoid dietary toxicity.     

Enhanced Pb Absorption by Hordeum vulgare L. and Helianthus annuus L. Plants Inoculated with an Arbuscular Mycorrhizal Fungi Consortium

The effect of an arbuscular mycorrhizal fungi (AMF) consortium conformed by (Glomus intraradices, Glomus albidum, Glomus diaphanum, and Glomus claroideum) on plant growth and absorption of Pb, Fe, Na, Ca, and ³²P in barley (Hordeum vulgare L.) and sunflower (Helianthus annuus L.) plants was evaluated. AMF-plants and controls were grown in a substrate amended with powdered Pb slag at proportions of 0, 10, 20, and 30% v/v equivalent to total Pb contents of 117; 5,337; 13,659, and 19,913 mg Pb kg^?1 substrate, respectively. Mycorrhizal root colonization values were 70, 94, 98, and 90%, for barley and 91, 97, 95, and 97%, for sunflower. AMF inoculum had positive repercussions on plant development of both crops. Mycorrhizal barley absorbed more Pb (40.4 mg Pb kg^?1) shoot dry weight than non-colonized controls (26.5 mg Pb kg^?1) when treated with a high Pb slag dosage. This increase was higher in roots than shoots (650.0 and 511.5 mg Pb kg^?1 root dry weight, respectively). A similar pattern was found in sunflower. Plants with AMF absorbed equal or lower amounts of Fe, Na and Ca than controls. H. vulgare absorbed more total P (1.0%) than H. annuus (0.9%). The arbuscular mycorrizal consortium enhanced Pb extraction by plants.     

Disposal of metal treated Salvinia biomass in soil and its effect on growth and photosynthetic efficiency of wheat

Phytoremediation technologies generate huge quantities of biomass, the disposal of which is a serious concern. Wastewater samples collected from electroplating industries were treated with Salvinia biomass. The effect of application of metal loaded Salvinia plant biomass in soil on growth and physiological indices of 10-day-old seedlings of Triticum aestivum was evaluated. Controls (A) consisted of soil supplemented with untreated plant biomass. Seed germination, seedling height, total chlorophyll, glucose and protein levels, photosynthetic efficiency (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (qn), quantum yield (Y), and electron transport rate (ETR) were not significantly affected in seedlings raised in soils supplemented with metal loaded biomass from most of the samples (B-F) in comparison to control. However, significant decline was noted in total chlorophyll, glucose, and quantum yield in plants grown in soil supplemented with biomass from sample E. Among elemental levels, C(%) remained largely unaffected, N(%) showed slight enhancement but a decrease in H(%) was noted in plants grown in soil supplemented with biomass from sample E. Our results, therefore, suggest that metal accumulated Salvinia biomass obtained after phytoremediation of heavy metal contaminated wastewater can be supplemented in soil. Further studies are required to assess long-term effects of disposal of metal loaded Salvinia plant biomass in soil.     

Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.

Experiments in semi-natural conditions were undertaken to assess hemp metal tolerance and its ability to accumulate cadmium, nickel and chromium. Cannabis sativa was grown in two soils, S1 and S2, containing 27, 74, 126 and 82, 115, 139 g g^–1 of Cd, Ni and Cr, respectively. After two months from germination and at ripeness, no significant alteration in plant growth or morphology was detected. On the contrary, a high hemp reactivity to heavy metal stress with an increase in phytochelatin and DNA content was observed during development, suggesting the Cannabis sativa ability to avoid cell damage by activating different molecular mechanisms. Metals were preferentially accumulated in the roots and only partially translocated to the above-ground tissues. The mean shoot Cd content was 14 and 66 g g^–1 for S1 and S2 soil, respectively. Although not negligible concentrations they were about 100 times lower than those calculated for the hyperaccumulator Thlaspi caerulescens. Similarly Ni uptake was limited if compared with that of the Ni-hyperaccumulator Alyssum murale. Chromium uptake was negligible. As expected on the base of the metal concentration detected in ripe plants, no statistically significant variation in soil metal content was detected after one crop of hemp. Nevertheless, a consistent amount (g) of Cd and Ni is expected to be extracted by 1 ha biomass of hemp (about 10 t) per year and along the time a slow restoration of deeper soil portions can be obtained by its wide root system (at least 0,5 m deep). In addition, the possibilities of growing hemp easily in different climates and using its biomass in non-food industries can make heavy metal contaminated soils productive. This means economical advantage along with a better quality of soil.     

Melatonin increases tissue accumulation and toxicity of cadmium in the bank vole (<Emphasis Type="Italic">Clethrionomys glareolus</Emphasis>)

Recent study has shown that a short photoperiod increases the accumulation and toxicity of cadmium (Cd) in the bank vole as compared to a long photoperiod. Since many of the effects of photoperiod on physiological processes in small mammals are transduced by the pineal gland and its hormone melatonin, in this study the effect of subchronic melatonin injection (7 mol/kg/day for 6 weeks) on the hepatic, renal and intestinal Cd accumulation in the bank voles raised under a long photoperiod and exposed to dietary Cd (0.9 mol/g) was examined. Simultaneously, histological examinations of the liver and kidneys, and analyses of metallothionein (MT) and lipid peroxidation were carried out. Melatonin co-treatment brought about a significant increase in the hepatic (61%), renal (79%) and intestinal (77%) Cd concentrations as compared to those in the Cd alone group. However, the concentrations of MT in the liver and kidneys of the Cd + melatonin co-treated bank voles did not differ from those in the Cd alone group. Also, histopathological changes in the liver (infiltration of leukocytes) and kidneys (glomerular swelling and a focal tubular cell degeneration) as well as an increase (2-fold) in the renal lipid peroxidation occurred only in animals from the Cd + melatonin group. These data indicate that (1) subchronic melatonin injection has similar effect on the tissue accumulation and toxicity of Cd to that produced by a short photoperiod and (2) the Cd-induced toxicity in the liver and kidneys of melatonin co-treated bank voles is probably due to increased Cd accumulation and decreased synthesis of MT.     

Artificial mycorrhization does not influence the effects of iron availability on Fe,Zn, Cu,Pb and Cd accumulation in leaves of a heavy metal tolerant white poplar clone

Abstract

In this study, the phytoextraction capacity of a heavy metal tolerant white poplar clone, grown in the presence of high iron availability and/or mycorrhizas was evaluated. A large amount of iron in available form was determined in initial high concentrations in leaf, which declined along time and affected Cd, Cu, Pb and Zn accumulation. Natural and artificial mycorrhization did not influence these dynamics.     

Effects of cadmium,copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains ofaquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reducedradial growth of most strains by 50% at concentrations between150–400 µM; in a liquid medium, the strains were more sensitive.The inhibitory effects of zinc were much less severe. Two isolates(Articulospora tetracladia and Tetracladium marchalianum) from a copper-minestream were more resistant against copper than conspecific strains from anon-polluted stream. Heliscus lugdunensis and Varicosporium elodeaeresponded to Cd exposure, but not to Cu or Zn exposure, by increasedsynthesis of SH-containing compounds. Glutathione levels showed a unimodalresponse to increasing Cd and Zn exposure. With copper, glutathionedecreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that wereabsent or produced at reduced rates in control cultures.     

Interactions of bacteria with cadmium

Cadmium pollution arises mainly from contamination of minerals used in agriculture and from industrial processes. The usual situation is of large volumes of soil and water that are contaminated with low — but significant — concentrations of cadmium. Therefore, detoxification of the polluted water and soil involves the concentration of the metal, or binding it in a way that makes it biologically inert.Cadmium is one of the more toxic metals, that is also carcinogenic and teratogenic. Its effects are short term, even acute (diseases like Itai-itai), or long term. The long term effects are intensified due to the fact that cadmium accumulates in the body.This paper describes a study involving several hundred cadmium-resistant bacterial isolates. These bacteria could be divided into three groups—the largest group consisted of bacteria resistant to cadmium by effluxing it from the cells. The bacteria of the other two groups were capable of binding cadmium or of detoxifying it. We concentrated on one strain that could bind cadmium very efficiently, depending on the bacterial biomass and on the pH. This strain could effectively remove cadmium from contaminated water and soil.     

Steady presence of cadmium and nickel affects root anatomy,accumulation and distribution of essential ions in maize seedlings

When growing in the field, plants are exposed to the effect of heavy metals as soon as the seed comes into contact with the soil solution. Therefore, we found important to study the effect of Cd and Ni on maize exposed to these heavy metals since sowing. The aim of this work was to examine which anatomical changes are induced by continuous intoxication of young maize root system with 0.1 mM Cd and Ni, thus modifying its growth and capacity for water and nutrient uptake. Concomitantly, the effect on concentration and distribution of Cd, Ni and some essential ions (Ca, Mg, Zn, Fe, Cu and Mn) was studied.     

Effects of cadmium, nickel and lead on growth, chlorophyll content and proteins of weeds

The effects of Cd, Ni and Pb on the growth, chlorophyll (Chl) and protein contents, and content of proteases of potted weed plants Cyperus difformis, Chenopodium ambrosioides and Digitaria sanguinolis were determined. The three heavy metals inhibited the shoot growth but were less suppresive to root growth. They also lowered leaf Chl content. The changes in root and shoot protein and proteases contents of weeds were interrelated. The heavy metal additions to soil increased their contents in both roots and shoots, several times more in roots than in shoots. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heavy Metal Resistance and Accumulation Characteristics in Willows

The resistance of Salix to Cu, Cd, Ni, and Zn was investigated in hydroponic culture, with phytoextraction potential evaluated for Cu. Root elongation (indicative of resistance level) was significantly affected, with considerable variation between and within individual clones. Resistance appeared to be clone- or hybrid-specific, rather than species-specific. S. caprea clones (and hybrids) were among the most resistant, but a secondary S. caprea clone from a different provenance was much less tolerant. S. viminalis and S. triandra clones were the most sensitive. Highest resistance was found in response to Cd, while Cu and Ni were extremely toxic. A resistant S. caprea ecotype originating from a metalliferous mine spoil was identified using this technique. Copper concentration reached a maximum of 2000, 400, and 82 μg g^-1 (d.wt) in roots, wood, and foliage, respectively, after 1 month in hydroponic culture. The level of variation in the response of Salix to metals may cause difficulties in phytoremediation screening programs, but may be essential in providing genetic variation for selection of metal resistance traits, where the contaminant profile is heterogeneous, mixed, or subject to change. Clone selection for metal phytoextraction is feasible, but a longer field-scale study on metal-contaminated soils is needed before their role in phytoremediation can be confirmed.     

Remediation of Pb and Cd Polluted Soils Using In Situ Immobilization and Phytoextraction Techniques

In situ immobilization and phytoextraction techniques have been used for remediation of Pb and Cd polluted soils. Three rates (0.25, 0.5 and 1.0%) of seven immobilizing agents (cement, slag, phosphate rock, bitumen, Fe- and Al-gels, and δ-MnO₂) were tested on three soils containing various levels of Pb (48–192.0 ug/g) and Cd (0.75–3.45 ug/g). All immobilizing agents reduced the plant available Pb and Cd as extracted by DTPA (diethylenetriaminepentaacetic acid). The effectiveness of the various agents in immobilizing Pb and Cd followed the descending order: bitumen > cement > slag > Fe-gel > Al-gel > phosphate rock > δ -MnO₂. Cement and phosphate rock fixed Pb and Cd mainly in the carbonate form, whereas the slag, bitumen, Fe-gel, Al-gel and δ -MnO₂ fixed the metals mainly in the oxide form.

The results of pot experiment proved the high ability of barnyard grass (Echinnochloa stagninum) to accumulate elevated amounts of Pb and Cd (ranging from 291–2421 and 6.1–45.9 ug metal/g dry matter, respectively). These amounts are higher than those reported for hyperaccumulators, particularly for Pb. The amounts of Pb and Cd removed by barnyard grass represent, on average, 46 and 72% of their initial total contents in the soils, respectively. These results proved that, without any other soil treatments, barnyard grass is highly efficient in removing considerable amounts of Pb and Cd from polluted soil within a reasonably short period of time. Therefore, use of barnyard grass for the phytoremediation of Pb and Cd polluted soils is feasible and recommended as an environmentally safe and cheap method. The most significant finding of this study is to name the barnyard grass as an efficient lead accumulator plant.     

超积累植物伴矿景天镉耐受基因SpMT2的分离及功能鉴定

超积累植物由于其对重金属具有地上部超积累以及超耐受等特性,不仅是研究植物离子转运及毒性耐受的理想模式,而且在植物修复的发展和应用中具有不可替代的作用。伴矿景天是近年在我国境内发现的一种景天科镉(Cd)/锌(Zn)超积累植物。为鉴定其富集和耐受Cd的关键基因,笔者构建了其酵母表达cDNA文库,利用酵母的遗传互补系统筛选到一个极大提高了酵母抗Cd能力的基因SpMT2。SpMT2属于富含半胱氨酸(Cys)的金属硫蛋白(Metallothionein)家族。亚细胞定位表明SpMT2表达于酵母细胞质中,并特异地提高酵母对Cd的抗性。进一步研究发现SpMT2的表达显著降低了酵母液泡中Cd含量,但酵母吸收的总Cd含量无显著变化。推测抗性增加是由于SpMT2在酵母细胞质中通过螯合Cd从而降低Cd对酵母的毒害。qRT-PCR分析表明SpMT2在伴矿景天的根和地上部都高丰度表达,且不受Cd诱导变化。鉴于SpMT2也定位于植物细胞质中,结合上述结果,推测SpMT2可能在伴矿景天细胞质中螯合Cd,在降低Cd毒害的同时可能还保持Cd在细胞质中的流动性,从而在Cd长途转运过程中也发挥重要作用。     

Role of the iron transporter OsNRAMP1 in cadmium uptake and accumulation in rice

The heavy metal cadmium (Cd) is toxic to humans, and its accumulation in rice grains is a major agricultural problem. Rice has seven putative metal transporter NRAMP genes, but microarray analysis showed that only OsNRAMP1 is highly up-regulated by iron (Fe) deficiency. OsNRAMP1 localized to the plasma membrane and transported Cd as well as Fe. OsNRAMP1 expression was observed mainly in roots and was higher in the roots of a high-Cd-accumulating cultivar (Habataki) than in those of a low-Cd-accumulating cultivar (Sasanishiki). The amino acid sequence of OsNRAMP1 in the Sasanishiki and Habataki cultivars was found to be 100% identical. These results suggest that OsNRAMP1 participates in cellular Cd uptake and that the differences observed in Cd accumulation among cultivars are because of differences in OsNRAMP1 expression levels in roots.     

The performance of vetivers (Chrysopogon zizaniodes and Chrysopogon nemoralis) on heavy metals phytoremediation: laboratory investigation

Abstract

Phytoremediation with vetiver was investigated in relation to heavy metal contaminated soil in Thailand. The work compared the performance of two species of vetiver named Songkhla 3 (Chrysopogon zizaniodes) and Prachuap Khiri Khan (Chrysopogon nemoralis) in absorbing lead, zinc, and cadmium in contaminated soils. Toxicity Characteristic Leaching Procedure (TCLP), and Allium tests were conducted to determine toxicity of treated soil. Ethylenediaminetetraacetic acid (EDTA) was also used to increase heavy metals concentration in solution in soil, which led to an increase in translocation and bioaccumulation factors. In general, results showed that concentration of heavy metals decreased in soil and increased in both the shoots and roots of vetivers during a 4-month treatment period. TCLP results indicated that the concentration of zinc and cadmium in contaminated soil was reduced over treatment time, and significantly increased after EDTA was applied. To confirm vetiver performance in phytoremediation, Allium testing showed that remained heavy metals in treated soils had no effect on nucleus aberration. Songkhla 3 and Prachuap Khiri Khan showed similar trends in their ability to remediate lead, zinc, and cadmium from contaminated soil. Both species could accumulate higher concentrations of heavy metals in their shoots and roots over time, and with EDTA application.