镉胁迫对向日葵幼苗生长和生理特性的影响

采用溶液培养方法,研究了不同浓度镉(0、0.05、0.1、0.5和1 mg/L)处理7 d对向日葵幼苗生长和生理特性的影响。结果表明：随着镉处理浓度的增加，向日葵幼苗对镉的吸收显著增加。1 mg/L镉浓度处理时，叶、茎和根中镉浓度分别为0.05 mg/L镉处理时的16.3、19.2和581倍；根中积累的镉含量明显高于叶和茎, 各浓度根部积累的镉分别为叶和茎的37.8～63倍和29.4～41倍。镉胁迫显著抑制向日葵幼苗生长和叶绿素合成，当镉浓度达1 mg/L时，整株植物生物量和总叶绿素含量分别为对照的55.9%和52.6%。镉胁迫下向日葵幼苗游离脯氨酸和丙二醛（MDA）含量显著增加，1 mg/L镉浓度时，根中含量分别为对照的4和5.8倍。向日葵幼苗可溶性蛋白含量和过氧化物酶(POD)活性变化与镉胁迫浓度呈明显的倒U字型关系，可溶性蛋白含量在0.05 mg/L镉浓度时达到最大值，叶、茎、根中的POD活性分别在0.1、0.1和0.05 mg/L镉浓度时达到最大值。     

镉胁迫对万寿菊生长及生理生态特征的影响

通过水培实验,研究了不同Cd浓度(0、0.1、0.5、1、2和5 mg/L)胁迫对万寿菊生长及生理生化指标的影响.研究表明,低浓度Cd(＜0.5 mg/L)胁迫下,万寿菊的生长末受到显著影响,说明万寿菊对低浓度Cd有一定的耐性.而Cd浓度超过0.5 mg/L时,万寿菊的相对生长速率较对照明显降低(P＜0.05),最高可...     

巯基化条件对巯基乙酰壳聚糖除镉性能的影响

为有效处理含镉废水,同时进一步拓展天然高分子絮凝剂壳聚糖(CTS)的应用范围,通过正交实验得到了一种可用于除镉的高分子絮凝剂——巯基乙酰壳聚糖(MAC)的最佳制备条件。实验结果表明,在该条件下得到的MAC对废水中镉的去除率最高可达99.96%,水中镉的残余量为0.01 mg/L,远低于我国废水排放标准(0.1 mg/L);同时巯基乙酰壳聚糖与壳聚糖相比水溶性大大增强,可溶于pH值11以下的废水。     

水溶性巯基壳聚糖对污染土壤吸附态汞的解吸作用研究

用两种巯基化试剂半胱氨酸(Cys)和硫代乙醇酸(Thi)与壳聚糖(CTS)反应,制备了两种水溶性巯基壳聚糖,即Cys-CTS和Thi-CTS,对比研究了这两种巯基壳聚糖与CTS对被染毒土壤中吸附态汞的提取能力.结果表明,Thi-CTS在pH=3、质量浓度为0.5g/L、用量为20 mL的条件下.对汞的提取率为59.44%,相同条件下CTS和cys-CTS对汞的最高提取率只有31.81%和10.15%.     

巯基酯化壳聚糖的合成及对Cd~(2+)的去除性能研究

采用化学方法,研究了以巯基甲壳质制备巯基酯化壳聚糖的最佳合成方案。研究表明,巯基甲壳质的脱乙酰条件(包括时间、温度、氢氧化钠浓度)影响其产物巯基酯化壳聚糖对重金属镉离子的吸附效果。当脱乙酰时间为2 h,温度为160℃,氢氧化钠浓度为20%时,20 mg的合成产物对30 mL Cd2+浓度为20 mg/L水样的去除率最高,达到85.46%,其对镉离子的吸附量达到28.5 mg/g。通过对产物进行红外分析发现,巯基甲壳质中出现脂基特征峰值,脱乙酰后脂基并没有消失,证明最后的产物为巯基酯化壳聚糖。     

亚硫酸钠和腐植酸对李氏禾生长和铬积累的影响

通过水培实验,研究了不同水平亚硫酸钠、腐植酸对李氏禾植株生长、铬吸收积累和营养液中铬含量的影响。亚硫酸钠和腐植酸能明显提高李氏禾对铬的吸收和富集能力。与对照相比,50 mg/L亚硫酸钠处理能显著提高李氏禾根、茎、叶中铬含量和积累量;10 mg/L腐植酸处理能显著提高李氏禾根、茎、叶中铬含量和积累量。亚硫酸钠和腐植酸能明显提高转运系数,促进铬从李氏禾根向地上部分的转移。50 mg/L亚硫酸钠和5 mg/L腐植酸处理下,转运系数大于1,地上部铬含量显著高于根中铬含量。亚硫酸钠显著提高营养液中Eh值,对p H值的影响不明显,李氏禾对铬的吸收以Cr(III)为主。     

巯基酯化壳聚糖的合成及对 Cd2 +的去除性能研究简

采用化学方法，研究了以巯基甲壳质制备巯基酯化壳聚糖的最佳合成方案。研究表明，巯基甲壳质的脱乙酰条件（包括时间、温度、氢氧化钠浓度）影响其产物巯基酯化壳聚糖对重金属镉离子的吸附效果。当脱乙酰时间为2 h，温度为160℃，氢氧化钠浓度为20%时，20 mg的合成产物对30 mL Cd²⁺浓度为20 mg/L水样的去除率最高，达到85.46%，其对镉离子的吸附量达到28.5 mg/g。通过对产物进行红外分析发现，巯基甲壳质中出现脂基特征峰值，脱乙酰后脂基并没有消失，证明最后的产物为巯基酯化壳聚糖。     

巯基酯化壳聚糖的合成及对Cd2＋的去除性能研究

采用化学方法，研究了以巯基甲壳质制备巯基酯化壳聚糖的最佳合成方案。研究表明，巯基甲壳质的脱乙酰条件（包括时间、温度、氢氧化钠浓度）影响其产物巯基酯化壳聚糖对重金属镉离子的吸附效果。当脱乙酰时间为2h，温度为160℃，氢氧化钠浓度为20％时，20mg的合成产物对30mLCd2＋浓度为20mg／L水样的去除率最高，达到85．46％，其对镉离子的吸附量达到28．5mg／g。通过对产物进行红外分析发现，巯基甲壳质中出现脂基特征峰值，脱乙酰后脂基并没有消失，证明最后的产物为巯基酯化壳聚糖。     

水溶性羧甲基壳聚糖对Cd2+的解吸行为研究

为改善壳聚糖(CTS)的水溶性及对重金属的配位能力,合成水溶性好并能与重金属形成配位作用的水溶性羧甲基壳聚糖(WSCC),研究了WSCC对镉的增溶、解吸行为,考察了pH、离子强度、有机质含量和WSCC初始浓度对镉的解吸影响。结果表明:WSCC对碳酸镉的增溶效果显著,当其质量浓度为2g/L时溶液中Cd2+可达到275mg/L;WSCC对镉解吸能力随着土壤中有机质含量的增加而降低,pH的升高、离子强度的增加和WSCC初始浓度的增加有利于镉的解吸;WSCC对镉污染土壤的解吸更符合准二级动力学方程,该静态解吸研究可以为镉污染土壤的修复提供基础信息及依据。     

磺胺甲恶唑对斑马鱼胚胎/仔鱼的毒性效应

为研究磺胺甲恶唑对斑马鱼胚胎/仔鱼的早期发育及抗氧化系统的影响,将受精2h的斑马鱼胚胎暴露在不同浓度的磺胺甲恶唑水溶液中,观察斑马鱼胚胎死亡率、孵化率、仔鱼心包囊肿率、心跳数、体长以及仔鱼内抗氧化酶活性、丙二醛(MDA)含量的变化。结果表明,磺胺甲恶唑对斑马鱼胚胎/仔鱼120h的急性毒性半数致死质量浓度(LC50)为1 250.5mg/L;斑马鱼胚胎孵化率随着暴露浓度的增加呈现明显的下降趋势,96h胚胎孵化率抑制的半数有效质量浓度(EC50)为1 299.7mg/L;当暴露质量浓度≥1 500mg/L时,斑马鱼胚胎患心包囊肿率明显升高,呈现剂量—效应关系;经磺胺甲恶唑暴露96h的斑马鱼仔鱼30s心跳数及120h斑马鱼仔鱼体长总体降低;10~(-2)mg/L磺胺甲恶唑染毒96h后,即观察到斑马鱼仔鱼细胞出现明显的氧化损伤,过氧化氢酶的酶活性受到显著抑制,超氧化物歧化酶和谷胱甘肽S-转移酶被显著诱导,MDA含量显著增加。研究表明,磺胺甲恶唑暴露对斑马鱼胚胎细胞产生了明显的损伤,进而可能影响斑马鱼仔鱼的发育。     

Phytochelatins do not correlate with the level of Cd accumulation in Chlamydomonas spp

Chlamydomonas acidophila KT-1 and Chlamydomonas acidophila DVB238 exhibit a strong heavy metal tolerance, but C. acidophila DVB238 can accumulate a much higher amount of Cadmium (Cd) than C. acidophila KT-1. Phytochelatins (PCs) are known to play an important role in the detoxification of several toxic heavy metals, but the relationship between PCs and Cd accumulation is not clear. PC metabolism and Cd accumulation were investigated by using three Chlamydomonas strains including Chlamydomonas reinhardtii C-9 as a standard alga. The results showed that the PC content did not correlate closely with the level of Cd accumulation, maintenance of a high GSH level seeming to be more important for Cd accumulation. The ultrastructure of C. acidophila KT-1 was extremely disrupted by a great increase in starch granules, which resulted in a moribund state, but hyper-accumulator C. acidophila DVB238 did not exhibit an increase in starch granules in its cells, in spite of Cd accumulation in its chloroplasts, cytosol and vacuoles. These results indicated that C. acidophila DVB238 probably has a developed detoxification system preventing such as destruction of the cells due to Cd toxicity.     

Phosphorus and cadmium interactions in Kandelia obovata (S. L.) in relation to cadmium tolerance

This study focused on the cadmium (Cd) tolerance of mangroves with application of phosphate (P) in order to explore whether exogenous P can alleviate Cd stress on these intertidal species. Kandelia obovata (S. L.) seedlings were cultivated in rhizoboxes under different levels of Cd and P concentrations. The speciation distributions of Cd in the rhizosphere and non-rhizosphere sediments were examined by sequential extraction procedures; organic acid in plant tissues and soil solution was measured by high-performance liquid chromatography; Cd and P accumulation in the plants was also determined. Results showed that considerable differences existed in Cd speciation distributions between rhizosphere and non-rhizosphere sediments. Root activity influenced the dynamics of Cd, P application increased the organic acid content in root tissues, P also increased Cd accumulation in roots whilst lowering Cd translocation from root to the above-ground tissues, and a significant positive correlation was found between Cd and P in roots (r?=?0.905). It is postulated that Cd detoxification of K. obovata (S. L.) is associated with higher Cd immobilization in the presence of higher P and organic acid contents in root tissue.     

Cd-induced phytochelatin synthesis in Dittrichia viscosa (L.) Greuter is determined by the dilution of the culture medium

In this paper, we examined Cd accumulation and PC synthesis in two clones of Dittrichia viscosa, one with a metallicolous (DV-A) and the other with a non-metallicolous origin (DV-W). The clones were cultured in vitro with 0 and 10 mg Cd L^?1 in both short-term treatments (up to 72 h) and over 10 days. We also examined the influence of the culture medium dilution and the PC-synthesis inhibitor, l-buthionine-sulfoximine (BSO), on these parameters. Similar Cd accumulation values were found in the two clones. No synthesis of new thiolic compounds was observed in Cd-treated plants cultured in vitro in Murashige and Skoog medium up to 72 h when compared to controls. Dilution of the culture medium affected PC production, increasing it in 1/2 MS and especially in 1/4 MS. Cd uptake did not increase in the same way, but still hyperaccumulation levels were exceeded in all Cd treatments. BSO addition increased the sensitivity of D. viscosa to Cd and diminished Cd accumulation. Nevertheless, a poor correlation between PCs and Cd accumulation capacity was observed since the highest Cd content did not correspond to the highest PC levels. All these results obtained suggest that PCs are important in Cd accumulation and detoxification in D. viscosa and also that other mechanisms might be involved in these traits.     

Overexpressing GSH1 and AsPCS1 simultaneously increases the tolerance and accumulation of cadmium and arsenic in Arabidopsis thaliana

The goal of this study was to develop transgenic plants with increased tolerance for and accumulation of heavy metals and metalloids from soil by simultaneous overexpression of AsPCS1 and GSH1 (derived from garlic and baker's yeast) in Arabidopsis thaliana. Phytochelatins (PCs) and glutathione (GSH) are the main binding peptides involved in chelating heavy metal ions in plants and other living organisms. Single-gene transgenic lines had higher tolerance to and accumulated more Cd and As than wild-type. Compared to single-gene transgenic lines, dual-gene transformants exhibited significantly higher tolerance to and accumulated more Cd and As. One of the dual-gene transgenic lines, PG1, accumulated twice the amount of Cd as single-gene transgenic lines. Simultaneous overexpression of AsPCS1 and GSH1 led to elevated total PC production in transgenic Arabidopsis. These results indicate that such a stacking of modified genes is capable of increasing Cd and As tolerance and accumulation in transgenic lines, and represents a highly promising new tool for use in phytoremediation efforts.     

Proteomic responses to lead-induced oxidative stress in Talinum triangulare Jacq. (Willd.) roots: identification of key biomarkers related to glutathione metabolisms

In this study, Talinum triangulare Jacq. (Willd.) treated with different lead (Pb) concentrations for 7 days has been investigated to understand the mechanisms of ascorbate–glutathione metabolisms in response to Pb-induced oxidative stress. Proteomic study was performed for control and 1.25 mM Pb-treated plants to examine the root protein dynamics in the presence of Pb. Results of our analysis showed that Pb treatment caused a decrease in non-protein thiols, reduced glutathione (GSH), total ascorbate, total glutathione, GSH/oxidized glutathione (GSSG) ratio, and activities of glutathione reductase and γ-glutamylcysteine synthetase. Conversely, cysteine and GSSG contents and glutathione-S-transferase activity was increased after Pb treatment. Fourier transform infrared spectroscopy confirmed our metabolic and proteomic studies and showed that amino, phenolic, and carboxylic acids as well as alcoholic, amide, and ester-containing biomolecules had key roles in detoxification of Pb/Pb-induced toxic metabolites. Proteomic analysis revealed an increase in relative abundance of 20 major proteins and 3 new proteins (appeared only in 1.25 mM Pb). Abundant proteins during 1.25 mM Pb stress conditions have given a very clear indication about their involvement in root architecture, energy metabolism, reactive oxygen species (ROS) detoxification, cell signaling, primary and secondary metabolisms, and molecular transport systems. Relative accumulation patterns of both common and newly identified proteins are highly correlated with our other morphological, physiological, and biochemical parameters.     

Strategies of heavy metal uptake by three plant species growing near a metal smelter

Some higher plant species have developed heavy metal tolerance strategies which enable them to survive and reproduce in highly metal-contaminated soils. We have investigated such heavy metal uptake and accumulation strategies of two absolute metallophyte species (Armeria maritima ssp. halleri and Cardaminopsis halleri) and one pseudometallophyte (Agrostis tenuis) growing near a former metal smelter. Samples of plant parts and soil were analysed for Zn, Cd, Pb, and Cu. In soil, there were two dominant types of metal concentration gradients with depth. Under the absolute metallophytes, extremely high metal contents were measured in the surficial Ah horizon, followed by a strong decrease in the underlying soil horizons (L(11) and L(12)). Under the pseudometallophyte, metal concentrations in the Ah horizon were much lower and fewer differences were observed in metal concentrations among the Ah, L(11), and L(12) horizons. The concentrations of Zn, Cd, Pb, and Cu in Agrostis tenuis roots were greater than concentrations in leaves, indicating significant metal immobilisation by the roots. For C. halleri, Zn and Cd concentrations in leaves were >20,000 and >100 mg kg(-1), respectively, indicating hyperaccumulation of these elements. Armeria maritima ssp. halleri exhibited root concentrations of Pb and Cu that were 20 and 88 times greater, respectively, than those in green leaves, suggesting an exclusion strategy by metal immobilisation in roots. However, Zn, Cd, Pb, and Cu concentrations in brown leaves of Armeria maritima ssp. halleri were 3-8 times greater than in green leaves, suggesting a second strategy, i.e. detoxification mechanism by leaf fall.     

Effects of exogenous organic chelators on phytochelatins production and its relationship with cadmium toxicity in wheat (Triticum aestivum L.) under cadmium stress

Phytochelatins (PCs) have been proposed as a potential biomarker for metal toxicity. In this study, cadmium (Cd) toxicity, PCs production and their relationship in wheat under Cd stress were examined using various exogenous organic chelator-buffered nutrient solutions. Single Cd stress produced strong toxic effects, as indicated by decreases of growth parameters, high level of lipid peroxidation in leaf and overproduction of PCs in root. Exogenous organic chelators with proper dose more or less reduced Cd toxicity by increasing growth parameters and decreasing lipid peroxidation in leaves. Of organic chelators (EDTA, DTPA, citric acid, malic acid and oxalic acid), EDTA was the most effective in decreasing Cd toxicity in plants, followed by DTPA and citric acid. Simultaneously, the concentrations of Cd-induced PCs in roots decreased, and the greatest decrease was caused by application of EDTA and DTPA. Linearly positive relationships were observed between Cd toxicity and root PCs concentrations under the influences of organic chelators, particularly EDTA, DTPA and citric acid. Furthermore, present results provide stronger evidence that PCs synthesis in plant cells was related to free Cd ion concentrations, not total Cd, and demonstrate that the levels of PCs production in plants correlated well with toxic effects caused by the bioavailable Cd levels.     

Role of salicylic acid in alleviating oxidative damage in rice roots (Oryza sativa) subjected to cadmium stress

Time-dependent changes in enzymatic and non-enzymatic antioxidants, and lipid peroxidation were investigated in roots of rice (Oryza sativa) grown hydroponically with Cd, with or without pretreatment of salicylic acid (SA). Exposure to 50 microM Cd significantly decreased root growth, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), but increased the concentrations of H(2)O(2), malondialdehyde (MDA), ascorbic acid (AsA), glutathione (GSH) and non-protein thiols (NPT). However, pretreatment with 10 microM SA enhanced the activities of antioxidant enzymes and the concentrations of non-enzymatic antioxidants, but lowered the concentrations of H(2)O(2) and MDA in the Cd-stressed rice compared with the Cd treatment alone. Pretreatment with SA alleviated the Cd-induced inhibition of root growth. The results showed that pretreatment with SA enhanced the antioxidant defense activities in Cd-stressed rice, thus alleviating Cd-induced oxidative damage and enhancing Cd tolerance. The possible mechanism of SA-induced H(2)O(2) signaling in mediating Cd tolerance was discussed.     

Remediation mechanisms of mercapto-grafted palygorskite for cadmium pollutant in paddy soil

The immobilization agent was the key factor that determined the success of remediation of heavy metal polluted soil. In this study, mercapto-grafted palygorskite (MP) as a novel and efficient immobilization agent was utilized for the remediation of Cd-polluted paddy soil in pot trials, and the remediation mechanisms were investigated in the aspect of soil chemistry and plant physiology with different rice cultivars as model plants. Mercapto-grafted palygorskite at applied doses of 0.1–0.3% could reduce Cd contents of brown rice and straws of different cultivars significantly. Both reduced DTPA-extractable Cd contents in rhizosphere and non-rhizosphere soil and decreasing Cd contents in iron plaques on rice root surfaces confirmed that MP was an efficient immobilization agent for Cd pollutant in paddy soil. In the aspect of soil chemistry, the pH values of rhizosphere and non-rhizosphere soils had no statistical changes in the MP treatment groups, but their zeta potentials decreased obviously, indicating that MP could enhance the fixation or sorption of Cd on soil compositions. In the aspect of antioxidant system, MP could increase POD activity of rice roots significantly to alleviate the stress of Cd to roots, and resulted in the decrease of T-AOC, SOD, and CAT activities of rice roots of the selected cultivars. MP had no inhabitation or enhancement effects on TSH of rice roots but enhance the contents of MTs and NPT to binding Cd to complete detoxification process. MP as a novel and efficient immobilization agent could complete the remediation effects through soil chemistry and plant physiological mechanisms.

     

Multi-generation cadmium acclimation and tolerance in Daphnia magna Straus

The cladoceran Daphnia magna was acclimated for seven generations to cadmium concentrations ranging from 0 (control) to 250 microg/l Cd (corresponding to a free ion activity of 4.60 nM Cd2+). Acute and chronic cadmium tolerance as well as cadmium accumulation were monitored as a function of acclimation time. After two to three generations of acclimation to concentrations ranging from 0.23 to 1.11 nM Cd2+ increases in acute tolerance were maximal (factor 7.2) and significant. Acclimation for seven generations to the same acclimation concentrations did result in an increased chronic cadmium tolerance (21 days EC50 values increased). Organisms acclimated to 1.93 nM Cd2+ were equally or more sensitive than non-acclimated daphnids in acute and chronic toxicity tests. Cadmium contents in D. magna increased significantly as a function of the acclimation concentration. Maximum body burdens of 236+/-30 microg Cd/g dry weight were measured in organisms exposed to 4.60 nM Cd2+, but detoxification mechanisms were only successful up to 82+/-20 microg Cd/g dry weight as this concentration did not cause major decreases in survival and reproduction in chronic toxicity tests. As the potential positive effect of acclimation on cadmium tolerance disappeared with successive acclimation generations and increasing acclimation concentrations, it is concluded that multi-generation acclimation studies are important for the evaluation of the long-term effects of environmental toxicants.