Impact of cadmium on aquatic bird Cairina moschata

The impact on palmiped Cairina moschata of two levels of dietary cadmium (Cd) contamination (C1: 1 mg kg⁻¹ and C10: 10 mg kg⁻¹) was investigated on liver gene expression by real-time PCR. Genes involved in mitochondrial metabolism, in antioxidant defences, detoxification and in DNA damage repair were studied. Metallothionein (MT) protein levels and Cd bioaccumulation were also investigated in liver, kidneys and muscle. Male ducks were subjected to three periods of exposure: 10, 20 and 40 days. Cd was mainly bioaccumulated in kidneys first and in liver. The concentrations in liver and kidneys appeared to reach a stable level at 20 days of contamination even if the concentrations in muscle still increased. Cd triggered the enhancement of mitochondrial metabolism, the establishment of antioxidant defences (superoxide dismutase Mn and Cu/Zn; catalase) and of DNA repair from 20 days of contamination. Discrepancies were observed in liver between MT protein levels and MT gene up-regulation. MT gene expression appeared to be a late hour biomarker.     

大羽藓(Thuidium cymbifolium)对Pb、Cd污染的指示与累积作用研究

在不同浓度的Pb、Cd 溶液中培养15 d 后, 随着培养浓度的增加, 大羽藓表现出不同程度的伤害症状, 主要是植株体失绿, 到高浓度时开始死亡。测定藓体内的Pb、Cd 含量, 结果表明:大羽藓对Pb、Cd 有较强的吸收累积能力, 特别是对Pb 的累积。Pb、Cd 的累积量随着培养浓度的增大而增加。对复合污染的研究显示出:复合污染中Pb、Cd 累积量远远大于单一污染, Pb、Cd 在大羽藓体内的累积表现为协同效应。     

Zinc effects on cadmium accumulation and partitioning in near-isogenic lines of durum wheat that differ in grain cadmium concentration

Here, we examined the effectiveness of two approaches for reducing cadmium (Cd) accumulation in durum wheat (Triticum turgidum L. var durum) grain: the application of supplemental zinc (Zn), and the use of cultivars exhibiting reduced grain Cd concentrations. Two durum wheat near-isogenic lines (NIL) that differ in grain Cd accumulation were grown to maturity in solution culture containing a chelating agent to buffer the free activities of Zn and Cd at levels approximating those of field conditions. The low Cd accumulating (L-Cd) isoline had Cd concentrations, in grains and shoot parts, which were 60-70% lower than those of the high Cd accumulating (H-Cd) isoline. Increasing the Zn activities in the nutrient solution from deficient to sufficient levels reduced the concentration of Cd in grains and vegetative shoot parts of both isolines. The results suggest that supplemental Zn reduces Cd tissue concentrations by inhibiting Cd uptake into roots. Cd partitioning patterns between roots and shoots and between spike components suggest that the physiological basis for the low Cd trait is related to the compartmentation or symplasmic translocation of Cd.     

镉对茶条槭和五角槭光合作用和叶绿素荧光特性的影响

以北方阔叶树种茶条槭(Acer ginnala)和五角槭(Acer mono)2年生苗木为材料,采用土壤和风化砂混合物作为盆栽基质,设置0(CK)、10、50、100、200 mg·kg-1 5种土壤镉浓度,研究了土壤镉胁迫对苗木叶片光合作用和叶绿素荧光特性的影响.结果表明:随着土壤镉胁迫浓度增加,茶条槭净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)先升后降,胞间二氧化碳浓度(Ci)则先降后升,且均在10 mg·kg-1 Cd2+时达到峰值或谷值;同时五角槭的Pn逐渐降低,Ci持续升高,Gs和Tr则先升后降且均在10 mg·kg-1 Cd2+时达到峰值.随土壤镉处理浓度的增加,茶条槭和五角槭的Fv/Fm、Fv/F0和qN均呈先升后降趋势,ΦPSⅡ则均持续下降;qP在茶条槭表现为先升后降,而在五角槭则逐渐下降.所有指标(除Ci外)在随镉浓度的变化过程中,其上升幅度均为茶条槭大于五角槭,而下降幅度则为五角槭大于茶条槭.研究发现,重金属镉通过破坏或抑制光合作用过程来影响茶条槭和五角槭的生长,高浓度镉导致的Pn下降是由非气孔限制因素所致;茶条槭对土壤镉的耐性大于五角槭,100和50 mg·kg-1 Cd2+可能分别是茶条槭和五角槭对土壤镉污染的耐受极限.     

一株龙葵内生细菌SDE06去除Cd2+的实验

植物内生菌广泛存在于各种植物中, 对宿主的生命活动产生了各种影响。本研究通过对重金属镉(Cd)超累积植物龙葵(Solanum nigrum L.)内生菌优势种进行分离纯化, 并用含Cd2+培养基初步筛选, 得到7株有抗性的菌株, 分别命名为SDE01-07,其中SDE06在Cd2+浓度为80 mg/L的条件下仍能生长。经鉴定此株菌属芽孢杆菌属(Bacillus sp.)。对SDE06在不同条件下去除Cd2+的情况进行研究, 结果表明：正交实验得最佳实验条件为培养时间36 h, pH 6.0, 温度37°C     

Contributions of apoplasmic cadmium accumulation,antioxidative enzymes and induction of phytochelatins in cadmium tolerance of the cadmium-accumulating cultivar of black oat (<Emphasis Type="Italic">Avena strigosa</Emphasis> Schreb.)

The contributions of cadmium (Cd) accumulation in cell walls, antioxidative enzymes and induction of phytochelatins (PCs) to Cd tolerance were investigated in two distinctive genotypes of black oat (Avena strigosa Schreb.). One cultivar of black oat ‘New oat’ accumulated Cd in the leaves at the highest concentration compared to another black oat cultivar ‘Soil saver’ and other major graminaceous crops. The shoot:root Cd ratio also demonstrated that ‘New oat’ was the high Cd-accumulating cultivar, whereas ‘Soil saver’ was the low Cd-accumulating cultivar. Varied levels of Cd exposure demonstrated the strong Cd tolerance of ‘New oat’. By contrast, low Cd-accumulating cultivar ‘Soil saver’ suffered Cd toxicity such as growth defects and increased lipid peroxidation, even though it accumulated less Cd in shoots than ‘New oat’. Higher activities of ascorbate peroxidase (EC 1.11.1.11) and superoxide dismutase (EC 1. 15. 1. 1) were observed in the leaves of ‘New oat’ than in ‘Soil saver’. No advantage of ‘New oat’ in PCs induction was observed in comparison to Cd-sensitive cultivar ‘Soil saver’, although Cd exposure increased the concentration of total PCs in both cultivars. Higher and increased Cd accumulation in cell wall fraction was observed in shoots of ‘New oat’. On the other hand, in ‘Soil saver’, apoplasmic Cd accumulation showed saturation under higher Cd exposure. Overall, the present results suggest that cell wall Cd accumulation and antioxidative activities function in the tolerance against Cd stress possibly in combination with vacuolar Cd compartmentation.     

Involvement of Cd Bioaccumulation in Spinal Deformities Occurrence in Natural Populations of Mediterranean Killifish

The aim of this study was to investigate the possible influence of environmental exposure to cadmium (Cd) on the spinal deformities occurrence in the Mediterranean killifish, Aphanius fasciatus (Pisces: Cyprinodontidae). For this purpose, some indicators of skeletal bone mineralization, Cd, and calcium (Ca) concentrations in spinal column as well as bioaccumulation of Cd from the water and the sediment have been compared in normal and deformed fish collected from polluted (S1) and nonpolluted (S2) areas in the Gulf of Gabès in Tunisia. When compared to the normal fish, the deformed fish showed signs of spinal column demineralization such as significant decrease in the ash weight/dry weight ratio, percentage of nonorganic components content, and Ca concentration. Cd concentrations in spinal column and liver were significantly higher in deformed fish than in normal fish. A highly significant negative correlation (r = −0.915, p < 0.01) between Cd and Ca concentrations was noted in spinal column of deformed fish. Bioaccumulation factors of Cd in the liver from the water and the sediment in deformed fish were also significantly higher (p < 0.0001) than in normal fish from S1 and S2. These findings suggest that the ability to accumulate large amount of Cd may represent a potential risk to induce spinal deformities in natural populations of Mediterranean killifish.     

Exogenous nitric oxide enhances cadmium tolerance of rice by increasing pectin and hemicellulose contents in root cell wall

To study the mechanisms of exogenous NO contribution to alleviate the cadmium (Cd) toxicity in rice (Oryza sativa), rice plantlets subjected to 0.2-mM CdCl₂ exposure were treated with different concentrations of sodium nitroprusside (SNP, a NO donor), and Cd toxicity was evaluated by the decreases in plant length, biomass production and chlorophyll content. The results indicated that 0.1 mM SNP alleviated Cd toxicity most obviously. Atomic absorption spectrometry and fluorescence localization showed that treatment with 0.1 mM SNP decreased Cd accumulation in both cell walls and soluble fraction of leaves, although treatment with 0.1 mM SNP increased Cd accumulation in the cell wall of rice roots obviously. Treatment with 0.1 mM SNP in nutrient solution had little effect on the transpiration rate of rice leaves, but this treatment increased pectin and hemicellulose content and decreased cellulose content significantly in the cell walls of rice roots. Based on these results, we conclude that decreased distribution of Cd in the soluble fraction of leaves and roots and increased distribution of Cd in the cell walls of roots are responsible for the NO-induced increase of Cd tolerance in rice. It seems that exogenous NO enhances Cd tolerance of rice by increasing pectin and hemicellulose content in the cell wall of roots, increasing Cd accumulation in root cell wall and decreasing Cd accumulation in soluble fraction of leaves.     

Antioxidative defense and proline/phytochelatin accumulation in a newly discovered Cd-hyperaccumulator, Solanum nigrum L.

Changes in the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the contents of malondialdehyde (MDA), chlorophyll, free proline and phytochelatins (PCs) in Solanum nigrum, the newly discovered Cd-hyperaccumulator were examined and compared with a non-hyperaccumulator Solanum melongena. It was indicated that leaf SOD and POD activity of S. nigrum was significantly higher than that of S. melongena. The Cd treatments significantly increased root SOD activity, leaf POD activity, and CAT activity and free proline content in the leaves and roots of S. nigrum. On the contrary, the Cd treatments decreased SOD activity, and did not change CAT activity in the leaves and roots of S. melongena. Moreover, there were no significant differences in free proline levels in the roots of S. melongena. These results validated that S. nigrum had a greater capacity than S. melongena to adapt to oxidative stress caused by Cd and free proline accumulation might be responsible for the tolerance of S. nigrum to Cd. Treated with 10 μg Cd g⁻¹, growth of S. nigrum and its contents of chlorophyll and MDA were basically unaffected. In contrast, there were a decrease in the growth and chlorophyll content, and an increase in MDA in the roots of S. melongena. Although lipid peroxidation was promoted in both the hyperaccumulator and non-hyperaccumulator by high Cd stress, the greater increase took place in the tissues of S. melongena. The PCs level in roots of S. nigrum was significantly lower than that of S. melongena. On the contrary, the content of leaf PCs was much higher in S. nigrum than that in S. melongena. These results further suggested that antioxidative defense in the Cd-hyperaccumulator might play an important role in Cd tolerance, and PCs synthesis is not the primary reason for Cd tolerance although PCs in S. nigrum increased significantly by Cd.