Multi-Wall Carbon Nanotubes Effects on Plant Seedlings Growth and Cadmium/Lead Uptake In Vitro

The effects of multi-wall carbon nanotubes (MWCNTs) on plant growth and Cd/Pb accumulation was investigated on seedlings of three plant species including Brassica napus L., Helianthus annus L. and Cannabis sativa L. The experiment consisted of MWCNTs on three concentration levels (0, 10, 50 mg/L) and 200 μM CdCl₂ or 500 μM Pb(NO₃)₂. MWCNTs application effectively improved root and shoot growth inhibited by Cd and Pb salts. In B. napus, total chlorophyll (Chl) content increased by both MWCNTs 10 and 50 mg/L exposure under cadmium or lead stress. MWCNT 10 mg/L mitigated the deleterious effects of Cd ions on total chlorophyll content of H. annus and C. sativa. Wherease higher concentration of MWCNTs decreased Chl content under either Cd or Pb treatments on sunflower seedlings. MWCNT10 effectivly raised cadmium accumulation in seedlings of all three species. MWCNT10 and 50 mg/L also caused higher Pb accumulation in canola and cannabis seedlings, respectively. Based on the results, it seems that the effects of MWCNTs on growth parameters and heavy metal accumulation in plant seedlings is strongly depends on heavy metal type, MWCNTs concentration and plant species.     

Effects of Cadmium on the Metabolic Activity of Avena sativa Plants Grown in Soil or Hydroponic Culture

Oat (Avena sativa L.) plants cultured in soil and hydroponic culture were treated with cadmium [0.154 mg g^–1 (dry soil) and 100 M CdSO₄, respectively] for 21 d and growth rate and various biochemical processes were studied. Applied cadmium reduced plant growth and chlorophyll content. Changes in activity of enzymes involved in C, N and S metabolism and in guaiacol peroxidase activity were observed. In particular, O-acetylserine sulphydrylase (OASS; EC 4.2.99.8) activity was increased by Cd exposure in both growth conditions, probably as a resistance mechanism to cadmium based on the production of phytochelatins. Results show that both field and hydroponic conditions represent suitable systems for investigating Cd effects on plant growth and metabolism.     

Hyper-osmoregulatory capacity of the Chinese mitten crab (Eriocheir sinensis) exposed to cadmium; acclimation during chronic exposure

The aim of this study was to evaluate the effects of waterborne cadmium on hyper-osmoregulatory capacity of the Chinese mitten crab Eriocheir sinensis acclimated to freshwater. For this purpose, crabs were submitted to acute (0.5 mg Cd L(-1) for 1, 2 or 3 days), chronic (10 or 50 microg Cd L(-1) for 30 days) or chronic, immediately followed by acute, exposure. While no effect was observed after 1 or 2 days, hemolymph osmolality, Na(+) and Cl(-) concentrations were significantly reduced after 3 days of acute exposure. Under this latter condition, the respiratory anterior gill ultrastructure, Na(+)/K(+)-ATPase and cytochrome c oxidase activities were significantly impaired. In contrast, the osmoregulatory posterior gill was unaffected for all treatments. As a consequence, we suggest that the observed hyper-osmoregulatory capacity impairment is the result of increased dissipative flow of ions and/or water through anterior gills. In contrast to acute exposure, chronic exposure did not induce any observable effect. However, crabs submitted to a known deleterious acute condition (0.5 mg Cd L(-1) for 3 days) directly after chronic exposure to 50 microg Cd L(-1) for 30 days showed normal hyper-osmoregulatory capacity with no change in gill Na(+)/K(+)-ATPase activity, and only little disturbance of anterior gill ultrastructure. These results demonstrate that a chronic cadmium exposure can induce acclimation mechanisms related to osmoregulation in this euryhaline decapod crustacean.     

Activity of lysosomal exoglycosidases in submandibular glands of rats intoxicated by cadmium at doses related to human chronic environmental and occupational exposures

Work in cadmium (Cd) smelter and smoking cigarettes damages teeth and oral mucosa which are protected by tissue and salivary glycoconjugates: glycoproteins, glycolipids, and proteoglycans. We worked out a rat model imitating human "environmental" and "occupational" exposure to cadmium using 5 mg Cd and 50 mg Cd/l in drinking water, respectively. In submandibulary glands of exposed to Cd rats, we found the time and dose dependent accumulation of Cd and simultanous decrease in activity of beta-N-acetylhexosaminidase (HEX). In homogenates of submandibulary glands of control rats, beta-N-acetylhexosaminidase showed the highest activity. The activities of alpha-mannosidase and beta-galactosidase were very low. None of these exoglycosidases were inhibited by Cd even at 44 mM concentration.     

Physiological and Biochemical Mechanisms Preventing Cd Toxicity in the New Hyperaccumulator <Emphasis Type="Italic">Abelmoschus manihot</Emphasis>

Abelmoschus manihot, an ornamental plant, was examined for phytoremediation purposes in accordance with the ability to accumulate cadmium and physiological mechanisms of cadmium tolerance. A net photosynthetic rate (A _N) glasshouse experiment for 60 days was conducted to investigate the influence of different cadmium amounts (0–100 mg kg^?1) on the growth, biomass, photosynthetic performance, reactive oxygen species (ROS) production, antioxidative enzyme activities, Cd uptake and accumulation of A. manihot. Exposure to cadmium enhanced plant growth even at 100 mg kg^?1, without showing symptoms of visible damage. The cadmium concentration of shoots (stems or leaves) and roots was more than the critical value of 100 mg kg^?1 and reached 126.17, 185.26 and 210.24 mg kg^?1, respectively. BCF values of A. manihot plants exceeded the reference value 1.0 for all the Cd treatments, and TF values were greater than 1 at 15–60 mg kg^?1 Cd treatment. The results also showed that cadmium concentrations of 60 mg kg^?1 or less induced a significant enhancement in plant net photosynthetic rate (A _N), stomatal conductance (G _s), transpiration rate (T _r), photosynthetic pigments and F _v/F _m. These parameters were slightly decreased at the higher concentration (100 mg kg^?1). The ROS production (O₂ ^?, H₂O₂) and antioxidative response including SOD, CAT and POD were significantly enhanced by increasing cadmium. These results suggest that A. manihot can be considered as a Cd-hyperaccumulator and the hormetic effects may be taken into consideration in remediation of Cd contamination soil.     

Cadmium(II) Removal by a Hyperaccumulator Fungus <Emphasis Type="Italic">Phoma</Emphasis> sp. F2 Isolated from Blende Soil

A cadmium(II)-resistant fungus, strain F2, isolated from blende soil was identified as Phoma sp. by morphological study and internal transcribed spacer sequencing. This strain could accumulate 280 mg of Cd(II)/g dry weight mycelium. In liquid medium containing 163.8 mg Cd(II)/L, 96% of Cd(II) was removed by the actively growing mycelium. In addition, both oven-dried and lyophilized mycelium could effectively adsorb Cd(II). There were removed 91% and 46.2% of Cd(II) from 51.6 mg Cd(II)/L solution by lyophilized biomass and oven-dried biomass respectively. Transmission electron microscopy and energy-dispersive X-ray analysis showed the accumulation of Cd(II) in the mycelium cell walls. Our results demonstrated that Phoma sp. F2 was a hyperaccumulator for the removal of Cd(II) from contaminated soil and water.     

四种抗寒花卉对镉的生理响应和富集特征

以矮型四季菊、羽扇豆、欧报春和虞美人等冬春季常见花卉为试验材料,通过盆栽试验,研究了不同浓度Cd处理下4种花卉对Cd的生理响应和富集特征,探讨利用这4种花卉在冬春季寒冷时期修复Cd污染土壤的可行性,为提高植物修复技术的效率提供参考。结果表明:(1)在所有Cd处理下,羽扇豆各部位生物量与对照均无差异;欧报春仅根系生物量在80 mg·kg^-1Cd处理时显著低于对照,为对照的74.51%;矮型四季菊和虞美人全株生物量分别在Cd处理浓度高于10、40 mg·kg^-1时开始显著低于对照,并在80 mg·kg^-1Cd处理时全株生物量均达到最小值,分别为对照的41.21%和64.15%。(2)在所有Cd处理下,羽扇豆体内抗氧化酶活性均显著高于对照,MDA含量与对照无显著性差异,清除活性氧能力最强,未受到伤害;欧报春体内抗氧化酶活性升高幅度较小,MDA含量和REC有小幅度增加,清除活性氧的能力较强,受到的伤害程度较低;矮型四季菊和虞美人对活性氧清除能力最差,受到了严重的氧化伤害。(3)在所有Cd处理下,Cd在矮型四季菊体内的分布均为地上部>根系,BCF和TF均大于1,地上部含量和富集量最大值分别为136.20mg·kg^-1和1118.20μg·plant^-1;Cd在羽扇豆、欧报春、虞美人体内表现为地上部<根系,TF均小于1,地上部Cd含量、富集量、BCF和TF均为羽扇豆>欧报春、虞美人。综上所述,与欧报春和虞美人相比,矮型四季菊对Cd耐性相对较差,但对Cd有较强的吸收转移能力,适合用于冬春季Cd污染土壤的修复;羽扇豆对Cd的耐性强,对Cd吸收转移能力也较强,也适合用于冬春季Cd污染土壤的修复。     

Physiology and selected genes expression under cadmium stress in Arundo donax L

The effects of cadmium stress (0, 25, 50, 75, and 100 mg/L) on morpho-physiological features and selected genes (carotenoid hydroxilase, amidase, GR, bHLH, NRAMP and YSL) expression were demonstrated in Arundo donax L. The plants were assessed for Cd uptake and its effects on chlorophyll and antioxidants after 30 days of exposure. The expression of genes conferring metal tolerance was evaluated after 10 days of Cd exposure. The results showed a maximum Cd uptake in roots (872 mg/kg) followed by stem (734 mg/kg) and leaves (298 mg/kg) at highest supplied Cd concentration. The Cd uptake reduced dry weight, Chla, Chlb, and total Chl contents of giant reed. The SOD, CAT, POD activities and MDA content increased at the maximum Cd concentration over control. The highest genes expression for carotenoid hydroxylase, glutathione reductase and amidase was observed in plants exposed to 100 mg/L. However, differential bHLH gene expression and slightly increased gene expression of NRAMP was noted for different Cd treatments. Amidase expressed under Cd stress which is pioneer report in A. donax. These results provided insights into the mechanisms of A. donax tolerance and survival under Cd Stress.     

镉长期暴露对黑斑蛙的氧化胁迫和抗氧化能力的影响

在实验条件下,将黑斑蛙暴露于12．5mg／L和25．0mg／L浓度的镉溶液中30d,分别测定了黑斑蛙在暴露10、20和30d时肝、肾组织中镉（Cd）含量、过氧化产物丙二醛（MDA）的含量、还原型谷胱甘肽（GSH）含量和超氧化物歧化酶（SOD）活性,以探讨镉对机体的脂质过氧化作用及机体的抗氧化损伤机制。实验结果表明,不同剂量组黑斑蛙肝、肾镉含量、MDA含量均随着镉暴露时间的延长而升高,且肝MDA含量与镉在肝中的蓄积量呈显著正相关（R^2=0．8643,n=9）。肝脏GSH含量随镉暴露时间的延长而被显著诱导,且与MDA含量呈显著正相关（R^2=0．5933,n=9）;肾GSH含量则随暴露时间的延长而显著下降,与MDA含量呈显著负相关（R^2=0．8609,n=9）。不同剂量组肝SOD活性随镉暴露时间的延长而升高,肾SOD活性在高剂量组随镉暴露时间的延长表现为先升高后回落下降的趋势。可见,在镉的长期暴露下,细胞膜过氧化增强是镉伤害机体的主要原因,而GSH含量、SOD活性的升高则可能是机体抗过氧化的机理之一。     

Hydroxyl radical production and oxidative damage induced by cadmium and naphthalene in liver of Carassius auratus

Freshwater goldfish (Carassius auratus) were exposed to cadmium (Cd) from 0 to 5 mg/L, and naphthalene (NAP) from 0 to 50 mg/L. Twenty-four hours after the exposure, reactive oxygen species (ROS) was trapped by phenyl-tert-butyl nitrone and detected by electron paramagnetic resonance (EPR). Protein carbonyl (PCO) and lipid peroxidation (LPO) content were determined. The activities of superoxide dismutase (SOD) and catalase (CAT) were also measured. The EPR spectra signals were characterized by prominent six-line spectra, which were defined as hydroxyl radical ((.)OH). As compared to the control group, Cd and NAP significantly induced (.)OH production marked by the intensity of the prominent spectra at higher concentrations. Both xenobiotics also increased LPO content and PCO content, depending on the concentrations. Either LPO or PCO content showed significant relation with (.)OH production. Cd increased the activity of SOD and decreased that of CAT at 5 mg/L, and NAP increased the activities of SOD and CAT at 5 mg/L. The results clearly indicated that these two structurally different non-redox cycling xenobiotics could induce (.)OH generation and result in oxidative damage in liver of C. auratus, and these effects were concentration-dependent.     

Influence of Cadmium Exposure on Growth and Fecundity of Freshwater Mosquitofish Gambusia affinis: In Situ and In Vivo Studies

This study aims to investigate the effect of cadmium (Cd) exposure on growth and fecundity of mosquitofish Gambusia affinis. For this purpose, two natural populations of pregnant females of G. affinis captured from two sites were differently contaminated with Cd (S1 present Cd levels 5-fold higher than S2) and a sublethal exposure to 0.4 mg CdCl(2)/L (10% of LC(50)) during 56 days was conducted in vivo. The length-weight regression revealed a significant difference in the growth between these two populations. A significant difference in fecundity was also noted between the two populations. Indeed, the embryo numbers in pregnant females captured from S1 are significantly higher than those noted in pregnant females from S2 (21.17±5 and 7.97±2.12, respectively; p<0.05). Following Cd exposure, we noted a growth perturbation resulting in lower values of both indices BWG and SGR following 7 and 21 days (-5.21 and -1.18 for BWG, and -2.09 and -0.46 for SGR, respectively) and a recuperation of growing weight at 42 and 56 days (1.32 and 1.71 for BWG, and 0.45 and 0.54 for SGR, respectively). For CF index, we observed a significant difference (p<0.05) between control and Cd groups at 7 and 21 days of exposure, and at 21 and 56 days respectively for HSI and GSI indices. Furthermore, Cd contents in both tissues (liver and yolk sac) and fractions (cytosolic and membrane) are significantly different between groups during experimentation. In addition, the Cd contents noticed in the liver membrane fraction are significantly higher than those noted in the yolk sac tissue. The MTs levels revealed a significant difference between the control and Cd groups. In liver tissue, a significant difference was noted, in MTs levels, during the Cd exposure (7, 21, 42, and 56 days) while in the yolk sac tissue the difference was noted at 42 days of exposure. Taken together, these results imply the potential negative effect of Cd on physiological status of G. affinis as evidenced by decreasing growth and fecundity rate.     

Nitrogen nutrient status induces sexual differences in responses to cadmium in Populus yunnanensis

Populus yunnanensis was employed as a model species to detect sexual differences in growth, physiological, biochemical, and ultrastructural responses to cadmium (Cd) stress, nitrogen (N) deposition, and their combination. Compared with the control conditions, Cd decreased plant biomass, damaged the photosynthetic apparatus, visible as a decreased maximum efficiency of photosystem II (PSII; F(v)/F(m)) and effective quantum yield of PSII (Yield), depressed gas exchange capacity, and induced oxidative stress, visible as the disruption of antioxidative enzymes and accumulation of reactive oxygen species (ROS), in both sexes. On the other hand, Cd toxicity was mitigated by the recovery of gas exchange capacity, a decrease in ROS, and improvement of the redox imbalance in both sexes when N deposition was applied. However, males showed a higher gas exchange capacity, lower enzyme inhibition and ROS accumulation, stronger abilities to maintain cellular redox homeostasis, and a better maintenance of chloroplast ultrastructure than did females when exposed to Cd stress alone. Although males exhibited a higher Cd content in leaves than did females, males also accumulated higher levels of non-protein thiols (NP-SHs) and free amino acids (FAAs) for detoxification than did females. Sexual differences induced by Cd, visible, for example, in F(v)/F(m), Yield, net photosynthesis rate (A), and stomatal conductance (g(s)), decreased under N deposition, as no significant differences between the sexes existed in these parameters under the combined treatment. The results indicated that females are more sensitive to Cd stress and suffer more injuries than do males. Moreover, N deposition can mitigate Cd toxicity and decrease sexual differences in Cd sensitivity.     

Cadmium biosorption by yeast, Candida tropicalis CBL-1, isolated from industrial wastewater

The present study is aimed at assessing the ability of metal-resistant yeast, Candida tropicalis CBL-1, to uptake metal from liquid medium. The minimum inhibitory concentration of Cd(II) against Candida tropicalis CBL-1 was 2,800 mg/L. The yeast could also tolerate Zn(II) (3,100 mg/L), Hg(II) (2,400 mg/L), Ni(II) (2,200 mg/L), Cr(VI) (2,000 mg/L), Pb(II) (1,100 mg/L), and Cu(II) (2,200 mg/L). The yeast isolate showed typical growth curves but lag and log phases extended in the presence of cadmium. The yeast isolate showed optimum growth at 30oC and pH 7. The metal processing ability of the isolate was determined in a medium containing 100 mg/L of Cd(II). Candida tropicalis CBL-1, could reduce Cd(II) 59%, 64% and 70% from the medium after 48, 96 and 144 h, respectively. C. tropicalis CBL-1 was also able to remove Cd(II) 46% and 60% from the wastewater after 6 and 12 days, respectively. Cd produced an increase in glutathione and non-protein thiols level by 37% (17.50±0.8-24.0±1.2) and 18% (3.30±0.7- 3.90±0.8) at 100 mg/L concentration, respectively. Metal tolerance and accumulation together with changes in the GSH status and non-protein thiols under Cd exposure were studied in C. tropicalis.     

镉胁迫对大弹涂鱼肝脏黄螵呤氧化酶和抗氧化酶活性的影响

研究了不同浓度镉离子对大弹涂鱼肝脏黄嘌呤氧化酶（XOD）、抗氧化酶（超氧化物岐化酶SOD、过氧化氢酶CAT）活性和丙二醛（MDA）含量的影响,以探讨其用于污染暴露的生物标记的可行性.结果表明,低浓度Cd²⁺（0.05 mg·L^-1）暴露使大弹涂鱼肝脏XOD和SOD活性随时间延长升高,第10天达到最大值,中高浓度暴露（0.5 和5 mg·L^-1 Cd²⁺）XOD和SOD活性显著或极显著升高;低和高浓度镉胁迫处理的CAT活性在12 h显著降低,随时间的延长低浓度组CAT活性恢复正常,高浓度组在第7天降到最低值, 并在恢复期的5 d中高浓度组CAT活性却极显著升高;低和中浓度镉胁迫处理的MDA含量12 h极显著升高,而高浓度却极显著下降,随时间延长低浓度恢复正常, 中浓度先上升后下降并到第5天达到最大值,而中高浓度在恢复5 d后MDA含量都极显著降低.     

Cadmium removal by living cells of the marine microalga Tetraselmis suecica

Cadmium removal by living cells of the marine microalga Tetraselmis suecica was tested in cultures exposed to different cadmium concentrations (0.6, 3, 6, 15, 30 and 45 mg/l). The EC50 for growth was 7.9 mg Cd/l after six days of exposure. The cadmium removed was proportional to the concentration of this metal in the medium and it was dependent on the time of exposure; cultures with higher cadmium concentration removed a higher amount of this metal. In cultures exposed to 0.6 mg/l, T suecica cells removed 98.1% of added cadmium with 0.392 x 10(-6) microg Cd/cell, whereas in cultures with 45 mg/l only 7.7% was removed with 16.052 x 10(-6) microg Cd/cell. The highest amount of cadmium removed per liter of culture was observed in cultures exposed to 6 mg/l, with 3.577 mg/l of cadmium. After six days of incubation, the higher proportion of cadmium was bioaccumulated intracellularly in all cultures except in 45 mg/l cultures, the percentage of intracellular cadmium being always more than 50%. The highest percentage of bioadsorbed cadmium (60.1%) was found in cells of cultures with the highest cadmium concentration (45 mg/l). Furthermore, a relation between intracellular cadmium and the concentration of sulfhydryl groups was observed.     

A comparison of dressed crab and a cadmium salt (CdCl2) as cadmium sources in rat diets

1. A long term low level exposure experiment was conducted on rats in order to determine the metabolic patterns of realistic environmental dietary levels of cadmium from different sources. 2. Male and female rats were fed a diet for 6 months with a high crab content containing 4 mg Cd/kg as organic bound cadmium from dressed crab, a diet with low crab content containing 0.2 mg Cd/kg as organic bound cadmium, a casein based diet containing 4 mg Cd/kg as cadmium chloride and a low cadmium level control diet. 3. Analysis of the cadmium levels in the kidney, liver and spleen showed that uptake from the dressed crab was only half of that from the diet fortified with cadmium chloride.     

Effect of pulsed exposure to heavy metals (copper and cadmium) on some population variables of <Emphasis Type="Italic">Brachionus calyciflorus</Emphasis> Pallas (Rotifera: Brachionidae: Monogononta)

Heavy metals are widely recognized as potential toxic agents to zooplankton, yet experiments are usually performed with a continuous exposure to the metal being analyzed. Here we describe experiments that examined the influence of pulsed exposure of the heavy metals copper and cadmium to a parthenogenetic population of the planktonic rotifer Brachionus calyciflorus. Our protocol called for exposure durations of 3, 6, 12, and 24 h to either copper (as CuSO₄) at concentrations of 0.0375, 0.075, 0.15 mg l⁻¹ or cadmium (as CdCl₂) at concentration of 0.025, 0.05, 0.1 mg l⁻¹. Control animals were treated in similar ways but did not receive exposure to heavy metals. Four end points were used to evaluate the outcome of exposure: population growth (r), body size, egg ratio, and egg hatching percent. Increase in heavy metal concentration and exposure time had an adverse influence on the population growth of B. calyciflorus. However, while the response of B. calyciflorus was similar for both heavy metals, the magnitude of the impact of cadmium was more severe. Population growth varied depending on which heavy metal was tested, as well as its concentration and the duration of exposure (r = 0.11–0.28 day⁻¹). There was a significant reduction in lorica size of B. calyciflorus subjected to different exposure times and concentrations of both Cd and Cu. Egg ratios were inversely related to population density in controls and in treatments involving Cu, but not for Cd. While nearly 100% of eggs hatched in the control treatments, egg hatching in experimental treatments containing Cu, were reduced (range = 16–41%) depending on the exposure time and the concentration. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research     

Effect of Cd-containing wood ash on the microflora of coniferous forest humus

The use of wood ash in forestry has been questioned because the cadmium (Cd) concentration of ash, which varies between 1 and 20 mg kg(-1) ash, exceeds the level allowed for fertilizers (3 mg kg(-1)) used in agriculture. To investigate the combined and separated effects of Cd and ash on the forest humus microflora, pumice or wood ash, spiked with a water-soluble (CdCl(2)) or -insoluble (CdO) form of Cd at three levels (0, 400 and 1000 mg kg(-1)), were applied at a fertilization level of 5000 kg ha(-1) in a laboratory microcosm study. The trial consisted of 60 microcosms (five replications per treatment), which were incubated in darkness at +20 degrees C and a constant relative air humidity of 60%. After two months the humus in the microcosms was sampled. Analyses of CO(2) evolution to measure the overall microbial activity and of phospholipid fatty acid (PLFA) pattern to measure microbial community structure were performed. The substrate-use patterns of Biolog EcoPlates were analyzed as a measure of bacterial functionality. Finally the bacterial (3)H-thymidine incorporation in the presence of different concentrations of Cd and the number of colony forming units (cfu) of bacteria on nutrient agar in the presence of 0, 5 and 20 mg Cd l(-1) agar were applied to measure Cd tolerance. The use of pumice (pH of humus under the pumice 4.0) did not induce any changes in the above variables compared to two untreated microcosms (humus pH 3.9). Pumice was therefore used to distribute the Cd evenly over the humus surface in order to estimate the possible effect of Cd without ash (pH of humus under the ash 7.0). The application of ash increased the microbial activity, changed the PLFA and substrate-use patterns and increased cfu compared to the humus under pumice. The form and level of Cd in the ash had no further effect on this result. In the humus under pumice the level, but not the form of Cd decreased the microbial activity and changed the PLFA pattern compared to the unspiked pumice. None of the treatments induced bacterial tolerance to Cd. Ash thus protected the humus microflora from the harmful effects of Cd.     

Synthesis of phytochelatins and modulation of antioxidants in response to cadmium stress in Cuscuta reflexa--an angiospermic parasite

Effect of cadmium on growth, antioxidative enzymes namely catalase, peroxidase, glutathione reductase, level of glutathione and phytochelatin synthesis was investigated in callus and seedlings of Cuscuta reflexa. A time, concentration and tissue dependent response of Cd was observed. Cd inhibited the growth of callus and seedlings by 50% at 300 and 500 micromol/L concentrations, respectively. Shorter exposure of low concentration of Cd led to augmentation of antioxidant activity, both in callus and seedlings, while longer exposure and high concentration of Cd led to a concentration dependent decrease in callus. Analysis of phytochelatin (PC) synthesis in callus and seedlings of C. reflexa revealed both quantitative and qualitative changes. Cd at low concentrations led to synthesis of predominantly PC4, while at higher concentrations, PC3 was the major form being synthesized. Amelioration of antioxidative systems of C. reflexa in response to Cd stress might be playing a protective role, alleviating the damaging effects of ROS, generated during Cd stress. Concomitantly, chelation and sequestering of toxic Cd ions in this parasite was mediated by synthesis of PC. The response to Cd stress shown by this holoparasitic plant was found to be similar to those of non-parasitic plants (hosts).