Accumulation of Four Metals in Tissues of Corchorus olitorius and Possible Mechanisms of Their Tolerance

Corchorus olitorius plants treated by 5 μg cm⁻³ of Cd, Pb, Al or Cu in hydroponic culture accumulated in leaves 190, 150, 350 and 325 μg g⁻¹(d.m.) of these metals, respectively, after 6 d of exposure. Exposure of Corchorus plants to tested metals resulted in a sharp rise in content of amino acids in leaf tissues, however the magnitude of accumulation was different from one metal to another. Presence of sulphur in the growth medium significantly increased uptake of Cd and Pb and cysteine (cyst) was more effective than K₂SO₄. Similarly, addition of salicylic acid (SA) in the growth medium significantly enhanced the ability of Corchorus plants to accumulate all these metals. Growth of Corchorus plants was significantly reduced by treatment with any of the four metals except Cu and added cyst, K₂SO₄ or SA alleviated the growth retarding effect of metals. This revised version was published online in July 2006 with corrections to the Cover Date.     

草酸处理对热胁迫下辣椒叶片膜透性和钙分布的影响

研究了外源草酸对热胁迫下辣椒叶片中细胞膜相对透性、谷胱甘肽(GSH)和抗坏血酸(AsA)含量变化以及Ca2+分布的影响.结果表明热胁迫使叶肉细胞膜相对透性升高,草酸处理则减轻升高幅度.热胁迫使叶片中GSH和AsA含量下降;草酸处理则使二者在热胁迫下含量下降幅度较小.常温下辣椒叶肉细胞的焦锑酸钙沉淀颗粒主要分布于液泡、胞间隙和叶绿体中,热胁迫下液泡、细胞间隙中减少,但在细胞核和细胞质中出现;经过草酸处理的叶肉细胞,焦锑酸钙沉淀颗粒在胞间隙中明显增多,液泡中减少.     

Accumulation of cadmium, lead and strontium, and a role of calcium oxalate in water hyacinth tolerance

Eichhornia crassipes plants brought from the River Nile were cultured in jars containing river water supplemented with various concentrations of Cd, Pb, and Sr (0 to 100 μg cm-3), added simultaneously. Treatment continued for 20 d during which each cultivation solution was being replaced with fresh one every 3 d. The growth of Eichhornia was drastically retarded at heavy metal concentrations higher than 15 μg cm-3. At concentrations 15 or 25 μg cm-3, the accumulation of Cd and Pb to levels several times higher than those in control plants was found. More than 50 % of the uptaken metals were retained by roots alone. Leaves and leaf petiols received around 30 and 20 % of the accumulated metals, respectively. X-ray microanalysis indicated the presence of the three heavy metals in Ca oxalate crystals. Content of metals in the crystals increased progressively over time of exposure in a way similar to those in whole plant tissues. These results suggest a possible role for Ca oxalate crystalization in toxic heavy metal deposition and thus tolerance by Eichhornia. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oxalate Accumulation as Regulated by Nitrogen Forms and Its Relationship to Photosynthesis in Rice （Oryza sativa L.）

Four-leaf rice seedlings (Oryza sativa L.), which had been cultivated in Kimura B complete nutrient solution, were treated with two nitrogen forms by replacing the nitrogen element in the complete solution with sole nitrate or ammonium (2.86 mmol/L). Nitrate-N nutrition tended to increase oxalate content in all parts of the plant, including the leaves, stems, roots, and root exudates, whereas ammonium had the opposite effect. Consequently, marked differences in oxalate content were observed between the two treatments throughout the time tested (0-12 d), with maximal differences of approximately 12-fold at 6d after treatment. Photosynthetic/respiratory parameters were examined over time simultaneously with changes in oxalate content. Net photosynthetic rate, chlorophyll fluorescence parameters (i.e. maximal photochemical efficiency (Fv/Fm) and photochemical quantum yields of photosystem (PS)II (ΦPSⅡ)), and respiratory rate were not significantly different between plants treated with the two nitrogen forms, although ammonium-fed plants had apparently higher leaf chlorophyll content than nitrate-fed plants. Leaf glucose content was altered little, but the content of fructose, sucrose, and total soluble sugar was significantly higher in the leaves of ammonium-fed plants than nitrate-fed plants. The results indicate that nitrate/ammonium may serve as efficient regulators of oxalate accumulation owing to regulation of metabolism in rice leaves rather than oxalate downward transfer and root excretion, and that photosynthetic metabolism is not directly correlated with the regulation of oxalate accumulation in rice plants.     

Oxalate Accumulation as Regulated by Nitrogen Forms and Its Relationship to Photosynthesis in Rice (Oryza sativa L.)

Four-leaf rice seedlings (Oryza sativa L.), which had been cultivated in Kimura B complete nutrient solution, were treated with two nitrogen forms by replacing the nitrogen element in the complete solution with sole nitrate or ammonium (2.86 mmol/L). Nitrate-N nutrition tended to increase oxalate content in all parts of the plant, including the leaves, stems, roots, and root exudates, whereas ammonium had the opposite effect. Consequently, marked differences in oxalate content were observed between the two treatments throughout the time tested (0--12 d), with maximal differences of approximately 12-fold at 6 d after treatment. Photosynthetic/respiratory parameters were examined over time simultaneously with changes in oxalate content. Net photosynthetic rate, chlorophyll fluorescence parameters (i.e. maximal photochemical efficiency (Fv/Fm) and photochemical quantum yields of photosystem (PS)Ⅱ (φ PSⅡ)), and respiratory rate were not significantly different between plants treated with the two nitrogen forms, although ammonium-fed plants had apparently higher leaf chlorophyll content than nitrate-fed plants. Leaf glucose content was altered little, but the content of fructose, sucrose, and total soluble sugar was significantly higher in the leaves of ammonium-fed plants than nitrate-fed plants, The results indicate that nitrate/ammonium may serve as efficient regulators of oxalate accumulation owing to regulation of metabolism in rice leaves rather than oxalate downward transfer and root excretion, and that photosynthetic metabolism is not directly correlated with the regulation of oxalate accumulation in rice plants.     

苏南丘陵火炬松林对重金属元素和磷、硫的吸收与累积

由于工农业的迅速发展 ,土壤重金属污染随之加剧 ,国内外学者对重金属在植物体内的吸收、积累、转化进行了广泛的研究[1,6,10 ,14 ] ,但多以一年生草本植物为主。关于木本植物与重金属元素关系的研究报道较少[4 ,5] 。火炬松 (Ｐｉｎｕｓｔａｅｄｅ)是我国引种成功的常绿树种 ,它具有生长快、成材早、干形通直、出材率高、适应性强的特点 ,已在我国南方广泛栽培 ,对该种的生物学和生态学特征已有学者进行了研究[9] 。本文旨在研究火炬松林对重金属元素Ｐｂ ,Ｃｄ ,Ｃｒ,Ｃｕ ,Ｍｎ ,Ｎｉ,Ｚｎ和非金属元素Ｐ和Ｓ的吸收、积累与分布 ,探讨重…     

Biological cost of tolerance to heavy metals in the mosquito Anopheles gambiae

The global rate of heavy metal pollution is rapidly increasing in various habitats. Anopheles malaria vector species (Diptera: Culicidae) appear to tolerate many aquatic habitats with metal pollutants, despite their normal proclivity for ‘clean’ water (i.e. low levels of organic matter). Investigations were conducted to establish whether there are biological costs for tolerance to heavy metals in Anopheles gambiae Giles sensu stricto and to assess the potential impact of heavy metal pollution on mosquito ecology. Anopheles gambiae s.s. were selected for cadmium, copper or lead tolerance through chronic exposure of immature stages to solutions of the metals for three successive generations. Biological costs were assessed in the fourth generation by horizontal life table analysis. Tolerance in larvae to cadmium (as cadmium chloride, CdCl₂), copper [as copper II nitrate hydrate, Cu(NO₃)₂ 2.5 H₂O] and lead [as lead II nitrate, Pb(NO₃)₂], monitored by changes in LC₅₀ concentrations of the metals, changed from 6.07 µg/L, 12.42 µg/L and 493.32 µg/L to 4.45 µg/L, 25.02 µg/L and 516.69 µg/L, respectively, after three generations of exposure. The metal‐selected strains had a significantly lower magnitude of egg viability, larval and pupal survivorship, adult emergence, fecundity and net reproductive rate than the control strain. The population doubling times were significantly longer and the instantaneous birth rates lower in most metal‐selected strains relative to the control strain. Our results suggest that although An. gambiae s.s. displays the potential to develop tolerance to heavy metals, particularly copper, this may occur at a significant biological cost, which can adversely affect its ecological fitness.     

Evaluation of Potential Exposure to Metals in Laundered Shop Towels

We reported in 2003 that exposure to metals on laundered shop towels (LSTs) could exceed toxicity criteria. New data from LSTs used by workers in North America document the continued presence of metals in freshly laundered towels. We assessed potential exposure to metals based on concentrations of metals on the LSTs, estimates of LST usage by employees, and the transfer of metals from LST-to-hand, hand-to-mouth, and LST-to-lip, under average- or high-exposure scenarios. Exposure estimates were compared to toxicity criteria. Under an average-exposure scenario (excluding metals’ data outliers), exceedances of the California Environmental Protection Agency, U.S. Environmental Protection Agency, and the Agency for Toxic Substances and Disease Registry toxicity criteria may occur for aluminum, cadmium, cobalt, copper, iron, and lead. Calculated intakes for these metals were up to more than 400-fold higher (lead) than their respective toxicity criterion. For the high-exposure scenario, additional exceedances may occur, and high-exposure intakes were up to 1,170-fold higher (lead) than their respective toxicity criterion. A sensitivity analysis indicated that alternate plausible assumptions could increase or decrease the magnitude of exceedances, but were unlikely to eliminate certain exceedances, particularly for lead.     

Investigation of Vetiver Grass Capability in Phytoremediation of Contaminated Soils with Heavy Metals (Pb,Cd, Mn,and Ni)

ABSTRACT

Soil contamination with heavy metals has become a worldwide concern. A sustainable technology to mitigate heavy metal contamination is extremely important. Phytoremediation is a cost-effective method, environmentally friendly, and esthetically pleasing. The aim of this study was to investigate the potential of Vetiver phytoremediation of soils contaminated with heavy metals. This research was conducted as a factorial design with four different heavy metals (lead, cadmium, manganese, and nickel) with three varying levels and also three replications for each treatment. Statistical analysis of data was performed using SPSS19 software and analysis of variance, Duncan and Pearson correlation tests. The results showed that, the highest uptake rate was related to lead metal with 282.45 mg/kg of dry soil and 83.4% uptake percentage. Then, the mean and percentage of adsorption for cadmium, nickel and manganese were 248.3 mg/kg (53.2%), 69.4 mg/kg (65.5%), and 63.29 mg/kg (61%), respectively. Lead was found to be the main component of uptake by Vetiver plant. It was found that the roots of the plant have absorbed more heavy metals than the shoots. And at the roots in total 1089.05 and on average 363.01 mg/kg and at the shoots 901.19 and on average 300.39 mg/kg, the metals used were adsorbed on three levels and four treatments. The results of analysis of variance, Duncan test and Pearson correlation showed that the effect of applied treatments on lead uptake in roots and shoots increased significantly (P ≤ 0.05) with increasing levels of treatments. The biological concentration factor was more than one, and the transfer factor was close to one. Therefore, it can be used as a phytostablization plant. The results showed that Vetiver can be considered as a refining plant due to its vegetative characteristics, cost-effectiveness and high adaptation to environmental conditions.     

Comparative Impacts of Heavy Metals on Root Growth as Related to Their Specificity and Selectivity

Two-day-old maize (Zea mays L.) seedlings were incubated on the solutions of Ag, Cd, Pb, Zn, Cu, Tl, Co, and Hg salts (0.001 to 3 g/l). Toxicity of heavy metals was assessed as the inhibition of root growth on the first, second, and third days, the change in the length of the lateral root zone, and the duration of lateral root development from the first division in pericycle to emergence. For all salts under study, the ratio of the lethal concentration to the lowest concentration slowing down root growth was about ten, and growth inhibition was not almost enhanced in the course of three days. With concentrations calculated as g/l, metal toxicity declined in the following order: Cu Tl > Ag > Cd > Hg > Co > Zn > Pb; for molar concentrations, the order was the following: Tl³⁺ > Cu²⁺ > > Ag⁺ > Hg²⁺ Cd²⁺ > Zn²⁺ Pb²⁺ Co²⁺. Duration of lateral root development was least affected by heavy metals. Metal affinity of biological compounds for SH-groups was closely correlated (r = 0.9) with the molar concentration that inhibited primary root growth by 50%. Because of the narrow range of effective concentrations, only slightly increasing inhibition over the exposure time, tolerant root branching, and close relationship between the toxicity and the constant of binding to SH-groups, we conclude that the salts under study exert nonselective inhibition and root growth is slowed down due to the general toxicity of heavy metals rather than selective inhibition of any particular process or processes.     

The Effect of Metal Concentration in Bottom Sediments on the Accumulation of Metals by the Mytilids Crenomytilus grayanus and Modiolus kurilensis

The relationship between the concentration of Pb, Cu, Cd, Zn, and Ag in soft tissues of mytilids Crenomytilus grayanus and Modiolus kurilensis and in bottom deposits was studied to determine the potential and limitations in the use of these molluscs as bioindicators of contamination of coastal waters near Vladivostok (northwest of the Sea of Japan). It was found that the mussel C. grayanus began to accumulate Pb and Cu after certain threshold concentrations of these metals (60 and 150 g/g respectively) in fine fractions of sediments was reached. Accumulation of Pb and Cu by M. kurilensis also depended on the level of sediment contamination, but the higher initial metal content in tissues and the higher individual variability reduced the sensitivity of this species as a bioindicator. Accumulation of Cd and especially of Zn in mytilid tissues is adjusted by the organism, which restricts the opportunity of their use for tracking the anthropogenic input of bioavailable forms of these metals.     

Comparative strategies of heavy metal accumulation by crustaceans: zinc,copper and cadmium in a decapod,an amphipod and a barnacle

This study investigates the comparative strategies of accumulation under standardised laboratory conditions of the essential metals zinc and copper, and the non-essential metal cadmium by three crustaceans of different taxa; vizPalaemon elegans Rathke (Malacostraca: Eucarida: Decapoda),Echinogammarus pirloti (Sexton & Spooner) (Malacostraca: Peracarida: Amphipoda) and the barnacleElminius modestus Darwin (Cirripedia: Thoracica).The decapodP. elegans regulates body zinc concentrations to a constant level (ca. 79 µg Zn g^–1) over a wide range of dissolved metal availabilities until regulation breaks down at high Zn availabilities and net accumulation begins. The amphipodE. pirloti accumulates zinc at all dissolved zinc concentrations but at a low net rate such that the accumulation strategy approaches that of regulation. The barnacleE. modestus accumulates zinc to high body concentrations with no significant excretion of accumulated zinc. In the case of copper,P. elegans similarly regulates body copper concentrations to a constant level (ca. 129 µg Cu g^–1) over a range of dissolved copper availabilities until regulation breaks down at high copper concentrations. Both the amphipodE. pirloti and the barnacleE. modestus on the other hand accumulate copper at all dissolved copper exposures with no evidence of regulation. All three crustaceans accumulate the non-essential metal cadmium at all dissolved cadmium concentrations without regulation.Heavy metal accumulation strategies therefore vary between crustacean taxa and between metals. Uptake rates for zinc and cadmium have been estimated for the three crustaceans and can be interpreted in terms of cuticle permeability and way of life of each crustacean. Examination of these uptake rates provides an insight into possible reasons behind the adoption of particular metal accumulation strategies.     

Changes in the Photosynthetic Apparatus of Broad Bean Leaves as Dependent on the Content of Heavy Metals in the Growth Medium

The content of chlorophyll, the rate of O₂ evolution, the slow phase of fluorescence induction, and photoinduced changes in the intensity of electron paramagnetic resonance (EPR) signal I from the reaction center of photosystem I (P⁺700) were studied in leaves of Vicia faba L. grown in 10^–7–10^–3 M aqueous solutions of CdCl₂, SnCl₂, CuCl₂, and MgCl₂. At low concentrations of heavy metal (Cd, Sn, and Cu) chlorides, the content of chlorophyll per fresh weight decreased. However, the rate of O₂ evolution calculated per chlorophyll basis, O₂/(t chlorophyll), increased. High concentrations of heavy metals significantly suppressed plant development and inhibited photosynthetic O₂ evolution. In contrast, plant treatment with MgCl₂ (10^–5–10^–3 M) resulted in an increase in the content of chlorophyll and a stimulation of leaf photosynthetic activity. A positive correlation between the F _M/F _T ratio and O₂/(t chlorophyll) (r = 0.89, P > 0.999) was found. We observed a negative correlation between the values of P/P ₀ of EPR signal I (white/far-red light) and O₂/(tchlorophyll) (r = –0.89, P > 0.999). The data obtained indicate nonspecific and nonmonotone changes in the photosynthetic apparatus of plants treated with heavy metals: low concentrations of heavy metals (10^–7–10^–6 M) stimulated photosynthetic activity, whereas high concentrations (10^–4–10^–3 M) suppressed it.     

Novel type of ion channel activated by Pb2+, Cd2+, and Al3+ in cultured mouse neuroblastoma cells

Summary Superfusion with Pb²⁺ induces a slow, noninactivating and reversible inward current in voltage-clamped N1E-115 neuroblastoma cells. The amplitude of this inward current increases in the range of 1–200 m Pb²⁺. Single-channel patch-clamp experiments have revealed that this inward current is mediated by discrete ion channels. Reversal potentials from linearI–V relationships are close to 0 mV for whole-cell and single-channel currents and the single-channel conductance amounts to 24 pS. The Pb²⁺-induced membrane current is not mediated by various known types of ion channels, since it is not blocked by external tetrodotoxin, tetraethylammonium,d-tubocurarine, atropine, ICS 205-930 and by internal EGTA. In Na⁺-free solutions superfusion with Pb²⁺ neither evokes a whole-cell inward current, nor single-channel openings. At –80 mV the open-time distribution of the single channels activated by 1m Pb²⁺ is dual exponential with time constants of 17 and 194 msec. When the Pb²⁺ concentration is increased from 1 to 20 m these time constants decrease to 2 and 13 msec, but the amplitude of single-channel currents remains –1.9 nA. Cd²⁺ and Al³⁺ induce inward currents and single-channel openings similar to Pb²⁺. Time constants fitted to the open-time distribution of single channels are 14 and 135 msec in the presence of 1 m Cd²⁺ and 15 and 99 msec in the presence of 50 m Al³⁺. Conversely, Cu²⁺ induces an irreversible inward current in neuroblastoma cells. Single-channel openings are undetected in the presence of Cu²⁺ and in Na⁺-free solutions Cu²⁺ is still able to induce an inward current. It is concluded that Pb²⁺, Cd²⁺ and possibly Al³⁺ activate a novel type of metal ionactivated (MIA) channel in N1E-115 cells.     

Accumulation of Cd and Pb in successive stages ofGalleria mellonella and metal transfer to the pupal parasitoidPimpla turionellae

Larvae ofGalleria mellonella L. (Lepidoptera, Pyralidae) were exposed to Pb (4, 43, 430 μg Pb/g food dw) and Cd (4, 20, 40 μg Cd/g food dw) applied singly and in combination. Metal transfer of Pb and Cd was investigated from food to larvae and successive stages ofG. mellonella and also to the pupal parasitoidPimpla turionellae L. (Hymenoptera, Ichneumonidae). Larvae/food concentration factors (CFs) were highest in controls (Cd 5.25, Pb 3.07) and ranged from 0.19 to 0.92 for Cd and from 0.18 to 0.83 for Pb in contaminated groups; in general, the CFs decreased with an increasing contamination level in food.G. mellonella eliminated most of its larval metal load before pupation (metal concentration in larvae ς> pupae). Although pupae were only moderately contaminated (0.11–1.61 μg Cd/g dw), concentrations inP. turionellae ranged from 0.5 to 6.8 μg Cd/g dw. Again, CFs (parasitoid/pupa) decreased with enhanced levels of metal in the host pupae (Cd 3.07–14.05, Pb 0.0–2.47). The CFs calculated for both species were lower at combined contamination compared to single application.G. mellonella can be classified as a ‘deconcentrator’ (CF<1) along with other lepidopteran species, whereasP. turionellae is apparently a ‘macroconcentrator’ (CF>2).     

Concentration of 17 trace elements in serum and whole blood of plains viscachas (Lagostomus maximus) by ICP-MS, their reference ranges, and their relation to cataract

The reference ranges of the trace elements Al, As, Be, B, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Li, Rb, Se, Sr, and Zn were determined by inductively coupled plasma-mass spectrometry (ICP-MS) in sera of a group of free-ranging plains viscachas of the pampa grasslands of Argentina. The values were compared with those of a small group of captive plains viscachas of the Zurich Zoo with diabetes and bilateral cataracts. In addition, a method for digestion of whole-blood samples is described for the trace element determination. Significant differences in the concentration of trace elements in the two groups of animals are discussed. No correlation was found between the levels of selenium and of other trace elements compared to the formation of cataracts.