The role of root damage in the chelate-enhanced accumulation of lead by Indian mustard plants

In the present study, increasing ethylenediaminetetraacetic acid (EDTA) concentration from 0 to 0.5 mmol L(-1) resulted in progressive increases in root elongation and in shoot and root dry matter (DM) of Indian mustard seedlings (Brassica juncea. L.) exposed at 0.5 mmol L(-1) of lead (Pb). The highest concentration of Pb in the shoots of Indian mustard reached 1140 mg kg(-1) dry weight (DW) in the treatment with 0.5 mmol L(-1) of Pb + 0.25 mmol L(-1) of EDTA. A significantly positive correlation was found between the concentrations of Pb and EDTA in the shoots of mustard. Roots were pretreated with an MC (methanol:trichloromethane) solution, 0.1 mol L(-1) of HCl, and 65 degrees C hot water. The plants were then exposed to 0.5 mmol L(-1) of Pb + 3 mmol L(-1) of EDTA in solution for 2 d. The pretreatments with MC, HCl, and hot water all increased the concentration of Pb in shoots by 14-, 7-, and 15-fold, respectively, compared with the shoots that had not been pretreated. Therefore, some physiological damage to roots would be useful to enhance the uptake of metal by plants and to minimize the application of doses of chelates in the practical operation of chelate-assisted phytoremediation.     

EFFECT OF INDOLE-3-ACETIC ACID,KINETIN, AND ETHYLENEDIAMINETETRAACETIC ACID ON PLANT GROWTH AND UPTAKE AND TRANSLOCATION OF LEAD,MICRONUTRIENTS, AND MACRONUTRIENTS IN ALFALFA PLANTS

Alfalfa plants germinated and grown for 15 d in soil containing 80 mg Pb kg^?1 were treated with ethylenediaminetetraacetic acid (EDTA) at 0.8 mM and indole-3-acetic acid-kinetin (IAA-KN) at 100 μM. Fifteen days after the treatment application, the concentration of lead (Pb), macronutrients, and micronutrients was determined using inductively coupled plasma/optical emission spectroscopy. The chlorophyll content and plant growth were also measured. Roots of plants exposed to Pb alone, Pb–EDTA, and Pb–EDTA-IAA-KN had 160, 140, and 150 mg Pb kg^?1 DW, respectively. Pb was not detected in the stems of plants exposed to Pb alone; however, stems of plants treated with EDTA and EDTA–IAA-KN had 78 and 142 mg Pb kg^?1 DW, respectively. While the Pb concentration in leaves of plants treated with EDTA and EDTA–IAA-KN was 92 and 127 mg kg^?1 DW, respectively. In addition, EDTA and EDTA–IAA-KN significantly increased the translocation of zinc and manganese to leaves. The x-ray absorption spectroscopic studies demonstrated that Pb(II) was transported from roots to leaves without a change in the oxidation state.     

乙二胺四乙酸对孔雀草和一串红铅富集的影响

通过盆栽试验,研究了乙二胺四乙酸(EDTA)对根际土壤Pb的有效性以及孔雀草(Tagetespatula)和一串红(Salviaspendens)富集Pb能力的影响.结果表明:施加EDTA(3mmol.kg-1)7d后,2种花卉根际土壤中乙酸铵溶液(1mol.L-1)可提取的有效态Pb含量极显著提高(P<0.01);孔雀草和一串红叶片中Pb的含量分别达2415.88和1083.68mg.kg-1,为对照处理的61.36和5.37倍;茎中Pb含量也明显增高,而根系Pb含量则略有下降.     

Ameltolide. I: Developmental toxicology studies of a novel anticonvulsant

Ameltolide, a novel anticonvulsant agent, has been shown in animal models to be effective in controlling seizures. The developmental toxicity of ameltolide was evaluated in two species. Naturally mated rats and rabbits were dosed once daily by gavage on gestation days (GD) 6-17 and 6-18, respectively. Rats were given doses of 0, 10, 25, or 50 mg/kg; rabbits were given 0, 25, 50, or 100 mg/kg. Laparotomy was performed on rats on GD 20 and on rabbits on GD 28. In rats, maternal toxicity was indicated at the 25- and 50-mg/kg dose levels by depressed body weight gain. Fetal body weight was depressed at the 50-mg/kg dose level. Fetal viability and morphology were not affected. The no-observed effect levels (NOEL) for adult and developmental toxicity in the rat were 10 and 25 mg/kg, respectively. In rabbits, maternal toxicity was indicated by a net loss in body weight at the 50- and 100-mg/kg dose levels. Fetal viability and body weight were depressed at the 100 mg/kg dose level. Shortened digits occurred on the right forepaw of one fetus at the 50-mg/kg dose level (in conjunction with severe maternal toxicity) and on the hindpaws of two fetuses from separate litters at the 100-mg/kg dose level. Incomplete ossification of the phalanges occurred on the forepaws of nine fetuses from four litters at the 100-mg/kg dose level. Ameltolide was weakly teratogenic in the rabbit. The NOEL for adult and developmental toxicity in the rabbit was 25 mg/kg.     

Enhancing phytoremediative ability of Pisum sativum by EDTA application

The aim of our research was to demonstrate how the presence of EDTA affects resistance of pea plants to Pb and Pb-EDTA presence, and to show the effectivity of lead ions accumulation and translocation. It was determined that EDTA not only increased the amount of Pb taken up by plants but also Pb ion transport through the xylem and metal translocation from roots to stems and leaves. It can be seen in the presented research results that addition of the chelator with Pb limited metal phytotoxicity. We also demonstrated a significant effect of EDTA not only on Pb accumulation and metal transport to the aboveground parts but also on the profile and amount of thiol compounds: glutathione (GSH), homoglutathione (hGSH) or phytochelatins (PCs), synthesized by the plants. We observed a significant effect of the synthetic chelator on increasing the level of Pb accumulation in roots of plants treated with Pb including EDTA (0.5 and 1 mM). Pisum sativum plants treated only with 1 mM Pb(NO3)2 accumulated over 50 mg Pb x g(-1) dry wt during 4 days of cultivation. Whereas in roots of pea plants exposed to Pb+0.5 mM EDTA 35% more Pb was observed. When 1 mM EDTA was applied roots of pea accumulated over 67% more metal. The presence of EDTA also increased metal uptake and transport to the aboveground parts. In pea plants treated only with 1 mM lead nitrate less than 3 mg Pb x g(-1) dry wt was transported, whereas in P. sativum treated with Pb-EDTA doubled amount of Pb was observed in stems and leaves.     

Lead toxicity at different life stages of the giant prawn (Macrobrachium rosenbergii,de Man): considerations of osmoregulatory capacity and histological changes in adult gills

This study evaluated the acute toxicity of lead in different life stages of the freshwater prawn Macrobrachium rosenbergii, determined the effect of sublethal Pb concentrations on osmoregulatory capacity (OC), measured the Pb level in gills, and investigated the effect of Pb on the structure of the gills of adult prawns. The 24-, 48-, and 96-h LC₅₀ values for Pb to M. rosenbergii increased progressively with increasing life stage, from post-larvae (PL), juvenile to adult. The 24- and 48-h LC₅₀ values for post-larvae ranged from 0.01- to 0.09-mg Pb/L. The 24-, 48-, and 96-h LC₅₀ values for Pb were lower at 12 ppt than those at 0 ppt for either the juveniles or the adults. At 12 ppt, the 96-h LC₅₀ values in PL11, juvenile and adult were 0.47-, 0.58-, and 2.03-mg Pb/L, respectively. Meanwhile, at 12 ppt, the 96-h LC₅₀ values in PL11, juvenile and adult were 0.63-, 4.44-, and 7.98-mg Pb/L, respectively. In adults, the OC values of controls and prawns exposed to 2- and 4-mg Pb/L at 0 ppt were not significantly different. The OC of prawns exposed to and 2-mg Pb/L at 12 ppt increased by 72 and 109% from the OC of the control prawns. At media 12 ppt, the OC value of prawns exposed to 1-mg Pb/L was significantly different from that of prawns exposed to 2-mg Pb/L. The concentrations of Pb in gill tissues increased significantly in Pb exposed prawns both at 0 and 12 ppt. The level of Pb in gills of prawns exposed to 2-mg Pb/L at 12 ppt was not significantly different from those exposed at 0 ppt. The severe toxic actions of Pb were noted in gills of prawns exposed in media 12 ppt. Hyperplasia and necrosis were observed in gill lamellae, resulting in abnormal gill tips after Pb exposure at media 12 ppt. Since the effect of Pb is more pronounced in higher salinity (12 ppt) than in freshwater (0 ppt) it is clear that aquaculture of M. rosenbergii should be conducted in freshwater ponds.     

Chemically enhanced phytoextraction of lead-contaminated soils

The effects of the combined application of soil fungicide (benomyl) and ethylenediaminetetraacetic acid (EDTA) on lead (Pb) phytoextraction by ryegrass (Lolium perenne) were examined. Twenty-five pots of Pb-contaminated soil (200 mg Pb kg(-1)) were seeded with ryegrass and randomly arranged into the following treatments: (1) Control, (2) benomyl, (3) EDTA, (4) benomyl and EDTA (B+E), and (5) benomyl followed by an application of EDTA 14 days later (B .. . E). Chemicals were applied when plants had reached maximum growth. Plants were analyzed for foliage Pb concentration using inductively coupled argon plasma (ICAP) spectrometry. The synergistic effects of the combined benomyl and EDTA application (treatments 4 and 5) were made evident by the significantly (p < 0.05) highest foliage Pb concentrations. However, the foliage dry biomass was significantly lowest for plants in treatments 4 and 5. The bioaccumulation factor (BF) and phytoextraction ratio (PR) were highest for plants in treatment 5 followed by plants in treatment 4.     

Lead uptake and translocation by willows in pot and field experiments

Plant growth and lead (Pb) uptake by seven willow varieties were investigated in pot and field experiments to assess the suitability of willows for phytoremediation of Pb at heavily contaminated sites such as skeet ranges. Differences in uptake and translocation of Pb in Salix were observed between pot and field experiments. In the pot experiment, willows grown in Pb-contaminated field soil for 6 months showed tolerance to very high soil Pb concentration (21,360 mg kg(-1)), and with the addition of EDTA were able to take up and translocate more than 1000 mg kg(-1) Pb into above-ground tissues. In the field experiment, all willow varieties showed tolerance to heterogeneously high soil Pb concentrations. Plants were also able to take up and translocate Pb into above-ground tissues. However, after 4.5 months, the lead concentration in the above-ground tissues of willows grown in soil amended with EDTA was less than 200 mg kg(-1). The results from the pot experiment suggest that Salix varieties have the potential to take up and translocate significant amounts of Pb into above-ground tissues using EDTA. However, to verify the phytoextraction abilities of Salix in the field, additional research is needed.     

Effects of Lead on the Activities of Antioxidant Enzymes in Watercress, <Emphasis Type="Italic">Nasturtium officinale</Emphasis> R. Br.

The aim of the present study is to evaluate the oxidative effects of lead with increased concentrations by the determination of antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (AP)) and lipid peroxidation levels in the stem and leaves of watercress (Nasturtium officinale R. Br.) which was exposed to lead acetate, Pb (CH₃COOH)₂ regime with concentrations of 0, 50, 100, 200, 250, and 500 mg/L Pb in a hydroponic culture. After 14 days, accumulation of lipid peroxidation in stems and leaves and changes in activity of antioxidant enzymes were determined spectrophotometrically. The maximum accumulation was observed in the highest concentration group. In this group, lipid peroxidation levels were three times higher than the control group in the stem and leaves. The highest induction in SOD and GR activities were determined at 200 mg/L Pb group in stem, whereas CAT and AP activities were higher than other groups at the concentration of 250 and 100 mg/L Pb, respectively. The increase in CAT activity was found to be greater than GR, SOD, and AP activities in stems of watercress under Pb treatment. Both lead accumulation and antioxidant enzyme responses were higher in stems than in leaves. The results of the present study suggested that the induction in antioxidant responses could be occurring as an adaptive mechanism to the oxidative potential of lead accumulation.     

Gossypol modulation of nucleotide metabolizing enzymes in the reproductive tract of male rats

The activities of several pivotal nucleotide metabolizing enzymes from the testis and vasal sperm of rats treated for 7 wk with 0, 20 or 30 mg X kg X day gossypol acetic acid were examined. Total testicular lactate dehydrogenase (LDH) activity increased 40% above control in the highest treatment group examined. However, the specific activity of the testis-specific isozyme of LDH, LDH-C4, decreased to 50 and 20% of control in the 20 and 30 mg X kg X day treatment groups, respectively. Basal soluble adenylate cyclase from a 100,000 X g supernatant of testis homogenate exhibited a 25% decrease in activity only in the 30-mg treatment group. Basal adenylate cyclase activity in the testicular membrane fraction increased 20 to 30% above control in response to gossypol administration. Testis membranes from the 20- and 30-mg treatment group exhibited a 2- and 4-fold greater activation of adenylate cyclase by guanine nucleotides. In vitro dose-response curves showed a half-maximal inhibitory concentration (IC50) for inhibition of soluble testicular adenylate cyclase by gossypol of 400 microM in each treatment group. Caudal epididymal sperm adenylate cyclase activity decreased to 25% of control levels in gossypol-treated animals, and the in vitro sensitivity of the enzyme to the inhibitory effects of gossypol increased 4-fold. IC50 values for gossypol inhibition of sperm adenylate cyclase decreased from 200 microM in control animals to 75 and 50 microM in the 20 and 30 mg X kg X day treatment groups, respectively. Cyclic adenosine 3':5' monophosphate phosphodiesterase activity in caudal sperm increased 6-fold in the 20- and 30-mg treatment groups. These results demonstrate that nucleotide metabolizing enzymes in sperm are major targets for the actions of gossypol and provide a possible mechanism for the inhibition of normal sperm function by this compound.     

铅胁迫对斜纹夜蛾生长发育与生殖的影响

在植食性昆虫斜纹夜蛾幼虫标准人工饲料中添加不同浓度的重金属铅(Pb),研究Pb胁迫对其生长发育与生殖的影响.结果表明:斜纹夜蛾不同发育阶段(幼虫、蛹和成虫)的存活率和体质量随着饲料中Pb浓度的增加而下降,引起存活率显著下降的最低Pb胁迫浓度是100 mg·kg-1,引起体质量显著减少的最低Pb胁迫浓度是50 mg·kg-1.在取食Pb浓度为25～ 200 mg·kg-1的人工饲料后,斜纹夜蛾成虫的产卵天数显著减少;产卵力和生育力随着饲料中Pb浓度的增加而显著下降;1000粒卵的平均质量显著低于对照;卵孵化率显著下降.重金属Pb胁迫对斜纹夜蛾生长发育和生殖具有显著的抑制作用.     

Overnight (1 mg) dexamethasone suppression testing reliably distinguishes non-cushingoid obesity from Cushing's syndrome.

To determine the sensitivity of the overnight 1-mg dexamethasone suppression test in diagnosing Cushing's syndrome, we evaluated the cortisol responses of 55 subjects (25 non-obese individuals with body mass index less than 25 kg/m2, 20 obese individuals with body mass index greater than 30 kg/m2, and 10 patients with surgically proven Cushing's syndrome) following ingestion of 1 mg dexamethasone at midnight. The basal 8 AM plasma cortisol levels among non-obese and obese individuals and patients with Cushing's syndrome were 310 +/- 85, 377 +/- 91, and 813 +/- 270 nmol/L, respectively. Following 1 mg of dexamethasone, Cushing's syndrome patients showed minimal suppression of cortisol to 609 +/- 180 nmol/L (P = 0.79). Non-obese and obese individuals suppressed to 18.7 +/- 6.0 nmol/L (P less than 0.001) and 22 +/- 7.1 nmol/L (P = 0.003), respectively. The results demonstrated similar cortisol responses to overnight dexamethasone suppression in obese and non-obese groups, and clearly distinguished these subjects from those with Cushing's syndrome. Obesity is not a confounding factor in the 1-mg dexamethasone suppression test.     

Effects of soil amendments and EDTA on lead uptake by Chromolaena odorata: greenhouse and field trial experiments

Greenhouse and field trial experiments were performed to evaluate the use of Chromolaena odorata with various soil amendments for phytoextraction of Pb contaminated soil Pb mine soils contain low amount of nutrients, so the additions of organic (cow manure) and inorganic (Osmocote and NH4NO3 and KCl) fertilizers with EDTA were used to enhance plant growth and Pb accumulation. Greenhouse study showed that cow manure decreased available Pb concentrations and resulted in the highest Pb concentration in roots (4660 mg kg(-1)) and shoots (389.2 mg kg(-1)). EDTA increased Pb accumulation in shoots (17-fold) and roots (11-fold) in plants grown in soil with Osmocote with Pb uptake up to 203.5 mg plant(-1). Application of all fertilizers had no significant effects on relative growth rates of C. odorata. Field trial study showed that C. odorata grown in soil with 99545 mg kg(-1) total Pb accumulated up to 3730.2 and 6698.2 mg kg(-1) in shoots and roots, respectively, with the highest phytoextraction coefficient (1.25) and translocation factor (1.18). These results indicated that C. odorata could be used for phytoextraction of Pb contaminated soil. In addition, more effective Pb accumulation could be enhanced by Osmocote fertilizer. However, the use of EDTA in the field should be concerned with their leaching problems.     

Lead induced changes in the growth and antioxidant metabolism of the lead accumulating and non-accumulating ecotypes of Sedum alfredii

The phytotoxicity and antioxidative adaptations of lead （Pb） accumulating ecotype （AE） and non-accumulating ecotype （NAE） of Sedum alfredii Hance were investigated under different Pb treatments involving 0, 0.02 mmol/L Pb, 0.1 mmol/L Pb and 0.1 mmol/L Pb/0.1 mmol/L ethylenediaminetetraacetic acid （EDTA） for 6days. With the increasing Pb level, the Pb concentration in the shoots of AE plants enhanced accordingly, and EDTA supply helped 51% of Pb translocation to shoots of AE compared with those treated with 0.1 mmol/L Pb alone. Moreover, the presence of EDTA alleviated Pb phytotoxicity through changes in plant biomass, root morphology and chlorophyll contents. Lead toxicity induced hydrogen peroxide （H2O2） accumulation and lipid peroxidation in both ecotypes of S. alfredii. The activities of superoxide dismutase （SOD）, guaiacol peroxidase （G-POD）, ascorbate peroxidase, and dehydroascorbate reductase elevated in both leaves and roots of AE as well as in leaves of NAE with the increasing Pb levels, but SOD and G-POD declined in roots of NAE. Enhancement in glutathione reductase activity was only detected in roots of NAE while a depression in catalase activity was recorded in the leaves of NAE. A significant enhancement in glutathione and ascorbic acid （AsA） levels occurred in both ecotypes exposed to Pb and Pb/EDTA treatment compared with the control, however, the differences between these two treatments were insignificant. The dehydroascorbate （DHA） contents in roots of both ecotypes were 1.41 to 11.22-fold higher than those in leaves, whereas the ratios of AsA to DHA （1.38 to 6.84） in leaves altering more to the reduced AsA form were much higher than those in roots. These results suggested that antioxidative enzymes and antioxidants play an important role in counteracting Pb stress in S. alfredii.     

The use of water lettuce (Pistia stratiotes L.) for rhizofiltration of a highly polluted solution by cadmium and lead

The effectiveness of heavy metal uptake from contaminated nutrient solution by four aquatic macrophytes (Pistia stratiotes L., Salvinia auriculata AubL, Salvinia minima Baker, and Azolla filiculoides Lam) was estimated in this study. The influence of cadmium (3.5 mg L(-1) and 10.5 mg L(-1)) and lead (25 mg L(-1) and 125 mg L(-1)) on the stress symptoms was observed through the determination of chlorophyll content and transpiration rate over 14 days of the experiment. The results of the present study showed extreme reductions in Cd and Pb concentrations in solution during the first 4 days. The accumulation of Pb in plant tissues was the highest during the first 4 days and was more than 10 times higher in the roots (42,862 mg kg(-1)) than in the leaves (3867 mg kg(-1)). The accumulation of Cd slowly increased and was the highest at the end of the experiment. Concentrations in roots (3923 mg kg(-1)) were roughly 6 times higher than in the leaves (624 mg kg(-1)). Results showed significant decrease in the transpiration rate at Pb treatment and a significant increase at Cd treatment during 48 hours of exposition.     

Effect of calcium on growth performance and essential oil of vetiver grass (Chrysopogon zizanioides) grown on lead contaminated soils

The aim of this study was to investigate effect of calcium on growth, survival, essential oil yield and chemical compositions of vetiver grass grown on lead contaminated soils. Calcium inform of CaCO3 (0, 2000, 4000, 6000 mg Ca kg(-1)) was added to river sand soils containing 4000 mg Pb kg(-1) dry soil. Results showed that, in the absence of calcium treatment, no plants survived after 2 weeks of cultivation, while the rest grew well to the end of the experimental period (42 weeks). Calcium treatments generally resulted in a slight decrease in biomass. Interestingly, an increase in calcium over 2000 mg kg(-1) did not result in a decrease in accumulation of lead in vetiver roots and shoots. The levels of lead in roots and shoots under calcium treatments were around 2000 and 90 mg kg(-1) dry weight, respectively. The addition of CaCO3 did not improve vetiver essential oil yield and chemical composition compared to the control. A level of applied CaCO3 about half of the lead concentration in soils was sufficient to improve vetiver growth and survival, and accumulate high concentrations of lead in the roots. This finding can be applied for re-vegetation of lead contaminated soils using vetiver.     

Preliminary study of Lead (Pb) immobilization by meat and bone meal combustion residues (MBMCR) in soil: Assessment of Pb toxicity (phytotoxicity and genotoxicity) using the tobacco model (Nicotiana tabacum var. xanthi Dulieu)

Lead (Pb) is a major chemical pollutant in the environment. The present investigation evaluates the possible use of Meat and Bone Meal Combustion Residues (MBMCR), to sequester Pb from the soil compartment using the heterozygous tobacco model (Nicotiana tabacum var. xanthi Dulieu) characterized by the a1+ /a1 a2+ /a2 system. The toxic potential of Pb-contaminations (50, 100, 1,000, 2,000 and 10,000 mg Pb kg(-1)) as Pb(NO3) in standard soil was investigated in lab conditions according to three endpoints: (i) acute toxicity of plants (mortality, height and surface area parameters), (ii) Pb-accumulation in roots, stems and leaves, and (iii) genetic effects as the expression of reversion in the leaf of plants. Moreover, chemical investigations of Pb interactions with soil were realized to complete the toxicity evaluation. The results demonstrated that: (i) MBMCR were not acutely toxic or genotoxic to tobacco plants, (ii) Pb is acutely toxic to tobacco plants at 10,000 mg Pb kg(-1) of soil, (ii) but is not genotoxic, and (iii) Pb-bioaccumulation is significant in leaves, stems and roots (from 1,000, 2,000, and 50 mg Pb kg(-1) of soil, respectively). In contrast, in the presence of MBMCR, the toxic impacts of Pb were inhibited and Pb-accumulation in tobacco plants was reduced. In complement, chemical analyses highlighted the high capacity of the standard soil to immobilize Pb. The results suggest that even if Pb is bioavailable from soils to plants, complex mechanisms could occur in plants protecting them from the toxic impact of Pb.     

一种新的铅富集植物--富集生态型东南景天

对浙江一古老铅锌矿区的土壤和植物种群进行调查后发现一种新的具有耐铅特性和铅富集能力的植物--景天科景天属东南景天(Sedum alfredii Hance),称为铅富集生态型植物.进一步比较和分析了不同浓度硝酸铅处理对富集和非富集生态型东南景天的生长及其对铅的吸收特性的影响.结果表明, 320 mg Pb/L处理对富集生态型的地上部分生长无显著影响,而非富集生态型在20 mg Pb/L时即出现受害症状.富集和非富集生态型的地上部分铅含量、根系铅含量以及单株铅积累速率均随处理浓度的增加而表现出先升后降的变化趋势.其中富集生态型的地上部分铅含量、根系铅含量以及单株铅积累速率最高可达到514 mg/kg、13 922 mg/kg和8.62 μg/plant/d,分别是非富集生态型的2.27、2.62和7.16倍.由于具有生长速度快和高积累铅的能力,从植物修复的观点来说,东南景天铅富集生态型在铅污染土壤的修复方面具有巨大的潜力.     

Lead uptake,toxicity and accumulation in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> plants

The effects of lead were investigated in bean plants (Phaseolus vulgaris L. cv. Zlota Saxa) grown hydroponically in nutrient solution and exposed to Pb(NO₃)₂ (0.1, 0.5, 1 mM) with or without equimolar concentrations of chelator ethylenediaminetetraacetic acid (EDTA). The roots treated only with Pb(NO₃)₂ accumulated up to 25 g(Pb) kg⁻¹(d.m.), during 4-d exposure. However, in bean plants exposed to 0.5 mM Pb + 0.5 mM EDTA or 1 mM Pb + 1 mM EDTA 2.5 times less Pb was determined. In bean plants treated only with Pb, less than 6 % of total lead accumulated was transported to the aboveground parts, while in the case of plants grown with Pb + EDTA, around 50 % of total Pb was transported to the shoots.     

Toxicity of arsenic (III) and (V) on plant growth, element uptake, and total amylolytic activity of mesquite (Prosopis juliflora x P. velutina)

The effects of arsenite [As(III)] and arsenate [As(V)] on the growth of roots, stems, and leaves and the uptake of arsenic (As), micro- and macronutrients, and total amylolytic activity were investigated to elucidate the phytotoxicity of As to the mesquite plant (Prosopis juliflora x P. velutina). The plant growth was evaluated by measuring the root and shoot length, and the element uptake was determined using inductively coupled plasma optical emission spectroscopy. The root and leaf elongation decreased significantly with increasing As(III) and As(V) concentrations; whereas, stem elongation remained unchanged. The As uptake increased with increasing As(III) or As(V) concentrations in the medium. Plants treated with 50 mg/L As(III) accumulated up to 920 mg/kg dry weight (d wt) in roots and 522 mg/kg d wt in leaves, while plants exposed to 50 mg/L As(V) accumulated 1980 and 210 mg/kg d wt in roots and leaves, respectively. Increasing the As(V) concentration up to 20 mg/L resulted in a decrease in the total amylolytic activity. On the contrary, total amylolytic activity in As(III)-treated plants increased with increasing As concentration up to 20 mg/L. The macro- and micronutrient concentrations changed in As-treated plants. In shoots, Mo and K were reduced but Ca was increased, while in roots Fe and Ca were increased but K was reduced. These changes reduced the size of the plants, mainly in the As(III)-treated plants; however, there were no visible sign of As toxicity.