腐植酸对四溴双酚A在金鱼藻体内的富集及氧化胁迫的影响

通过室内静态模拟实验,研究了在不同浓度的腐植酸（Humic acid,HA）条件下,四溴双酚A（tetrabromobisphenol A,TBBPA）在金鱼藻中的生物富集及对金鱼藻氧化胁迫的影响。结果表明,HA的存在降低了TBBPA在金鱼藻中的富集;低浓度HA及0.5mg·L^-1TBBPA共存条件下,金鱼藻组织中自由基强度、还原型谷胱甘肽（GSH）含量以及超氧化物歧化酶（SOD）活性均恢复到对照水平;加入高浓度的HA及0.5mg·L^-1TBBPA,金鱼藻组织中自由基强度显著增加,GSH含量受到抑制,SOD活性受到显著诱导;氧化型谷胱甘肽含量没有显著差异。考虑TBBPA的生物有效性和生态毒性时,不能忽视环境因子如HA的影响。     

Cadmium accumulation in eurasian watermilfoil plants

The aquatic vascular plant Eurasian watermilfoil (Myriophyllum spicatum L.) was investigated for its potential to take up Cd from nutrient-rich water in a short-term growth and harvest regime. Eurasian watermilfoil plants were grown in and harvested weekly from 0.10M Hoagland nutrient solutions containing concentrations of Cd from 0.04 to 7.63μg Cd mL^?1. Dry weights of plants significantly decreas4ed when exposed to 7.63μg Cd mL^?1. For both 0.04 and 1.03μg Cd mL^?1 treatment the greatest concentration of Cd in plants occurred during the first two weeks. The greatest Cd concentration of Cd in plants for the 7.63μg Cd ML^?1 treatment occurred during week one and decreased through week 2. Tissue P concentration in control plants increased over time but did not increase significantly over time when plants were exposed to 0.04 and 1.03μg Cd mL^?1 levels. Tissue P concentration decreased over time when plants were exposed to 7.63μg Cd mL^?1. Stem length, root dry weights, and root number significantly increased over time in control plants and in those exposed to the 0.04 and 1.03μg Cd mL^?1 treatments. Plants treated with 7.63μg Cd mL^?1 did not grow. These results suggest that Eurasian watermilfoil would be useful for absorbing Cd from nutrient-rich water when the solution concentration was in the range of 0.04 to 7.63μg Cd mL^?1. However, in solutions having the highest concentration of Cd, the harvest regime would have to sustain plant vigor, avoid tissue Cd loss, and realize maximum uptake of Cd from solution.     

镉在两种菊芋品种中的吸收与转移特性研究

Jerusalem artichoke(Helianthus tuberosus L.) not just can be used for bioethanol production but may be potentially used in phytoremediation for the removal of heavy metal pollutants.Two Jerusalem artichoke cultivars,N2 and N5,were subjected to six cadmium(Cd) concentrations(0,5,25,50,100 and 200 mg L1) to investigate Cd tolerance and accumulation.After 21 days of growth,the effects of Cd on growth,chlorophyll content,net photosynthetic rate,intercellular CO2 concentration and malondialdehyde content were evaluated.Most growth parameters were reduced under Cd stress.The two Jerusalem artichoke cultivars had relatively high Cd tolerance and accumulation capacity(> 100 mg kg1),with N5 being more tolerant and having higher Cd accumulation than N2.Roots accumulated more Cd than stems and leaves.The bioconcentration factors(far higher than 1) and translocation factors(lower than 1) decreased with an increase in Cd applied.The results suggested that Jerusalem artichoke could be grown at relatively high Cd loads,and N5 could be an excellent candidate for phytoremediation of Cd-contaminated soils.     

Cadmium concentrations in the phloem sap of rice plants (Oryza sativa L.) treated with a nutrient solution containing cadmium

To obtain direct evidence for the translocation of cadmium (Cd) via the phloem, we measured the Cd concentrations in the phloem sap of 5-week-old rice plants (Oryza sativa L. cv. Kantou) treated with a nutrient solution containing Cd. The phloem sap was collected from the leaf sheaths through the cut ends of stylets of the brown planthopper (Nilaparvata lugens Stål.). Cd concentrations in the phloem sap from the plants treated with 10 and 100 µM Cd for 3 d were 4.6 ± 3.4 and 17.7 ± 9.8 µM, respectively. Detection of Cd in the phloem sap indicated that Cd was translocated via sieve tubes in rice plants. Cd concentrations in the xylem exudate collected from the cut basis of the leaf sheaths of the plants treated with 10 and 100 µM Cd for 3 d were 18.9 ± 6.4 and 64.2 ± 14.6 µM, respectively. Cd concentrations in the phloem sap were significantly lower than those in the xylem exudate, indicating that Cd is not concentrated during the transfer from xylem to phloem. To our knowledge, this is the first determination of Cd concentrations in the phloem sap of plants, and the first direct proof that Cd is translocated via sieve tubes in rice plants.     

Carbon costs of nitrate reduction in broad bean (Vicia faba L.) and pea (Pisum sativum L.) plants

The present study aimed at the assessment of carbon (C) costs for nitrate reduction by measuring the additional CO₂ amounts released from roots of nitrate‐fed plants in comparison with urea‐fed plants. Only roots were suitable for these determinations, because nitrate reduction in illuminated shoots is fed nearly exclusively by reducing equivalents coming directly from photosynthetic processes. Therefore, in a first experiment, the sites of nitrate reduction were determined in nodule‐free broad bean (Vicia faba L.) and pea (Pisum sativum L.) plants grown in pots filled with quartz sand and supplied with KNO₃. The extent of nitrate reduction in the various plant organs was determined by measuring in vitro nitrate reductase activity and in situ ¹⁵NO reduction. Only between 9% and 16% of nitrate were reduced in roots of German pea cultivars, whilst 52% to 65% were reduced in broad bean roots. Therefore, C costs of the process could be determined only in broad bean, using an additional pot experiment. The C costs amounted to about 4.76 mol C (mol N)^–1 or 4 mg C (mg N)^–1, similar to those measured earlier for N₂ fixation. The high proportion of nitrate reduction in shoots of pea plants implies that only very little C is required for this nitrate fraction. This can explain the better root growth of nitrate‐nourished pea plants in comparison with N₂‐fixing organisms, which need C compounds for N₂ reduction in roots. Moreover, a different availability of photosynthates in roots of plant genotypes could explain physiologically the occurrence of “shoot and root reducers” in nature.     

水体氮浓度对狐尾藻和金鱼藻片段萌发及生长的影响

为了厘清水体氮浓度对沉水植物片段萌发及生长的影响,通过模拟控制试验,设计了水体总氮浓度分别为0 (CK)、 0.5 mg/L (N1)、 2 mg/L (N2)、 8 mg/L (N3)和12 mg/L (N4）共5个处理,研究了水体不同氮浓度条件下狐尾藻 (Myriophyllum spicatum) 和金鱼藻 (Ceratophyllum demersum)片段(3节)萌芽数、 萌发位置、 芽长和生物量的差异。结果表明, 水体氮浓度对不同沉水植物片段萌发的影响存在差异,较高的水体氮浓度不利于狐尾藻片断萌发,而对金鱼藻片段却有一定程度的促进;氮浓度处理促进了狐尾藻顶端优势,却抑制了金鱼藻的顶端优势。狐尾藻以0.5 mg/L处理的芽长较长,生物量以2 mg/L处理最大;而金鱼藻以8 mg/L处理芽长最长,生物量以2 mg/L处理最大。由此可见,不同沉水植物对水体氮适应性存在差异,水体氮浓度较低时,沉水植物断枝可以进行萌发和生长, 而当氮浓度超过2 mg/L时,对沉水植物断枝萌发及生长反而有抑制作用;金鱼藻片段比狐尾藻对水体氮浓度的耐受性强。     

Improving iron bioavailability and nutritional value of maize (Zea mays L.) in sulfur-treated calcareous soil

Soil factors such as pH, calcium, carbonate, and bicarbonate precipitation products in calcareous soils reduce iron (Fe) availability to crops and limit grain Fe concentrations. In the present greenhouse study, we evaluated the potential of Fe fertilizer amendments combined with organic amendments, like biochar (BC) and poultry manure, in sulfur (S)-treated low pH calcareous soils (pH_S1) to assess Fe biofortification of maize. Elemental sulfur (S) was used both for lowering soil pH and Fe solubilization. Soil pH was successfully lowered down from 7.8 to 6.5 by S application at the rate of 2.5 g kg^?1 soil. Pot experiment results revealed that Fe fertilizer combined with BC and S (pH_S1) significantly increased root and shoot dry weight, grain weight, photosynthetic rate, transpiration rate, and stomatal conductance by 69%, 86%, 28%, 74%, 57%, and 33%, respectively, relative to the control. Similarly, combined application of Fe + BC in S-amended (pH_S1) soil increased starch (34%), protein (64%), and fat (1 fold) while antinutrient phytate and polyphenols were decreased up to 29% and 40%, respectively, over control. Regarding the maize nutrients profiles, application of Fe with BC gave the maximum increase of Fe and ferritin was increased 1.7 fold at pH_S1. The results of this study showed that Fe fertilization with BC at pH_S1 soil is beneficial for crop growth and Fe bioavailability.     

Cadmium uptake by Lupinus albus (L.): Cadmium excretion,a possible mechanism of cadmium tolerance

Cadmium (Cd) uptake by white lupin (Lupinus albus) was studied at low Cd concentrations (0.05nM to 5 μM) in hydroponic solution. Ten 12‐day old seedlings were pretreated in 0.5 mM CaCl₂ solution in presence and absence of metabolic inhibitors (DCCD, DNP or NaN3). Cadmium solutions were labelled with carrier free ¹⁰⁹CdCl2. Cadmium uptake was measured after a 2 h desorption in unlabelled CdCl2 solution. In the absence of any metabolic inhibitor and at 5 [μM Cd, roots absorbed 235.23 μg Cd/g root dry weight. Over the range of lnM to 5 μM Cd, exchangeable Cd represented approximately 5% of the absorbed fraction, and about 25 % of the total absorbed Cd was adsorbed to the root. Cadmium was passively absorbed to about 30% as observed in the presence of the inhibitor (DCCD). Ative absorption which represented 70% of Cd uptake involved H⁺‐ATPase carriers. Cadmium absorption was reduced to 30 and 20% in presence of lanthanum (La³⁺) and zinc (Zn²⁺), respectively which suggested that calcium (Ca), Cd, and Zn use the same carriers. Cadmium uptake in presence of DNP or NaN3 was approximately 4‐ fold that in control. Data showed presomption for an excretion of Cd out of root cells which could be the expression of a detoxification process limiting cell contamination.     

Dynamic influence of S fertilizer on Cu bioavailability in rice (Oryza sativa L.) rhizosphere soil during the whole life cycle of rice plants

Journal of Soils and Sediments - Addition of S fertilizer influences the behavior of metals in soil, the mechanism of which has not been extensively studied to date. We explored the dynamic...     

镉胁迫下小麦根系的生理生态变化

本文通过水培和砂培两种方法 ,研究了镉胁迫下小麦 (TriticumaestivmL .)根系的生理生态变化。通过研究镉对小麦根系生长发育状况 ,根系活力 ,根系对矿质元素的吸收 ,探讨镉胁迫下植物根系的生理生态效应。研究结果表明 :镉影响根系的长度、生物量、体积和根系活力。Cd2 + 在低浓度 (处理浓度低于 5mg/L)作用下 ,随处理浓度的升高 ,刺激小麦根系的长度、生物量、体积相应地升高 ;当处理浓度高于相应浓度时 ,根长度、生物量、体积相应随浓度升高而降低。镉胁迫下根系活力受到抑制。水培和砂培中 ,镉对根系的影响趋势一致 ,但是影响幅度有差异。砂培好于水培。镉影响小麦根对矿质元素的吸收 ,Ca、Cu、Fe、K、Mg、Mn、Na、Zn吸收情况不太一致。Ca、Cu、Fe、Mg、Mn、Na的吸收量随Cd2 + 浓度升高而增加 ,K、Zn的吸收量随Cd2 + 浓度升高而减少     

Effect of humic acid amendment on cadmium bioavailability and accumulation by pak choi (Brassica rapa ssp. chinensis L.) to alleviate dietary toxicity risk

Cadmium (Cd) contamination in soil and its movement into food chain through vegetable dietary poses a risk to human health. A pot experiment was conducted to investigate the effect of humic acid (HA) and two cultivars of Brassica rapa ssp. chinensis L. (pak choi) with differing Cd accumulation abilities on Cd accumulation in different Cd contaminated Ferralsol, Histosol and Luvisol soils. The results showed that HA significantly increased soil pH and cation exchange capacity in Ferralsol (acidic) and Histosol (neutral) soils. HA was more effective in Ferralsol and Histosol soil in reducing bioavailable Cd and its accumulation in both cultivars. Low and high Cd accumulating cultivars combined with HA effectively reduced shoot Cd concentration by 7–34% and 19–35% in Histosol soil, whereas 22–34% and 11–26% in Ferralsol soil, respectively. However, no such reduction was observed for Cd accumulation and bioavailability in Cd-contaminated Luvisol (alkaline) soil. Application of HA enhanced shoot dry biomass in both cultivars grown in Histosol and Ferralsol soils. Therefore, the HA amendment combination with low Cd accumulating cultivars of pak choi could be an effective method for phytostabilization and reduce health risks associated with consuming this vegetable grown in Cd-contaminated acidic and neutral pH soils.     

Site of nitrogen accumulation in tulip (Tulipa gesneriana L.) roots during winter

Abstract

Plants (60 species in 37 genera, 27 families) grown on granite weathered soils of temperate natural forest in central Japan were sampled and analyzed for Fe, Mn and Cu. Soil samples coIlceted from the site of plant stands were also analyzed. Results showed that considerable difference existed amons plant species with less variations amons plant samples of the same plant species. Similar responses were frequently found among plant species in the same genus and sometimes in the same family. Variations due to soU also occurred but to a lesser degree. Pe, Mn and Cu were generaIly low in coniferous trees. On the other hand Acantiropanax sciadophylloides accumulated higher amount of Mn in the leaves (4.6 × 10³ ppm, dry matter basis) which is about 180 times more than that of low content species. Other Mn accumulating species were found in Anacardiaceae and Aceraceae. Cryptomeria japonica was the lowest in Mn content (26 ppm). Mean concentration ratio for Mn was 113. Cu was found to be slightly rich in scattering species including Lastrea japonica, Magnolia salleifolia, Acer mono var. connivens and Callicarpa japonica. Mean concentration ratio for Cu was 17.     

Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

不同基因型小白菜硝酸盐积累差异及筛选研究

采用溶液培养方法研究了43种基因型小白菜在不同硝铵比条件下体内硝酸盐含量的变化情况。结果表明,不同基因型小白菜的硝酸盐含量差异较大,东妃青梗菜、上海白叶四月蔓和夏优高抗为低硝酸盐含量基因型小白菜,而高雄甜脆小白菜、宝大矮棋青和苏州青为高硝酸盐含量基因型小白菜。硝铵比50/50是最适宜筛选的氮素形态比例,而叶片中的硝酸盐含量也是最适宜的筛选指标。对上述6个基因型小白菜进一步分析结果表明,不同部位硝酸还原酶、根系硝态氮最大吸收速率以及亲和力这三个因素对小白菜各部位的硝酸盐积累都有显著的影响,但在不同部位,这三个因素所起的贡献率不同。     

三种类型阻控剂对不同品种水稻富集镉的影响

如何降低水稻中镉(Cd)的含量已经成为一个研究热点。在湖南省衡阳县某地受轻度镉污染的农田上种植两季水稻(早稻、晚稻),随机采购市场上销售的阻控剂(石灰、硅肥和叶面锌肥),研究这3种类型阻控剂对水稻富集镉及稻谷中镉含量的影响,这3种类型的阻控剂的施用方式是石灰和硅肥作为基肥施于土壤,叶面锌肥通过叶面喷施。结果表明:与没有施加阻控剂相比,除石灰和晚稻锌处理之外,其他处理增产效果显著。在3种类型的阻控剂中,叶面锌肥对籽实富集镉的阻控效果最佳,分别使早稻Y俩优792和晚稻农香130降低了51.28%和50.92%,基施硅肥阻镉效果次之。田间试验结果进一步表明施硅肥和喷施叶面锌肥可作为当地的水稻镉污染阻控剂,但叶面锌肥与稻谷中镉的交互作用需要更深入的探讨。     

盐胁迫下氮素形态对油菜和水稻幼苗离子运输和分布的影响

【目的】土壤盐碱化是制约农作物产量的主要因素之一,盐胁迫影响养分运输和分布,造成植物营养失衡,导致作物发育迟缓,植株矮小,严重威胁着我国的粮食生产。在必需营养元素中,氮素是需求量最大的元素,NO-3和NH+4是植物吸收氮素的两种离子形态。植物对盐胁迫的响应受到不同形态氮素的调控,研究不同形态氮素营养下植物的耐盐机制对提高植物耐盐性及产量具有重要的意义。【方法】本文以喜硝植物油菜(Brassica napus L.)和喜铵植物水稻(Oryza sativa L.)为试验材料,采用室内营养液培养方法,研究了NO-3和NH+4对Na Cl胁迫下油菜及水稻苗期生长状况、对Na+运输和积累的影响,以对照与盐胁迫植株生物量之差与Na+积累量之差的比值,评估Na+对植株的伤害程度。【结果】1)在非盐胁迫条件下,硝态氮营养显著促进油菜和水稻根系的生长;盐胁迫条件下,油菜和水稻生物量均显著受到抑制,Na Cl对供应铵态氮营养植株的抑制更为显著。2)盐胁迫条件下,两种供氮形态下,油菜和水稻植株Na+含量均显著增加,硝态氮营养油菜叶柄Na+显著高于铵态氮营养,叶柄Na+含量/叶片Na+含量大于铵营养油菜,硝态氮营养水稻根系Na+含量显著低于铵营养,地上部则相反。3)铵营养油菜和水稻Na+伤害度显著高于硝营养植株。4)盐胁迫条件下,硝态氮营养油菜地上部和水稻根系K+含量均显著高于铵态氮营养。5)盐胁迫条件下,硝营养油菜和水稻木质部Na+浓度,韧皮部Na+和K+浓度及水稻木质部K+浓度均高于铵营养植株。【结论】与铵营养相比,硝营养油菜和水稻具有更好的耐盐性。硝态氮处理油菜叶柄Na+显著高于铵态氮处理,能够截留Na+向叶片运输。同时,供应硝态氮营养更有利于油菜和水稻吸收K+,有助于维持植物体内离子平衡。盐胁迫下,硝营养油菜和水稻木质部Na+浓度,韧皮部Na+和K+浓度及水稻木质部K+浓度均高于铵营养植株,表明硝态氮营养油菜和水稻木质部-韧皮部对离子有较好的调控能力,是其耐盐性高于铵营养的原因之一。     

Ferrous and ferric iron ratio in normal and chlorotic bean plants (Vicia faba L.)

The objective of this study was to determine the ratio and amount of Fe II and Fe III iron in different parts of 20 and 40 day old bean plants grown in pots under normal and HCO-treatment. The Fe II and Fe III iron determination was carried out by a modification of a method described by Vogel (1969). The Fe II and Fe III concentrations in the plant varied according to its age, the plant part, the order of leaves and HCO-treatment. At the second sampling date, the lower total iron content in the lower leaf particularly under the HCO-treatment suggests that the supply of iron from the roots was restricted. The iron content of the different leaves was almost evenly divided into Fe II and Fe III at the first date. At the second date, most of the iron in the bud leaf was present as Fe II. Under HCO-treatment the Fe II content of the bud leaf and the flower was similar as in the corresponding parts of the normal green plants whereas the Fe III content was considerably lowered in these plant parts as result of the HCO-treatment. The results indicate a substantial retranslocation of iron from older to younger leaves and a higher Fe II/Fe III ratio in flowers and bud leaves particularly under HCO-induced chlorosis.     

Improvement of drought tolerance in Tobacco (Nicotiana rustica L.) plants by Silicon

Ameliorative effect of silicon (Si) (2 mM as sodium silicate (Na₂SiO₃)) was studied in tobacco (Nicotiana rustica L.) plants grown under control at 100% field capacity (FC), mild drought (60% FC), and severe drought (30% FC) conditions. Si-treated plants had higher biomass of particularly above-ground parts both under drought and control conditions. Plants with Si supply had significantly higher net assimilation rates but lower transpiration rates. Silicon supply enhanced osmotic potentials only in the leaves, but not in the roots. A considerable rise in the concentrations of soluble sugars was observed particularly in the leaves under both drought and Si treatments. Soluble proteins, free α-amino acids, and proline concentrations increased in Si-treated plants under all watering treatments. Si enhanced the activity of antioxidative enzymes and decreased hydrogen peroxide (H₂O₂) concentrations. Results indicate that Si supplementation alleviates drought stress via improvement of water relation parameters, enhancement of photosynthesis, and elevation of antioxidant defenses.     

Influences of Cadmium and Zinc Interaction and Humic Acid on Metal Accumulation in Ceratophyllum Demersum

Interactions between Zn and Cd on the accumulation of these metals in coontail, Ceratophyllum demersum were studied at different metal concentrations. Plants were grown in nutrient solution containing Cd (0.05–0.25 mg l^?1) and Zn (0.5–5 mgl^?1). High concentrations of Zn caused a significant decrease in Cd accumulation. In general, adding Cd solution decreased Zn accumulation in C. demersum except at the lowest concentration of Zn in which the Zn accumulation was similar to that without Cd. C. demersum could accumulate high concentrations of both Cd and Zn. The influence of humic acid (HA) on Cd and Zn accumulation was also studied. HA had a significant effect on Zn accumulation in plants. 2 mg l^?1 of HA reduced Zn accumulation at 1 mg l^?1 level (from 2,167 to 803 mg kg^?1). Cd uptake by plant tissue, toxicity symptoms and accumulation at 0.25 and 0.5 mg l^?1, were reduced (from 515 to 154 mg kg^?1 and from 816 to 305 mg kg^?1, respectively) by addition of 2 mg l^?1 of HA. Cd uptake reached a maximum on day 9 of treatment, while that of Zn was observed on day 15. Long-term accumulation study revealed that HA reduced toxicity and accumulation of heavy metals.