Effect of soil chloride level on cadmium concentration in sunflower kernels

Understanding soil factors related to cadmium (Cd) uptake and accumulation in plants is important for development of agronomic technologies, and breeding strategy to produce low Cd crops. The objective of the study was to examine the effect of soluble salts (chloride and sulfate) and other soil factors on the Cd concentration in sunflower (Helianthus annuus L.) kernels. Commercial nonoilseed hybrid kernels and soils were sampled from 22 farmer's production fields in North Dakota and Minnesota. The sites sampled included saline and nonsaline variants from 7 soil series. Soils were sampled at four depths. Relationships between kernel Cd level and soil physical and chemical characteristics were examined. The soil pH covered a narrow range (7.3–8.1) at these sampled sites. Regression analysis showed that there was no correlation between kernel Cd and soil pH at any depth. The kernel Cd level was highly correlated with DTPA-extractable Cd in all 4 depths, and with clay content in sub-soils. Soil chloride and sulfate concentrations varied among soil series and within soil series. The absence of a statistically significant effect of soil sulfate level on kernel Cd concentration, indicated that soil sulfate levels did not affect Cd uptake by sunflower plants. However, soil chloride levels in sub-soil were correlated with kernel Cd. The most important soil factor was DTPA-extractable Cd. When chloride was included in the multiple regression equations, R square (R²) values improved significantly. These results demonstrate that soil chloride concentration is another important factor related to Cd uptake in sunflower plants.     

Root vs pod infection by root-knot nematodes on aflatoxin contamination of peanut

Aflatoxins are potent carcinogens produced by some Aspergillus spp. Infection of peanut (Arachis hypogaea) by root-knot nematodes (Meloidogyne arenaria) can lead to an increase in aflatoxin contamination of kernels when the plants are subjected to drought stress during pod maturation. It is not clear whether the increased aflatoxin contamination is primarily due to greater invasion of the galled pods by toxigenic Aspergillus spp. or whether root galling is also involved. Our objective was to determine the contribution of root and pod galling caused by root-knot nematodes to the increase in aflatoxin contamination in peanut. Two greenhouse experiments were conducted in which pods and roots were physically separated. Pod set was restricted to soil-filled pans (41 cm dia. x 10 cm depth), while the roots grew underneath the pan into a pot. The experiments had a factorial arrangement of treatments: pod zone with and without nematodes, and root zone with and without nematodes. In Experiment 1, 5000 eggs of M. arenaria were added to the root zone14 days after planting (DAP) and 8000 eggs were added to the pod zone 60 and 80 DAP. In Experiment 2, 3000 eggs were added to the root zone 30 DAP and 8000 eggs were added to the pod zone every week starting 60 DAP. The four treatment combinations were replicated 10 to 13 times. Conidia of Aspergillus flavus/A. parasiticus was added to the soil surface (pods zone) at mid bloom. Plants were subjected to drought stress 40 days before harvest. In Experiment 1, adding nematodes to the pod zone had no effect on aflatoxin concentrations in the peanut kernel. However, the lack of an effect may have been to due to the low occurrence of galling on the hulls. In pots where nematodes were added to the root zone, 50 to 80% of the root system was galled. Adding nematodes to the root zone increased aflatoxin concentrations in the peanut kernels from 34 ppb in the control to 71 ppb. In Experiment 2, there was heavy pod galling with galls present on 53% of the pods. Adding nematodes to the pod zone increased aflatoxin concentrations in the kernels from 19 ppb in the control to 572 ppb. Based on the results of the two experiments, it appears that infection of either the roots or pods by M. arenaria can lead to greater aflatoxin contamination of peanut kernels.     

Role of rhizosphere mechanisms in Cd uptake by various wheat cultivars

In each wheat type, cultivars have different propensities to accumulate Cd in their grains, likely depending on Cd uptake by roots and/or Cd distribution in the plant. This study investigates the processes in the root–soil interface and their role in high or low grain Cd accumulation. Twenty-four cultivars of spring bread, winter bread, durum, and spelt wheat with different grain Cd accumulation levels were investigated regarding removal of Cd from soil, pH, Cd and organic acids in root exudates, and cation-exchange capacity of roots (rootCEC). In addition, we investigated ¹⁰⁹Cd uptake from a nutrient solution resembling soil solution. The removal of Cd from the rhizosphere soil increased, likely due to increased rootCEC with increased grain Cd accumulation propensity, except in spring bread wheat. The ¹⁰⁹Cd uptake from solution did not differ between high and low grain Cd accumulators. If the soil Cd concentration was elevated, rootCEC increased, as did pH, and succinic acid levels in the exudates, while lactic and citric acid levels in root exudates decreased. This work indicates that high grain Cd accumulators take up more Cd from soil than do low accumulators. But not by a different capacity to take up Cd from soil solution. The higher rootCEC in high accumulating cultivars may influence the release of Cd from the soil particles.     

钙对镉胁迫下花生生理特性、产量和品质的影响

通过盆栽试验,选用高油品种豫花15和高蛋白品种XB023,研究了不同浓度钙对镉胁迫下不同类型花生品种营养生长、叶片叶绿素含量、光合速率、保护酶活性等生理特性及产量和品质的影响.结果表明： 施钙可以缓解镉胁迫对花生植株主茎高和侧枝长的抑制作用,增加花生植株干物质量,提高叶片叶绿素含量和光合速率,提高叶片超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）活性和可溶性蛋白质含量,降低丙二醛（MDA）的积累量,减轻镉胁迫对花生叶片的伤害;施钙可以缓解镉胁迫对花生的减产作用,增加花生荚果和籽仁产量,其增产的主要原因是增加了单株结荚数和出仁率;施钙可以促使籽仁中可溶性糖向粗脂肪和蛋白质转化,增加籽仁中脂肪和蛋白质含量,改善镉胁迫下花生籽仁品质.施钙可以降低两花生品种籽仁中镉含量,对豫花15的降低效果好于XB023.     

Accumulation and detoxification of cadmium in <Emphasis Type="Italic">Brassica pekinensis</Emphasis> and <Emphasis Type="Italic">B. chinensis</Emphasis>

The effect of excessive Cd on the growth and metal uptake by leafy vegetables Brassica chinensis L. (cv. Wuyueman) and Brassica pekinensis (Lour.) Rupr. (cv. Qingyan 87-114) were studied in hydroponic solution culture. The Cd concentration higher than 10 μM significantly decreased the root elongation and leaf chlorophyll contents of both plant species. The shoots of B. pekinensis had significantly higher concentrations of total and water-soluble Cd than B. chinensis. The roots of both species accumulated more Cd than the shoots in all the Cd treatments. Most of the Cd in the roots was found in the cell walls. The shoot/root ratio of Cd concentrations in B. pekinensis was always greater than that in B. chinensis. But, the concentration and proportion of Cd in the cell walls in B. chinensis were higher than that in B. pekinensis. Cadmium treatments also increased the concentrations of total non-protein thiols (NPT) in the shoots of the both species. A significant correlation was found between the concentrations of soluble Cd and NPT in plant shoots.     

Elucidating Cd-mediated distinct rhizospheric and in planta ionomic and physio-biochemical responses of two contrasting Zea mays L. cultivars

Cadmium (Cd) in soil–plant system can abridge plant growth by initiating alterations in root zones. Hydroponics and rhizoboxes are useful techniques to monitor plant responses against various natural and/or induced metal stresses. However, soil based studies are considered more appropriate in order to devise efficient food safety and remediation strategies. The present research evaluated the Cd-mediated variations in elemental dynamics of rhizospheric soil together with in planta ionomics and morpho-physio-biochemical traits of two differentially Cd responsive maize cultivars. Cd-sensitive (31P41) and Cd-tolerant (3062) cultivars were grown in pots filled with 0, 20, 40, 60 and 80 µg/kg CdCl₂ supplemented soil. The results depicted that the maize cultivars significantly influenced the elemental dynamics of rhizosphere as well as in planta mineral accumulation under applied Cd stress. The uptake and translocation of N, P, K, Ca, Mg, Zn and Fe from rhizosphere and root cell sap was significantly higher in Cd stressed cv. 3062 as compared to cv. 31P41. In sensitive cultivar (31P41), Cd toxicity resulted in significantly prominent reduction of biomass, leaf area, chlorophyll, carotenoids, protein contents as well as catalase activity in comparison to tolerant one (3062). Analysis of tolerance indexes (TIs) validated that cv. 3062 exhibited advantageous growth and efficient Cd tolerance due to elevated proline, phenolics and activity of antioxidative machinery as compared to cv. 31P41. The cv. 3062 exhibited 54% and 37% less Cd bio-concentration (BCF) and translocation factors (TF), respectively in comparison to cv. 31P41 under highest Cd stress regime. Lower BCF and TF designated a higher Cd stabilization by tolerant cultivar (3062) in rhizospheric zone and its potential use in future remediation plans.     

土壤类型与作物基因型对花生籽实镉积累的影响

以花生主产区的棕壤和潮土为供试土壤,以种植面积最大的白沙1016、花育22和湛油27基因型花生(Arachis hypogaea)为供试作物,采用不添加Cd(对照)和添加Cd(1.5 mg· kg-1)处理进行盆栽试验,研究土壤类型和作物基因型对花生籽实Cd积累的影响.结果表明:两种土壤对照处理的3种基因型花生籽实Cd含量均低于国家食品安全标准,而Cd处理下均高于食品安全标准.同种土壤Cd处理3种基因型花生籽实Cd含量显著高于对照,不同基因型间表现为湛油27＞白沙1016＞花育22,棕壤花生籽实Cd含量及总量均高于潮土.对照处理3种基因型花生籽实Cd生物富集系数均大于1.0,Cd处理下多小于1.0,表明花生籽实对土壤中Cd的累积能力较强,土壤Cd含量进一步增加时,其生物富集能力降低.     

土壤类型与作物基因型对花生籽实镉积累的影响

以花生主产区的棕壤和潮土为供试土壤,以种植面积最大的白沙1016、花育22和湛油27基因型花生(Arachis hypogaea)为供试作物,采用不添加Cd(对照)和添加Cd(1.5 mg·kg^-1)处理进行盆栽试验,研究土壤类型和作物基因型对花生籽实Cd积累的影响.结果表明：两种土壤对照处理的3种基因型花生籽实Cd含量均低于国家食品安全标准,而Cd处理下均高于食品安全标准. 同种土壤Cd处理3种基因型花生籽实Cd含量显著高于对照,不同基因型间表现为湛油27＞白沙1016＞花育22,棕壤花生籽实Cd含量及总量均高于潮土. 对照处理3种基因型花生籽实Cd生物富集系数均大于1.0,Cd处理下多小于1.0,表明花生籽实对土壤中Cd的累积能力较强,土壤Cd含量进一步增加时,其生物富集能力降低.     

Cadmium and zinc influx characteristics by intact corn (Zea mays L.) seedlings

Summary Cadmium and zinc uptake parameters were determined for intact corn (Zea mays L.) seedlings grown for 15 and 22 in nutrient solutions containing levels of Cd and Zn that were similar to those found in soil solutions. Uptake of both elements was assumed to follow Michaelis-Menten kinetics. Calculations were based on the concentrations of free ionic Cd (Cd²⁺) and Zn (Zn²⁺) rather than the total solution concentration. Rates of Zn uptake were measured by determining depletion of Zn for periods of up to 30 h from solutions containing initial concentrations of 1.5 and 10μmol Zn 1⁻¹. Depletion curves suggested that Zn uptake characteristics were similar at both levels of Zn in solution. The Imax for Zn uptake decreased from 550 to 400 pmol m⁻² root surface s⁻¹ between 16 and 22 d of growth while Km decreased from 2.2 to 1.5 μmol Zn²⁺ 1⁻¹. Cadmium uptake parameters were measured by controlling Cd²⁺ activities in nutrient solution betwen 6.3 to 164 nmol l⁻¹ by continuous circulation of nutrient solution through a mixed-resin system. Imax for Cd uptake was 400 pmol m⁻² root surface s⁻¹ at 15 and 22 d of growth. The magnitude of Km increased from 30 to 100 nmol Cd²⁺ 1⁻¹ during this time period. The Km value suggests that corn is efficient for Cd uptake. The results of these uptake studies are consistent with the observed uptake of Zn and Cd by corn seedlings in soils.     

Cadmium accumulation and its effects on metal uptake in maize (Zea mays L.)

The effects of different concentrations of Cd on growth of maize (Zea mays L.) and metal uptake were investigated. Cd accumulations in roots and shoots and the interactions among other metals (Mn, Fe, Cu and Zn) were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The concentrations of cadmium chloride (CdCl(2).2.5H2O) used ranged from 10(-4) M to 10(-6) M. Cd had stimulatory effects during the first 5 days on root length of Nongda No. 108 at 10(-6) M and 10(-5) M Cd concentrations. Seedlings exposed to 10(-4) M Cd solution exhibited substantial growth reduction, and root growth even stopped. Root growth of Liyu No. 6 was stimulated at concentrations of 10(-5) M and 10(-6) M Cd during the entire experiment (15 days). Cadmium inhibited root growth of Liyu No. 6 at 10(-4) M Cd after 10 days of treatment. The Cd accumulation in roots and shoots of the two cultivars increased significantly (P < 0.05) with increasing Cd concentration and duration of treatment. Cadmium concentrated mainly in the roots, and small amounts were transferred to shoots. The proportion of Cd in the roots of Nongda No. 108 decreased with increases in Cd concentrations and duration of treatment, except for the group exposed to 10(-4) M Cd. In Liyu No. 6, the proportion of Cd in the root decreased progressively with an increase in Cd concentrations. Liyu No. 6 has a greater ability to remove Cd from solution and accumulate it when compared with Nongda No. 108. Liyu No. 6 can be considered a Cd-hyperaccumulator, according to the current accepted shoot concentration that defines hyperaccumulation as 0.01% (w/w) for cadmium. This cultivar, producing many roots and a high biomass and with great ability to accumulate Cd can play an important role in the treatment of soils stressed by Cd.     

Cadmium Accumulation Retard Activity of Functional Components of Photo Assimilation And Growth of Rice Cultivars Amended with Vermicompost

Cadmium (Cd) uptake mediated alterations in functional components of photo assimilation during conversion of cow dung and poultry cast to vermicompost were studied in two Indian rice cultivars; MO 16 and MTU 7029. It was found that higher amount of Cd accumulate in plants grown in soil amended with vermicompost which in turn damaged functional components in photo assimilation. Enhancement of root growth was recognized as reason for Cd accumulation. Metabolic alterations noticed among plants were not taken place during application of raw materials used for vermicomposting such as cow dung and poultry cast amendment. Rice varieties accumulated Cd differentially where MTU 7029 accumulated more Cd compare to MO 16. It was also noticed that existence of negative correlation between zinc status of the plant and Cd accumulation.     

内生真菌与苍术粉对连作花生根际微生物区系和微量元素的影响

通过盆栽试验,研究了内生真菌拟茎点霉B3(Phomopsis liquidambari)及苍术(Atractylodes lancea)粉联合施用对连作花生根际土壤微生物区系、酶活性及有效态微量元素(Mo、B、DTPA-Fe、Zn、Cu、Mn)含量的影响。结果表明:内生真菌B3和苍术粉复合处理比内生真菌B3处理的荚果和秸秆产量分别增加10.28%和14.11%,内生真菌B3处理与正常施肥相比显著提高了根瘤数量、荚果和秸秆产重,各处理组与正常施肥对照相比分枝数和根长无显著差异。B3处理与对照相比显著提高了种子期、结荚期和成熟期根际土壤可培养细菌和放线菌数量,B3和苍术粉复合处理与对照相比显著提高种子期、花期和成熟期可培养真菌和放线菌数量;细菌DGGE指纹图谱聚类分析表明,B3和苍术粉复合处理相对于正常施肥处理,显著改变种子期、苗期、花期和成熟期花生根际土壤细菌群落结构,同时苗期、花期和结荚期的细菌条带数和香农指数也有所提高,真菌DGGE指纹图谱聚类分析表明,B3和苍术粉复合处理对真菌群落影响较大,除种子期以外的生育期真菌条带数和香农指数都有明显提高,花期真菌群落结构变化最大,相似度仅为49.6%。花生关键生育期(花期和结荚期)根际土壤脲酶和蔗糖酶活性B3处理和复合处理都显著高于正常施肥对照,促进了连作花生生态系统的物质循环和能量流动。B3和苍术粉复合处理促进了花生生长发育必需微量元素Mo、B、Fe、Zn、Mn的活化,花生叶片和籽粒中微量元素Mo、B、Fe的积累显著增加。研究结果表明,内生真菌和苍术粉联合施用能有效改善连作花生根际微生物区系,提高土壤酶活性,促进微量元素的活化和吸收,对缓解花生连作障碍具有重要意义。     

Arbuscular mycorrhiza decreases cadmium phytoextraction by transgenic tobacco with inserted metallothionein

The effect of arbuscular mycorrhiza (AM) on the phytoextraction efficiency of transgenic tobacco with increased ability to tolerate and accumulate cadmium (Cd) was tested in a pot experiment. The tobacco plants bearing the yeast metallothionein CUP1 combined with a polyhistidine cluster were compared to non-transgenic tobacco of the same variety at four Cd concentrations in soil, non-inoculated or inoculated with two isolates of the AM fungus Glomus intraradices. Mycorrhizal inoculation improved the growth of both the transgenic and non-transgenic tobacco and decreased Cd concentrations in shoots and root to shoot translocation. Differences were found between the two AM fungal isolates: one isolate supported more efficient phosphorus uptake and plant growth in the soil without Cd addition, while the other isolate alleviated the inhibitory effect of cadmium on plant growth. The resulting effect of inoculation on Cd accumulation was dependent on Cd level in soil and differed between the more Cd tolerant transgenic plants and the less tolerant non-transgenic plants. Mycorrhiza mostly decreased the phytoextraction efficiency of transgenic plants while increased that of non-transgenic plants at Cd levels in soil inhibitory to tobacco growth. Mechanisms of the observed effects of inoculation on growth and Cd uptake are discussed as well as the possible implications of the results for the exploitation of AM in phytoextraction of heavy metals from contaminated soils.     

不同质地土壤对花生根系生长、分布和产量的影响

为了探究土壤类型与花生(Arachis hypogaea)根系生长及产量之间的关系, 采用箱栽的方法, 研究了不同质地土壤(砂土、壤土、黏土)对花生根系生长、分布和产量的影响。砂土和壤土中花生根系干物质重各时期均显著高于黏土中, 但生育后期黏土中花生根系干物质重比壤土和砂土下降相对较慢。从不同类型土壤质地根系分布及根系活力来看, 黏土根系主要分布在上层土壤, 但上层土壤根系活力后期下降慢; 砂土有利于花生根系向深层土壤生长, 但上层土壤根系活力后期下降快; 而壤土对花生根系生长和活力时空分布的影响介于黏土和砂土之间。砂土有利于花生荚果的膨大, 且花生荚果干物质积累早而快, 但后期荚果干物质重积累少; 壤土的花生荚果干物质积累中后期多, 黏土则在整个生育期均不利于花生荚果干物质积累。最终荚果产量、籽仁产量和有效果数均表现为壤土最大、砂土次之、黏土最小。研究表明通气性和保肥保水能力居中的壤土更适合花生的根系生长发育及产量的形成。     

花生镉污染研究进展

花生既是世界主要的油料作物,又是重要的植物蛋白来源和食品加工原料.随着花生直接食用和食品加工的不断增加,国际上对花生籽粒Cd含量问题越来越关注.我国是世界上重要的花生生产国和出口国.近年来,花生Cd含量偏高已经成为制约我国出口贸易的重要因素.本文从花生籽粒Cd富集能力、花生Cd含量的种内差异、籽粒中Cd的分布规律、影响花生籽粒Cd积累的机制和降低花生籽粒Cd含量技术等方面,对花生Cd污染研究的现状与问题进行了论述.指出在花生Cd污染控制方面有2种策略可以考虑,一是降低花生对土壤Cd的吸收;二是控制Cd向籽粒的迁移富集.为此需要从3个方面加强对花生籽粒Cd积累机制的研究,即花生根系活性特征参数及其与籽粒Cd积累的关系;花生果荚Cd吸收机制及其对籽粒Cd含量的贡献;花生植株体内Cd迁移机制及其与籽粒Cd含量的关系.     

Differences between Bradyrhizobium strains NC92 and TAL1000 in their nodulation and nitrogen fixation with peanut in iron deficient soil

The effects of Bradyrhizobium (strains NC92 and TAL1000) and Fe supply on nodulation and nitrogen fixation of two peanut (Arachis hypogaea L.) cultivars (cv. Tainan 9 (Fe inefficient) and cv. 71-234 (Fe efficient)) grown under Fe deficient conditions (imposed by adding 40% CaCO₃ to a ferruginous soil) were examined in a glasshouse experiment. When inoculated with TAL1000 without Fe, both cultivars had low shoot N concentration, very low nodule numbers and weight and no measurable acetylene reduction activity per plant. Inoculation with NC92 without Fe increased all these parameters substantially; addition of Fe with NC92 had no further effect on N concentration but doubled nodule number, weight and acetylene reduction activity per plant. Addition of Fe with TAL1000 increased all parameters to the same level as Fe+NC92, indicating that the poorer nodulation and N₂ fixation of TAL1000 in the absence of Fe, resulted from a poorer ability in getting its Fe supply from the alkaline soil. The nodules from all treatments with measurable activity had the same specific acetylene reduction activity suggesting that Fe deficiency limited nodule development.The results support previous suggestions that Bradyrhizobium strains differ greatly in their ability to obtain Fe from soils and that selection of Fe efficient strains could complement plant breeding in the selection of legume crops for Fe deficient soils.     

Morphophysiological responses and programmed cell death induced by cadmium in <Emphasis Type="Italic">Genipa americana</Emphasis> L. (Rubiaceae)

Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings. Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l⁻¹, in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration, while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted morphophysiological changes and caused cell death in roots and leaves tissues of G. americana.     

Effect of mycorrhiza and biofertilisers on reducing the incidence of Fusarium root and pod rot diseases of peanut

Pathogenicity tests of twenty-six fungal isolates were tested on peanut plants (Giza 5 cv.) and the results revealed that, Fusarium oxysporum isolate (No. I) followed by F. solani (No. II) then F. moniliforme (No III) significantly caused highest incidence of root rot disease. Also, F. moniliforme (No III) followed by F. solani (No II) then F. oxysporum (No I) gave the highest incidence of pod rot disease. The effectiveness of vescular arbuscular-mycorrhiza (VAM) at different application rates on the incidence of root rot, pod rot diseases and plant growth parameters of peanut was studied. All soil treatments with each rate of VAM significantly reduced root and pod rot diseases compared with control (rate 0%). The best reduction in the severity of both diseases with VAM was found at the rate of 3%. Application of rhizobacterin, microbin and cerialin biofertilisers at the different concentrations decreased the severity of both root rot and pod rot severity diseases compared with non-treated seeds. The greatest reduction in both diseases was achieved at a concentration of 8/100?g seeds. The highest number of pods and fresh weight (g) was achieved in seed supplemented with each biofertiliser at concentration of 8/100?g seed.     

The phytoremediation potential of bioenergy crop Ricinus communis for DDTs and cadmium co-contaminated soil

Cadmium (Cd) and dichlorodiphenyltrichloroethane (DDT) or its metabolite residues are frequently detected in agricultural soils and food, posing a threat to human health. The objective of this study was to compare the ability of 23 genotypes of Ricinus communis in mobilizing and uptake of Cd and DDTs (p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE) in the co-contaminated soil. The plant genotypes varied largely in the uptake and accumulation of DDTs and Cd, with mean concentrations of 0.37, 0.43 and 70.51 for DDTs, and 1.22, 2.27 and 37.63 mg kg⁻¹ dw for Cd in leaf, stem and root, respectively. The total uptake of DDTs and Cd varied from 83.1 to 267.8 and 66.0 to 155.1 μg per pot, respectively. These results indicate that R. communis has great potential for removing DDTs and Cd from contaminated soils attributed to its fast growth, high biomass, strong absorption and accumulation for both DDTs and Cd.     

INCREASED CONCENTRATION OF SOIL CADMIUM AFFECTS ON PLANT GROWTH,DRY MATTER ACCUMULATION,Cd, AND Zn UPTAKE OF DIFFERENT TOBACCO CULTIVARS (NICOTIANA TABACUM L.)

Cadmium (Cd) is a toxic trace metal pollutant for humans, animals, and plants. Tobacco is a wellknown efficient accumulator of Cd and the genotypic differences in Cd uptake and the response to Cd was not determined. The objectives of this study were to investigate: 1) the effects of Cd on the growth and development of different tobacco cultivars; 2) the differences among tobacco cultivars in Cd concentration, uptake, and use for the phytoremediation of polluted soils with Cd; and (3) the interactions between Cd and Zn with respect to concentration and uptake. The Cd level affected the number of leaves and dry matter accumulation, and there were differences among the different cultivars that were used. Furthermore, some cultivars showed a higher reduction in growth than others, indicating that they are more sensitive to Cd level in the soil. Moreover, differences existed among the cultivars for the Cd concentration and uptake. There also were negative correlations between Cd and Zn concentrations; as Cd accumulation increased, Zn accumulation decreased, which showed that the two heavy metals were antagonistic. These results suggest that tobacco cultivars differed greatly in their growth and developmental responses to Cd and in the concentration and uptake of Cd and Zn. In addition, it is possible to use certain tobacco cultivars to lower the Cd concentration in the soil.