不同铅水平下紫茎泽兰细胞内铅的分布和化学形态的分析

该研究运用差速离心法和化学试剂逐步提取法,分析了重金属铅在紫茎泽兰亚细胞内的分布和主要化学形态。结果表明:随着Pb浓度的升高,紫茎泽兰的叶、根、茎中各亚细胞组分Pb含量逐渐增加;紫茎泽兰中的Pb在叶片分布于可溶性部分和细胞壁中,两者占总量的75.34%~84.63%;茎也主要分布于可溶性部分和细胞壁中,占总量的36.10%~57.14%和20.07%~36.52%;而在根中则富集于细胞壁和可溶性部分,分别占39.2%~49.78%和28.27%~37.62%,其他细胞器中的Pb含量均较少。紫茎泽兰叶中的Pb以盐酸提取态和水提取态为主,两者占总量的58.74%~73.04%;茎中的Pb以醋酸提取态和氯化钠提取态为主;而根中的Pb则以醋酸提取态和盐酸提取态占优势,两者占总量的39.15%~52.91%。     

不同类型镉积累水稻细胞镉化学形态及亚细胞和分子分布

利用水培试验结合亚细胞组分分级分离和凝胶过滤等技术，研究了水稻根和叶中镉的化学结合形态及其亚细胞和分子分布，比较了低镉积累品种“广源占No.3”和高镉积累品种 “珍桂矮”的差异.结果表明：随着营养液中镉浓度的升高，根和叶亚细胞镉含量显著上升，大部分镉积累在细胞壁（F_Ⅰ）和细胞可溶部分（F_Ⅲ）.高镉积累品种“珍桂矮”根和叶中可溶部分镉含量显著高于低镉积累品种“广源占No.3”.根和叶各种形态镉中，以氯化钠提取态占优势，其次是醋酸提取态，盐酸提取态镉含量最低.与“广源占No.3”相比，“珍桂矮”中迁移性较强的去离子水和乙醇提取态镉比例较高.凝胶过滤结果表明，两种类型的水稻可溶部分镉的出峰位置与样品流份中可溶性蛋白的出峰位置大致相同.可溶部分中的镉大多与分子量为3kD的物质结合，属于植物鳌合肽（PCs）或低分子量物质.“广源占No.3” 根系中镉与PCs配合的组分（Cd-PCs）含量远小于“珍桂矮”.“广源占No.3”细胞可溶部分较低的镉含量以及根系中较少的Cd-PCs形成量，降低了镉的移动及其向地上部转运的可能性.     

镉在旱柳中亚细胞分布及存在的化学形态

以2个旱柳无性系幼苗为材料,通过营养液培养并结合差速离心与化学试剂提取法,分析了不同浓度Cd2+胁迫下旱柳叶和根中Cd的亚细胞分布及其存在的化学形态.结果显示,(1)随着培养介质Cd2+浓度升高,旱柳无性系幼苗叶和根中各亚细胞组分Cd含量随之增加.叶片的Cd主要富集于细胞壁、叶绿体和可溶性部分,它们的含量分别占65%～69%、14%～22%、6.8%～7.7%,仅少量Cd发现于膜部分;而根中Cd主要积累于细胞壁和可溶性部分,其中含量分别占59%～66%和14%～25%,Cd在根亚细胞组分中积累量依次为细胞壁>可溶性部分>质体>膜部分.(2)旱柳体内Cd以不同的化学形态存在,大部分为HCl(FHCl)、NaCl(FNaCl)、醋酸(HAC,FHAC)提取态,极少部分为乙醇(EtOH,FEtOH)和水提取态(Fwater),叶和根中5种Cd提取态含量依次为FHCl>FNaCl>FHAC>Fwater>FEtOH,而叶和根中HCl和NaCl提取态Cd占有比例大于30%以上.研究表明,旱柳无性系中Cd主要与蛋白质和有机酸螯合或以金属磷酸盐沉淀的形态存在,其根、叶的细胞壁和液泡在Cd忍耐与解毒中起到重要作用.     

镉在不同类型蕹菜(Ipomoea aquatica Forsk.)中的积累及其化学形态和分子分布

采用水培幼苗试验研究不同蕹菜品种("台湾308"和"强坤青骨")Cd的积累及其化学形态和分子分布。结果表明,1.0 mg·L-1Cd浓度处理下,"台湾308"和"强坤青骨"叶、茎、根Cd含量分别为3.17、3.55、39.1和2.06、2.35、33.5 mg·kg-1;5.0 mg·L-1Cd浓度处理下,"台湾308"和"强坤青骨"叶、茎、根Cd含量分别为3.75、4.15、55.8和2.68、3.43、83.7 mg·kg-1。2个蕹菜品种Cd化学结合形态研究表明,叶中以乙醇提取态为主,茎、根中以乙醇和氯化钠提取态为主。"台湾308"叶、茎、根中活性较强的水提取态Cd所占比例均明显高于"强坤青骨",而醋酸和盐酸提取态Cd所占比例均明显低于"强坤青骨"。Cd处理水平和蕹菜品种类型对体内Cd化学结合形态均有一定影响,在根中表现尤为明显。分子分布结果表明,蕹菜叶片可溶部分中的Cd大部分与高分子量化合物和小分子量物质相配合,而根中可溶部分的Cd主要与植物螯合肽(PCs)和分子量为10~20 kDa的蛋白质结合。"强坤青骨"根系中Cd与PCs配合的组分(Cd-PCs)含量小于"台湾308",降低了Cd向地上部转运的可能性,进而成为其地上部分Cd含量较低的原因之一。     

复合胁迫下茭白体内镉、铅的亚细胞分布和植物络合素的合成

以茭白（Zizania latifoliaTurcz.）的单季茭品种‘蒋墅茭’和双季茭品种‘葑红早’为试材,进行Cd2＋、Pb2＋的单一及复合胁迫处理,测定了茭白根系和叶片中的非蛋白巯基（NPT）、谷胱甘肽（GSH）、植物络合素（PCs）的含量,同时测定了茭白植株各亚细胞组分中Cd2＋、Pb2＋的积累量,以探讨茭白对重金属镉、铅胁迫的耐性机理。结果表明：Cd2＋、Pb2＋的单一及其复合胁迫均能促进两茭白品种根系和叶片中NPT、GSH、PCs的含量及茭白各亚细胞组分中Cd2＋、Pb2＋积累量的显著增加;复合胁迫时两茭白品种的NPT、GSH、PCs含量及各亚细胞组分中Cd2＋、Pb2＋的积累量均高于单一胁迫,茭白的不同部位间,以根系中的NPT、GSH、PCs含量显著高于叶片;茭白各亚细胞组分中Cd2＋、Pb2＋的积累量表现为：细胞壁高于原生质体,而可溶性部分高于细胞器。     

寒潮过程中4个茶树品种光合特性和保护酶活性变化及品种间差异

以茶树品种龙井43号(Longjing No.43)、鸠坑(Jiukeng)、乌牛早(Wuniuzao)、福鼎大白茶(Fortin white tea)为试材,研究了一次寒潮过程对4个茶树品种叶片的光合特性、叶绿素荧光参数和保护酶活性的影响,并利用主成分分析方法确定4个茶树品种的抗寒性。结果表明:寒潮初期,随着气温的降低,4个茶树品种的叶绿素含量、最大光合速率(P_(max))、表观量子效率(AQY)、最大光化学量子产量(Fv/Fm)、非光化学淬灭(q N)均呈现下降趋势,在气温回升期间随气温升高而有所增加,且福鼎大白茶的叶绿素含量、P_(max)、AQY、Fv/Fm的值为4个品种中最大,q N的平均值以乌牛早为最小,鸠坑最大;4种茶树的过氧化物酶(POD)活性在寒潮及恢复期间持续增强;4种茶树POD活性的平均值以龙井43号最小,福鼎大白茶最大;叶片的气孔限制值(Ls)和丙二醛(MDA)含量在降温和气温回升过程中,表现出先增加后降低的趋势,整个期间的Ls和MDA含量的平均值以福鼎大白茶为最小,龙井43号最大;利用主成分分析法对4品种茶树的光合参数、荧光参数和抗氧化酶活性进行分析,得到4个品种茶树的抗寒性顺序为:福鼎大白茶乌牛早鸠坑龙井43号。研究结果为茶树的引种及茶叶生产布局提供理论依据。     

低温对茶树叶片膜脂脂肪酸和蛋白质的影响

本文研究低温胁迫过程中龙井43 和大叶云峰叶片膜脂脂肪酸的变化。结果发现,低温下不同品种茶树叶片膜脂脂肪酸配比变化趋势不同,较抗寒的龙井43,不饱和脂肪酸指数(IUFA)和亚麻酸(183)比例随低温期间不同阶段呈现出“低—高—低”的变化趋势;而不抗寒的大叶云峰的变化趋势无明显规律性。此外,还研究了越冬过程中龙井43 叶片可溶性蛋白和膜蛋白的变化,发现低温期间龙井43 叶片可溶性蛋白含量和组分基本稳定,而膜蛋白含量在低温胁迫时大幅度上升,且经低温诱导出现了46KD、38KD 两种新的蛋白组分,并在温度升高后消失。     

霞多丽苗木中镉的积累、亚细胞分布及化学存在形态

以一年生盆栽葡萄品种霞多丽(Vitis vinifera L.cv.Chardonnay)自根苗及SO4砧嫁接苗为试材,采用CdCl2和CaCl2根部灌入的方法,研究了镉在霞多丽植株内的亚细胞分布和存在形态,以及外源添加氯化钙对植株镉吸收的影响.结果表明:大部分镉积累在霞多丽自根苗及嫁接苗的地下部器官;4 mmol·L-1浓度的CdCl2处理下,镉在自根苗根及根颈部分的积累量占77.1％,在叶片中的积累量占1.4％,而嫁接苗中镉在嫁接口以下部分的积累量高达93.9％,叶片中的积累量仅占0.1％;5 mmol·L-1外源钙缓解了植株对镉的吸收积累,而10mmol ·L-1外源钙则显著增加了植株对镉的吸收积累.镉在根系和叶片中的亚细胞分布规律为细胞壁＞可溶性部分＞细胞器,且在细胞壁中积累50％以上;镉在根系中主要以氯化钠提取态存在,其次为乙酸提取态,去离子水提取态含量最少.随着镉处理浓度的增加,各提取态含量有所变化.     

两种生态型香根草对镉的耐受和积累特性比较

以Monto和Veriveria nermorlis两种生态型香根草［Chrysopogon zizanioides (L.) Roberty］为材料,采用室内水培试验,在不同浓度(0、200、800、2 000 μmol·L^-1)硝酸镉溶液处理7 d后,比较、分析两类型香根草的叶片生长状况、叶绿素荧光参数、镉的积累、亚细胞分布和化学形态分布等指标的差异,明确两类香根草对镉的耐受能力和积累特性。结果表明,(1)在中度(800 μmol·L^-1)和重度(2 000 μmol·L^-1)镉胁迫条件下,Monto的叶片生长状况优于Veriveria nermorlis,其F_m、F_v/F_m和F_v/F_o等叶绿素荧光参数显著高于Veriveria nermorlis,而其叶片、根部镉含量、富集系数和镉转移系数则显著低于Veriveria nermorlis。(2)镉主要分布在香根草根和叶细胞壁组分和可溶性组分中,两者镉含量占比之和达95%以上;对于两种生态型香根草的叶片和Monto的根部而言,细胞壁组分和可溶组分镉占比随着镉胁迫浓度增加分别呈增加和下降趋势,但两参数在Veriveria nermorlis根中的变化趋势则相反;Monto叶中细胞壁组分的镉占比要高于Veriveria nermorlis。(3)镉的化学形态分布分析显示,两种生态型香根草叶片中以氯化钠提取态镉为主,而根中以乙醇提取态和氯化钠提取态镉为主;Monto根中乙醇提取态的镉含量占比远大于Veriveria nermorlis。研究发现,Monto香根草的镉耐受能力较强,主要因为其根、叶中的镉积累量、镉富集系数和转移系数均低于Veriveria nermorlis,且Monto叶片中细胞壁组分的镉占比和根中乙醇提取态镉的占比更高。     

镉在水生植物中的富集与亚细胞分布及其化学形态特征

以7种水生植物(长苞香蒲、水生美人蕉、黑藻、粉绿狐尾藻、花叶芦竹、香根鸢尾、水葫芦)为研究材料,构建生物塘系统,通过差速离心法和五步提取法,提取植物各亚细胞组分和不同化学形态的镉,并用原子吸收分光光度法测定镉含量,分析镉在水生植物体中富集特征,揭示植物对镉的耐性机制。结果表明:(1)水生植物根中镉富集量大于茎和叶;3种类型水生植物富集镉能力表现为沉水植物(粉绿狐尾藻、黑藻)浮水植物(水葫芦)挺水植物(长苞香蒲、水生美人蕉、花叶芦竹、香根鸢尾)。(2)镉在黑藻、水葫芦和花叶芦竹中的亚细胞分布量均呈现为细胞壁可溶组分原生质体线粒体,所占比例分别为37.16%~50.86%、20.69%~31.21%、10.81%~23.83%、8.15%~19.83%。(3)赋存化学形态表现为以氯化钠提取态、醋酸提取态为主,所占比例分别为29.37%~56.27%和15.06%~36.19%。研究发现,粉绿狐尾藻、水葫芦、水生美人蕉和花叶芦竹4种植物为富集镉较好的植物,而黑藻、香根鸢尾和长苞香蒲3种植物的镉富集能力相对较弱;镉主要以果胶酸盐、蛋白质结合态或吸附态存在于植物根的细胞壁和液泡中,以减弱镉对根细胞器和植物地上部分的毒害。     

Characteristics of distribution and chemical forms of Pb in tea plant varieties

A hydroponics experiment combined with subcellular fractionation and sequential extraction was conducted to study the Pb concentration in different organs of two tea plant varieties (Longjing 43 and Yingshuang) and the Pb subcellular distribution and chemical forms in the roots of the varieties. Under Pb stress, the root system of the two varieties had different features in morphology. With the increasing concentration of Pb in culture solution, the Pb concentration in Longjing 43 young leaves increased, but that in Yingshuang' s had no significant variation. A marked difference was observed in the Pb subcellular distribution and its chemical forms in roots between the two varieties under Pb stress. In Longjing 43 roots, all subcellular fractions except soluble ones had a lower Pb concentration at low Pb stress, and all the subcellular fractions except cell wall ones had a higher Pb concentration at higher Pb stress, compared with those in Yingshuang's. In Longjing 43 roots, the HAc-extractable Pb occupied the greatest proportion, followed by NaCl-extractable Pb, HCl- and H2O- extractable Pb, and ethanol-extractable Pb; while in Yingshuang's, NaCl-extractable Pb had the greatest proportion, followed by HAc-extractable Pb, HCl- and H2O-extractable Pb, and ethanol-extractable Pb. Based on these findings, tea plant variety Yingshuang was likely to possess a higher tolerance to Pb than Longjing 43 did.     

不同蚕豆品种对铅污染的光合生理响应特征

以3个蚕豆品种(分别为K0883、K0502、K0697)为试验材料,通过大田模拟小剂量Pb污染(浓度为40和250 mg·kg^-1),研究了净光合速率、气孔导度、蒸腾速率、细胞间隙CO₂浓度、水分利用效率、叶绿素含量等光合生理响应特征的变化在不同品种中的差异.结果表明,Pb污染下3个蚕豆品种气孔导度和蒸腾速率没有显著变化,叶绿素含量有不同程度的上升;在250 mg·kg^-1 Pb浓度下,K0883蚕豆品种净光合速率、水分利用效率、细胞间隙CO₂浓度分别升高121.80％、上升193.70％、下降42.76％.3个蚕豆品种对Pb污染的抗性大小顺序为K0883＞K0697＞K0502.蚕豆不同光合生理指标对小剂量Pb污染的响应特征不同.不同蚕豆品种对小剂量Pb污染的响应特征存在差异,这种种内的差异性采用单个生理指标难以反映,只有通过对多个指标的整合分析才能表现出来.     

Variations in Metal Tolerance and Accumulation in Three Hydroponically Cultivated Varieties of Salix integra Treated with Lead

Willow species have been suggested for use in the remediation of contaminated soils due to their high biomass production, fast growth, and high accumulation of heavy metals. The tolerance and accumulation of metals may vary among willow species and varieties, and the assessment of this variability is vital for selecting willow species/varieties for phytoremediation applications. Here, we examined the variations in lead (Pb) tolerance and accumulation of three cultivated varieties of Salix integra (Weishanhu, Yizhibi and Dahongtou), a shrub willow native to northeastern China, using hydroponic culture in a greenhouse. In general, the tolerance and accumulation of Pb varied among the three willow varieties depending on the Pb concentration. All three varieties had a high tolerance index (TI) and EC50 value (the effective concentration of Pb in the nutrient solution that caused a 50% inhibition on biomass production), but a low translocation factor (TF), indicating that Pb sequestration is mainly restricted in the roots of S. integra. Among the three varieties, Dahogntou was more sensitive to the increased Pb concentration than the other two varieties, with the lowest EC50 and TI for root and above-ground tissues. In this respect, Weishanhu and Yizhibi were more suitable for phytostabilization of Pb-contaminated soils. However, our findings also indicated the importance of considering the toxicity symptoms when selecting willow varieties for the use of phytoremediation, since we also found that the three varieties revealed various toxicity symptoms of leaf wilting, chlorosis and inhibition of shoot and root growth under the higher Pb concentrations. Such symptoms could be considered as a supplementary index in screening tests.     

Lead bioaccumulation,subcellular distribution and chemical form in sugarcane and its potential for phytoremediation of lead-contaminated soil

Abstract

Sugarcane is a promising species for lead (Pb) phytoextraction due to its large biomass and high tolerance toward Pb content. To understand the mechanisms involved in Pb tolerance and detoxification and its potential for phytoremediation in sugarcane, the bioaccumulation, subcellular distribution, and chemical forms of Pb in different tissues were investigated through pot cultivation sugarcane with increasing Pb concentrations in the present study. Results showed that sugarcane could tolerate high concentrations of Pb (up to 1250.0–1750.0?mg/kg); the Pb content in roots and shoots increased with increasing Pb concentration. A large amount of Pb content was stored in roots. The subcellular distribution of Pb in sugarcane revealed that the majority of Pb was bound to the cell wall. Meanwhile, the greatest amount of Pb was extracted by 2.0% acetic acid and 0.6?mol/L HCl, which indicated that most of Pb was combined with undissolved phosphate and oxalate. These results implied that the Pb formation of undissolved salts and compartmentalization in the cell wall may be a key strategy for Pb detoxicity and tolerance in sugarcane.     

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.     

玉米各器官积累Pb能力的品种间差异

 为了研究不同玉米（Zea mays）品种及不同器官对Pb积累能力的差异,在土壤Pb含量为595.55 mg•kg－1 的高Pb胁迫和含量为195.55 mg•kg－1的低Pb胁迫（对照）条件下,采用盆栽试验结合火焰原子吸收等方法,测定了25个玉米品种各器官Pb的含量。结果表明：Pb 胁迫下供试玉米品种各器官含Pb量表现为根>茎≌叶>籽实;与对照相比,根、茎、叶Pb含量均大幅度提高,籽实含量的提高幅度相对较小;Pb胁迫条件下,有近半数的供试玉米品种的籽实Pb含量超过了国家规定的卫生标准,显示了在受重金属污染农田生产的玉米产品存在着较高的受Pb污染的风险。有22个品种平均籽实生物量在较强Pb胁迫下有所下降,降幅为0.9% ～ 38.7%,但平均降幅仅为12.6%,显示玉米在Pb胁迫下的减产不易察觉,从而增加了在受污染农田中玉米产品受Pb污染的风险。但研究也表明,在较高Pb胁迫下尚有52%的品种籽实Pb含 量未超过国家卫生标准最高限量值,因此可以利用这些品种在受Pb污染农田中进行玉米生产 ,以降低Pb经玉米产品进入人类食物链的风险。研究结果还发现供试玉米品种各营养器官间 Pb含量均呈极显著正相关,但营养器官与籽实Pb含量间无显著相关。其中在较强的胁迫条件下营养器官Pb含量特别高的品种No.1的籽实中Pb含量（0.19 mg•kg－1）比较低,未超过国家卫生标准;品种No.2、No.3和品种No.6也有类似的特点。除上述品种以及品种No.4外,其余品 种籽实Pb含量遵循与营养器官Pb含量成正比的一般规律。根中Pb含量特别高的品种No.1,籽 实产量在Pb胁迫下略有下降,但下降幅度最小。胁迫条件下,品种No.1的营养器官Pb总量最高（51.69 mg•plant－1）,是对照的近12倍;籽实Pb含量符合国家标准的品种No.2 ,No. 3和No.6的营养器官Pb总量也较高,在36～42 mg•plant－1之间。由此可见,存在着在受Pb污染农田利用这些品种进行玉米生产同时修复受污染土壤的可能。     

Sorption of Cd(II) and Pb(II) by exopolymeric substances (EPS) extracted from activated sludges and pure bacterial strains: Modeling of the metal/ligand ratio effect and role of the mineral fraction

The present study deals with the sorption of Cd(II) and Pb(II) by exopolymeric substances (EPS) extracted from activated sludges or pure bacterial strains. The percentage of sorbed metal increases with the concentration of the EPS–water solution. Pb(II) always presents a higher affinity than Cd(II) for EPS. For the EPS extracted from pure bacterial strains, only one global binding constant from a simple equilibrium sorption model, may be used to assess the effect of microbial products such as EPS on Cd(II) and Pb(II) speciation or mobility in the environment. However, for EPS extracted from activated sludges, the wide variation of the global binding constants determined for Cd(II) and Pb(II) do not permit such a simple approach. The differences in sorption to metals between the two types of EPS (bacterial, activated sludges) could be explained by the differences in EPS composition: organic macromolecules, as well as the nature of the mineral fraction.     

Differences on Pb accumulation among plant tissues of 25 varieties of maize (Zea mays)

Pollution of agricultural land by heavy metals has imposed an increasingly serious risk to environmental and human health in recent years.Heavy metal pollutants may enter the human food chain through agricultural products and groundwater from the polluted soils.Progress has been made in the past decade on phytoremediation,a safe and inexpensive approach to remove contaminants from soil and water using plants.However,in most cases,agricultural land in China cannot afford to grow phytoremediator plants instead of growing crops due to food supply for the great population.Therefore,new and effective methods to decrease the risk of heavy metal pollution in crops and to clean the contaminated soils are urgently needed.If we can find crop germplasms (including species and varieties) that accumulate heavy metals in their edible parts,such as the leaves of vegetables or grains of cereals,at a level low enough for safe consumption,then we can grow these selected species or varieties in the lands contaminated or potentially contaminated by heavy metals.If we can find crop germplasms that take in low concentrations of heavy metals in their edible parts and high content of the metals in their inedible parts,then we can use these selected species or varieties for soil remediation.In this study,the feasibility of the method is assessed by analyzing Pb concentrations in edible and inedible parts of 25 varieties of maize (Zea mays) grown in Pb-contaminated soils.The soil concentrations of Pb were 595.55 mg/kg in the high Pb exposed treatment and 195.55 mg/kg in the control.The results showed that the Pb concentrations in different tissues were in the order of root ＞ shoot ≌ leaf＞ grain.Compared with the control,the Pb concentrations in root,shoot and leaf were greatly increased under the high Pb exposed condition,while the increments of Pb concentration in grain were relatively lower.Under the high Pb exposure,the grain Pb concentrations of 12 varieties exceeded the maximal Pb limitation of the National Food Hygiene Standard of China (NFHSC) and were inedible.This indicates that there is a high Pb pollution risk for maize grown on Pb polluted sites.Although 22 of the 25 tested varieties had harvest loss under the highly Pb stressed condition,ranging from 0.86%-38.7% of the grain biomass acquired at the control,the average harvest loss of all the tested varieties was only 12.6%,which is usually imperceptible in normal farming practices.Therefore the risk of Pb pollution in maize products cannot be promptly noticed and prevented based only on the outcome of the harvest.However,we did find that 13 of the 25 tested varieties had grain Pb concentrations lower than the limitation of the NFHSC.It is,therefore,possible to reduce the pollution risk if these favorable varieties are used for maize production in Pb-contaminated or potentially contaminated agricultural lands.Pb concentrations in vegetative tissues (root,stem and leaf) were significantly correlated with each other,while Pb concentrations of each vegetative tissue were not significantly correlated with that of grain.Among the 25 tested varieties,some varieties had Pb concentrations in grain lower than (No.1-3 and No.6) or slightly above (No.4) the limitation of the NFHSC,while their Pb concentrations in the vegetative tissues were among the highest.When excluding these varieties,correlations between the Pb concentrations of grain and those of vegetative tissues of the rest of the tested varieties became highly significant.In addition,variety No.1 had the lowest harvest loss under high Pb exposed,and the highest Pb accumulation in vegetative tissues (51.69 mg/plant,12 times as much as in the control).Similar features were also observed in varieties No.2,No.3 and No.6,which absorbed Pb for 36-42 mg/plant under high Pb exposed.We recommend these varieties of maize to be used for bioremediation of Pb contaminated soil and crop production at the same time.     

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.     

Differences on Pb accumulation among plant tissues of 25 varieties of maize ( Zea mays )

Pollution of agricultural land by heavy metals has imposed an increasingly serious risk to environmental and human health in recent years. Heavy metal pollutants may enter the human food chain through agricultural products and groundwater from the polluted soils. Progress has been made in the past decade on phytoremediation, a safe and inexpensive approach to remove contaminants from soil and water using plants. However, in most cases, agricultural land in China cannot afford to grow phytoremediator plants instead of growing crops due to food supply for the great population. Therefore, new and effective methods to decrease the risk of heavy metal pollution in crops and to clean the contaminated soils are urgently needed. If we can find crop germplasms (including species and varieties) that accumulate heavy metals in their edible parts, such as the leaves of vegetables or grains of cereals, at a level low enough for safe consumption, then we can grow these selected species or varieties in the lands contaminated or potentially contaminated by heavy metals. If we can find crop germplasms that take in low concentrations of heavy metals in their edible parts and high content of the metals in their inedible parts, then we can use these selected species or varieties for soil remediation. In this study, the feasibility of the method is assessed by analyzing Pb concentrations in edible and inedible parts of 25 varieties of maize (Zea mays) grown in Pb-contaminated soils. The soil concentrations of Pb were 595.55 mg/kg in the high Pb exposed treatment and 195.55 mg/kg in the control. The results showed that the Pb concentrations in different tissues were in the order of root > shoot ≅ leaf > grain. Compared with the control, the Pb concentrations in root, shoot and leaf were greatly increased under the high Pb exposed condition, while the increments of Pb concentration in grain were relatively lower. Under the high Pb exposure, the grain Pb concentrations of 12 varieties exceeded the maximal Pb limitation of the National Food Hygiene Standard of China (NFHSC) and were inedible. This indicates that there is a high Pb pollution risk for maize grown on Pb polluted sites. Although 22 of the 25 tested varieties had harvest loss under the highly Pb stressed condition, ranging from 0.86%–38.7% of the grain biomass acquired at the control, the average harvest loss of all the tested varieties was only 12.6%, which is usually imperceptible in normal farming practices. Therefore the risk of Pb pollution in maize products cannot be promptly noticed and prevented based only on the outcome of the harvest. However, we did find that 13 of the 25 tested varieties had grain Pb concentrations lower than the limitation of the NFHSC. It is, therefore, possible to reduce the pollution risk if these favorable varieties are used for maize production in Pb-contaminated or potentially contaminated agricultural lands. Pb concentrations in vegetative tissues (root, stem and leaf) were significantly correlated with each other, while Pb concentrations of each vegetative tissue were not significantly correlated with that of grain. Among the 25 tested varieties, some varieties had Pb concentrations in grain lower than (No.1–3 and No.6) or slightly above (No.4) the limitation of the NFHSC, while their Pb concentrations in the vegetative tissues were among the highest. When excluding these varieties, correlations between the Pb concentrations of grain and those of vegetative tissues of the rest of the tested varieties became highly significant. In addition, variety No. 1 had the lowest harvest loss under high Pb exposed, and the highest Pb accumulation in vegetative tissues (51.69 mg/plant, 12 times as much as in the control). Similar features were also observed in varieties No.3, No.3 and No.6, which absorbed Pb for 36–42 mg/plant under high Pb exposed. We recommend these varieties of maize to be used for bioremediation of Pb contaminated soil and crop production at the same time. Translated from Acta Phytoecologica Sina, 2006, 29(6): 992–999 [译自: 植物生态学报]