镉处理对油菜生长和抗氧化酶系统的影响

通过盆栽实验研究了Cd处理对油菜生长和抗氧化酶系统的影响.结果表明,油菜整株鲜重、叶鲜重随Cd胁迫呈显著降低趋势.逐步回归表明,叶鲜重下降导致油菜整株鲜重下降.油菜叶细胞膜渗透性和MDA随Cd胁迫增大而增加.Cd处理浓度为20 mg·kg^-1时,叶细胞膜渗透性和MDA分别增加29.68％和15.19％,叶细胞膜渗透性和 MDA呈显著正相关,相关系数为0.823^*.Cd处理浓度为5 mg·kg^-1时,叶绿素a、b和a+b含量达到峰值,分别比对照高23.97%、33.63%和26.45%;Cd胁迫对类胡萝卜素含量无显著影响.几种色素对Cd敏感顺序为：叶绿素b>叶绿素a>叶绿素a+b>类胡萝卜素;3种抗氧化酶对Cd敏感顺序为：POD>CAT>SOD.各生理指标IC50表明,油菜只适宜种植在Cd含量小于5 mg·kg^-1的土壤中.     

龙须草对镉的耐受性和富集特征

利用盆栽试验,研究了龙须草对Cd的耐受能力和富集特征.结果表明:低浓度Cd处理(5 mg·kg-1)能促进龙须草的生长,增强其生理活性,生物量、净光合速率等12个指标比对照提高1.0%～15.5%;高浓度Cd处理(>5 mg.kg-1)对龙须草的生长产生抑制作用,但当Cd浓度达到100 mg.kg-1时,龙须草仍能完成正常的生理周期,生物量、净光合速率仅比对照分别下降27.0%和25.6%.龙须草各器官的Cd含量随Cd污染程度的上升而大幅度增加,根的Cd含量为350～500 mg.kg-1,茎叶为15～35 mg·kg-1.在Cd浓度<50 mg·kg-1时,吸Cd量随添加浓度的增大而增大,茎叶吸Cd量占总吸Cd量的15.7%～38.4%,茎叶与根的吸Cd量比值最高可达0.62.龙须草对Cd污染的耐受性、富集和转运能力均较强,是一种潜在的Cd超富集植物.     

不同施氮水平下灌水量对小麦水分利用特征和产量的影响

在田间高产条件下,研究了不同施氮水平［180 kg·hm^-2（N₁₈₀）和240 kg·hm^-2（N₂₄₀）］下灌水量对小麦耗水特征和旗叶水分生理特性及产量的影响.结果表明：不灌水的W₀处理100 cm以下土层的土壤贮水消耗量低于各灌水处理,W₁（灌底墒水60 mm）和W₂（灌底墒水和拔节水各60 mm）处理100～200 cm土层和0~200 cm土层土壤贮水消耗量高于W₃（灌底墒水、拔节水和开花水各60 mm）处理;N₂₄₀处理0～80 cm土层土壤贮水消耗量、开花至成熟阶段耗水模系数和农田耗水量高于N_180. W₂和W₃处理灌浆中后期旗叶相对含水量和水势高于W₀和W₁处理;灌浆后期旗叶相对含水量和水势为N₂₄₀W₀和N₂₄₀W₁处理分别高于N₁₈₀W₀和N₁₈₀W₁处理,N₂₄₀W₂和N₂₄₀W₃处理与N₁₈₀W₂和N₁₈₀W₃处理之间无显著差异.施氮180 kg·hm^-2,底墒水和拔节水分别灌60 mm的W₂处理籽粒产量、水分和氮素利用效率高,农田耗水量较低;增加灌水量,籽粒产量无显著变化,农田耗水量增高,土壤贮水消耗量、水分利用效率、灌溉水利用效率和灌溉效益降低.     

一种新发现的镉超积累植物--钻叶紫菀(Aster subulatus Michx.)

通过野外调查和温室营养液砂培试验,发现并鉴定出钻叶紫菀（Aster subulatus Michx.）是一种新的镉（Cd）超积累植物。调查结果发现,钻叶紫菀对土壤中高含量的Cd有很强的忍耐、吸收和积累能力,其地上部茎、叶Cd含量分别为90.0-150.7mg/kg和119.8-172.6mg/kg,平均值分别为132.8mg/kg和139.2mg/kg。砂基营养液培养试验证明,钻叶紫菀对生长介质中的Cd有很强的忍耐能力,当生长介质中Cd浓度高达150mg/L时,植株仍生长正常,其株高与对照相比无显著差异;地上部Cd含量及其积累量均随生长介质中Cd浓度的增加而增加,当生长介质中Cd浓度为120mg/L时,地上部茎Cd含量和积累量达到最高值,分别为5672.50mg/kg、4.93mg/株。结果表明,钻叶紫菀是一种新的Cd超积累植物,为今后探明植物超积累Cd的机理和Cd污染土壤的植物修复提供一种新的种质资源。     

镉胁迫对小报春幼苗生长及生理特性的影响

该研究采用盆栽控制试验,测定不同浓度(0、5、50、100、150、200 mg/kg)土壤Cd胁迫下小报春幼苗生长及生理生化指标,以探究小报春(Primula forbesii Franch.)对重金属镉(Cd)污染的抗性和敏感性,为新型香花地被植物应用于Cd污染土壤提供理论依据。结果表明:(1)低浓度(5 mg/kg)Cd胁迫能促进小报春株高和根长的伸长,高浓度(≥150 mg/kg)Cd胁迫下株高、根长和生物量明显降低。(2)随Cd胁迫浓度增加,小报春幼苗叶片光合作用、叶绿素含量、SOD和CAT活性先上升后下降,而其超氧阴离子产生速率、过氧化氢、丙二醛含量、叶相对电导率和POD活性持续升高。(3)在Cd胁迫条件下,小报春体内K、Zn含量降低,叶和根中Ca、Mg含量显著增加,体内Cd含量明显升高,且根系Cd含量远远高于叶和叶柄。研究发现,小报春幼苗对Cd胁迫具有一定的耐性,低浓度(5 mg/kg)Cd胁迫对小报春生长影响较小,但高浓度(≥150 mg/kg)Cd胁迫对小报春产生明显的毒害作用,影响其正常生长;小报春可能通过增强体内抗氧化酶系统活性、增加叶和根中Ca、Mg含量和根系截留镉来减轻镉胁迫的伤害,提高自身耐受镉胁迫能力。     

Accumulation of cadmium, zinc, and copper by Helianthus annuus L.: impact on plant growth and uptake of nutritional elements

We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg(-1) of Cd; 5 and 300 mg kg(-1) of Cd and Zn, respectively; 5, 300, and 400 mg kg(-1) of Cd, Zn, and Cu, respectively. Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment in which leaf area and total dry matter were reduced, by 15%. The contamination with Cd alone did not affect neither growth nor physiological parameters, despite considerable amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects on chlorophyll content and water relations due to greater accumulation of trace elements in tissues, with imbalances in nutrients uptake. Highly significant was the interaction between shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.     

Tissue metallothionein, apoptosis and cell proliferation responses in Atlantic salmon (Salmo salar L.) parr fed elevated dietary cadmium

Atlantic salmon parr were reared for 4 months on experimental diets supplemented with 0 (control), 0.5, 5, 25, 125, or 250 mg Cd x kg(-1) feed to establish a threshold concentration for dietary cadmium exposure by assessing early adaptive cellular responses. At the end of the experiment, the lowest dietary Cd concentration that caused significant accumulation in the gut, kidney and muscle was 5 mg Cd x kg(-1) compared to the control group. Over time, dietary Cd accumulated first in the gut (after 1 month), followed by the kidney (2 months), and later by muscle (4 months). Highest Cd accumulation (100-fold) was found in the gut. A significant increase in regulated cell death and proliferation in salmon fed 125 mg Cd x kg(-1) compared to control fish appeared efficient in preventing gross histopathological damage in the intestine. The highest increase in metallothionein levels was found in the kidney, and metallothionein (MT) levels increased disproportionally to Cd accumulation at increased exposure concentrations. It was concluded that MT was not directly associated with long-term Cd accumulation. Atlantic salmon showed increased metallothionein levels in the kidney at a median effective concentration (concentration of dietary Cd giving 50% of the maximum increase in metallothionein, EC50) of 7 mg Cd x kg(-1), indicating toxic exposure at this concentration.     

Phytoremediation of soil contaminated with cadmium, copper and polychlorinated biphenyls

A pot experiment and afield trial were conducted to study the remediation of an aged field soil contaminated with cadmium, copper and polychlorinated biphenyls (PCBs) (7.67 +/- 0.51 mg kg(-1) Cd, 369 +/- 1 mg kg(-1) Cu in pot experiment; 8.46 +/- 0.31 mg kg(-1) Cd, 468 +/- 7 mg kg(-1) Cu, 323 +/- 12 microg kg(-1) PCBs for field experiment) under different cropping patterns. In the pot experiment Sedum plumbizincicola showed pronounced Cd phytoextraction. After two periods (14 months) of cropping the Cd removal rates in these two treatments were 52.2 +/- 12.0 and 56.1 +/- 9.1%, respectively. Total soil PCBs in unplanted control pots decreased from 323 +/- 11 to 49.3 +/- 6.6 microg kg(-1), but with no significant difference between treatments. The field microcosm experiment intercropping of three plant species reduced the yield of S. plumbizincicola, with a consequent decrease in soil Cd removal. S. plumbizincicola intercropped with E. splendens had the highest shoot Cd uptake (18.5 +/- 1.8 mg pot(-1)) after 6 months planting followed by intercropping with M. sativa (15.9 +/- 1.9 mg pot(-1)). Liming with S. plumbizincicola intercropped with M. sativa significantly promoted soil PCB degradation by 25.2%. Thus, adjustment of soil pH to 5.56 combined with intercropping with S. plumbizincicola and M. sativagave high removal rates of Cd, Cu, and PCBs.     

芦竹修复镉汞污染湿地的研究

以湿土盆栽方法研究了芦竹在Cd和Hg污染模拟湿地中的富集能力及其在植株中的分布.结果表明,芦竹在101mg·kg^-1Hg污染环境中生长8个月后,对Hg的富集量是根系>茎>叶片,植物地上部分对Hg富集量为200±20mg·kg^-1DW;而在115mg·kg^-1Cd污染环境中生长8个月后,其对Cd的富集量是叶片>根系>茎,芦竹叶片对Cd的富集量在160±26mg·kg^-1DW.重金属在芦竹各器官内的含量随种植时间的延长而增加,8个月生长期富集量比4个月生长期富集量高30%～50%.芦竹生物富集系数(Bio concentrationfactorBCF)随土壤中重金属含量增加而减小.在污染土壤中,芦竹叶、茎对Hg的BCF为1.9和2.1、对Cd为1.5和0.3;在未受污染的空白对照湿土中(含Hg6.8mg·kg^-1,Cd8.5mg·kg^-1),芦竹叶、茎对Hg的BCF为6.8和12.2,对Cd为7.0和2.7,表明芦竹具有生物量大、根系发达、适应性强等特点,对Cd、Hg有较大富集量和较好的耐受性.     

减量施氮下基肥后移对南方冬小麦产量和氮素利用效率的影响

过量施用氮肥导致氮肥利用率降低,环境风险加大.合理降低施氮量、优化氮肥运筹对于小麦高产高效栽培具有重要意义.本研究采用大田试验,以常规施氮方式(240 kg N·hm^-2, 基肥∶拔节肥∶孕穗肥=5∶3∶2)为对照,研究了不同施氮量(240、180、150 kg N·hm^-2,分别用N₂₄₀、N₁₈₀、N₁₅₀表示)及基苗肥施用时期(基施、4叶期施、6叶期施,分别用L₀、L₄、L₆表示)对小麦产量和氮素利用效率的影响.结果表明: 小麦籽粒产量随施氮量的降低而降低,但N₁₈₀与N₂₄₀处理相比无显著差异,而N₁₅₀处理显著降低;氮肥农学效率和吸收效率均以N₁₈₀处理最高.不同施肥时期间,L₄处理的籽粒产量和氮肥利用率最高.N₁₈₀四叶施肥(N₁₈₀L₄)处理的产量与对照无显著差异,但氮肥利用率显著提高.N₁₈₀L₄处理叶面积指数、旗叶光合速率、叶片氮含量、旗叶硝酸还原酶和谷氨酰胺合成酶活性、拔节后干物质和氮素积累量较对照未显著降低.适量降低氮肥用量配合基肥后移能够提高生育后期光合生产能力和氮素吸收同化能力,在保持高产的条件下实现氮素利用效率的同步提高.     

Physiological responses,tolerance efficiency,and phytoextraction potential of Hylotelephium spectabile (Boreau) H. Ohba under Cd stress in hydroponic condition

Abstract

A sand hydroponic experiment with different concentrations of 0, 5, 10, 20, 40?mg L^?1 Cd was used to study the growth and physiological response of Hylotelephium spectabile (Boreau) H. Ohba. and its phytoextraction potential for Cd. The results showed that total plant biomass under 5?mg L^?1 Cd treatment was slightly affected. The content of malondialdehyde (MDA) in leaf exposed to Cd was higher, and the POD and CAT activity exhibited a positive response to the low level of Cd addition (5?mg·L^?1). The photosynthesis pigments were slightly inhibited, and the ultrastructure of chloroplast remained intact after treatment with 10?mg L^?1 Cd. The maximum leaf Cd content (603?mg·kg^?1) was found in 5?mg L^?1 Cd treatment, then decreased with the Cd level increased. The maximum Cd content in the shoots far exceeds the threshold level (100?mg kg^?1) for a Cd-hyperaccumulator plant with the value of translocation factor (TF_shoot/root) for Cd reaching up to 5.62. In conclusion, H. spectabile showed normal growth and physiological response and high shoot Cd accumulation under 5?mg L^?1 Cd stress, which made it to be a good candidate for phytoextraction of low-level Cd polluted environment.     

Cd对蒌蒿生理生化及叶片超微结构的影响

采用Cd砂土污染试验,研究了Cd对蒌蒿生理生化特征及叶片超微结构的影响,结果表明在砂土Cd含量>180mg/kg,蒌蒿出现中毒症状,叶绿素含量、a/b值、POD含量均下降,MDA积累,膜质过氧化,叶绿体形状球形化、片层结构解体、双层膜边界模糊、嗜锇颗粒增多,细胞核形状凹陷,核质分布不均匀、染色质凝胶化。低于180mg/kg的砂土Cd浓度,蒌蒿的上述生理生化指标和叶片超微结构基本正常。蒌蒿可以耐受的Cd浓度不超过180mg/kg。     

Chromium supplementation improves glucose tolerance in diabetic Goto-Kakizaki rats

Chromium supplementation (Cr) may be useful in the management of diabetes and appears to improve some aspects of glucose handling. However, several studies have used either high doses of Cr supplementation or have placed control animals on a Cr-deficient diet. We therefore wanted to test whether Cr dosages in the ranges that more closely approximate recommended levels of supplementation in humans are efficacious in glycemic control under normal dietary conditions. Euglycemic Wistar or diabetic Goto-Kakizaki (GK) rats (a model of nonobese NIDDM) were assigned to water (control) or chromium picolinate (Cr-P) supplementation (1 or 10 mg/kg/day) groups for up to 32 weeks. Glucose tolerance was tested following an overnight fast by injecting sterile glucose (1.0 g/kg, i.p.) and then measuring blood glucose at select times to determine the sensitivity to glucose by calculation of the area under the curve. Cr-P did not significantly alter the growth of the animals. In the euglycemic Wistar rats, Cr-P supplementation did not alter the response to a glucose tolerance test. In the GK rats, Cr-P supplementation significantly improved glucose tolerance at both levels of Cr-P supplementation (1 mg/kg/day: H20; 100 +/- 11%; Cr-P 70 +/- 8%; 10 mg/kg/day: H(2)0; 100 +/- 10%; Cr-P 66 +/- 9 %). Cr-P supplementation produced a small improvement in some indices of glycemic control. There were no differences observed for the two levels of Cr-P supplementation suggested that we did not identify a threshold for Cr-P effects, and future studies may use lower doses to find a threshold effect for improving glucose tolerance in diabetics.     

土壤Cd胁迫对三七生长和根系DNA损伤及抗氧化酶活性的影响

采用盆栽实验法,研究了土壤中添加0.0(对照)、0.1、0.3、0.6、1.0、3.0、6.0、10.0和30.0 mg·kg-1Cd对三七〔Panax notoginseng(Burk.)F.H.Chen〕生长和抗氧化酶活性的影响,并采用彗星实验对Cd胁迫条件下三七根尖细胞的DNA损伤进行了分析。结果显示:随土壤Cd添加量增加,三七的成活率、株高、单株复叶数和单株叶面积以及单株根、茎和叶片的干质量及鲜质量总体上呈先升高后降低的趋势;其中,各处理组三七植株的成活率和单株复叶数均高于对照,而株高和单株叶面积则在Cd添加量较低的条件下高于对照、在Cd添加量较高的条件下低于对照;单株根、茎和叶的鲜质量及干质量在Cd添加量30 mg·kg-1条件下均小于对照但差异不显著。随Cd添加量的提高,三七根系中SOD和CAT活性呈先上升后下降、再上升再下降的变化趋势,而POD活性总体上逐渐升高;其中,Cd添加量0.6、1.0、3.0和30.0 mg·kg-1处理组的SOD活性极显著或显著低于对照,而各处理组的POD和CAT活性总体上均高于对照且在Cd添加量1.0~30.0 mg·kg-1条件下与对照有极显著差异。彗星实验结果表明:各处理组三七根尖细胞的彗尾长、尾部DNA相对含量和Olive尾矩均有差异,其中,在Cd添加量较高的条件下各指标均高于对照但差异均不显著。研究结果显示:在较低水平的土壤Cd胁迫条件下,三七的生长、抗氧化酶活性和根系DNA均没有受到明显伤害,而较高水平的Cd胁迫则对其生长和抗氧化酶活性有抑制作用,且根尖细胞DNA损伤也较严重。     

镉胁迫下三种藓类植物的细胞伤害及光合色素含量的变化

采用水培试验研究了不同浓度Cd 胁迫下3种藓类植物的细胞伤害、光合色素含量和Cd 含量的变化,以探讨其对Cd 胁迫的反应敏感性和耐性.结果表明：低浓度Cd （1 mg·L^-1）胁迫显著损伤尖叶拟船叶藓和匍枝青藓叶细胞,3种藓的叶细胞伤害率随Cd 浓度的升高而显著增加,高浓度Cd （100 mg·L^-1）胁迫下的细胞伤害率大小为匍枝青藓>湿地匍灯藓>尖叶拟船叶藓.低浓度Cd 胁迫（1 mg·L^-1）对3种藓类植物的总叶绿素含量无显著影响,随着Cd 胁迫浓度的增加（≥ 10 mg·L^-1）,3种藓类植物总叶绿素含量显著下降,降幅顺序为匍枝青藓>湿地匍灯藓>尖叶拟船叶藓;1和10 mg·L^-1 Cd胁迫对3种藓类植物叶绿素a/b值无显著影响,100 mg·L^-1 Cd胁迫下湿地匍灯藓和匍枝青藓叶绿素a/b值显著下降;Cd胁迫对匍枝青藓类胡萝卜素含量的影响最大,1 mg·L^-1 Cd下其类胡萝卜素含量显著降低.3种藓类植物均能显著地富集Cd,其体内Cd累积量以尖叶拟船叶藓最高,湿地匍灯藓次之,匍枝青藓最少.细胞伤害率、叶绿素和类胡萝卜素含量的变化可用来指示3种藓类植物对Cd胁迫的敏感性差异.尖叶拟船叶藓对Cd胁迫的耐受性最强,湿地葡灯藓和匍枝青藓相对较弱.3种藓类植物对Cd胁迫的耐受性与其体内Cd累积量呈明显的正相关关系.     

Screen of Chinese Weed Species for Cadmium Tolerance and Accumulation Characteristics

The cadmium (Cd) tolerance and metal-accumulation characteristics of 29 species (18 families) of weed were studied by using outdoor pot-culture experiments. The results of this screening showed that Bidens pilosa and Kalimeris integrifolia (both Asteraceae) expressed some properties that are characteristic of Cd hyperaccumulators. In 10 mg/kg Cd-spiked soil, they accumulated a good deal of Cd in shoots (28 and 25 mg/kg DW, respectively) with high Cd enrichment factors (EFs; concentration in plant/soil). Cd accumulations in shoots were greater than those in roots (translocation factor (TF) >1, concentration in shoot/root) and the shoot biomasses did not decreased significantly compared to the unspiked control. The other weed species showed little accumulation of Cd, Pb, Cu, or Zn. In a concentration-gradient experiment, the Cd accumulation potentials of B. pilosa and K. integrifolia were examined further. Cd concentrations in leaves of B. pilosa growing in soils spiked with 25, 50, and 100 mg/kg Cd were up to 145, 160, and 192 mg/kg, respectively, and the Cd content in stems in the 100 mg/kg Cd-spiked soil was 115 mg/kg, all greater than the 100 mg/kg notional criterion for Cd hyperaccumulation. The Cd EFs and TFs were all greater than 1. The shoot biomasses did not decrease significantly compared to the controls. B. pilosa was thus shown to have some characteristics of a true Cd hyperaccumulator plant.     

Response of stem sap flow and leaf photosynthesis in <Emphasis Type="Italic">Tamarix chinensis</Emphasis> to soil moisture in the Yellow River Delta,China

Soil moisture is the main limiting factor for vegetation growth at shell ridges in the Yellow River Delta of China. The objective of this study was to explore the soil moisture response of photosynthetic parameters and transpiration in Tamarix chinensis Lour., a dominant species of shell ridges. Leaf photosynthetic light-response parameters and sap flow were measured across a gradient of relative soil water content (RWC), from drought (23%) to waterlogging (92%) conditions. Leaf photosynthetic efficiency and stem sap flow of T. chinensis showed a clear threshold response to soil moisture changes. Leaf net photosynthetic rate, water-use efficiency (WUE), light-saturation point, apparent quantum yield, maximum net photosynthetic rate, and dark respiration rate peaked at moderately high RWC, decreasing towards high and low values of RWC. However, peak or bottom RWC values substantially differed for various parameters. Excessively high or low RWC caused a significant reduction in the leaf photosynthetic capacity and WUE, while the high photosynthetic capacity and high WUE was obtained at RWC of 73%. With increasing waterlogging or drought stress, T. chinensis delayed the starting time for stem sap flow in the early morning and ended sap flow activity earlier during the day time in order to shorten a daily transpiration period and reduce the daily water consumption. The leaf photosynthetic capacity and WUE of T. chinensis were higher under drought stress than under waterlogging stress. Nevertheless, drought stress caused a larger reduction of daily water consumption compared to waterlogging, which was consistent with a higher drought tolerance and a poor tolerance to waterlogging in this species. This species was characterized by the low photosynthetic capacity and low WUE in the range of RWC between 44 and 92%. The RWC of 49–63% was the appropriate range of soil moisture for plant growth and efficient physiological water use of T. chinensis seedlings.     

Assessing the potential for cadmium phytoremediation with Calamagrostis epigejos: a pot experiment

A pot experiment was conducted for three vegetation periods on a sandy soil (pH 7.5) to study the uptake and distribution of Cd in plant tissues of Calamagrostis epigejos (L.) Roth. Cadmium was applied as CdCl2 (a total of 11 solution of 0, 20. 100, and 200 mg Cd l(-1)). HNO3- and water-extractable concentrations of Cd in 2- and 20-cm soil depths were correlated with the applied Cd showing that Cd was very mobile in the soil. The uptake of Cd from soil by Calamagrostis epigejos was directly related to the total soil Cd content and to the water-soluble pool of Cd. The concentrations of Cd in plant tissues (roots, rhizomes, leaves) and litter increased with increased applied Cd. Most of the Cd that was taken up was accumulated in roots (range from 1.88+/-0.42 to 40.96+/-16.71 mg kg(-1) dry mass), followed by rhizomes (0.52+/-0.13 to 25.70+/-6.35 mg kg(-1)) and leaves (0.30+/-0.06 to 9.20+/-1.93 mg kg(-1)). Cd concentrations of the litter were about twofold greater than the concentrations in the leaves (0.67+/-0.07 to 18.98+/-7.00 mg kg(-1)). The bioaccumulation factor (leaf/soil concentration ratio) increased significantly from 0.70+/-0.10 (control) to 1.1+/-0.17 (100 mg Cd l(-1)), but decreased again at the highest Cd level (200 mg Cd l(-1)) toward 0.74+/-0.34, which was not significantly different from the control. The low transfer of Cd from soil to above-ground organs at higher soil Cd concentrations indicates an exclusion mechanism. The leaf/root Cd concentration ratio (translocation factor) shows no significant relationship to increasing soil contamination. Only 4-7% of the total plant Cd was accumulated in the above-ground tissues. The phytoextraction potential (total Cd removed from soil) within three growing seasons ranged from 0.11 to 0.25% of the total soil Cd. Total output in above-ground living and dead plant material of C. epigejos would be approximately 20 g ha(-1) a(-1) for the lowest contamination level (+20 mg Cd per pot) and approximately 275 g ha(-1) a(-1) for the highest contamination level (+200 mg Cd per pot). This is within the range where an application for phytoextraction of Cd has been suggested by other authors. However, we conclude that the practical use of C. epigejos for phytoremediation is not mainly in the field of phytoextraction, but phytostabilization. C. epigejos has the capability to structurally stabilize the soil and reduce Cd contamination spread due to erosion. The uptake of the available Cd pool and accumulation in below-ground biomass may further prevent leaching into ground water.     

Effect of Cd-containing wood ash on the microflora of coniferous forest humus

The use of wood ash in forestry has been questioned because the cadmium (Cd) concentration of ash, which varies between 1 and 20 mg kg(-1) ash, exceeds the level allowed for fertilizers (3 mg kg(-1)) used in agriculture. To investigate the combined and separated effects of Cd and ash on the forest humus microflora, pumice or wood ash, spiked with a water-soluble (CdCl(2)) or -insoluble (CdO) form of Cd at three levels (0, 400 and 1000 mg kg(-1)), were applied at a fertilization level of 5000 kg ha(-1) in a laboratory microcosm study. The trial consisted of 60 microcosms (five replications per treatment), which were incubated in darkness at +20 degrees C and a constant relative air humidity of 60%. After two months the humus in the microcosms was sampled. Analyses of CO(2) evolution to measure the overall microbial activity and of phospholipid fatty acid (PLFA) pattern to measure microbial community structure were performed. The substrate-use patterns of Biolog EcoPlates were analyzed as a measure of bacterial functionality. Finally the bacterial (3)H-thymidine incorporation in the presence of different concentrations of Cd and the number of colony forming units (cfu) of bacteria on nutrient agar in the presence of 0, 5 and 20 mg Cd l(-1) agar were applied to measure Cd tolerance. The use of pumice (pH of humus under the pumice 4.0) did not induce any changes in the above variables compared to two untreated microcosms (humus pH 3.9). Pumice was therefore used to distribute the Cd evenly over the humus surface in order to estimate the possible effect of Cd without ash (pH of humus under the ash 7.0). The application of ash increased the microbial activity, changed the PLFA and substrate-use patterns and increased cfu compared to the humus under pumice. The form and level of Cd in the ash had no further effect on this result. In the humus under pumice the level, but not the form of Cd decreased the microbial activity and changed the PLFA pattern compared to the unspiked pumice. None of the treatments induced bacterial tolerance to Cd. Ash thus protected the humus microflora from the harmful effects of Cd.     

珊瑚树（Viburnum odoratissinum）对污染土壤中镉的耐受和富集特征

通过温室盆栽试验,研究珊瑚树对土壤中镉(Cd)的耐受和富集特征。研究结果表明,珊瑚树对污染土壤中Cd具有较强的耐受能力。培养56 d内,土壤中Cd含量对珊瑚树生物量影响不明显;随着培养时间的延长(105—203 d),珊瑚树的生长明显受到土壤中Cd的抑制作用。与对照处理(土壤中Cd含量为3.6 mg/kg)相比,培养154 d后,土壤中Cd含量为24.6 mg/kg处理下珊瑚树叶片中叶绿素a、叶绿素b、类胡萝卜素和丙二醛(MDA)含量没有明显变化;培养203 d后,土壤中Cd含量为24.6mg/kg处理下珊瑚树叶片中类胡萝卜素和MDA含量无明显变化,但叶片中叶绿素a和叶绿素b含量明显受到抑制,从而导致珊瑚树叶片的生长明显受到抑制(P0.05)。培养203 d后,珊瑚树对土壤中Cd的富集系数和转运系数均大于1,表明珊瑚树对土壤中Cd具有一定的富集和转运能力。上述结果表明,珊瑚树对Cd污染土壤具有一定的生态修复潜力。