镉与锌复合污染对栝楼幼苗生理特性的影响

通过室内盆栽实验,研究镉(Cd)、锌(Zn)复合污染对栝楼(Trichosanthes kirilowii Maxim.)幼苗生理特性的影响.结果显示,随着Cd、Zn浓度的升高,叶绿素a、叶绿素b、总叶绿素、可溶性糖及紫外吸收物含量下降;超氧化物歧化酶(SOD)活性先升高再下降,过氧化物酶(POD)活性及类胡萝卜素含量呈升—降—升趋势;丙二醛(MDA)和可溶性蛋白含量分别呈S"型及倒N"型曲线变化.与对照相比,在不同浓度复合污染条件下,光合色素、可溶性糖、可溶性蛋白、紫外吸收物含量及SOD活性均有所下降,POD活性和MDA含量上升.研究表明,栝楼幼苗对Cd、Zn胁迫具有一定的耐受力,但高浓度Cd、Zn对幼苗正常生长有较为显著的抑制作用.     

外源硫对镉胁迫下马齿苋光合性状和矿质元素吸收的影响

从光合反应系统揭示外源硫(S)诱导马齿苋镉(Cd)耐受性的生理机制,为外源S缓解重金属毒害提供理论依据.采用营养液培养,研究外源S供体(NH4)2SO4对100 mg/L Cd胁迫下马齿苋叶片光合色素、光合特性、叶绿素荧光参数和矿质营养元素的影响.结果表明,Cd胁迫可显著降低马齿苋叶片中叶绿素a和叶绿素b含量;净光合速率、蒸腾速率、气孔导度均显著降低,而胞间二氧化碳浓度上升,表明非气孔因素是Cd胁迫诱导马齿苋光合抑制的主要因素;同时,PSⅡ实际光化学效率(ФPSII)、电子传递效率(J)、化学猝灭系数(qP)显著下降,而非化学猝灭系数(qN)显著上升,表明Cd胁迫影响马齿苋PSⅡ反应系统的正常运行.外施400 mg/L(NH4)2SO4显著提高马齿苋叶片叶绿素a含量、叶绿素b含量和叶绿素a/b比值,增强马齿苋叶片光合作用和PSⅡ原初光化学反应量子效率.对5种与光反应系统密切相关的矿质元素含量进行分析发现,Cd处理显著增加马齿苋叶片中的Ca和Fe含量,显著抑制马齿苋对Mg、Mn和Cu的吸收.Cd胁迫下马齿苋叶片的变黄与Mg、Mn的亏缺有关,而与Fe缺乏无关;添加外源S可显著提升马齿苋叶片中Ca、Mg、Fe、Cu和Mn含量,从而增强Cd胁迫下马齿苋叶片的PSII反应系统功能.     

外源水杨酸对镉胁迫下甜瓜幼苗生长、光合作用和活性氧代谢的缓解效应

以甜瓜耐镉品种‘哈密绿’和镉敏感品种‘秀绿’为试验材料,在人工气候箱内采用基质栽培法,研究了外源水杨酸(SA)处理对镉(Cd)胁迫下甜瓜幼苗生长、光合作用和活性氧代谢的缓解效应。结果显示:与对照(CK)比较,Cd处理显著抑制了甜瓜幼苗的生长和光合作用,降低了叶绿素含量,抗氧化酶活性、脯氨酸(Pro)含量、丙二醛(MDA)含量和超氧阴离子(O2ˉ·)产生速率增加;在Cd胁迫下,SA处理可以有效促进甜瓜幼苗的生长,增加了叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls)和水分利用效率(WUE),降低了胞间CO2浓度(Ci);提高了超氧化物歧化酶(SOD)、过氧化酶酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX),增强植株抗氧化能力,使Pro和可溶性蛋白含量升高,MDA含量和O2ˉ·产生速率下降,能有效抑制镉胁迫引起的膜脂过氧化伤害;镉敏感品种‘秀绿’变化幅度大于耐镉品种‘哈密绿’。研究结果说明,SA有利于甜瓜幼苗在Cd胁迫下活性氧代谢的提高和对光能的捕获与转换,促进了甜瓜幼苗的生长,降低Cd胁迫对甜瓜幼苗的抑制作用,且对镉敏感品种‘秀绿’效果大于耐镉品种‘哈密绿’。     

外源油菜素内酯对镉胁迫下菊芋幼苗光合作用及镉富集的调控效应

以两种菊芋(Helianthus tuberosus L.)品系南芋2号(NY2)和南芋5号(NY5)为材料,研究了外源24-表油菜素内酯(24-EBL)对镉胁迫下菊芋幼苗干重、根冠比(R/S)、光合色素含量、叶片气体交换参数和水分利用效率(WUE)的调节效应,还测定了其不同器官的镉(Cd)含量.结果表明:在镉胁迫下,2种菊芋幼苗的干重、R/S、光合色素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、WUE均呈下降趋势,而胞间二氧化碳浓度(Ci)升高.(2)与镉胁迫相比,胁迫下外源喷施10-10、10-9、10-8、10-7mol/L 24-EBL作用下,两品系植株干重和R/S值均不同程度的上升,NY2、NY5的植株干重分别在10-9 mol/L 24-EBL(EBL2)和10-8mol/L 24-EBL(EBL3)处理下达到最大值,分别增加50％和64％.镉胁迫下,外源24-EBL处理均提高菊芋的叶绿素(Chl)和类胡萝卜素(Car)含量,Pn、Gs、Tr也由此得到不同程度的上升,而Ci均下降,NY5的Ci下降更显著.镉胁迫下,外源EBL2和EBL3作用下均不同程度地提高其WUE,NY5的WUE增幅远大于NY2.镉胁迫下NY5的新完全展开叶Cd含量的积累明显高于NY2;而EBL2处理下可降低NY2的新完全展开叶Cd含量,但EBL3却显著增加NY5的叶片Cd含量.镉胁迫下,喷施EBL2的NY2的不同器官、NY5根的Cd含量均显著下降,而NY5其他器官的Cd含量变化不显著.NY5不同器官的Cd含量均明显高于NY2.上述表明,24-EBL可明显提高菊芋的耐镉水平,主要是因为外源喷施24-EBL能显著促进其光合和提高水分利用效率,从而改善Cd胁迫下菊芋幼苗的生长;而24-EBL对菊芋NY5非气孔限制的更显著改善是其促进其光合、水分利用的重要原因,也是其对NY5的生长调控效果优于NY2的重要原因之一.结果还显示,菊芋NY5植株生物量大,从环境中提取Cd的能力较好,因此可作为重金属污染土壤的植物修复的材料来利用.     

外源脱落酸对小麦幼苗抗镉胁迫能力的影响

以小麦(Triticum aestivum L.)为试材,采用水培法研究了100mg/L镉(Cd2+)胁迫条件下施用外源脱落酸(ABA)对小麦幼苗生长及某些生理生化指标的影响。结果表明:(1)100mg/L Cd2+胁迫下,小麦叶片膜脂过氧化产物丙二醛(MDA)含量显著提高,植株生长受到抑制;(2)外源ABA能够明显提高Cd2+胁迫小麦幼苗的根系活力,增加其叶片SOD、CAT和POD活性,促进其脯氨酸积累,降低MDA的含量,并以5.0μmol/L ABA的效果最明显;(3)1.0～5.0μmol/L外源ABA不同程度地缓解Cd2+胁迫对小麦幼苗生长的抑制作用,且5.0μmol/L时效果最明显,其株高、根长、总干重分别比单一Cd2+胁迫处理显著提高6.73%、149%和10.52%,而10.0μmol/LABA反而加重了Cd2+对小麦幼苗生长的伤害。因此,适宜浓度的外源ABA能够通过增加体内保护酶活性和脯氨酸含量来缓解Cd2+胁迫对小麦幼苗生长的抑制作用,增强小麦幼苗的抗Cd2+胁迫能力,并以5.0μmol/L ABA处理效果最好。     

硒对镉胁迫下水稻幼苗生长及生理特性的影响

采用溶液培养 ,研究不同浓度的硒和镉处理对稻苗的株高、叶片干重、叶绿素、还原糖、叶片丙二醛含量以及保护酶 SOD、POD、CAT活性的影响。结果表明 ,镉胁迫下稻苗矮化 ,镉毒害使叶片失绿 ,干重降低 ,还原糖含量下降 ,叶片 MDA含量增加 ,POD活性增强 ,而 SOD、CAT活性降低 ;硒可减轻镉对水稻的毒害 ,表现为 :减轻镉胁迫对株高增加的抑制 ,提高叶绿素含量 ,增加叶片干物质积累 ,提高叶片还原糖含量 (Cd0 .5 mg/ L加 Se 0 .1 0～ 0 .5 0 mg/ L例外 ) ,降低 MDA含量与 POD活性 ,提高 SOD、CAT活性     

镉胁迫对鸡冠花种子萌发及幼苗生理生化特性的影响

采用水培法和盆栽法测定分析不同浓度Cd(0、50、100、150、200 mg/L)胁迫对鸡冠花种子萌发、幼苗生物量、叶片光合色素、渗透调节物质(可溶性蛋白、可溶性糖、脯氨酸)、丙二醛(MDA)、低分子巯基化合物(GSH、GSSG、Cys、NPT)含量以及抗氧化酶 (SOD、POD、CAT、APX)活性的影响,探讨鸡冠花耐受Cd胁迫的能力及其生理机制,为植物解毒机制提供基础资料。结果显示：(1)鸡冠花种子的发芽势、发芽率和发芽指数在低浓度Cd处理下提高,而活力指数、根长及苗长在各浓度Cd胁迫下均不同程度降低,以上指标均在低浓度(50、100 mg/L)Cd胁迫下受到显著抑制,且根长受抑制程度显著高于苗长;幼苗生物量(整株鲜重、地上部分鲜重及地下部分鲜重)在200 mg/L Cd胁迫时受到显著抑制,较对照分别下降了61.9%、58.4%和72.7%;根冠比及主根长虽未受到显著影响,但总体呈现降低趋势。(2)鸡冠花幼苗叶片叶绿素和类胡萝卜素含量在100~200 mg/L Cd胁迫下均显著降低,叶片可溶性蛋白、可溶性糖和脯氨酸含量在Cd胁迫下总体呈升高趋势,并分别在50、150、200 mg/L时显著升高。(3)鸡冠花幼苗叶片各抗氧化酶活性在Cd胁迫下呈不同变化趋势,POD和APX活性在各浓度Cd胁迫分别增加23.1%~304.2%和160.0%~280.0%;SOD活性在各浓度Cd胁迫均受到抑制,但仅在150 mg/L时显著降低43.2%;CAT活性在50~150 mg/L Cd胁迫下显著增强了46.6%~66.5%,但在200 mg/L Cd胁迫却显著降低59.5%。(4)高浓度(200 mg/L)Cd胁迫下鸡冠花幼苗叶片巯基化合物GSH、GSSG、Cys、NPT含量分别比对照上升了53.2%、164.2%、53.9%和0.79%,而GSH/GSSG比值显著降低。研究发现,鸡冠花种子萌发期和幼苗期对Cd胁迫均具有一定的耐受力,但高浓度Cd胁迫仍致使幼苗部分抗氧化酶活性降低,ROS过量积累,引起膜脂过氧化程度加深,其产物MDA含量逐渐升高;Cd胁迫促进低分子巯基化合物含量呈不同幅度的增加,但GSH/GSSG比值下降,细胞内氧化还原反应(Redox)受到抑制,导致幼苗正常生长代谢受阻,生物量持续降低。     

壳聚糖对镉胁迫条件下小麦生长及生理的影响

以小麦为材料,研究了镉对水培小麦幼苗的胁迫作用及壳聚糖对镉胁迫的缓解效应。结果表明:250μmol·L-1的镉胁迫处理后,小麦幼苗的生长受到严重抑制,叶片中叶绿素含量明显下降,金属硫蛋白和丙二醛的含量显著上升(P<0.05);培养液中添加0.01%的壳聚糖能降低小麦幼苗中镉的积累,对小麦幼苗的镉胁迫具有明显地缓解效应。     

外源钙对黑藻抗镉胁迫能力的影响

以分布广泛的沉水植物——黑藻为实验材料,对比研究了Cd胁迫和施加适宜浓度的外源Ca后,黑藻体内Cd积累、矿质营养、光合色素、可溶性蛋白、渗透调节物质、抗氧化能力以及非蛋白巯基(NP-SH)和植物络合素(PCs)的变化,以探讨Ca缓解水生植物Cd毒害的生理生化机制。结果表明:(1)Cd胁迫使黑藻体内Cd含量极显著增加,并造成明显的矿质营养失衡,主要表现为显著降低了P、K、Fe、Cu、Mn的含量,而外源Ca则削弱了黑藻对Cd的蓄积,并在一定程度上减轻了Cd胁迫所造成的矿质元素失衡;(2)Cd处理使黑藻体内叶绿素含量、叶绿素a/b值和可溶性蛋白含量大幅度下降并显著降低了黑藻的总抗氧化能力(T-AOC)和小分子保护物质[谷胱甘肽(GSH)、抗坏血酸(AsA)]的含量,而外源Ca延缓了黑藻的失绿症状,促进了可溶性蛋白的合成并提高了黑藻的抗氧化能力;(3)Cd胁迫使黑藻体内脯氨酸积累显著,而外施Ca减缓了其积累;可溶性糖变化趋势与之相反;(4)Cd胁迫诱导了NP-SH和PCs在黑藻体内的大量累积,外源Ca处理后,其增加幅度减小。以上结果说明外源Ca能通过抑制Cd的吸收,促进光合色素、可溶性蛋白和可溶性糖的合成,维持高的总抗氧化能力和抗氧化物质含量以及矿质营养平衡等途径来增强黑藻对Cd胁迫的抗性。     

镉胁迫对紫花苜蓿幼苗生理特性和镉富集的影响

以"甘农三号"紫花苜蓿幼苗为材料,在水培条件下,探究了在10 d内不同浓度(0～2.0 mmol·L^-1)镉(Cd)胁迫对其根长、茎长、生物量、叶绿素和丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性、Cd富集及其亚细胞分布的影响。结果表明:低浓度(0.125 mmol·L^-1) Cd能促进幼苗根和茎的生长,增加叶片叶绿素含量,较高浓度(0.5～2.0 mmol·L^-1) Cd显著抑制幼苗根和茎的生长,叶绿素及生物量显著降低; Cd胁迫使MDA含量显著增加,而SOD和POD活性显著增强,其中Cd胁迫浓度为0.5mmol·L^-1时,SOD和POD活性达到最大值,这可能是植物对环境胁迫的一种应激保护反应; Cd在各亚细胞组分中的含量依次为细胞壁>细胞质>线粒体>叶绿体,且均随Cd胁迫浓度的升高而增加。当Cd胁迫浓度为0.125 mmol·L^-1时,水培10 d的紫花苜蓿幼苗单株地上部对Cd的净化率最高可达0.214%,而整盆植株在单位体积内对Cd的净化率最高可达15.5%;当Cd胁迫浓度为2.0 mmol·L^-1时,紫花苜蓿幼苗地上部Cd含量达89.36μg·g-1。这些结果表明紫花苜蓿对Cd具有很强的富集能力,虽未达到Cd超富集植物的临界标准,但从植株生物量、耐Cd能力、富集Cd量及对Cd的净化率等方面综合考虑,紫花苜蓿在Cd污染土壤的植物修复中具备良好的应用价值。     

Comparison of the immunological properties of mammalian (rodent), bird,fish, amphibian (toad), and invertebrate (crab) metallothioneins

Summary Immunoassays such as rocket immunoelectrophoresis, western dot blot hybridization, and competitive ELISA analysis were used to estimate and compare homology among fishes (several species), crab, toad, chicken and rodent metallothioneins. The relative abundance of tissue-specific metallothionein in catfish was highest in liver followed by kidney and pancreas like mammalian systems. Immunologically, considerable homology exists among fish metallothioneins, although the extent of homology differs to some extent. No homology was found between fish or chicken metallothioneins. The amphibian (toad) and invertebrate (crab) metallothioneins showed only partial homology with fish metallothioneins in antigenic determinants.Abbreviations MT Metallothionein - PBS Phosphate Buffered Saline - SDS Sodium Dodecyl Sulfate - PAGE Polyacrylamide Gel Electrophoresis - ELISA Enzyme Linked Immunosorbent Assay - ME 2-Mercaptoethanol - BSA Bovine Serum Albumim     

Putrescine Effect on Nitrate Reductase Activity, Organic Nitrogen, Protein, and Growth in Heavy Metal and Salinity Stressed Mustard Seedlings

Putrescine effect on nitrate reductase activity, organic nitrogen and protein contents, and plant growth under Cd or Pb (0.1 – 2 mM) and salinity (5 and 100 mM NaCl) stresses was examined in Indian mustard (Brassica juncea L. cv. RH-30) seedlings. Cd or Pb and salinity inhibited nitrate reductase activity and decreased organic nitrogen and protein contents in leaf tissue. The increased nitrate reductase activity induced by putrescine was correlated with increased organic nitrogen and protein contents and growth of plants.     

Genetic and physiological parameters associated with cadmium toxicity in Drosophila melanogaster

Two strains of Drosophila melanogaster represent the extremes in resistance and sensitivity to the lethal effects of CdCl₂. The strain containing the mutations vermilion and brown (v; bw) and the strain Austin had LC₅₀'s of 3.3 and 1.3mm CdCl₂, respectively. The three major chromosomes from these two strains were assorted genetically into the six possible combinations. The measured LC₅₀'s for CdCl₂ for these six genotypes fell into two groups according to the X chromosome; those containing the X chromosome from v; bw had LC₅₀'s 0.5–1.0mm greater than those in which the X chromosome was from Austin. Since the parent strains differed by 2mm, we suggest that the X chromosome is a major, but not the sole, site of genes to produce resistance to CdCl₂. When ¹⁰⁹Cd was in the diet the uptake by v; bw and Austin over 2 days was the same. After 4 days of uptake, the Austin strain excreted the ¹⁰⁹Cd five times faster than v; bw but the six genotypes did not differ appreciably in excretion rate from one another and resembled the sensitive parent Austin more than the resistant one. Thus a second process is indicated that distinguishes resistance to CdCl₂ that apparently is not associated with the X chromosome.This research was sponsored by the Office of Health and Environmental Research, U.S. Department of Energy, under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.     

镉胁迫对瘤突苍耳、苍耳及其杂合体种子萌发与幼苗生长的影响

入侵种与本地种杂交可能会改变其某些性状,影响其生理生化过程,增强其对一些重金属的耐受性。镉是目前造成土壤污染的主要重金属元素之一,为探讨杂交是否能够增强植物对重金属镉的耐受性,采用培养皿滤纸法比较了不同浓度镉(0,10,40,80和120 mg/L)处理下瘤突苍耳(Xanthium strumarium)、苍耳(Xanthium sibiricum)及二者杂合体(X.strumarium♀×X.sibiricum♂,X.sibiricum♀×X.strumarium♂)种子萌发与幼苗生长情况。结果表明:1)入侵种瘤突苍耳与本地种苍耳之间存在杂交现象;2)镉促进了杂交瘤突苍耳(X.strumarium♀×X.sibiricum♂)种子的萌发,当镉浓度为80 mg/L时,其萌发率、发芽势、发芽指数最高;3)杂交瘤突苍耳在80、120 mg/L镉处理下根长和叶绿素含量低于瘤突苍耳,但子叶受到的氧化胁迫并未高于瘤突苍耳。研究结果显示,杂交有可能提高了瘤突苍耳在高浓度镉胁迫时对重金属镉的转运能力,幼苗根系吸收大量的镉并向上运输给子叶,导致根系生长受到抑制、子叶叶绿素含量下降,抗氧化酶系统可能在降低子叶氧化程度上发挥了作用。     

Toxicity of inorganic cadmium salts to the microalga Scenedesmus armatus (Chlorophyta) with respect to medium composition, pH and CO2 concentration

Batch cultures of algae grown at low (0.1 %) and elevated (2.0 %) concentrations of CO₂, as well as in original BBM (Bold Basal Medium) and BBM modified with phosphate, EDTA and a combination of both, were exposed to cadmium (Cd(NO₃)₂·4H₂O, 3CdSO₄·8H₂O and CdCl₂·H₂O) for 24 h. Regardless of the salt applied, the concentration-dependent relationships of Cd toxicity were found to be biphasic, suggesting the different affinity of target sites to cadmium. Nominal values of EC₅₀ obtained for algae grown in original BBM and at low CO₂ were 18.0, 16.44 and 15.37 mg·dm⁻³ for cadmium nitrate, sulphate and chloride, respectively. However, it was estimated that 97 % of the free cadmium in the added salts were bound by components of original BBM such as EDTA, phosphates, chloride and sulphate. The effect of Cd-salts at concentrations corresponding to EC₅₀ values on algae were tested in media with 10-fold reduced phosphates (BBM-P), BBM depleted of EDTA (BBM-EDTA) and of both phosphates and EDTA (BBM-P-EDTA). For algae grown at low CO₂ and BBM-P, cadmium was about 25 % less toxic than those applied in original BBM. Cadmium greatly inhibited (about 85 % of the control) the growth of algae cultured in BBM-EDTA; this effect was only slightly dependent on the CO₂ concentration. Deficits of both EDTA and P led to effects similar to those brought about by the absence of EDTA only. The toxicity of cadmium depends on CO₂ concentration only when algae are grown in original BBM. The growth of algae under high CO₂ conditions was reduced considerably less (about 80% of control) compared with low CO₂ concentrations (about 50 % of control). A relationship was found between the toxicity of cadmium salts and final pH values only in variants of low-CO₂ grown algae; with an increase of medium pH the toxicity decreased. The results suggest that both growth conditions and the binding ability of the medium markedly affect the toxicity of cadmium towards microalgae.     

Induction of peroxisome proliferation and increase of catalase activity in yeast,Candida albicans,by cadmium

The effects of cadmium on the growth rate, catalase activity, and peroxisome proliferation in yeast,Candida albicans, were evaluated. The yeast growth was markedly inhibited by 1 mM cadmium at the initial hours. The toxic effect of cadmium on the cell growth persisted. The catalase activity of the cells treated with 1 mM Cd²⁺ first decreased, and then rose at 24 h to about 2.6 times that of the controls. The average number of peroxisomes per cell in the yeast treated with 1 mM Cd²⁺ was about sixfold higher than the control groups. The proliferation of peroxisomes and the increase of catalase activity following cadmium toxicity gives credence to the hypothesis that cadmium toxicity is related to its potential to induce oxidative stress in cells.     

香根草对镉毒害的生理响应——采用傅里叶变换红外光谱法(FTIR)

为阐明香根草(Vetiveria zizanioides)对镉(Cd~(2+))胁迫的耐性机理及其对重金属Cd~(2+)的积累特征,通过水培试验,采用傅里叶变换红外光谱法(FTIR)研究在不同Cd~(2+)浓度处理时香根草根、茎、叶化学组分的变化,同时测定香根草叶Cd~(2+)的亚细胞分布和其重金属Cd~(2+)含量。结果表明,其根组织在2927 cm~(-1)处峰高先下降后上升,表明在低Cd~(2+)(Cd~(2+)3 mg/L)处理条件下香根草分泌的有机酸不断螯合Cd~(2+),造成羧酸O—H的减少,但随着Cd~(2+)含量的升高,其羧酸螯合力变弱,有机酸含量渐渐升高;茎组织在1631 cm~(-1)峰高处先上升后下降,表明在低Cd~(2+)(Cd~(2+)3 mg/L)处理条件下香根草产生氨基酸、多肽和蛋白质等物质,通过渗透调节来增强抗逆性,但随着Cd~(2+)含量的升高,蛋白质二级结构中肽键间氢键的结合力受影响较大。当Cd~(2+)处理浓度为7 mg/L时,香根草生长10 d后,地上部分及根组织富集Cd~(2+)量分别高达212.49 mg/kg和290.59 mg/kg。香根草地上部分的Cd~(2+)含量随Cd~(2+)处理浓度的增加而增加。香根草叶片富集的Cd~(2+)主要分布于细胞质中,其次为细胞壁,而在线粒体和叶绿体中含量最低。     

Chromosomal and mutagenic study of the marine macroalga,Gracilaria tenuistipitata

A pressing need of algal aquaculture is the availability of strains with favourable characteristics. Since this goal cannot be achieved easily by traditional breeding methods for Gracilaria tenuistipitata, we developed mutagenesis and selection procedures that bypass the necessity for protoplast isolation and cultivation. A haploid gametophyte was identified through chromosome analysis and used for mutagenesis. Chromosomal analyses showed that the haploid plant contains several layers of mononucleated cells at the surface and many large multinucleated syncytiums in the internal region. Chromosomal division of all nuclei in a syncytium was in synchrony. Mononucleated cells were more sensitive to both UV and DNA insertion mutagenesis. UV treatment generated many cadmium (Cd) resistant mutants, but most mutants exhibited retarded growth rate. However, several stable Cd resistant mutants were obtained through reselection. Plasmid pCaMVCAT could be used for DNA insertion mutagenesis in G. tenuistipitata. Stable mutants with increased resistance to chloramphenicol were selected.     

Effect of chronic exposure to cadmium and copper on Asellus aquaticus (L.) (Crustacea,Isopoda)

The effects of chronic exposure to 5 g·1^–1 cadmium or copper on the crustacean Isopod Asellus aquaticus (L.) were studied by analyzing survival and body growth in the first stages of the life-cycle and by determining fecundity and survival of embryo-bearing females. Juveniles survival is differently affected by the two metals in that embryonic development is more sensitive to cadmium while juvenile development is more sensitive to copper. Juvenile body growth is stimulated by cadmium and depressed by copper. Embryo-bearing female survival and fecundity are significantly reduced by cadmium but are not affected by copper. The consequence of environmental contamination by a sublethal cadmium or copper concentration is discussed.     

一株耐Cd菌株的分离、鉴定及基本特性

【目的】从活性污泥中筛选耐镉(Cd)菌株,并研究其生长特性及对溶液中Cd~(2+)吸附的最佳条件,以期为重金属Cd污染水体的微生物修复提供菌株资源和应用技术参考。【方法】采用平板划线法,从活性污泥中分离、筛选、驯化出耐Cd菌株,通过16SrRNA基因序列分析及溶血试验、蛋白质毒素结晶试验进行初步鉴定,并采用单因素实验优化菌株的培养条件,通过正交实验确定菌粉吸附溶液中Cd~(2+)的最佳条件,同时利用SEM-EDS及FTIR分析探讨菌粉吸附Cd~(2+)的机理。【结果】经分离、驯化得到1株耐Cd细菌菌株,命名为H6,初步鉴定为蜡样芽孢杆菌(Bacilluscereus),最大Cd~(2+)耐受浓度为350 mg/L。菌株H6的最佳生长条件为:pH 6.0–8.0,温度28°C,转速120–210 r/min,接种量1%–5%;菌株H6在生长过程中,培养液pH值先稍微下降然后不断上升。菌粉吸附Cd~(2+)的正交优化条件为:菌粉用量0.125 g/L,吸附时间2 h,pH 5.0,温度30°C,此条件下吸附量为205 mg/g。SEM-EDS分析和红外光谱(FTIR)分析表明,在吸附过程中主要作用基团有羟基、羧基、羰基、酰胺基和烷基,此外,Ca~(2+)与Cd~(2+)发生了离子交换。【结论】从活性污泥中分离出的菌株H6,初步鉴定为蜡样芽孢杆菌(Bacillus cereus),是1株具有较强Cd~(2+)吸附能力的细菌菌株。