匍茎翦股颖对Cu2+、Zn2+、Cd2+与Pb2+ 胁迫的生长响应与阈限浓度

采用砂培法,研究了匍茎翦股颖对Cu2+、Zn2+、Cd2+与Pb2+胁迫的生长响应及阈限浓度,结果表明:种子萌发率随着4种重金属浓度的增加而下降。对株高的影响是当重金属浓度小于100mg/L时会促进株高生长,高于100mg/L则产生抑制作用。Cu2+显著抑制根系生长,并随浓度的增加抑制效应愈加显著;在Cu2+浓度为600mg/L时匍茎翦股颖的根长比对照下降了93.75%。Cu2+、Zn2+、Pb2+浓度小于200mg/L时会促进地上生物量的增加,但高于200mg/L时,地上生物量会随着3种重金属的增加而减少。Cu2+、Zn2+浓度小于100mg/L或Cd2+、Pb2+浓度小于200mg/L会增加叶绿素的含量,高浓度会降低叶绿素的含量;Cd2+在浓度为600mg/L时显著降低叶绿素含量,与对照相比,下降了43.55%。匍茎翦股颖生长的综合效应分析表明,匍茎翦股颖对Cu2+胁迫最敏感,具有较低的阈限浓度,而Zn2+胁迫对匍茎翦股颖的生长影响最小,阈限浓度相对较高。     

Cd2+处理对5个柳树无性系气体交换参数及叶绿素荧光参数的影响

该实验以筛选的速生、抗逆性强的5个柳树无性系(‘竹柳’、‘苏柳172’、‘苏柳795’、‘旱快柳’、‘旱柳’)一年生扦插幼苗为试验材料,设置对照、轻度(30mg·L-1)、中度(60mg·L-1)和重度(90mg·L-1)4个重金属Cd2+处理水平,通过水培方式探究Cd2+对各柳树无性系气体交换参数、荧光参数及叶绿素含量的影响。结果显示:(1)在Cd2+浓度为30mg·L-1时,导致‘苏柳172’、‘苏柳795’和‘旱快柳’净光合速率降低的原因主要是气孔因素;当Cd2+浓度≥60mg·L-1时,‘苏柳172’、‘苏柳795’、‘旱快柳’及‘竹柳’净光合速率下降的主要原因是非气孔因素,而‘旱柳’在整个Cd2+胁迫过程中净光合速率下降的因素均属于非气孔限制型。(2)整个Cd2+胁迫过程中,‘苏柳172’、‘苏柳795’、‘旱快柳’和‘旱柳’叶片叶绿素含量和Chl a/Chl b值与对照相比均呈下降趋势,而竹柳先上升后下降至低于对照水平。(3)随着Cd2+胁迫程度的增加,叶片PSⅡ最大光化学量子产量(Fv/Fm)和光化学淬灭(qP)整体呈下降趋势,非光化学淬灭系数(NPQ)呈逐渐上升的趋势,而表观光合电子传递速率(ETR)先增加后下降,但5个柳树无性系叶绿素荧光参数的变化幅度以‘竹柳’最小,‘旱柳’最大。研究表明,5个柳树无性系均能在Cd2+浓度为30mg·L-1的培养液中正常生长,且竹柳的光合作用较对照有略微增加,且在90mg·L-1 Cd2+浓度下各无性系生长虽受到抑制但仍能存活,说明它们对重金属Cd2+胁迫都有一定的耐受性,并以‘竹柳’的耐受性最强。     

Cu2+对铜锈微囊藻生长及叶绿素荧光特性的影响

利用浮游植物荧光仪（Photo-PAM）研究了不同Cu²⁺浓度处理不同时间（12、24、48、72、96 h）对铜锈微囊藻（Microcystis aeruginosa）生长及叶绿素荧光特性的影响。结果表明:在一定时间（96 h）内,低浓度Cu²⁺(1μmol·L^-1)处理的铜锈微囊藻的藻细胞密度以及PSII最大光合效率（Fv/Fm）、PSII实际光合效率（ΦPSII）、光能利用效率（α）与对照相比变化不显著,最大电子传递速率（Pm）显著下降;高浓度Cu²⁺(2、4、6、8μmol·L^-1)处理下,藻细胞密度及Fv/Fm、ΦPSII、α、Pm随着Cu²⁺浓度的加大和胁迫时间的延长均显著降低,浓度为6、8μmol·L^-1 Cu²⁺处理48 h,铜锈微囊藻Fv/Fm、ΦPSII、α、Pm的测得值为0。可见,高浓度Cu²⁺(≥2μmol·L^-1)处理极大地影响铜锈微囊藻的生长及叶绿素荧光特性,胁迫作用显著。     

微量元素营养对桉树无性系苗木叶绿素及荧光参数影响

研究了不同微量元素营养液,对栽培的三种桉树无性系苗木叶绿素及荧光参数变化。结果表明:各无性系苗木在全部测试性状的差异表现出极显著。在六个测试的微量元素因子中,Fe(B)显著地影响苗木的Fo、Fm、Fv/Fo、Fv/Fm,Zn(C)显著地影响Fo、Fv/Fm,Mn(D)显著地影响叶绿素含量(SPAD值),Mo(F)显著地影响叶绿素含量、Fo,B(G)显著地影响叶绿素含量Fo、Fv/Fo、Fv/Fm。相关分析表明Fm与Fo、Fv/Fo与Fo、叶绿素含量与Fo、Fm、Fv/Fm与Fv/Fo均存在显著的相关性。随着微量元素Fe、Zn、Cu、Mo、B浓度增大,Fo、Fv/Fm均呈增大趋势,但在不利的高浓度环境下,Fv/Fm降低。对三个无性系叶绿素荧光比较,U₆与DH_32-29具有高的Fo、Fm和低的Fv/Fm、Fv/Fo,DH_201-2却具有低的Fo、Fm和高的Fv/Fm、Fv/Fo。对微量元素浓度变化,DH_32-29较敏感。因此,叶绿素荧光参数可作为诊断植物微量元素营养状况的指标之一。     

水分胁迫对牛心朴子叶片光合色素及叶绿素荧光的影响

研究了水分胁迫对牛心朴子叶片光合色素及叶绿素荧光动力学参数的影响。结果表明,在长期的水分胁迫中,牛心朴子叶片的叶绿素a(Chl a)、叶绿素b(Chl b)和类胡萝卜素(Car)含量没有下降或下降不明显。直到处理末期才显著下降;叶片叶绿素荧光动力学参数Fo、Fm、Fv、Fv／Fm变化不大,在处理末期各处理Fo降低,轻度、重度水分胁迫的Fm、Fv、Fv／Fm升高。说明K期水分胁迫后牛心朴子的光合功能受到影响,但牛心朴子仍表现出较强的适应干旱的能力。     

大气CO2浓度升高对绿豆叶片光合作用及叶绿素荧光参数的影响

利用FACE系统在大田条件下通过盆栽试验研究了大气CO2浓度升高[CO2浓度平均为(550+60) μmol·mo1-1]对绿豆叶片光合生理和叶绿素荧光参数的影响.结果表明:与对照[ CO2浓度平均为(389+40) μmol·mol-1左右]相比,大气CO2浓度升高使花荚期绿豆叶片净光合速率(Pn)和胞间CO2浓度(Ci)分别升高11.7％和9.8％,气孔导度(Gs)和蒸腾速率(Tr)分别下降32.0％和24.6％,水分利用效率(WUE)提高83.5％;在蕾期,CO2浓度升高对绿豆叶片叶绿素初始荧光(Fo)、最大荧光(Fm)、可变荧光(Fv)、Fv/Fm和Fv/Fo没有显著影响;在鼓粒期,CO2浓度升高使绿豆叶片Fo增加19.1％,Fm和Fv分别下降9.0％和14.3％,Fv/Fo和Fv/Fm分别下降25.8％和6.2％.表明大气CO2浓度升高可能使绿豆生长后期光系统Ⅱ反应中心结构受到破坏,叶片的光合能力下降.     

藿香蓟的镉积累、生物量及叶绿素荧光参数对不同梯度镉胁迫的响应

通过盆栽试验,研究藿香蓟(Ageratum conyzoides)的地上部和地下部Cd含量、干重、转运系数、根冠比及叶片叶绿素荧光参数对不同梯度Cd胁迫的响应。结果表明:随Cd胁迫浓度增加,藿香蓟转运系数逐渐降低,地上部和地下部Cd含量随Cd胁迫浓度的增加而逐渐升高,在Cd(300 mg·kg-1)胁迫下,植株地上部Cd含量为125.50 mg·kg-1,这一结果已超过Cd超富集植物的临界值(100 mg·kg-1);植株地上部及地下部干重随Cd胁迫浓度的增加均逐渐降低,且中、高浓度Cd胁迫对植物的生长具有显著的抑制作用,各处理间的根冠比呈上升趋势并比对照高,可见高浓度Cd胁迫可阻碍根系的生长,从而影响植物地上部对营养和水分的吸收,最终抑制植株生长及生物产量的提高;PSⅡ的最大光化学效率(Fv/Fm)、PSⅡ的潜在光化学效率(Fv/Fo)随着Cd胁迫浓度的增加均逐渐升高,初始荧光(Fo)和最大荧光(Fm)均逐渐降低,光量子产量(ФPSⅡ)、电子传递效率(ETR)、光化学猝灭系数(q P)及非光化学猝灭系数(q N)均出现先升后降的趋势;Cd胁迫扰乱叶片正常时期的光合特性及延缓植株衰老,但各处理间的叶绿素荧光动力学参数差异不显著,Cd胁迫对叶片PSⅡ反应中心的电子传递、光化学反应及散热能力影响较弱;高浓度Cd胁迫明显抑制植株的生长,但植株地上部及地下部的Cd积累能力较强,可作为植物修复重金属污染土壤的备选植物并用来治理Cd污染的土壤。     

Cu2+与Zn2+递进胁迫下高羊茅的初期生长效应及生态阈限研究

通过重金属 Cu2 +、Zn2 +递进胁迫高羊茅初期生长效应及生态阈限的研究 ,结果表明 :在 Cu2 +与 Zn2 +递进胁迫作用下 ,高羊茅生长在各处理浓度均不同程度上受到抑制作用 ,其抑制效应随重金属浓度的增加而增强 ,各项测定指标与胁迫浓度呈极显著负线性关系 ,并各相关系数均达到极显著水平 ( r>-0 .90 0 0 * * ) ;生长综合效应分析比较 ,Cu2 +比 Zn2 +的负向效应为明显。根与茎叶对 Cu2 +与 Zn2 +的富集状况分析采用 ICP-AES法 ,分析结果表明 ,随着重金属 Cu2 +与 Zn2 +胁迫浓度的增加 ,高羊茅根系和茎叶的重金属含量均随之增加 ,根系对 Cu2 +与 Zn2 +的富集系数均明显大于茎叶。从绿度分析看 ,本实验条件下的 Cu2 +与 Zn2 +胁迫 ,均未出现草坪草绿度的明显变化。     

外源NO对NaHCO3胁迫下黑麦草幼苗光合生理响应的调节

采用营养液砂培方法,研究了外源一氧化氮(NO)对100 mmol/L NaHCO3胁迫下黑麦草幼苗叶片叶绿素含量、光合气体交换和叶绿素荧光参数、光能分配及叶黄素循环的影响。结果表明:(1)外施60μmol/L NO供体硝普钠(SNP)显著缓解了NaHCO3胁迫下叶绿素含量、净光合速率(Pn)、气孔导度(Gs)和气孔限制值(Ls)的下降及胞间CO2浓度(Ci)的升高,提高了光系统Ⅱ(PSⅡ)的潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)和光化学猝灭(qP),降低了初始荧光(Fo)和非光化学猝灭(NPQ)。(2)NaHCO3胁迫下,外施SNP显著抑制了天线转换效率(Fv’/Fm’)的下降,降低了光系统间激发能分配的不平衡性(β/α-1)和天线热耗散的比例(D),提高了吸收光能中用于光化学反应的比例(P),而对PSⅡ反应中心的过剩光能(Ex)无明显影响。(3)外施SNP显著降低了NaHCO3胁迫下叶黄素循环库(V+A+Z)下降和叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)上升的幅度。但SNP对NaHCO3胁迫的缓解效应可被NO清除剂血红蛋白(Hb)部分或完全地逆转,SNP的分解产物NaNO2处理对NaHCO3胁迫无明显改善。表明外源NO可能通过提高光化学效率,缓解了碱胁迫引起的光抑制对光合机构的破坏,从而提高黑麦草的光合效率。     

Cd2+对紫球藻生长及光化学活性的影响

以紫球藻(Porphyridium purpureum)为供试材料, 研究了5个不同浓度的Cd2+对紫球藻的细胞密度、叶绿素a含量、藻红蛋白含量及ATP含量的影响, 以及对紫球藻的最大光量子产额(F_v/F_m)、实际光量子产额(YII)、相对电子传递效率(ETR)及非光化学淬灭(NPQ)的影响, 探讨了各荧光参数在不同浓度的Cd2+胁迫下的变化规律。研究结果表明, 在Cd2+胁迫的6d内, 紫球藻的生长速度显著下降, 且Cd2+的浓度越高, 生长速度下降越快; Cd2+胁迫显著的减少叶绿素a、藻红蛋白及ATP含量, 且浓度越高, 减少的幅度越大; 在Cd2+浓度低于200 μmol/L时, 紫球藻的叶绿素荧光参数F_v/F_m、YII及ETR呈现先下降后上升的趋势,而且随着胁迫时间的延长, 下降幅度逐步增大; NPQ在低浓度下(<200 μmol/L)呈现显著上升趋势, 高浓度下(>500 μmol/L)呈现显著下降趋势。因此, 水体中浓度超过50 μmol/L的Cd2+就会显著影响紫球藻的生长及光化学活性, 水生环境中不断累积的Cd2+将会对紫球藻的生态平衡产生影响。     

Effects of heavy metals Cd2+, Pb2+ and Zn2+ on DNA damage of loach Misgurnus anguillicaudatus

The effects of heavy metals Cd²⁺, Pb²⁺ and Zn²⁺ at 0.05, 0.5 and 5.0 mg/L level and their interactions at 0.5 mg/L level on DNA damage in hepatopancreas of loach Misgurnus anguillicaudatus for 1–35 days exposure were examined by single cell gel electrophoresis (SCGE). For each test group, 20 loaches with similar body size (5.17–7.99 g; 11.79–13.21 cm) were selected and kept in aquaria with dechlorinated water at (22±1)°C and fed a commercial diet every 48 h. According to the percentage of damaged DNA with tail and its TL/D (tail length to diameter of nucleus) value, the relationship between DNA damage degree and heavy metal dose and exposure time was determined. Results showed that the percentage of damaged DNA and the TL/D value were increased with the prolonged exposure time. The highest percentage (84.85%) of damaged DNA was shown in 5.0 mg/L Zn²⁺ group after 28 days exposure and the biggest TL/D value (2.50) in all treated groups after 35 days exposure. During the first treated week, the damnification of DNA was mainly recognized as the first level, after that time, the third damaged level was mostly observed and the percentage of damaged DNA was beyond 80%. The joint toxic effects among Cd²⁺, Pb²⁺ or Zn²⁺ revealed much complexity, but it generally displayed that the presence of Cd²⁺ could enhance the genotoxicity of Pb²⁺ or Zn²⁺. In conclusion, the results suggested that there was a significant time-and dose-depended relationship between the heavy metal and DNA damage in hepatopancreas of loach, and SCGE could represent a useful means to evaluate the genotoxicity of environmental contamination on aquatic organisms. __________ Translated from Acta Hydrobiologica Sinica, 2006, 30(4): 399–403 [译自: 水生生物学报]     

Na+、K+、Mg2+、Ca2+和葡萄糖溶液作为授精-激活介质对中华鲟精子受精率的影响

以不同浓度的NaCl、KCl、MgCl2、CaCl2溶液和葡萄糖溶液作为授精介质,研究了中华鲟(Acipenser sinensis)的受精效果.结果显示,适量的阳离子和葡萄糖作为激活授精介质时中华鲟卵受精率都有所提高.在实验设置浓度范围内25 mmol/L NaCI溶液、0.1 mmol/L KCl溶液、1 mmol/L MgCl2溶液、1 mmol/LCaCh溶液和50 mmol/L葡萄糖溶液浓度下,受精率分别可达到最高值,依次为87.72%、86.82%、82.24%、89.76%、80.92%.随着实验浓度继续增加,受精率反而呈下降趋势.结果显示,作为人工配制的中华鲟精子授精一激活介质,最适NaCI溶液浓度在25 mmol/L附近,最适葡萄糖溶液浓度在25 mmol/L附近,最适KCI溶液浓度≤0.1 mmol/L,最适MgCl2溶液浓度≤1 mol/L,最适CaCh溶液浓度≤1 mmol/L.     

Contributions of Ca2+ and Zn2+ to spreading depression-like events and neuronal injury

The phenomenon of spreading depression (SD) involves waves of profound neuronal and glial depolarization that spread throughout brain tissue. Under many conditions, tissue recovers full function after SD has occurred, but SD-like events are also associated with spread of injury following ischemia or trauma. Initial large cytosolic Ca²⁺ increases accompany all forms of SD, but persistently elevated Ca²⁺ loading is likely responsible for neuronal injury following SD in tissues where metabolic capacity is insufficient to restore ionic gradients. Ca²⁺ channels are also involved in the propagation of SD, but the channel subtypes and cation fluxes differ significantly when SD is triggered by different types of stimuli. Ca²⁺ influx via P/Q type channels is important for SD generated by localized application of high K⁺ solutions. In contrast, SD-like events recorded in in vitro ischemia models are not usually prevented by Ca²⁺ removal, but under some conditions, Zn²⁺ influx via L-type channels contributes to SD initiation. This review addresses different roles of Ca²⁺ in the initiation and consequences of SD, and discusses recent evidence that selective chelation of Zn²⁺ can be sufficient to prevent SD under circumstances that may have relevance for ischemic injury.     

普通小球藻对复合重金属镉和铬的生物吸附及影响因素

【背景】微藻对重金属具有极强的耐受性,而且有较高的吸附率,是一种优良的生物吸附剂。【目的】探究环境因素对小球藻吸附镉离子(Cd²⁺)和铬离子(Cr³⁺)的影响。【方法】以普通小球藻（Chlorella vulgaris）在不同条件下对重金属离子的吸附率为基准,利用CdCl₂·2H₂O和CrCl₃·7H₂O提供重金属离子,根据不同处理下小球藻吸附率的变化情况探讨重金属离子浓度、p H和温度等环境因素对普通小球藻吸附Cd²⁺和Cr³⁺的影响。【结果】在温度为30°C、p H值为5.5、Cd²⁺和Cr³⁺浓度分别为0.4 mg/L和4.0 mg/L及生物量为0.59 g/L的条件下,普通小球藻对复合Cd²⁺和Cr³⁺吸附率达到最大,吸附率分别达到84.5%和75.2%,同时发现普通小球藻对Cd²⁺的吸附率大于C...     

Effect of Mn2+ and Ca2+ on O2 evolution and on the variable fluorescence yield associated with Photosystem II in preparations of Anacystis nidulans

Extraction with EDTA of lyophilized and lysozyme treated preparations of the blue-green algae Anacystis nidulans resulted in loss of the capacity for photoevolution of O₂. Reactivation was achieved by the addition of both cations: Mn²⁺ and Ca²⁺ (or to a smaller extent by Mn²⁺ and Sr²⁺). The dual requirement for Mn²⁺ and Ca²⁺ could be demonstrated when the O₂ evolution under short saturating light flashes and the variable chlorophyll fluorescence associated with the reduction of the primary acceptor of Photosystem II was examined. The fluorescence experiments in addition showed that incorporation of the cations was a light dependent step, since the fluorescence rise only started after a lag period.     

不同浓度Fe2+与Zn2+对羊草幼苗生长和生理特性的影响

以羊草幼苗为研究对象,通过调整全营养培养基(CK,0.05 mmol/L Fe²⁺、0.015 mmol/L Zn²⁺)中铁或者锌含量设置0、10倍、20倍Fe²⁺(Zn²⁺)浓度处理Fe₀(Zn₀)、Fe₁₀(Zn₁₀)、Fe₂₀(Zn₂₀),以及在高铁培养基中单独添加0.15 mmol/L Zn²⁺或同时添加10 mmol/L Ca²⁺、5 mmol/L Mg²⁺、20 mmol/L K⁺处理,测定培养6 d后幼苗生长指标和矿质元素含量、以及高铁(Fe₂₀)处理下幼苗根中抗氧化指标和相关基因表达量,探究不同浓度Fe²⁺、Zn²⁺对羊草幼苗生长、矿质元素吸收积累及抗氧化指标、基因表达的影响。结果表明：(1)缺锌(Zn₀)显著抑制羊草幼苗鲜重的增加和Zn元素的积累,但促进Fe、Mg元素的积累;高浓度锌(Zn₁₀、Zn₂₀)显著促进幼苗叶片生长和Zn元素的积累;缺铁(Fe₀)显著抑制幼苗的根长、鲜重和Fe元素的积累,促进Mg、Zn元素的积累;高浓度铁(Fe₁₀、Fe₂₀)显著抑制羊草幼苗根叶生长、根毛发育和Ca、Zn、Mg、K元素的积累。(2)增加Zn²⁺和Ca²⁺、Mg²⁺、K⁺浓度无法恢复高铁胁迫对幼苗生长的抑制作用。(3)高浓度铁(Fe₂₀)处理羊草幼苗48 h后,根部过氧化物酶、超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶活性和丙二醛、抗坏血酸、还原型谷胱甘肽含量显著升高;烟酰胺合成酶基因、过氧化物酶基因表达量显著下调,植物类萌发素蛋白基因表达量显著上调。研究发现,羊草幼苗生长发育和矿质元素积累对环境中Zn²⁺浓度变化不敏感,却受到环境中高浓度Fe²⁺的显著抑制,并造成严重的氧化胁迫伤害,这种伤害无法在添加Zn²⁺或同时添加Ca²⁺、Mg²⁺、K⁺的条件下恢复。     

Relative roles of Ca2+, Sr2+, Ba2+ and Mg2+ in controlling lens permeability characteristics

The effects of barium, strontium and magnesium upon lens permeability characteristics were studied in the presence and absence of 2 mM calcium in the bathing medium. Permeability characteristics were determined by measuring lens potential, resistance and ⁴²K efflux rates. Barium and strontium at equimolar concentrations to calcium were able to substitute for calcium in controlling lens sodium permeability. Magnesium was ineffective in this respect.Small changes in resistance and ⁴²K efflux rates occurred when calcium was eliminated from bathing solution containing either 2 mM barium or strontium. These changes were interpreted to be the result of an increase in lens permeability to potassium. When 2 mM strontium was added to calcium-containing solution, there was no significant change in the electrical or flux parameters of the lens. However, the addition of 2 mM barium to calcium-containing solution resulted in a 54% increase in lens resistance and a 13 mV depolarization. These observations indicated a barium-induced decrease in lens permeability to potassium, and this was confirmed by an observed decrease in ⁴²K efflux rate constant under similar experimental conditions.The rapid time course of all the observed changes implies that they are the result of changes in the permeability characteristics of membranes lying close to the surface of the lens.     

Effect of calmodulin,Ca2+ and Mg2+ on the (Ca2+ + Mg2+)-ATPase of erythrocyte membranes

Calmodulin-depleted isotonic erythrocyte ghosts contain 200 ng residual calmodulin/mg protein which is not removed by extensive washings at pCa²⁺ > 7. Specific activity and Ca²⁺-affinity of the (Ca²⁺ + Mg²⁺)ATPase increase at increasing calmodulin, with K_{0.5 Ca} of 0.38 μM at calmodulin concentrations corresponding to that in erythrocytes. High Ca²⁺ concentrations inhibit the enzyme. Specific activity and Ca²⁺-affinity of the enzyme decrease at increasing Mg²⁺ concentrations. The Ca²⁺ ? Mg²⁺ antagonism is likewise observed at inhibitory Ca²⁺ concentrations.     

Cd2+和Pb2+对花翅摇蚊(Chironomus kiiensis)幼虫生长发育的影响及富集效应

河流、湖泊等水生环境中普遍存在的重金属污染破坏水生生态系统并间接威胁人类健康。为探究重金属胁迫下水生昆虫花翅摇蚊（Chironomus kiiensis）生态毒理,测定了重金属Cd²⁺和Pb²⁺胁迫对花翅摇蚊化蛹率和羽化率的影响,检测了摇蚊的口器致畸与富集效应。研究结果表明,Cd²⁺和Pb²⁺影响摇蚊幼虫化蛹和羽化过程,单一重金属离子处理14 d Pb²⁺处理组的化蛹率和羽化率分别为22.22%和8.89%,低于Cd²⁺的化蛹率（25.56%）和羽化率（11.11%）,表现出更强的抑制效应。混合离子1：2和2：1配比处理组化蛹率和羽化率均为11.11%和4.44%,显著低于单一重金属离子胁迫下的化蛹率和羽化率。单一重金属离子及混合离子处理均能导致花翅摇蚊幼虫口器致畸,表现为上颚前齿断裂,中齿和基齿磨损、缺失,下唇板齿部不规则,下唇板边缘齿与中央齿磨损、断裂、增生、缺失。不同重金属离子处理下幼虫口器致畸率不同,并与暴露时间呈正相关,其中1：2配比处理14 d致畸率达到40.61%。重金属离子在摇蚊幼虫体内产生生物富集效应,单一重金属离子处理下的Pb²⁺富集含量7 d至14 d由11.46 mg/kg上升至31.32 mg/kg,不同配比混合离子处理下Pb²⁺富集含量均呈增加趋势,其中1：2配比处理组由15.48 mg/kg上升至42.50 mg/kg,而Cd²⁺在单一重金属与1：1混合离子处理组7 d至14 d的富集含量无显著性变化,2：1配比处理组由14.20 mg/kg下降至9.52 mg/kg,1：2配比由5.85 mg/kg上升至20.99 mg/kg。这些研究结果表明Cd²⁺和Pb²⁺胁迫影响花翅摇蚊幼虫生长发育且口器出现畸型,与重金属在幼虫体内的富集密切相关,为研究重金属对水生生态系统多重效应提供了理论依据。     

Binding of Cd2+, Ni2+, Cu2+ and Zn2+ by isolated envelopes of Pseudomonas fluorescens

Abstract Cell envelopes of Pseudomonas fluorescens , cytoplasmic membrane, peptidoglycan and outer membrane were obtained from a fractionation procedure and tested for their metal binding capacity. Isolated envelopes (cytoplasmic membrane, peptidoglycan and outer membrane) were chemically modified and functional carboxyl groups transformed to electropositive amine groups, using carbodiimide ethylenediamine. Transformation of carboxyl groups was evaluated by measuring total amine groups in all fractions (modified or not). Using equilibrium dialysis and Scatchard plots for the data, we have established that isolated unmodified cell envelopes (cytoplasmic membrane, peptidoglycan and outer membrane) possess at least two types of metal binding sites with different association constants ( K _a and K '_a). Introduction of positive charges into the bacterial envelopes resulted in the disappearance of one type of metal binding site which had the highest association constant value for Ni²⁺, Cu²⁺ and Zn²⁺. All fractions, modified or not, always presented at least two types of binding sites with different association constants for Cd²⁺.