植物对镉胁迫响应的研究进展

总结了近年来植物对一重要环境污染物镉的反应研究报道。探讨了镉对植物的各种毒性效应,并论述植物对镉胁迫采取的相应防御机制,如络合（PC、MT）、应激（应激乙烯、应激蛋白）,及额外防御机制,如细胞壁固定化、原生质膜排除,区域化、过氧化物酶等。     

Effects of Exogenous Spermidine on Antioxidant System Responses of Typha latifolia L. Under Cd2+ Stress

The effects of foliar spraying with spermidine (Spd), ranging in concentration from 0.25 to 0.50mmol/L, on the antioxidant system under Cd2 stress (range 0.1- 0.2 mmol/L Cd2 ) in Typha latifolia L.grown hydroponically were investigated in order to offer a referenced evidence for an understanding of the mechanism by which polyamines (PAs) relieve the damage to plants by heavy metal and improve the phytoremediation efficiency of heavy metal-contaminated water. The results showed that Cd2 stress inhydrogen peroxide (H2O2) and malondialdehyde (MDA) contents in both leaves and caudices. With theexception of superoxide dismutase (SOD) activity in the leaves, an increase in the activities of catalase (CAT), guaiacol peroxidase (GPX), and glutathione reductase (GR) was observed in both leaves and caudices,SOD activity was increased in caudices, and ascorbate peroxidase (APX) activity was increased in leaves following Cd2 treatment. The reduced glutathione (GSH) content in both leaves and caudices and the reductive ascorbate content in leaves was obviously increased, which were prompted by the application of exogenous Spd. Spraying with Spd increased the activity of GR and APX in both leaves and caudices,whereas the activity of SOD, CAT, and GPX was increased only in caudices following spraying with Spd.with Spd. The decrease in MDA was more obvious following the application of 0.25 than 0.50 mmol/L Spd.It is supposed that exogenous Spd elevated the tolerance of T. latifolia under Cd2 stress primarily by increasing GR activity and the GSH level.     

Cadmium hyperaccumulation and reproductive traits in natural Thlaspi caerulescens populations

During the last decade, the metal hyperaccumulating plants have attracted considerable attention because of their potential use in decontamination of heavy metal contaminated soils. However, in most species, little is known regarding the function, the ecological and the evolutionary significances of hyperaccumulation. In our study, we investigated the parameters influencing the Cd concentration in plants as well as the biological implications of Cd hyperaccumulation in nine natural populations of Thlaspi caerulescens. First, we showed that Cd concentration in the plant was positively correlated with plant Zn, Fe, and Cu concentrations. This suggested that the physiological and/or molecular mechanisms for uptake, transport and/or accumulation of these four heavy metals interact with each other. Second, we specified a measure of Cd hyperaccumulation capacity by populations and showed that T. caerulescens plants originating from populations with high Cd hyperaccumulation capacity had better growth, by developing more and bigger leaves, taller stems, and produced more fruits and heavier seeds. These results suggest a tolerance/disposal role of Cd hyperaccumulation in this species.     

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。     

秋茄幼苗叶片单宁、可溶性糖和脯氨酸含量对Cd胁迫的响应

在温室条件下,采用土壤盆栽技术研究了红树植物秋茄的幼苗在不同浓度的Cd(0~50mg·kg-1)胁迫下叶片单宁、可溶性糖和脯氨酸的含量变化。研究表明:秋茄幼苗叶片中的单宁、可溶性糖和脯氨酸含量均随着Cd胁迫浓度的增加出现不同程度先升后降的趋势,这表明秋茄幼苗对低浓度的Cd有一定的抵抗能力,但在高浓度的Cd胁迫下则受到伤害;单宁、可溶性糖和脯氨酸的含量分别在土壤Cd处理浓度为30mg·kg-1、20mg·kg-1、40mg·kg-1时达到最高,相应地,单宁、可溶性糖和脯氨酸浓度最高分别达到66·2mg·g-1、105·0mg·g-1和12·22mg·g-1;Cd胁迫对脯氨酸含量的影响极显著,因此可以作为秋茄对Cd污染的检测指标。     

过表达白鳍鲨硒结合蛋白1对HL-7702细胞镉胁迫的解毒作用

硒结合蛋白1（Selenium—binding protein 1,SBP1）与肿瘤相关,并可以与重金属镉直接结合。该研究构建了白鳍鲨SBP1重组质粒Myc-SBP1并转染人HL-702细胞,利用CCK-8和CFDASE检测Cd胁迫下的细胞增殖情况,利用流式细胞仪检测细胞内ROS的水平。结果显示,过表达白鳍鲨sBP1可拮抗cd对HL-7702细胞的毒害作用。在100μmol／L的CdCl2应激下,表达SBP1组存活率为76．4％。约为对照组存活率的2倍,实验组的细胞增殖指教和分裂能力也略高于对照组。一级结构分析表明,白鳍鲨SBP1具有两个CXXC区域,为抗氧化位点,具有2个HxD和3个HXXH保守区域,它们为推测的Cd结合位点,为在HL-7702细胞中表达白鳍鲨SBP1蛋白能拮抗Cd的结构基础。此外,ROS检测实验表明白鳍鲨SBP1蛋白能显著降低胞内ROS水平,提示硒结合蛋白除通过直接与Cd结合降低毒性外,降低重金属引起的氧化胁迫也可能发挥一定解毒作用。     

一株龙葵内生细菌SDE06去除Cd2+的实验

植物内生菌广泛存在于各种植物中, 对宿主的生命活动产生了各种影响。本研究通过对重金属镉(Cd)超累积植物龙葵(Solanum nigrum L.)内生菌优势种进行分离纯化, 并用含Cd2+培养基初步筛选, 得到7株有抗性的菌株, 分别命名为SDE01-07,其中SDE06在Cd2+浓度为80 mg/L的条件下仍能生长。经鉴定此株菌属芽孢杆菌属(Bacillus sp.)。对SDE06在不同条件下去除Cd2+的情况进行研究, 结果表明：正交实验得最佳实验条件为培养时间36 h, pH 6.0, 温度37°C     

Heavy metal accumulation in iron plaque and growth of rice plants upon exposure to single and combined contamination by copper, cadmium and lead

A pot experiment was conducted to evaluate the bioaccumulation of heavy metals and growth response of rice plants after exposure to single and combined contamination by Cu, Cd and Pb. The results showed that the biomass production was not significantly affected by either single or combined treatment of Cu, Cd and Pb. Adding Cu (Cd, or Pb) separately all increased concentrations of the respective element in root and shoot (p < 0.001). In the combined contamination, Pb promoted both root and shoot absorption of Cu and Cd (p < 0.001), and Cu affected Cd and Pb absorption in the root, but Pb concentrations in both root and shoot were not affected by Cd application. The formation of iron plaques varied obviously with soil types. Heavy metal accumulation in iron plaques was induced by the three elements (p < 0.001). Furthermore, the three heavy metals exhibited an interactive relationship as measured by the Cu, Cd, Pb and Fe concentrations in root surface iron plaques. The iron plaques partially inhibited transfer of Pb to root and shoot, but no such effect was observed for Cu and Cd. This research indicates that the interaction among different heavy metal elements is very complex. It is very important to have a clear understanding on the associated mechanism and the consequential impact on plant growth.     

纳米管和镉对蚕豆幼苗根系的毒害效应

以蚕豆幼苗为实验材料,采用水培法研究不同浓度(0、2、4、8、16 mg·L~(-1))羟基化多壁碳纳米管(MWCNTs-OH)与10μmol·L~(-1)镉(Cd)单一和联合作用对蚕豆幼苗根系生长、生理及Cd含量的影响。结果表明:(1)单一MWCNTs-OH处理下,随着MWCNTs-OH浓度(2～8 mg·L~(-1))的增加,蚕豆的根长度增加,且■产生速率增加的同时会伴随着SOD、POD活性升高。(2)单一Cd处理的幼苗根系MDA含量和■产生速率均高于对照,其中■产生速率较对照增加了1.98倍。(3)MWCNTs-OH联合处理诱导了蚕豆根■的产生和MDA含量增加,16 mg·L~(-1) MWCNTs-OH和Cd共同作用对蚕豆幼苗根的损伤最大,会促使部分根尖细胞受损脱落,Cd含量明显下降。研究发现,低浓度MWCNTs-OH可促进蚕豆的根生长,降低Cd的毒性;高浓度MWCNTs-OH(16 mg·L~(-1))和Cd对蚕豆幼苗根的致毒性表现为协同效应。     

不同炭化温度制备的蚕丝被废弃物生物炭对重金属Cd2+的吸附性能

以蚕丝被废弃物为原料,在300、500和700 ℃高温缺氧条件下热解炭化制备成3种生物炭(BC300、BC500和BC700).利用扫描电镜(SEM)、傅里叶红外光谱仪(FT-IR)、X-射线衍射仪(XRD)、比表面积分析仪等对其理化性质进行表征,并研究了不同温度下制备的生物炭对溶液中Cd²⁺的吸附特性.结果表明: 随着炭化温度上升,BET比表面积、pH、灰分均增大,生物炭表面形态结构越来越不规则.XRD结果显示:不同温度下获得的生物炭中均含有一定量的方解石,FT-IR光谱图上的峰主要为-OH和方解石典型的吸收峰;pH对生物炭吸附Cd²⁺的影响不大;Langmuir方程能更好地拟合3种生物炭对Cd²⁺的吸附等温过程,其最大吸附量分别为25.61、52.41和91.07 mg·g^-1.3种生物炭对Cd²⁺吸附过程均更符合准二级动力学方程,且BC700对Cd²⁺的吸附效果最佳.进一步研究离子浓度及阳离子共存对BC700吸附Cd²⁺的影响,结果显示: NaCl浓度越高,对Cd²⁺的吸附抑制越明显;共存阳离子中,Ca²⁺和Mg²⁺对Cd²⁺的吸附抑制更明显,而K⁺几乎无影响.因此,以蚕丝被废弃物制备的生物炭作为去除水体中Cd²⁺的吸附剂具有较强的应用潜力.