重金属对土壤中小麦种子发芽与根伸长抑制的生态毒性

测定了4种土壤（红壤、草甸棕壤、暗棕壤和栗钙土）条件下,Cu,Zn,Pb和Cd单一污染对小麦种子发芽与根伸长抑制主及其复合污染效应（暗棕壤条件下）。结果表明,同一浓度下,重金属对小麦根伸长抑制率均明显大于对种子发芽抑制率,植物根对金属污染的生态毒性比种子发芽敏感,土壤有机质和土壤N含量与Cu,Zn,Pb和Cd污染对小麦根伸长抑制率显著负相关（R^2OR=0.91,R^2K-N=0.92),土壤PH和阳离子交换量与Cu,Zn,Pb和Cd污染对小麦根伸长抑制率的相关性不显著（R^2PH=0.62,R^2CEC=0.60),在单一污染对小麦根伸长为刺激作用浓度（较低浓度）或为抑制作用浓度下（较高浓度）,复合污染均表现为协同作用。^     

小麦不同生育时期Cd、Cr、Pb污染监测指标体系

以小麦为供试材料,分别采用发芽试验、溶液培养、土柱栽培等毒理试验方法,研究了小麦萌芽期、幼苗期及成株期受重金属污染毒害的指标体系。结果表明,①小麦根伸长抑制率可作为萌芽期重金属污染评价的一项生物指标;Cd、Cr、Pb对小麦根生长的7d半效应浓度(EC50)值分别为1.39、0.20mmo.lL-1和2.75mmol.L-1,据此得到3种重金属对小麦同一性状的毒性次序为CrCdPb;此外各性状抑制率与胁迫浓度的关系可用双曲线模型y=x/(a+x/100)或指数曲线模型y=a(1-exp(-bx))较好模拟。②Cd、Cr、Pb单一污染胁迫对小麦幼苗性状的毒性次序均以影响叶面积和冠部干重为主,表明叶面积和冠部干重为幼苗期污染监测的敏感指标;重金属对除根干重外所有性状的毒性次序:CrCdPb,该毒性次序是根据引起50%抑制的临界浓度即EC50值确定的;各性状抑制率与胁迫浓度的关系可用直线模型、或双曲线模型、或指数曲线模型较好模拟。③重金属单一污染胁迫造成小麦籽粒产量下降幅度是CdCrPb;二元互作对产量影响的重要性次序为CdCrCdPbCrPb;在Cd、Cr、Pb复合污染胁迫条件下,穗数可以作为成株期重金属污染监测的首选指标。以上指标可为农田小麦重金属污染的监测和综合治理提供一些理论依据。     

基于小麦种子发芽和根伸长的麝香酮污染毒性效应

研究了新型污染物麝香酮对小麦种子发芽及幼苗生长的影响.结果表明,土壤麝香酮（10 mg·kg^-1）污染对小麦发芽率抑制作用达到显著水平（P<0.05）,对小麦根长和芽长的抑制作用达极显著水平（P<0.01）,并且芽长、根长与土壤中麝香酮浓度之间存在极显著（P<0.01）的剂量 效应关系.表明小麦根和芽伸长可以指示土壤麝香酮的污染程度.在土壤麝香酮污染条件下,小麦幼苗的根长和芽长之间呈极显著（P<0.01）的正相关性,发芽率和生物量之间呈极显著（P<0.01）的负相关性.有机污染物的毒性除了与它在水中的溶解度有关外,还与其化学性质及对靶标生物的毒性机制有关.     

香附浸提液对小麦种子的萌发及幼苗生长的影响

为了了解香附有效成分对小麦种子萌发和幼苗生长的影响,采用室内培养皿培养法,分析不同浓度的香附浸提液浸种后对小麦种子发芽率、发芽指数、活力指数及幼苗高度、根长、根数、整株鲜重及干重等指标的影响。结果表明,香附浸提液对小麦种子的萌发及幼苗的生长有明显抑制作用,抑制作用随着香附浸提液浓度的增加,抑制效果增强,与浸泡蒸馏水的对照相比,香附浸提液浸种处理显著降低了小麦的种子发芽率、发芽指数、种子活力、苗高、根长、植株鲜重和干重。     

环丙沙星和铜复合污染对小麦早期生长的影响

以小麦为供试生物,采用高等植物毒理诊断试验方法研究了土壤外源环丙沙星和铜复合污染对小麦早期生长的影响,以探讨粪源污染土壤潜在的生态风险。结果表明:在供试浓度范围内,铜和环丙沙星单一污染下,小麦种子早期生长指标均产生了不同程度的响应,其中芽长和根长主要表现为抑制效应,而小麦种子发芽率未受影响;指标对污染物反应敏感顺序为芽长根长发芽率、环丙沙星与铜复合污染对小麦根长和芽长的影响表现出不同的效应;20和80 mg·kg-1铜与环丙沙星复合时相对单一作用对小麦根长的抑制有毒性增强的趋势,表现为协同效应;而200 mg·kg-1单一铜处理对小麦芽长的抑制效应在与环丙沙星复合后有所缓解,表现为拮抗特征;环丙沙星和铜在环境介质中交互作用产生络合物可能是导致不同生物效应的原因。     

菲和芘对土壤中植物根伸长抑制的生态毒性效应

测定了草甸棕壤条件下 ,菲、芘对小麦、白菜、西红柿 3种植物根伸长抑制率 ,以及复合污染毒性效应。结果表明 ,菲、芘浓度与植物根伸长抑制率呈显著线性或对数相关 (P =0 0 5 )。 2种有机物对植物根伸长抑制强度为菲 >芘。这与菲、芘的水中溶解度明显相关。与土壤脱氢酶活性和蚕豆根尖微核实验结果相比 ,植物根伸长对菲、芘毒性更敏感。小麦为有机污染的最敏感指示植物。菲、芘复合污染产生明显协同作用。     

硒对小麦和水稻种子萌发的生态毒理效应的比较研究

通过水培试验,比较研究了硒在不同浓度下对小麦和水稻种子萌发及幼苗生长的生态毒理效应。结果表明,硒在适量范围内(<0.5 mg.L-1)对种子萌发过程中各生理指标有促进作用,高剂量(>5 mg.L-1)时,对种子活力、α-淀粉酶及幼苗和根生长具有胁迫效应。硒对小麦种子发芽各指标抑制率大于水稻,硒对种子根伸长的抑制率远远大于发芽抑制率。对硒浓度与种子发芽各项指标抑制率相关分析,呈显著正相关。应用小麦根伸长抑制率可作为化学物质生态风险评价的一项生物标志物。     

Cd2+胁迫对小麦幼苗生长及呼吸作用的影响

以小麦品种郑州9023为材料,研究了不同浓度Cd2 胁迫对小麦幼苗生长及呼吸作用的影响.结果显示:(1)随Cd2 胁迫浓度的升高,小麦幼苗根和芽的呼吸速率及琥珀酸脱氢酶(SDH)活性均呈先上升后下降的趋势.(2)Cd2 胁迫对小麦幼苗根中细胞色素氧化酶(COD)、苹果酸脱氢酶(MDH)、异柠檬酸脱氢酶(IDH)同工酶表达的影响较小,都呈低浓度诱导、高浓度抑制的效应,且Cd2 处理诱导了根中新的MDH、IDH同工酶带的表达;而不同浓度Cd2 对小麦幼苗芽中COD、MDH、IDH同工酶的表达影响较小.(3)随Cd2 胁迫浓度的增加,芽长、根长、芽干重、根干重均呈持续下降的趋势,且对根的抑制作用明显大于对芽.研究表明,Cd2 胁迫可以改变小麦幼苗根和芽中SDH、COD、MDHI、DH等呼吸作用关键酶的活性或同工酶表达,从而影响其呼吸作用,最终抑制了幼苗的生长.     

六种常见抗生素对小白菜种子萌发及生理特性的影响

以小白菜为受试生物,研究了6种常用抗生素(四环素、土霉素、金霉素、强力霉素、氯霉素和磺胺二甲嘧啶)对小白菜种子萌发、根(芽)伸长、可溶性蛋白及抗氧化酶系统的毒理效应。结果表明,0.5~5 mg·L-1抗生素胁迫下,小白菜种子的发芽率无显著变化,随着抗生素暴露浓度的增加,小白菜种子的发芽率受到了显著抑制;抗生素暴露浓度与小白菜根(芽)伸长抑制率之间具有良好的剂量效应关系。由抗生素对小白菜根长的半抑制效应浓度(EC50)可知,6种抗生素对小白菜种子萌发的毒性大小依次为:磺胺二甲嘧啶氯霉素金霉素四环素强力霉素土霉素。实验浓度范围内的抗生素对小白菜幼苗体内可溶性蛋白含量具有显著的诱导效应,且各处理组间差异显著。此外,抗生素的胁迫破坏了小白菜幼苗体内的抗氧化防御系统的平衡。     

Flor-essence对小麦种子萌发和幼苗生长的影响

研究不同浓度Flor-essence对小麦种子萌发及幼苗生长的影响,以开拓其在植物生长调节剂领域的新应用。通过室内水培试验,分别设定50、100、150、200和250 mg/L 5组不同浓度的Flor-essence溶液处理,测定小麦种子发芽和植株生长的相关指标,同时选取清水(0 mg/L Flor-essence)和0.015 mg/L的油菜素内酯(BR)作对照。结果显示,与对照相比,不同浓度Floressence浸种均促进了小麦种子的萌发和生长,小麦的发芽势、发芽率、发芽指数、根长、株高、鲜重、干重、叶绿素含量和根冠比均有不同程度提高。不同浓度处理中,以200和250 mg/L处理的幼苗发芽情况最好;以150 mg/L处理的株高最高;以200 mg/L处理的根长最长、根冠比最大;以250 mg/L处理的鲜重、干重和叶绿素含量最高。利用Flor-essence浸种可促进小麦种子萌发和幼苗生长,且浓度为150-250 mg/L Flor-essence更能够在不同程度上促进小麦苗期的生长。     

壳聚糖酶的克隆表达与壳寡糖的制备分析

目的:克隆壳聚糖酶基因于大肠杆菌中实现高表达,制备壳寡糖。方法:以枯草芽孢杆菌总DNA为模板扩增壳聚糖酶基因(CSN),克隆至载体pET23a(+)上,转化菌株BL21(DE3)。重组子经0.5 mmol/L IPTG诱导后,SDS-PAGE和质谱检测与鉴定重组酶。酶纯化后水解壳聚糖,薄层色谱分析其水解产物。结果:质谱证明壳聚糖酶(31.5kDa)成功表达,表达量占菌体总蛋白的45%左右。纯化后重组酶浓度为900 mg/L,纯度95%、回收率85%,酶活力为10 000 U/mg。壳聚糖降解产物为壳二糖至壳四糖。结论:原核表达载体pET23a(+)-CSN构建正确,壳聚糖酶表达量与活性高,适用于水解壳聚糖制备壳寡糖。     

国内外蝗害治理技术现状与展望

本文首先概述了国内外蝗虫发生与为害的态势,总结了现阶段我国蝗虫发生与为害的主要特点:即农田飞蝗暴发频繁而且严重,草原土蝗的发生时常造成严重的经济损失,而且侵入城市干扰市民生活,我国与周边国家之间蝗虫过境迁移频繁,使用化学农药污染环境和农产品;分析了国内外蝗虫防治对策与技术的发展现状,重点介绍了应急防治和可持续治理对策、...     

Coiled-coil nanomechanics and uncoiling and unfolding of the superhelix and alpha-helices of myosin

The nanomechanical properties of the coiled-coils of myosin are fundamentally important in understanding muscle assembly and contraction. Force spectra of single molecules of double-headed myosin, single-headed myosin, and coiled-coil tail fragments were acquired with an atomic force microscope and displayed characteristic triphasic force-distance responses to stretch: a rise phase (R) and a plateau phase (P) and an exponential phase (E). The R and P phases arise mainly from the stretching of the coiled-coils, with the hinge region being the main contributor to the rise phase at low force. Only the E phase was analyzable by the worm-like chain model of polymer elasticity. Restrained molecular mechanics simulations on an existing x-ray structure of scallop S2 yielded force spectra with either two or three phases, depending on the mode of stretch. It revealed that coiled-coil chains separate completely near the end of the P phase and the stretching of the unfolded chains gives rise to the E phase. Extensive conformational searching yielded a P phase force near 40 pN that agreed well with the experimental value. We suggest that the flexible and elastic S2 region, particularly the hinge region, may undergo force-induced unfolding and extend reversibly during actomyosin powerstroke.     

放牧对牧草光合作用、呼吸作用和氮、碳吸收与转运的影响

研究放牧对草地植物生理活动的影响,对于揭示草地放牧演替的生理机制有重要意义.大量研究表明,家畜放牧对牧草光合作用、呼吸作用以及C和N吸收与转运的影响,可以分为生理伤害和生理恢复2个阶段.放牧通过改变草地冠层结构影响牧草光合作用,净光合作用速率短期内迅速下降,随着叶面积指数增加又逐渐上升,呼吸作用有相似的变化趋势.牧草放牧后再生长所需的C和N最初主要来自根系和留茬中的贮藏物质,此后随着牧草生长恢复逐渐由同化作用供给,C代谢与土壤N水平负相关.放牧后牧草生理活动变化与牧草遗传特性、种间竞争、家畜放牧特征、非生物环境等因素密切相关.     

Kinetics and thermodynamics of peroxidase- and laccase-catalyzed oxidation of N-substituted phenothiazines and phenoxazines

N -substituted phenothiazines (PTs) and phenoxazines (POs) catalyzed by fungal Coprinus cinereus peroxidase and Polyporus pinsitus laccase were investigated at pH 4–10. In the case of peroxidase, an apparent bimolecular rate constant (expressed as k _cat/K _m) varied from 1 ×10⁷M⁻¹s⁻¹to 2.6×10⁸M⁻¹s⁻¹ at pH 7.0. The constants for PO oxidation were higher in comparison to PT. pH dependence revealed two or three ionizable groups with pK _a values of 4.9–5.7 and 7.7–9.7 that significantly affected the activity of peroxidase. Single-turnover experiments showed that the limiting step of PT oxidation was reduction of compound II and second-order rate constants were obtained which were consistent with the constants at steady-state conditions. Laccase-catalyzed PT and PO oxidation rates were lower; apparent bimolecular rate constants varied from 1.8×10⁵M⁻¹s⁻¹ to 2.0×10⁷M⁻¹s⁻¹ at pH 5.3. PO constants were higher in comparison to PT, as was the case with peroxidase. The dependence of the apparent bimolecular constants of compound II or copper type 1 reduction, in the case of peroxidase or laccase, respectively, was analyzed in the framework of the Marcus outer-sphere electron-transfer theory. Peroxidase-catalyzed reactions with PT, as well as PO, fitted the same hyperbolic dependence with a maximal oxidation rate of 1.6×10⁸M⁻¹s⁻¹ and a reorganization energy of 0.30 eV. The respective parameters for laccase were 5.0×10⁷M⁻¹s⁻¹ and 0.29 eV. Received: 20 September 1999 / Accepted: 24 February 2000     

Synthesis of hapten and conjugates of coumestrol and development of immunoassay

3-O-Carboxymethylcoumestrol was prepared as the hapten for immunoassay by a partial alkylation of coumestrol with ethyl chloroacetate in acetone alkalized with potassium carbonate. 3-O-Ethoxycarbonylmethylcoumestrol was separated by column chromatography and finally was hydrolyzed with formic acid. 1H and 13C NMR data (APT, COSY, HMQC, and HMBC) revealed that the reaction was regioselective, as 3-O-ethoxycarboxymethylcoumestrol was the only monosubstituted derivative. The hapten was then conjugated to bovine serum albumin and used for immunization of rabbits. A radioimmunoassay (RIA) system was established based on the polyclonal antiserum and a 125I-labeled hapten-tyrosine methyl ester conjugate as the radioligand. Parameters of the RIA: sensitivity: 12 pg per tube, 50% intercept: 140 pg per tube, working range: 20-4000 pg per tube. The cross-reactivity of a panel isoflavonoid and lignan phytoestrogens was either negligible (e.g. formononetin 0.07%; biochanin A 0.06%) or not detectable at all. The major immunoreactive peak in HPLC fractions from an alfalfa extract had the same retention time as coumestrol standard and represented 94.8% of the signal. The remaining 5.2% of immunoreactivity was distributed between five minor peaks. We conclude that after the validation for particular matrices, the method will be a useful tool for analysis of coumestrol, especially in low volume and low concentration samples.     

白术同源四倍体的诱导和鉴定及其与二倍体过氧化物酶的比较

以白术（Atractylodes macrooephala Koidz.）二倍体组培苗为材料,对其四倍体诱导方法进行研究,共获得45个白术同源四倍体株系,为优良株系的选育提供了材料。此外,还分析比较了其中8个白术四倍体株系与二倍体的过氧化物酶同工酶（POD）的酶谱差异,发现四倍体各株系过氧化物酶同工酶谱比二倍体的均多了Rf0.310的谱带,且总过氧化物酶比活力也发生了很大改变,对探讨白术四倍体优良株系的生理生化机理具有一定的参考价值。