渗透胁迫下多花黑麦草叶内过氧化物酶活性和脯氨酸含量以及质膜相对透性的变化

多花黑麦草幼苗于３ 叶期转移至１／２Ｈｏａｇｌａｎｄ 溶液中培养,同时加入ＰＥＧ６０００ 用以模拟５种强度的渗透胁迫。植物叶内过氧化物酶活性、游离脯氨酸含量和质膜相对透性均对渗透胁迫强度的增加作出了反应,但反应的敏感性依次降低。从时间进程上看,过氧化物酶活性升降在前,游离脯氨酸积累继之,嗣后出现质膜相对透性增高。每个测定日内叶片中游离脯氨酸含量与质膜相对透性呈显著至极显著正相关。     

渗透胁迫下多花黑麦草叶内过氧化物酶活性和脯氨酸含量以及质 …

多花黑麦草幼苗于３叶期转移至１／２Ｈｏａｇｌａｎｄ溶液中培养,同时加入ＰＥＧ６０００用以模拟５种强度的渗透胁迫。植物叶内过氧化物酶活性、游离脯氨酸含量和质膜相对透性均对渗透胁迫强度的增加作出了反应,但反应的敏感性依次降低。从时间进程上看,过氧化物酶活性升降在前,游离脯氨酸积累继之,嗣后出现质膜相对透性增高。每个测定日内叶片中游脯氨酸含量与质膜相对透性呈显著至极显著正相关。     

外源芦丁预处理对水分胁迫下玉米幼苗的生理效应

以玉米(Zeamays L.)品种'郏单958'为材料.采用营养液水培法,研究了外源芦丁(Rutin)对聚乙二醇(PEG)胁迫下幼苗叶片质膜相对透性、脯氨酸、可溶性糖含量及保护酶活性的影响.结果显示:(1)在15%PEG-6000胁迫下,玉米叶片的MDA含量、质膜相对透性、脯氨酸和可溶性蛋白质含量均显著增加,保护酶SOD、CAT、POD活性显著升高.(2)一定浓度芦丁(>0.40 g/L)预处理可显著抑制水分胁迫下玉米幼苗叶片MDA含量的上升,降低叶片质膜相对透性,并诱导SOD、POD和CAT活性提高.降低脯氨酸和可溶性蛋白质含量.说明外源芦丁能够提高玉米幼苗的抗氧化作用,缓解水分胁迫引起的膜脂过氧化,保护细胞膜免受或减少损伤·达到提高植物抗旱性的目的.     

高温胁迫对两种冷季型草坪草生理生化特性的影响

为研究高温胁迫对冷季型草坪草生理生化指标的影响,通过盆栽试验测定了昼夜(38/28℃)两种温度下两种冷季型草坪草的5种生理生化指标(质膜透性、脯氨酸含量、过氧化物酶(POD)活性、超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量)。结果表明:随着胁迫时间的延长,各品种叶片的相对电导率、丙二醛含量和游离脯氨酸含量均呈递增趋势,其增加幅度与胁迫时间呈正相关,胁迫后各指标相对于对照均有了显著的增加(P<0.05);过氧化物酶和超氧化物歧化酶活性则呈先上升后下降的趋势。高羊茅属3个品种的耐热性大于早熟禾属各品种的耐热性,其中高羊茅属的RebleⅣ和早熟禾属的Blue Sap-phire的耐热性优于种间其他品种。     

干旱胁迫下外源脱落酸和硅对沙枣幼苗叶片水势及保护酶活性的影响

以一年生沙枣幼苗为材料,研究了外源脱落酸和外源硅在干旱（T2:SRWC=35%~40%,处理时间30 d）胁迫下沙枣幼苗叶片相对含水量、叶片水势、质膜相对透性、丙二醛(MDA)含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的影响。结果表明：沙枣幼苗T2干旱处理时,与对照(ck)相比其叶片相对含水量和水势均极显著降低,质膜相对透性有所增大,沙枣幼苗被受到了一定程度的伤害。同时,向T2干旱处理的幼苗使用外源脱落酸(ABA)后,可以极显著提高其叶片相对含水量和过氧化氢酶活性,极显著降低叶片质膜相对透性和丙二醛含量,叶片水势也有所降低,这说明使用外源脱落酸能够减轻干旱胁迫对沙枣幼苗的伤害。同时,向T2干旱处理的幼苗使用外源硅(Si)时,与未使用外源硅的T2相比其叶片相对含水量和超氧化物歧化酶(SOD)活性极显著上升,叶片水势也有下降趋势,这说明使用外源硅在一定程度上能够缓解干旱胁迫对沙枣幼苗的伤害。     

外源NO对NaCl胁迫下辣椒幼苗氧化损伤的保护效应

以辣椒品种陇椒2号为试验材料,研究了外源NO供体硝普钠(SNP)对辣椒幼苗氧化损伤的影响.结果显示,在100 mmol/L NaCl胁迫下,辣椒叶片的MDA含量、质膜相对透性和脯氨酸含量均增加,保护酶SOD、CAT活性降低,而POD活性只在胁迫18 d时降低.0.1 mmol/L SNP处理可减缓NaCl胁迫下辣椒幼苗叶片MDA含量的上升,降低叶片质膜相对透性,并诱导SOD、POD和CAT活性增加,提高脯氨酸含量,表明外源NO可以通过提高盐胁迫下辣椒幼苗叶片组织的抗氧化能力来缓解氧化损伤.而SNP相似物NaNO2和K3Fe(CN)6处理对盐胁迫引起的氧化损伤并没有起到明显的缓解作用,进一步证实了NO对辣椒幼苗耐盐性具有专一性的调节作用.     

亚硫酸盐引起小麦幼苗细胞膜透性等改变的机制研究

研究亚硫酸盐胁迫后,小麦幼苗叶内超氧化物歧化菌(SOD)和过氧化物菌(POD)活性、游离脯氨酸含量和质膜透性变化等各项指标之间的关系。结果显示：从指标的敏感性来看,亚硫酸盐引起小麦幼苗的抗氧化酶活性、游离脯氨酸含量变化、质膜透性改变的反应敏感性依次降低;从时间进程来看,亚硫酸盐首先引起抗氧化酶活性改变,然后引起游离脯氨酸的积累,最后导致细胞质膜透性增加,并存在一定的时间一效应和剂量一效应的相关性。     

PEG胁迫及复水对不同抗旱性小麦幼苗脯氨酸代谢关键酶活性的影响

以两种不同抗旱性小麦品种幼苗为试验材料,采用PEG模拟干旱胁迫处理,探究干旱胁迫及复水对小麦幼苗叶片与根系脯氨酸累积及关键酶活性的影响。结果显示:(1)PEG胁迫下抗旱品种‘普冰143’根长和根干重下降不大,而水敏感品种‘郑引1号’根长和根干重下降显著;且于胁迫处理36h时‘普冰143’根系脯氨酸含量增加(75.0%)显著大于‘郑引1号’(37.7%),复水24h后均恢复至对照水平。(2)PEG胁迫下‘普冰143’叶片中谷氨酸合成途径关键酶P5CS和鸟氨酸合成途径关键酶δ-OAT活性均显著增加,且‘普冰143’叶片脯氨酸两条合成途径关键酶活性均得以加强;PEG胁迫处理36h时,‘郑引1号’叶片中P5CS活性增加显著,δ-OAT活性变化较小,且‘郑引1号’叶片脯氨酸合成可能以谷氨酸途径为主;但在PEG胁迫下两个不同抗旱性品种的根中P5CS、δ-OAT活性均变化较小。(3)PEG胁迫处理36h时‘普冰143’叶片脯氨酸降解酶PDH活性显著下降,而‘郑引1号’叶片PDH活性显著增加,复水后抗旱品种叶片该酶活性显著增加,水敏感品种恢复至对照水平;但PEG胁迫处理下两个不同抗旱性品种的根中PDH活性均显著下降。研究表明,PEG胁迫下小麦叶片是合成脯氨酸的主要部位,抗旱品种‘普冰143’根系脯氨酸持续积累与叶片中高的脯氨酸合成关键酶活性及脯氨酸转运有关。     

渗透胁迫下多效唑对刺槐幼苗体内多胺、脯氨酸和保护酶系统的影响

刺槐幼苗在PEG渗透胁迫下,相对含水量(RWC)降低,质膜透性增加,游离腐胺、脯氨酸的积累和超氧物歧化酶(SOD)、过氧化氢酶(CAT)活性提高,腐胺、亚精胺比值(Put/Spd)增加。渗透胁迫下用多效唑(PP_(333))作浸根和浸种处理,提高刺槐幼苗RWC和游离脯氨酸含量,减少质膜透性和 Put/Spd比值,降低SOD、CAT活性和腐胺含量。腐胺水平的变化与幼苗的水分状况有关,与质膜透性的变化趋势一致。     

壳聚糖对蝴蝶兰幼苗耐热性的诱导作用

为了评价壳聚糖对蝴蝶兰幼苗耐热性的诱导效应,分别采用0(以无壳聚糖为对照)、25、50、100、200和400 mg·L~(-1)壳聚糖溶液处理蝴蝶兰幼苗,并置于42℃下胁迫3 d,测定了蝴蝶兰幼苗的生理指标变化。结果表明:当壳聚糖浓度由25 mg·L~(-1)增大到100mg·L~(-1)时,蝴蝶兰幼苗叶片的SOD、POD、CAT活性、脯氨酸、可溶性糖、叶绿素和类胡萝卜素含量不断增加,而质膜透性和丙二醛含量不断下降,但可溶性蛋白含量没有显著变化;特别是在100 mg·L~(-1)时,SOD、POD和CAT活性、脯氨酸、可溶性糖、叶绿素和类胡萝卜素含量增加到最大值且极显著高于对照,而质膜透性和丙二醛含量下降至最小值且极显著低于对照,蝴蝶兰幼苗遭受了轻微的高温伤害;随着壳聚糖浓度由200 mg·L~(-1)增大至400mg·L~(-1),SOD、POD和CAT活性、脯氨酸、可溶性蛋白、可溶性糖、叶绿素和类胡萝卜素含量极显著下降,而质膜透性和丙二醛含量极显著上升,蝴蝶兰幼苗的受害趋于加重;由此可见,100 mg·L~(-1)壳聚糖处理能显著提高蝴蝶兰幼苗的耐热性。     

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、...     

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     

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.     

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。     

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.