Cr6+对菹草叶绿素荧光参数、抗氧化系统和超微结构的胁迫影响

研究了不同浓度的Cr⁶⁺(0、1、10、30、50 mg·L^-1)对菹草叶片叶绿素、叶绿素荧光参数、抗氧化系统、可溶性蛋白含量、膜脂过氧化产物、可溶性糖含量、超氧阴离子(O₂^—·)产生以及细胞超微结构的胁迫影响。结果表明,随着Cr⁶⁺浓度的增加,总叶绿素、叶绿素a、叶绿素b和叶绿素a/b均呈下降趋势,F_o先升后降,F_v/F_m、F_m及F_v/F_o均逐渐降低;可溶性蛋白和谷胱甘肽(GSH)含量先升后降,抗坏血酸(AsA)含量逐渐下降;超氧化物歧化酶(SOD)活性逐渐下降,而过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性均呈先升后降趋势; O₂^—·产生速率、丙二醛(MDA)和可溶性糖含量均表现先降后升趋势;电镜观察发现：随着Cr⁶⁺浓度的增加,对细胞超微结构的损伤也加剧,表现为叶绿体膨胀,被膜破裂,类囊体片层解体;线粒体嵴数目减少,呈空泡状。可见,Cr⁶⁺破坏了菹草正常生理活动的结构基础,造成菹草生理功能紊乱。     

氯化钠胁迫对不同品种南瓜幼苗阳离子含量的影响

选择19个不同类型南瓜品种,研究了300 mmol·L^-1 NaCl胁迫条件下,幼苗地上部和根系Na⁺、K⁺、Ca²⁺含量、Na⁺/K⁺、Na⁺/Ca²⁺、钠-钾和钠-钙运输选择性系数(S_Na⁺,K⁺和S_Na⁺,Ca²⁺值)的变化.结果表明：NaCl胁迫处理8 d后,不同品种南瓜幼苗Na⁺含量均明显增加,而K⁺含量下降,离子平衡被打破.青栗（Q₁）南瓜幼苗根系Na⁺含量、地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值均明显高于黑蜜南瓜（H₂）和黑籽南瓜（H₃）.不同品种南瓜幼苗体内Na⁺含量、地上部Na⁺/K⁺和Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值变化趋势与NaCI胁迫下不同品种南瓜幼苗盐害指数的结果基本一致,进一步验证了Q₁耐盐性强与NaCl胁迫下地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值较低以及K⁺、Ca²⁺含量较高有关;而H₂和H₃对盐敏感与NaCl胁迫下地上部Na⁺/K⁺、Na⁺/Ca²⁺、S_Na⁺,K⁺和S_Na⁺,Ca²⁺值较高,以及K⁺、Ca²⁺含量较低有关.     

红豆草与土壤氮含量对大气二氧化碳浓度升高的响应

在封闭的植物培养箱中,通过盆栽实验,研究了红豆草和土壤氮含量对CO₂浓度增加的响应.结果表明,与正常CO₂浓度(355～370 μmol·mol^-1)相比,CO₂浓度升高(700 μmol·mol^-1),植物生物量增加25.1%(P＜0.01),但植物体氮浓度降低25.3%(P＜0.001),植物全氮没有显著的变化.经3个月盆栽实验后,与原始土壤相比,两种CO₂浓度处理土壤全N、NO₃^--N和NH₄⁺-N都有所降低,而土壤微生物氮则显著增加,这可能与植物生长有关.不同CO₂浓度处理土壤NH₄⁺-N浓度基本一致,但在高CO₂浓度下,土壤NO₃^--N浓度显著降低,而微生物生物氮显著增加.对整个土壤-植物系统而言,盆栽实验后,整个系统全氮有少量增加,但变化不显著,特别是在高CO₂浓度条件下,土壤-植物系统全氮最大,这可能与培养材料红豆草为豆科植物,而且在高CO₂浓度下生物量增加,导致氮的固定量增加有关.     

铬对重金属去除菌影响的研究*

考察了Cr⁶⁺浓度和培养时间对4株重金属去除菌致死率的影响、重金属去除菌除铬性能的稳定性、吸附铬前后胞内外的变化、Cr⁶⁺对胞内可溶性还原糖含量的影响以及多种因素对重金属去除菌毒性,初步探讨了重金属去除菌的抗Cr⁶⁺机理。实验结果表明,4株实验菌的致死率随培养时间的变化趋势都是先升高后降低,最后再升高;假丝酵母的可驯化性较好;掷孢酵母73对高浓度Cr6+的耐受性最好;Cr⁶⁺对4株实验菌的各种代谢过程有一定影响;扫描电     

表层岩溶动力系统中土壤水分及其岩溶效应

对广西弄拉表层岩溶动力系统中森林和灌丛的土壤容重、非毛管孔隙度等物理性质以及土壤CO₂、土壤水和泉水水化学特征进行了研究.结果表明：森林和灌丛环境下的土壤物理性质存在显著性差异,影响土壤含水量.土壤水固定CO₂浓度和土壤CO₂之间存在显著的负相关关系.森林土壤水中游离CO₂浓度为0,灌丛为5.33×10³ mg·m^-3.土壤水和泉水中pH、Ca^2＋、Mg²⁺ 、Cl^-浓度存在一定的负相关关系,其K⁺、Na^＋、HCO₃^-浓度和有机碳含量存在正相关关系.经过雨水的淋溶,土壤层各离子浓度均大幅度增加,其溶蚀能力大大增强.森林环境下的岩溶作用稳定但强度大,灌丛环境下的岩溶作用活跃但强度小.     

野葛叶片和茎段高频再生体系的建立

探讨几种因子对野葛叶片和茎段高频再生体系建立的影响。采用植物组织培养、正交实验和单因子实验的方法。野葛叶片和茎段的最佳消毒方式为70%酒精处理30 s后再用0.1%HgCl₂处理15 min;野葛叶片愈伤组织诱导的最佳培养基为MS+NAA 1.0 mg·L^-1+2,4-D 2 mg·L^-1,野葛茎段愈伤组织诱导的最佳培养基为MS+NAA 0.5 mg·L^-1+6-BA 1.0 mg·L^-1+2,4-D 2 mg·L^-1;暗培养更有利于野葛愈伤组织的诱导;野葛叶片和茎段愈伤组织诱导的最佳蔗糖浓度均为30 g·L^-1;野葛叶片愈伤组织的最佳出芽培养基为MS+NAA 1.0 mg·L^-1+6-BA 3.0 mg·L^-1,而野葛茎段愈伤组织的最佳出芽培养基为MS+ NAA 0.5 mg·L^-1+KT 2 mg·L^-1;光照培养更有利于野葛叶片和茎段愈伤组织芽的再分化;野葛叶片愈伤组织再生芽生根的最佳培养基为MS+NAA 0.5 mg·L^-1+PP₃₃₃ 0.5 mg·L^-1,而野葛茎段愈伤组织再生芽生根的最佳培养基为MS+NAA 0.5 mg·L^-1+PP₃₃₃ 3.0 mg·L^-1;野葛叶片和茎段愈伤组织再生芽生根的最佳蔗糖浓度均为30 g·L^-1;叶片再生苗移栽的最佳PP₃₃₃浓度为1.0 mg·L^-1,茎段再生苗移栽的最佳PP₃₃₃浓度为3.0 mg·L^-1;叶片和茎段再生苗的最佳移栽基质均为蛭石:珍珠岩（2:1）。     

铝胁迫下北美车前和车前生长及叶绿素荧光特性的比较研究

采用系列浓度AlCl₃溶液（100、500、800、2 000 mg·L^-1）进行处理,在处理后不同时间（0,10、20、30 d）,测定北美车前（Plantago viriginica）和车前(P.asiatica)的生长及叶绿素荧光特征指数,旨在比较外来入侵种北美车前和同属本地种车前的生长及叶绿素荧光对铝胁迫响应的差异。结果表明,车前和北美车前的根冠比在轻度铝（Al³⁺=100 mg·L^-1）处理下略有上升,在中度（Al³⁺=500 mg·L^-1）以上铝浓度处理下开始显著下降;叶绿素a、b含量在轻度铝处理下变化不明显,随着铝浓度的增加和处理时间的延长呈现明显下降趋势;叶绿素荧光参数F_v/F_m、Φ_PSⅡ及F_v/F_o值在低浓度铝的短时间处理下略有上升,随着铝浓度的升高和处理时间的延长则明显下降。结果表明铝胁迫对上述两种植物的生长和叶绿素荧光参数均有一定影响,但北美车前各参数的下降幅度小于车前,表现出比车前更为耐铝的生理特性。     

浸种对镉胁迫下油菜种子萌发及幼苗生长的影响

通过水培实验研究了La(NO₃)₃浸种对镉胁迫下油菜（Brassica napus）种子萌发及幼苗生长的影响。结果表明,当镉浓度≤10 mg·L^-1时,La(NO₃)₃浸种（0～50 mg·L^-1）能提高油菜种子的活力,促进油菜幼苗的生长,并提高脂肪酶的活性和幼苗根细胞有丝分裂指数。其中以10 mg·L^-1 La(NO₃)₃浸种处理效果最佳,与对照相比,种子活力指数及油菜幼苗各生长指标显著提高,脂肪酶活性增加40.41%～65.09%,幼苗根细胞有丝分裂指数增加62.76%～77.02%。当镉浓度>10 mg·L^-1时,La(NO₃)₃浸种对镉胁迫的缓解效用明显减 弱,与对照相比,仅脂肪酶活性显著提高,其它指标无明显变化。     

外源抗坏血酸对镉胁迫下黑藻抗氧化系统的保护作用

研究了不同浓度抗坏血酸(ascorbic acid,AsA)对5 mg·L^-1Cd²⁺胁迫下黑藻（Hydrilla verticillata）体内超氧阴离子(O₂^-)产生速率、过氧化氢(H₂O₂)含量、抗坏血酸和谷胱甘肽(GSH)含量,以及超氧化物歧化酶(SOD)、超氧化物酶(POD)、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,与单一Cd²⁺胁迫相比,随着外源AsA浓度的升高,黑藻体内活性氧生成速率逐步降低;抗氧化物质AsA先升后降,GSH缓慢升高;抗氧化酶APX和CAT活性先升后降,POD活性逐步下降,并接近正常状态,对SOD活性影响不大.可见AsA能够有效缓解Cd²⁺对黑藻的毒害,且60 mg·L^-1浓度下的缓解效果最好.     

施氮水平对水稻生育后期地上部氨挥发的影响

采用温室盆栽模拟试验,研究了不同施氮水平下水稻开花后地上部氨挥发及其影响因素.结果表明：不同品种水稻开花后地上部日氨挥发量和开花至成熟期的氨挥发总量均随施氮量的增加而增加,且不同施氮水平间存在一定差异.花期和成熟期水稻地上部氨挥发量（y）与功能叶片谷氨酰胺合成酶（GS）活性（x₁）呈显著负相关,而与功能叶片质外体NH₄⁺浓度（x₂）呈显著正相关:y=-0.37846x₁+0.41821x₂+0.04925（R²=0.9471,n=16）.水稻氮素收获指数（x₁）和氮肥生理利用率（x₂）均与地上部氨挥发总量（y）呈显著负相关：y=-0.02117x₁+0.75186(R²=0.8426,n=8）和y=-1.10386x²+35.52676（R²=0.8489,n=8）,说明高氮水平下水稻氮肥利用率的下降与水稻地上部氨挥发量的增加有关.     

Protein degradation by peroxide catalyzed by chromium (III): role of coordinated ligand

In order to understand the role of coordinated ligands in controlling the biotoxicity of chromium (III), interactions of three types of chromium (III) complexes viz. trans-diaquo [1,2 bis (salicyledeneamino) ethane chromium (III) perchlorate, [(Cr(salen)(H(2)O)(2)](ClO(4)); tris (ethylenediamine) chromium (III) chloride, [Cr(en)(3)]Cl(3), and monosodium ethylene diamine tetraacetato monoaquo chromiate (III), [Cr(EDTA)(H(2)O)]Na with BSA has been investigated. Spectroscopic and equilibrium dialysis studies show that the two cationic complexes Cr(salen)(H(2)O)(+)(2) and Cr(en)(3+)(3) bind to the protein with a protein-metal ratio of 1:8 and 1:4. The anionic complex Cr(EDTA)(H(2)O)(-) binds to the protein with a protein-metal ratio of 1:2. The binding constant K(b) as estimated from the fluorescence quenching studies has been found to be 7.6 +/- 0.4 x 10(3) M(-1), 3.1 +/- 0.2 x 10(2) M(-1), and 1.8 +/- 0.2 x 10(2) M(-1) for Cr(salen)(H(2)O)(+)(2), Cr(en)(3+)(3), and Cr(EDTA)(H(2)O)(-) respectively indicating that the thermodynamic stability of protein-chromium complex is Cr(salen)(H(2)O)(+)(2) > Cr(en)(3+)(3) approximately Cr(EDTA)(H(2)O)(-). The complexes Cr(salen)(H(2)O)(+)(2) and Cr(EDTA)(H(2)O)(-) in the presence of hydrogen peroxide have been found to bring about protein degradation, whereas Cr(en)(3+)(3) does not bring about any protein damage. This clearly shows that the nature of the chromium (III) complex plays a major role in the biotoxicity of chromium (III).     

Stabilization of chromium(V) species in bovine serum albumin adduct

A detailed investigation of molecular interactions of the protein bovine serum albumin (BSA) with potassium dichromate has been made. Compelling evidence for the formation of a relatively stable Cr(V) species which decays only slowly to afford Cr(III) products has been obtained. The resulting final chromium(III) product mediates in cross-linking of BSA. The implications of the formation of a relatively stable chromium(V) as well as chromium(III)-mediated cross-links in the marker protein are discussed in the context of the metal ion-induced biotoxicity.     

铬胁迫对‘协优赣2号’水稻种子萌发的影响

以水稻‘协优赣2号’种子为材料,探讨不同浓度铬对其萌发的影响。结果表明：低浓度Cr6+（≤10 mg/L）对该水稻种子萌发没有抑制作用;当Cr6+浓度≥50 mg/L时对其萌发有显著抑制作用。Cr6+对该水稻种子的发芽率影响很小,但一定程度上延迟了发芽;Cr6+对胚根生长抑制作用最大。     

Chromium-associated 32P-labeling of proteins

The incubation of proteins with chromium (Cr3+ or Cr6+) in the presence of 32P ([gamma-32P]ATP or H3(32)PO4) at room temperature for 10-30 min resulted in the labeling of these proteins with 32P. The 32P-labeled proteins could be separated by SDS-polyacrylamide gel electrophoresis and identified by exposure to X-ray film. The characteristics of this procedure included: the optimal chromium concentration was 100 microM; the minimum requirement of each protein was 1 microgram; the optimal pH value was between 6 and 8; metal ions such as V5+, Mn2+ and Fe3+ strongly inhibited the effect of chromium, whereas Ca2+ and Mg2+ had little effect. It was concluded that chromium binds to the proteins and forms a complex with 32P to achieve the 32P-labeling of the proteins. This technique can be applied for the rapid preparation of 32P labels on protein markers for gel electrophoresis and for the identification of unknown protein species.     

Hexavalent chromium uptake by sensitive and tolerant mutants of Schizosaccharomyces pombe

Lysine and leucine auxotrophic, heterothallic (h+, h-) strains of Schizosaccharomyces pombe were used to obtain chromium (VI)-sensitive and -tolerant mutants by ultraviolet radiation-induced and nitrosoguanidine-induced mutagenesis. The minimal inhibitory concentrations of K2Cr2O7 on YEA media were 225 microM for the wild-type strain CW-6, 125 microM for the sensitive mutant CS-6.51 and 275 microM for the tolerant mutant CT-6.66. The mutants exhibited cross-sensitivity of various patterns to Cd2+, Cu2+, Ni2+, Zn2+ and VO3-(4). Cr(VI) was added to the actively growing cultures and the total chromium (TOCr) content of the cells was determined. The sensitive mutant exhibited a high bioaccumulation ability, with a dry biomass of 810 micrograms g-1 after 30 min, while the tolerant mutant had a significantly lower ability than the wild-type strain. In PIPES buffer, washed, lysine-starved biomasses were treated with 75 microM Cr(VI) and after 2 h, the TOCr and the organically bound chromium (OBCr) were determined. Under these conditions, the sensitive and tolerant mutants had the same TOCr content, 50% of which was OBCr. The wild-type strain exhibited a lower TOCr content than that of its mutants and only 35% of this was OBCr. The Cr(VI)-sensitivity was due to a significantly increased uptake of Cr(VI).     

Chromosomal aberrations and sister-chromatid exchanges in Chinese hamster cells treated in vitro with hexavalent chromium compounds.

Chinese hamster cells (CHO line) were treated in vitro for 30--39 h with hexavalent chromium compounds (K2Cr2O7 and Na2CrO7), at concentrations ranging from 0.1 to 1.0 microgram of Cr6+ per ml, in medium containing BUdr. Chromosomal aberrations and sister-chromatid exchanges were scored on BUdr-labelled 2nd division metaphases, collected at the end of treatment and stained with Giemsa. Treatment with mitomycin C 0.009--0.030 microgram/ml) was carried out as a control for the responsiveness of the cell system to chromosomal damage. Both chromium compounds induced marked mitotic delays. Chromosomal aberrations were increased about 10-fold by exposure to Cr6+ (1.0 microgram/ml). The principal aberrations observed were single chromatid gaps, breaks and interchanges, whose frequencies increased proportionally to the concentration of chromium. Dicentric chromosomes, isochromatid breaks, chromosome and chromatid rings were also induced. The frequenyc of sister-chromatid exchanges was hardly doubled 30 h after exposure to Cr6+ at 0.3 microgram/ml, whereas it was trebled 39 h after treatment, in the cells whose division cycle had been slowed down by chromium.     

高氯酸盐和铬复合污染对水稻生理特性的影响

通过盆栽试验,研究了不同浓度高氯酸盐(ClO4-)、六价铬(Cr6+)及其复合污染(ClO4-+Cr6+)胁迫条件下水稻叶片叶绿素荧光参数、叶绿素含量和水稻体内抗氧化酶活性及丙二醛含量的变化。结果表明,随着ClO4-、Cr6+和ClO4-+Cr6+处理浓度的升高,水稻叶片叶绿素荧光参数Fv/F0、Fv/Fm和叶绿素含量均明显下降,且生长前期下降程度高于后期;ClO4-、Cr6+及ClO4-+Cr6+均可显著提高水稻体内POD酶(peroxidase)、CAT酶(catalase)活性和MDA(malondialdehyde)含量,且复合处理显著高于单一处理;分蘖期水稻体内SOD酶(superoxide dismutase)活性随着污染物浓度的增加明显降低,而在抽穗期其SOD酶活性升高。复合处理对水稻的损伤和毒害作用比单一处理更为严重,其交互作用机理值得进一步研究。     

Chromium and yogurt effects on hepatic lipid and plasma glucose and insulin of obese mice

Dietary chromium (Cr) supplements in casein or yogurt-based diets were fed to genetically obese C57BL/6J-OB (ob/ob) mice to investigate the effects of Cr and yogurt on total hepatic lipid, plasma glucose, insulin, and cholesterol levels. Diet groups were casein control (C), yogurt control (Y), yogurt plus CrCl₃ (Y + Cr) (1.83 ppm Cr), and casein plus CrCl₃ (C + Cr) (1.85 ppm Cr). Food and water were availablead libitum. No significant differences were observed in final body weight. In obese mice, total hepatic lipid was significantly greater in the C than in the C + Cr group and in the Y than in the Y + Cr group. Plasma immunoreactive insulin levels tended to be lower in animals fed C + Cr and Y + Cr diets. Plasma insulin was significantly correlated with hepatic lipid and with plasma cholesterol. By analysis of variance, bone Cr was elevated by Cr supplementation. In the obese mouse, a model for insulin resistance, Cr supplementation apparently affects both hepatic lipid concentration and bone chromium.     

Bacteria reducing chromium in nature and in effluents of industrial plants

Bacteria capable of hexavalent chromium (Cr6+) reduction can be found in Cr6+-containing sewage and sediments of purification tanks of industrial plants. They cannot be detected in water and soil samples containing no chromium compounds. Bacteria reducing chromium belong to the genera Aeromonas, Escherichia, Pseudomonas and Enterobacter. Their activity of Cr6+ reduction correlates with the high resistance to the elevated content of this ion in the medium. The fine cell structure of these bacteria is described.     

六价铬在斜带石斑鱼胚胎中的生物累积及其对igf2、glut2和pparg基因表达的影响

以斜带石斑鱼(Epinephelus coioides)为研究对象, 探讨了水中不同浓度梯度六价铬(0、0.20、0.60、1、5、10、20、40、60和80 mg/L)在胚胎发育不同阶段(桑葚期、囊胚期、原肠末期、脑泡形成期和心脏跳动期)的生物累积及其对细胞生长基因igf2和营养代谢基因glut2、pparg的mRNA表达的影响。结果表明, 胚胎中Cr6+生物累积量和吸收率随暴露浓度的增加而增加, 且吸收率随胚胎发育时期的延伸而降低。在桑葚期时, 斜带石斑鱼胚胎吸收Cr6+能力最强, 是心脏跳动期的20倍。在桑葚期、囊胚期和原肠末期, Cr6+对胚胎中igf2和glut2基因mRNA表达水平有显著促进作用(P<0.05), 但对pparg基因mRNA表达水平有显著抑制作用(P<0.05)。在原肠末期和脑泡形成期, Cr6+对胚胎中pparg基因mRNA表达水平有显著促进作用(P<0.05)。研究表明水中Cr6+暴露在斜带石斑鱼胚胎发育过程中有明显的生物累积, 且对细胞生长水平和营养代谢有明显的影响, 研究为斜带石斑鱼早期生活史阶段适宜生境和资源保护提供了理论基础。