水杨酸在赭曲霉毒素A诱导的拟南芥毒性中的作用

赭曲霉毒素A(ochratoxin A,OTA)是一种分布广泛的真菌毒素,会对谷物、动物饲料、动物性食品等造成污染。OTA对多种动物具有较强的肾毒性和肝毒性,并有致畸、致突变和致癌作用。对植物的研究表明,OTA还具有植物毒性。本实验研究了植物中重要的内源信号分子水杨酸(Salicyli cacid,SA)在OTA对拟南芥(Arabidopsis thaliana)毒性中的作用。利用高效液相色谱测定了拟南芥叶片在OTA处理下SA含量的变化,结果显示,OTA胁迫促进了SA含量的上升;通过实时荧光定量PCR测定了OTA对SA途径中重要的病程相关蛋白1基因(pathogenesis-related gene1,PR1)相对表达量的影响,结果显示,OTA能诱导PR1的表达,并且这种诱导作用与OTA胁迫时间有关;SA与OTA同时处理拟南芥叶片后,观察到SA能造成OTA引起的叶片坏死斑的加重,相对电导率和活性氧含量的测定结果表明,SA能加重OTA对叶片的伤害,促进OTA诱导的活性氧的上升。本研究表明,SA参与了OTA诱导的拟南芥毒性过程,SA和OTA共同处理能增强OTA的植物毒性。     

Ca~(2+)参与外源NO增强低温胁迫下黄瓜幼苗叶片抗氧化能力

为探究Ca~(2+)在一氧化氮(NO)增强黄瓜抗氧化能力和耐冷性中的作用,本研究以津研四号黄瓜幼苗为试验材料,通过叶面喷施NO供体亚硝基铁氰化钠(SNP),游离Ca~(2+)螯合剂乙二醇-双-(2-氨基乙基)四乙酸(EGTA),质膜Ca~(2+)通道阻断剂三氯化镧(La Cl3),钙调素(Ca M)活性抑制剂三氟啦嗪(TFP)和钙调素激酶(Ca M-PK)阻断剂N-(6-氨基己基)-5-氯-1-萘磺胺(W-7),研究低温(10℃/6℃)胁迫下黄瓜幼苗叶片相对电导率、丙二醛(MDA)含量、抗氧化酶活性及其相关基因表达量、H_2O_2含量和O_2~(-·)含量的变化。结果表明,与CK相比,水+SNP处理在低温24 h和48 h提高了黄瓜幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性及其相关基因表达,降低了电导率以及MDA和H_2O_2含量,而EGTA+SNP、LaCl_3+SNP、TFP+SNP和W-7+SNP处理抑制了SNP作用效果,表明Ca~(2+)参与NO对低温胁迫下黄瓜幼苗叶片抗氧化过程的调节。此外,在低温0、3和6 h,H_2O_2组织染色显示水+SNP处理的黄瓜幼苗叶片H_2O_2积累量显著高于其他处理;在低温6 h,水+SNP处理黄瓜幼苗叶片O-·2积累量显著高于其他处理,表明活性氧(ROS)可能也作为一种信号分子,位于Ca~(2+)的下游参与NO增强黄瓜幼苗的抗氧化能力。本研究为阐明Ca~(2+)和NO信号系统在提高植物耐冷性中的作用机理提供了理论依据。     

钙对化学诱抗剂诱导番茄叶片木质素合成的影响

为探索钙对化学诱抗剂水杨酸（SA）、 茉莉酸甲酯（MeJA）、 龙胆酸（GA）和 -氨基丁酸（BABA）诱导番茄木质素合成的影响,在番茄六叶期用上述诱抗剂分别处理第3 叶片,然后喷施CaCl2、 蒸馏水、 乙二醇-双-(2-氨基乙醚)四乙酸（EGTA）或LaCl3,处理后0、 1、 2、 3、 5 d 测定各处理番茄第3 叶片（诱导叶）和第5 叶片（非诱导叶）中木质素含量的变化。结果表明, （1）用上述化学诱抗剂处理番茄第3 叶片,诱导叶及其上位非诱导叶中木质素含量均升高;（2）外源Ca2+ 进一步促进上述诱抗剂诱导番茄叶片中木质素含量的增加;而Ca2+ 螯合剂EGTA和质膜钙通道抑制剂LaCl3,则不同程度地抑制这些诱抗剂对木质素含量的诱导作用。这些结果表明,钙对上述4 种诱抗剂诱导番茄叶片中木质素的合成具有正调控作用。     

钙和NO对NaCl胁迫下黄瓜幼苗生长和活性氧代谢的影响

采用营养液培养的方法,研究了Ca2+对外源一氧化氮(Nitric oxide,NO)所诱导的NaCl胁迫下黄瓜幼苗生长、活性氧代谢的影响。结果表明,添加外源NO或Ca2+显著缓解了NaCl胁迫对黄瓜幼苗生长的抑制,叶片和根系超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性较单独NaCl胁迫处理显著提高,丙二醛(MDA)和过氧化氢(H2O2)的含量、超氧阴离子(O.-2)产生速率明显下降;添加NO的同时添加Ca2+通道抑制剂La3+抑制了NO的这些调节作用。结果表明Ca2+对NO诱导的NaCl胁迫下黄瓜幼苗植株活性氧清除能力的提高起重要作用,NO的作用可能依赖于胞浆Ca2+。     

赭曲霉毒素A引起HepG2细胞损伤及DNA甲基化水平降低

赭曲霉毒素A (ochratoxinA,OTA)是一种污染食品的真菌毒素,对许多动物具有肾毒性,肝毒性,免疫毒性,致畸和致癌作用.本研究以人肝癌细胞HepG2为体外模型,研究OTA引起的细胞损伤及对DNA稳定性的影响.MTT结果显示,OTA能抑制HepG2细胞的生长,存在时间剂量——效应关系.OTA引起细胞上清中酸脱氢酶(LDH),谷草转氨酶(GOT)和谷丙转氨酶(GPT)活性的升高,诱导细胞内活性氧(ROS)生成,降低超氧化物歧化酶(SOD)活力.彗星实验结果显示OTA引起DNA链断裂,形成拖尾现象.同时,本研究还首次研究了OTA对DNA甲基化的影响.HPLC/MS/MS结果显示,经OTA处理后的细胞,其DNA中5-甲基脱氧胞苷(5mdC)百分数显著低于对照组.这些结果表明OTA会抑制HepG2细胞生长,引起氧化损伤,破坏DNA的稳定性和完整性.本研究表明OTA引起的肝毒性可能与氧化损伤和DNA损伤有关.     

钙对苹果果实钙调蛋白含量和Ca2+ -ATPase活性及其基因表达的影响

研究不同浓度钙（0、1和10 mmo1/L CaCl2 ;5 mmo1/L EGTA）对苹果果实钙调蛋白（CaM）含量和Ca2+-ATPase活性及其基因表达的影响。利用同源克隆方法分离CaM和Ca2+-ATPase基因,采用荧光定量PCR方法研究它们表达特征。结果表明,果实切片外源补钙,可溶性Ca2+及CaM含量在高钙处理12 h达到高峰;高钙处理12 h质膜Ca2+-ATPase活性显著增加,与胞内CaM含量增加时间一致;高钙处理24 h液泡膜Ca2+-ATPase活性显著增加;随着质膜和液泡膜Ca2+-ATPase活性显著增加,可溶性Ca2+含量在加钙处理48 h显著下降。研究基因表达发现,加钙处理6 h苹果CaM基因的表达量显著增加;加钙处理12 h苹果Ca2+-ATPase基因的表达量显著增加,与CaM含量及质膜Ca2 +-ATPase活性变化一致。果实缺钙处理显著增加CaM基因表达量,而苹果Ca2 +-ATPase基因的表达量没有显著变化。上述研究表明,苹果补钙可以提高细胞内可溶性Ca2+和CaM含量以及CaM基因的表达量,有效启动钙信使系统;质膜及液泡膜Ca2+-ATPase是调控胞内Ca2+关键的酶,通过提高质膜及液泡膜Ca2+-ATPase的活性及Ca2+-ATPase基因的表达量,维持胞内Ca2+的稳态水平。     

赭曲霉毒素A(OTA)对拟南芥植物毒性的初步研究

赭曲霉毒素A主要由某些真菌产生的次级代谢产物,广泛分布于谷物、啤酒以及肉等动物性食品中,对动物和人体赭曲霉毒素A(OTA)具有肾脏毒性、肝脏毒性,以及致畸、致突变和致癌的作用.本研究主要通过Evans blue染色、trypan blue染色、琼脂糖凝胶电泳以及双向电泳等研究OTA对拟南芥(Arabidopsis thaliana)植物的毒性,结果表明:OTA对拟南芥植株生长有明显的抑制作用,尤其表现在根、叶等部位;DNA片段化,经Trypan blue和Evans blue染色证明发生细胞死亡,OTA导致拟南芥叶片细胞损伤或坏死,细胞膜完整性破坏,DNA降解;蛋白电泳结果表明OTA诱导拟南芥蛋白表达发生变化,一些蛋白表达量上调,一些蛋白表达量下调,甚至消失.研究提示OTA具有植物毒性.     

钙对大豆幼苗镍毒害的缓解效应及对抗氧化酶活性的影响

采用盆栽方法,研究了镍毒害条件下外源钙对大豆镍毒害的缓解效应以及对其叶片组织中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性的影响,以探讨钙缓解植物镍毒性的生理机制.研究结果表明:Ni2+60 mg/kg添加量对大豆幼苗生长表现出明显的抑制作用,但是当加入不同钙量后,大豆的镍毒害症状得到不同程度的缓解,Ca2+ 200 mg/kg处理的缓解作用好于Ca2+ 100 mg/kg.与不施镍处理相比,单施Ni2 60 mg/kg处理的大豆叶片组织SOD、CAT和APX活性明显下降,而POD活性明显上升.当配施Ca2以后,大豆叶片组织中SOD、CAT、POD和APX活性明显提高,且Ca2+ 200 mg/kg处理的上升程度比Ca2+ 100 mg/kg处理的大.因此,Ca2+是通过提高叶片组织抗氧化酶活性,增强活性氧清除能力,而使大豆的镍中毒症状得到缓解,这是Ca2+减轻大豆镍毒害的生理机制之一.     

NaCl胁迫下外源腐胺和钙对草莓幼苗离子吸收的影响

在150 mmol/L NaCl 胁迫条件下,以达塞莱克特草莓为试材,利用基质盆栽方法研究了外源腐胺和钙对草莓生长、叶片含水量、脯氨酸含量及Ca2+、Na+ 和 Cl- 吸收的影响。结果表明,在营养液中添加14 mmol/L 硝酸钙和叶面喷施 1×10-5 mol/L 腐胺均可提高盐胁迫草莓植株的地上部和地下部干鲜重,提高叶片含水量、脯氨酸含量,抑制 Na+ 和Cl- 的吸收及运输,提高根系和叶片的 K+/Na+ 值和 Ca2+/ Na+ 值,硝酸钙和腐胺同时处理的效果优于单独处理。缺钙条件下,喷施外源腐胺的 K+/Na+ 值和 Ca2+/ Na+ 值显著或极显著低于腐胺加钙处理,Cl- 含量显著高于腐胺加钙处理。外源腐胺对 Na+ 和 Cl- 吸收的调控作用受到 Ca2+ 的调节。     

钙对小麦氮同化关键酶活性的影响及其与蛋白质磷酸化的关系

为探讨氮素同化机理 ,小麦幼苗经溶液培养 (培养液中不含Ca2+)至二叶一心后 ,在培养液中分别设置不同浓度的Ca2+ 、Ca2+专一性螯合剂EGTA以及Ca2+通道阻塞剂LaCl3进行处理 (进行EGTA和LaCl3处理时 ,培养液中Ca2+浓度为 1mmol/L)。结果表明 ,氮同化关键酶硝酸还原酶 (NR)、谷氨酰胺合成酶 (GS)活性同Ca2+/CaM依赖性蛋白激酶 (Ca2+/CaM PK)活性之间存在明显的相关性。说明钙作为第二信使所介导的信号转导中 ,蛋白质可逆磷酸化可能参与了对氮素同化的调节作用。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.