小麦胁迫相关蛋白基因TaSAP12-D的耐盐性分析

胁迫相关蛋白（SAPs）是一类具有A20/AN1锌指结构域的蛋白,在植物中主要参与逆境胁迫响应。为探究小麦胁迫相关蛋白基因TaSAP12-D在耐盐胁迫中的功能,本研究以小麦品种旱选10号为试材,克隆得到TaSAP12-D基因,利用农杆菌瞬时注射烟草叶片进行亚细胞定位,利用实时荧光定量PCR(qRT-PCR)进行不同组织和盐胁迫条件下的表达模式分析,利用蘸花法将TaSAP12-D转化到拟南芥（Arabidopsis thaliana L.）中并进行耐盐性分析。结果表明,TaSAP12-D基因全长519 bp,编码172个氨基酸,预测蛋白分子量为18.41 kDa,等电点为9.21。亚细胞定位显示,TaSAP12-D在烟草细胞核和细胞质中均有表达。qRT-PCR结果显示,TaSAP12-D在小麦萌发期和幼苗期的胚芽、根和叶中均有表达,其中在幼苗期的叶中表达量最高。在盐胁迫条件下,TaSAP12-D的表达量显著上调。在150 mmol·L-1NaCl处理条件下,过表达TaSAP12-D拟南芥的存活率显著提高,表明TaSAP12-D可以增强转基因拟南芥的耐盐性。另外,在转基因拟南芥中盐胁迫相关...     

小麦耐热相关转录因子基因TabZIP28的分离及功能分析

碱性亮氨酸拉链(basic leucine zipper,bZIP)是植物中广泛存在的一类转录因子,参与多种胁迫响应与生长发育过程.本研究从小麦(Triticum aestivum)中克隆到一个热胁迫诱导的bZIP家族转录因子基因TabZIP28 (GenBank登录号:KT753298.1),ORF长度为1 713 bp,编码570个氨基酸.生物信息学分析结果表明,TabZIP28与拟南芥bZIP家族转录因子中B亚组的3个基因Atb ZIP17、AtbZIP28和AtbZIP49归为一类.氨基酸序列比对结果表明,该蛋白具有bZIP和跨膜结构域(transmembrane domain,TMD)两个保守结构域以及规范的位点1蛋白酶(site 1 protease,S1P)剪切位点.对该基因起始密码子ATG上游1 699bp的序列进行顺式作用元件分析,发现该基因的启动子区域包含众多激素和逆境胁迫响应元件.通过qRT-PCR对该基因在逆境胁迫下的表达模式进行分析,结果表明,TabZIP28在热胁迫处理1h即上调表达且达到最大值;用20％PEG 6000模拟干旱环境处理小麦幼苗后,TabZIP28在处理6h达到最大值,并在12h时急剧下降;对5mmol/L H2O2处理响应比较缓慢,在处理12h才上调表达;该基因不受到二硫苏糖醇(dithiothreitol,DTT)处理的诱导表达.在拟南芥(Arabidopsis thaliana)中过量表达TabZIP28基因,转基因株系在高温胁迫后的成活率和种子发芽率较野生型明显提高,说明该基因可能对植物的耐热性有贡献,可以作为耐热性育种的候选基因.     

植物同源结构域(PHD)-finger家族转录因子OsPHD1的过量表达可提高水稻的耐逆性能

OsPHDl基因属于水稻(Oryza sativa)植物同源结构域(PHD)-finger转录因子基因家族.逆境(干旱、高盐和低温)处理下,水稻内源基因OsPHDl的表达量明显升高.利用农杆菌介导法将OsPHDl基因转入水稻(Oryza sativa ssp.jap onica)中花11,获得OsPHDl的过表达植株.耐逆性实验表明,过表达OsPHDl基因使转基因株系对低温(4～8℃)、高盐(200mmol/L)和干旱胁迫(相对含水量70%～95%)的耐受性分别提高43.3%、60%和25%,且在T2中获得稳定遗传.同时转基因水稻在其他性状与对照无明显差异.在洋葱(Allium cepa)表皮亚细胞定位实验中OsPHDl与GFP的融合蛋白定位于细胞核中,qRT-PCR结果表明,OsPHDl蛋白可能通过调节胁迫反应基因的表达来调节植物的抗逆性.研究结果提示,OsPHDl基因在水稻抗逆育种上有重要的应用前景.     

小麦WDHN1基因的克隆、表达及功能分析

YSK2型脱水素(dehydrins,DHNs)是植物中存在最多的DHNs形式,参与植物响应各种非生物逆境胁迫.为了研究YSK2型DHN的功能,从小麦(Triticum aestivum)中克隆了WDHN1基因(GenBank No.KR709259),该基因编码区序列总长491 bp,含两个外显子和一个内含子,编码133个氨基酸;存在4个保守区域,即1个Y片段、1个S片段和2个K片段,与节节麦(Aegilops tauschii) DHN (EMT30992)亲缘关系最近.通过PCR扩增得到WDHN1启动子序列,该启动子存在2个脱落酸应答元件(abscisic acid (ABA)response element,ABRE)和3个MBS(MYB binding site)生物胁迫响应元件.通过qRT-PCR分析其非生物胁迫下的表达模式,结果表明,在低温、NaC1、ABA和PEG 6000胁迫下,小麦WDHN1基因表达均表现为先上升后下降的趋势,分别于6、60、12和48 h时表达量最高.组织特异性表达分析表明,WDHN1基因在小麦开花后22 d的胚芽中表达量最高,具有明显的组织特异性.将WDHN1基因片段连接于原核表达载体pET28a中,转化大肠杆菌(Escherichia coli) BL21(DE3),用异丙基硫代半乳糖苷(isopropyl β-D-1-thiogalactopyranoside,IPTG)诱导表达,获得20 kD的WDHN1蛋白.对重组大肠杆菌WDHNl-pET28a-BL21(DE3)及其总蛋白进行非生物胁迫,结果表明,WDHNl蛋白还可以阻止蛋白聚合引起的蛋白变性,提高非生物胁迫下大肠杆菌的耐受性及乳酸脱氢酶(lactic dehydrogenase,LDH)的稳定性.研究结果为进一步利用该基因进行小麦抗性改良提供了理论依据.     

普通小麦TaSEC14p-5基因的克隆及表达分析

磷脂酰肌醇转运蛋白Sec14是最先在酿酒酵母(Saccharomyces cerevisiae)中发现的磷脂酰肌醇转运蛋白,含有一个典型的SEC14保守结构域.S0ec14p磷脂酰肌醇转运蛋白广泛存在于真核生物细胞中,并参与膜运输途径、质膜发育、脂肪酸代谢、根毛的生长等生命活动,但未见此蛋白在作物逆境胁迫的有关报道.为研究Sec14p基因在小麦(Triticum aestivum)发育及逆境胁迫中的功能,本研究采用电子克隆方法从小麦京花9号中得到一个Sec14p基因,命名为TaSEC14p-5 (GenBank登录号:KU639968).氨基酸序列分析表明,该基因ORF全长为984 bp,编码327个氨基酸,相对分子质量为37.1 kD,理论等电点为7.70.在植物中该蛋白有典型的SEC14类基因家族保守域SEC14和一个CRAL_TRIO_N结构域.进化和聚类分析表明,小麦TaSEC14p-5基因与粗山羊草(Aegilops tauschii)磷脂酰肌醇转运蛋白AeSEC14p基因和水稻(Oryza sativa)磷脂酰肌醇转运蛋白Os02g0200000基因亲缘关系较近,蛋白相似度分别为96.45％和88.38％.采用qRT-PCR技术,对小麦孕穗期不同组织和不同非生物胁迫幼苗进行表达分析.发现该基因在根、茎、叶、颖壳、雄蕊和种子中均有表达,且在茎中表达量较高,雄蕊次之,根最低;该基因受高盐的强烈诱导,同时也受到脱落酸(abscisic acid,ABA) (200μmol/L)、干旱(PEG6000)和低温(4℃)不同程度的胁迫诱导.TaSEC14p-5在NaC1、ABA、PEG和4 ℃四种不同胁迫处理下,总体趋势为先上升后下降.结果推测,TaSEC14p-5基因可能参与了NaC1、ABA、PEG6000和4℃等不同程度的非生物胁迫处理,为进一步改良小麦抗逆性等分子机理研究提供了新的依据.     

葡萄VvJAZ9蛋白原核表达与多克隆抗体制备

JAZ蛋白是茉莉酸(JA)信号调控途径中的重要组分，也是调节JA参与植物生长发育以及逆境应答的关键因子。JAZ9基因是编码TIFY家族JAZs蛋白的基因之一。为研究欧洲葡萄VvJAZ9蛋白参与低温胁迫的功能，本试验以欧洲葡萄霞多丽叶片为研究材料，通过同源克隆获得了VvJAZ9基因序列，其全长807 bp，编码268个氨基酸，定位于第11条染色体，有5个外显子和4个内含子；VvJAZ9蛋白具有JAZs家族蛋白中特有且高度保守的TIFY和CCT＿2结构域，与拟南芥AtJAZ1和AtJAZ2亲缘关系最近。实时荧光定量PCR(qRT-PCR)分析结果表明，VvJAZ9基因在低温处理1～24 h后表达量呈上升趋势，在24 h表达量最高。亚细胞定位结果证实VvJAZ9定位于细胞核。将VvJAZ9的开放阅读框(ORF)序列克隆至原核表达载体pET28b上，在大肠杆菌(E. coli BL21)中经37℃、1.0 mmol·L^-1异丙基-β-d-硫代半乳糖苷(IPTG)诱导表达获得VvJAZ9-His融合蛋白，再经抗原免疫，血清纯化后制备anti-VvJAZ9兔源多克隆抗体。蛋白...     

茶树脱水素基因(CsDHN)的克隆及表达分析

脱水素(dehydrins,DHNs)是植物胚胎发育后期丰富蛋白(late embriogenesis abundant protein,LEA)中的一类,与低温、干旱以及盐胁迫等多种逆境反应相关.本研究采用cDNA末端快速扩增(rapidamplification of cDNA ends,RACE)技术从茶树(Camellia sinensis)中获得一种茶树脱水素基因CsDHN (GenBank登录号:FJ436978),序列分析显示,该基因cDNA全长960 bp,编码201个氨基酸,推测编码蛋白质分子量约为21kD,等电点为8.3,属于Y3SK2型脱水素.CsDHN基因有2个外显子和1个内含子.生物信息学预测显示,该脱水素蛋白亲水性强、无信号肽和跨膜区,亚细胞定位于细胞质中.表达特性分析表明,CsDHN在逆境及脱落酸(abscisic acid,ABA)诱导下可上调其转录水平,4℃低温处理下表达量可提高4.2倍,而脱水处理能提高93.4倍,高盐处理能提高17.8倍,CsDHN对脱水、高盐胁迫的响应程度优于低温胁迫.CsDHN在茶树各组织器官中都有表达,其中种子中表达量最高,为叶片的11.2倍.研究表明脱水素基因CsDHN可能在茶树防御非生物逆境胁迫和参与茶树种子成熟脱水的活力保护过程起一定作用,为了解茶树抗逆分子机制提供了一定的理论基础.     

柳枝稷根组织实时定量PCR分析中内参基因的选择

选择表达稳定性高的内参基因是提高实时荧光定量PCR分析(qRT-PCR)准确性的重要条件。本研究以能源植物柳枝稷(Panicum virgatum L.)根组织为材料,通过不同非生物条件胁迫,利用qRT-PCR技术检测UBQ1(泛素基因)、ACT2(肌动蛋白基因)、UBQ2(泛素基因)、TUB(β微管蛋白基因)、GAPDH(甘油醛-3-磷酸-脱氢酶基因)、CBP20(类胡萝卜素结合蛋白基因)、UCE2(泛素接合酶基因)、18S rRNA1(18S核糖体RNA基因)、NAC(NAC域蛋白基因)和CYP2(亲环蛋白基因)10个内参基因的mRNA的表达情况,并运用Delta-Ct method,Genorm(ver.3.5)、Bestkeeper(ver.1.0)和NormFinder(ver.0.953)软件综合分析10个内参基因的表达稳定性。结果显示,在不同的非生物环境胁迫条件下,最适合作为柳枝稷根组织研究的内参基因各不相同。10个内参基因平均表达稳定由高到低排序为:ACT2,TUB,UCE2,CBP20,CYP2,UBQ2,18S rRNA1,NAC,UBQ1,GAPDH。在干旱胁迫条件下,ACT2基因表达稳定性最高;在盐胁迫和热胁迫条件下,18S rRNA1基因表达稳定性最高;在冷胁迫和涝胁迫条件下,ACT2基因表达稳定性最高。经软件综合分析显示,ACT2、TUB和UCE2基因最适合作为柳枝稷非生物胁迫研究的内参基因;UBQ1和GAPDH基因最不合适作为内参基因。该研究结果可用于柳枝稷非生物胁迫下各种基因表达的进一步研究。     

叶用莴苣热激蛋白LsHsp70-3701基因的克隆及高温胁迫下的表达分析

为探讨热激蛋白Hsp70基因在高温胁迫下的响应机制及其分子机理,分析Hsp70基因与叶用莴苣耐热性的关系,本研究通过同源克隆及RACE技术,克隆了叶用莴苣热激蛋白Ls Hsp70-3701基因的c DNA全长序列,利用实时荧光定量PCR(qRT-PCR)分析该基因在叶用莴苣热敏品种P-S11和耐热品种G-S59中高温胁迫下的表达差异。该基因c DNA全长为2 191 bp,开放阅读框为1 950 bp,编码649个氨基酸,具有Hsp70家族特有的标签序列,与拟南芥、番茄、小麦等物种的Hsp70同源性达到90%以上。qRT-PCR分析显示,高温胁迫下该基因在2个品种中的表达均上调,在耐热品种中总体表达水平显著高于热敏品种,且在42℃高温下热敏品种P-S11中基因表达随着胁迫时间的增加受到抑制,而耐热品种G-S59中则能长时间保持较高的表达水平。结果表明,Ls Hsp70-3701基因可能与叶用莴苣耐热性相关。本研究为有效解决叶用莴苣高温抽薹问题提供了数据支持。     

砀山酥梨肉桂酸4-羟化酶基因的克隆及表达分析

木质素是梨(Pyrus)石细胞的重要成分之一,木质素合成代谢对石细胞形成发育有着重要影响.肉桂酸4-羟化酶(cinnamate 4-hydroxylase,C4H,EC l.14.13.11)是细胞色素单加氧酶超家族中CYP73A亚家族的一员,同时为木质素合成代谢中的一个关键酶.本研究从砀山酥梨(Pyrus bretschneideri cv.Danshan Su)果实中克隆出一条肉桂酸4-羟化酶基因的全长cDNA序列,命名为PbC4H,GenBank登录号为:KF663548.PbC4H全长1 764 bp,具有1 515bp的ORF,编码504个氨基酸.PbC4H与多个物种C4H基因编码的氨基酸序列具有较高的同源性,说明其在进化过程中较为保守.结构域分析表明,PbC4H具有跨膜结构域和典型的细胞色素P450结构域特征.qRT-PCR分析发现在梨果实发育的不同时期,PbC4H基因表达量呈现先增加后下降的趋势,其中在花后55 d达到最高.构建了PbC4H原核表达载体pET-32a-PbC4H,在大肠杆菌(Escherichia coli) BL21菌株中诱导表达出PbC4H融合蛋白.亚细胞定位表明PbC4H蛋白定位于细胞膜上.本研究结果为利用分子生物学技术调控梨木质素的合成和石细胞的发育提供了基础资料.     

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。     

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.     

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

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,     

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,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

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.