洋葱花青素合成相关基因(AcPAL1)的克隆和表达分析

苯丙氨酸解氨酶(PAL)作为植物苯丙烷类代谢途径中的关键酶,在其生长发育、抗病抗逆等多种生命进程中起重要作用,是花青素生物合成途径中的第一个酶。为了研究洋葱(Allium cepa L.)PAL基因的生物学功能及其与花青素合成之间的关系,利用不同植物PAL基因设计简并引物,通过RT-PCR和RACE技术克隆洋葱PAL基因全长cDNA序列(GenBank登录号:KF421110),并对该基因进行序列分析和Real-time PCR表达分析。结果表明,该序列全长2 363 bp,编码包含708个氨基酸残基的蛋白质多肽;Blast分析和系统进化分析表明,该多肽与大蒜(Allium.sativum)、石蒜(Lycoris radiate)PAL蛋白相似性很高,因此被命名为AcPAL1。Real-time PCR表达分析结果表明,AcPAL1基因在白皮、黄皮和红皮洋葱中表达量依次增加;而随着鳞茎的不断膨大,其表达量却不断降低。本实验初步证实了所克隆的洋葱AcPAL1基因与花青素合成相关联,为研究洋葱PAL基因同花青素合成积累之间的关系提供了依据。     

诸葛菜OvCYP86MF基因的克隆及其特性分析

为进一步阐明细胞色素P450基因CYP86MF在诸葛菜发育中的分子机理,本文根据已知同源基因保守序列设计特异引物,利用RT-PCR和RACE技术从诸葛菜中获得一个细胞色素P450基因(OvCYP86MF)全长cDNA序列,该序列全长为1876bp,含有1605bp的完整开放阅读框,可编码534个氨基酸,分子量和等电点分别为61.4kDa和6.90,具有细胞色素P450蛋白的典型特征,即保守结构域FNAGPRLCIG;原核表达显示该基因的融合蛋白在体外可以诱导表达;DANSTAR和Clustal W软件分析表明该基因的全长cDNA序列及其编码氨基酸序列与十字花科物种拟南芥相似性很高,达到80%以上,亲缘关系最近;与CYP86C亚家族成员在氨基酸水平上的相似性均高于50%,因此推断该基因属于CYP86C这个亚家族。Northern杂交分析表明该基因在花蕾中特异表达。     

Lox基因RNAi转基因小麦后代株系种子耐储藏性分析

小麦(Triticum aestivum)种子中脂氧合酶(lipoxygenase,LOX)可催化不饱和脂肪酸的氧化作用,在种子储藏期间产生氢过氧化物,导致小麦种子在储藏过程中种子活力和营养品质降低.因此,选育种子LOX活性低的小麦品种是小麦遗传改良的任务之一.为了获得种子脂氧合酶活性显著降低、外源Lox RNAi构件(Lox geneRNAiconstruct,Loxi)能稳定遗传且种子耐储藏性增强的转基因小麦新种质,本研究以小麦西农889、闫麦8911和陕优225转Loxi稳定遗传的TF7代转基因株系为材料,对转基因种子中Lox基因家族进行了半定量RT-PCR分析,结果表明,外源Loxi可有效抑制小麦籽粒中小麦脂氧合酶1(Triticum aestivum lipoxygenase Ⅰ,TaLox1)基因的表达,但小麦脂氧合酶2(Triticum aestivum lipoxygenase 2,TaLox2)和小麦脂氧合酶3(Triticum aestivum lipoxygenase 3,TaLox3)基因的表达量不变;对3个亲本及16个TF7代转基因株系的种子脂氧合酶活性检测,结果显示,与其亲本相比,转基因株系种子脂氧合酶活性显著降低;对人工加速老化处理7和14 d的转基因和对照种子分析发现,随着老化天数的增加种子活力降低,但转基因株系种子活力均显著高于其亲本材料;人工加速老化后脂肪酸组分和含量测定分析表明,转基因株系脂肪酸比其亲本材料氧化损失少.以上结果说明,转基因株系中Lox基因的RNAi可有效抑制其种子LOX活性,使转基因小麦后代种子耐储藏性增强;筛选鉴定得到的种子LOX活性显著降低且耐储藏性增强的转基因小麦株系可为小麦育种提供新的材料.     

早酥梨抗黑星病相关新基因Vnp1的克隆及其表达分析

在前期已克隆得到的早酥梨(Pyrus bretschneideri cv.Zaosu)抗病基因同源类似物Pb-Zs3(GenBank登录号:EU939783)的基础上,通过RT-PCR获得Pb-Zs3的cDNA序列,并利用RACE技术获得该基因的全长cDNA序列,命名为早酥梨抗黑星病相关基因(Vnp1),提交至GenBank(GenBank登录号:FJ763188).生物信息学分析表明,早酥梨Vnp1基因的全长cDNA序列为1200 bp,包含一个完整的921 bp的开放读码框架(ORF),编码306个氨基酸残基,预测其分子质量为34.6 kD.同时,该基因含有与抗病相关的功能结构域核酸结合位点(NB-ARC),同源性比对显示其与苹果黑星病菌(Venturia inaequails)诱导后的苹果EST序列ABEA004598(GenBank登录号:EB150292)同源性达71%.对早酥梨Vnp1基因进行半定量RT-PCR研究的结果表明,该基因在梨黑星病菌(Venturia nashicola)诱导后216 h内的叶片中的表达水平呈明显上升趋势.     

天祝白牦牛金属硫蛋白基因(MT-1)全序列分子克隆及生物信息学分析

金属硫蛋白-1基因(metallothionein-1,MT-1)是一类广泛存在于动物体内的金属结合蛋白,除维持金属动态平衡和重金属解毒外,还可参与清除自由基、拮抗电离辐射和抗应激等。为深入研究MT-1基因参与动物机体抗逆性的分子机制,本研究采用RT-PCR和RACE(rapid amplification of cDNA ends,RACE)技术获得天祝白牦牛(Bos grunneins)MT-1基因全长cDNA序列,运用生物信息学方法分析MT-1蛋白的理化性质、结构和不同物种间的同源性,并利用RT-qPCR方法分析MT-1基因在天祝白牦牛各个脏器和组织中的表达丰度。结果表明,天祝白牦牛MT-1基因cDNA序列全长为408 bp(GenBank登录号:KF770836),开放阅读框(ORF)长186 bp,编码61个氨基酸,氨基酸的分子量为5.981 kD;氨基酸序列分析显示,天祝白牦牛MT-1基因编码氨基酸序列与牛(Bos taurus)的同源性高达100%,同时与大多数哺乳动物相似;荧光定量PCR结果发现,MT-1 mRNA在天祝白牦牛8个不同脏器和组织中均有表达,心脏中表达量最高。天祝白牦牛MT-1基因的成功克隆为进一步研究该基因的功能提供了基础资料。     

猪MYL4基因的克隆及其在猪胚胎骨骼肌中的表达分析

克隆了猪(Sus scrota)MYL4基因的cDNA序列,并利用生物信息学方法进行验证.所得cDNA序列全长1105 bp,包含1个完整的开放阅读框,编码197个氨基酸.序列分析表明,该基因与已报道的狗(Canis lupus familiaris)、人(Homo sapiens)、黑猩猩(Pan troglodytes)和恒河猴(Macaca mulatta)等物种的MYL4基因高度同源,氨基酸序列同源性分别为98.4%、95.9%、95.4%和95.4%.该基因编码的蛋白具有EFH和FRQ1保守功能域.荧光定量分析该基因在猪胚胎骨骼肌(妊娠33、65和90d)中的表达,发现MYL4基因在通城猪和长白猪中呈波浪式表达模式,在妊娠第33天时中外猪品种间无显著差异,但在第65和90天时长白猪中显著高于通城猪.     

尼罗罗非鱼β2m基因的克隆、多态性分析及组织表达特征

β2-微球蛋白(β2-microglobulin,β2m)是主要组织相容性复合体(major histocompatibility complex,MHC)Ⅰ分子的亚基之一,与MHC-Ioα链非共价结合构成MHC Ⅰ分子.本实验通过反转录PCR(RT-PCR)和cDNA末端快速扩增技术(rapid-amplification of cDNA ends,RACE)克隆了尼罗罗非鱼(Oreochromis niloticus) β2m基因的全长cDNA序列及基因组序列,并对cDNA多态性、mRNA组织分布及感染链球菌后表达的变化进行了分析.结果共获得尼罗罗非鱼2条β2m基因cDNA,全长分别为900和906 bp.两cDNA均包括351 bp的ORF,共编码116个氨基酸残基,还包含68 bp的5'非编码区(5'-UTR)和486(492) bp的3'-UTR.两条cDNA对应各自不同的基因组序列.基因组序列分析发现,β2m基因含3个外显子和2个内含子.尼罗罗非鱼β2m基因推测氨基酸序列与其他物种的β2m基因相似性在39.20％～89.80％之间.β2m基因cDNA多态性分析表明,尼罗罗非鱼中共有2种不同类型的β2m cDNA,每种类型cDNA又有3种不同的亚型.定量PCR分析表明,β2m基因在尼罗罗非鱼脾脏、心脏和肾脏中表达量最高,鳃与肠中的表达量较高,在皮肤和肌肉中的表达量最低.腹腔注射无乳链球菌(Streptococcus agalactiae)后,尼罗罗非鱼β2mmRNA表达量在4个所检测组织(鳃,肾脏,心脏和脾脏)中均出现了先上升后下降的变化趋势.本实验结果表明,β2m基因可能参与尼罗罗非鱼的免疫应答,在免疫反应中发挥重要功能.本研究有助于进一步了解尼罗罗非鱼的免疫调节机制和更好地理解鱼β2类m的生理功能.     

重瓣山茶红十八学士花发育B功能基因CjDEF-1的分离与表达分析

为研究B功能基因在山茶重瓣花形成中作用,用同源克隆的方法从红十八学士(Camellia japonica Hongshibaxueshi)花芽cDNA中克隆到DEFICIENS(DEF)基因同源序列片段,用RACE(rapid amplification of cDNA end)技术获得该基因cDNA全长,命名为 CjDEF-1(GenBank登录号为HM773024.1).通过氨基酸序列比对分析了一些单瓣、重瓣植物DEF同源基因差别,并采用Real-time PCR技术研究CiDEF-1基因在红十八学士中的时、空表达特点.结果显示,红十八学士CiDEF-1基因cDNA全长1 013bp,包含一个完整开放阅读框,编码226个氨基酸.序列分析表明,红十八学士与近缘雪山茶(Camellia japonica subsp.rusticana)至少有4个编码氨基酸不同.在红十八学士不同发育时期中,GiDEF-1基因在小花苞表达量最高,中等花苞表达量最低,在开花期表达量又升高;在花不同组织中的表达情况从高到低排列为:中心花瓣＞外轮花瓣＞中间花瓣＞萼片＞苞片,这与同源GiDEF基因在单瓣雪山茶中表达情况不同.从这些研究的差异表明,GiDEF-1基因可能在山茶重瓣花形成中起作用.     

山药PAL基因全长cDNA序列的克隆、表达与分析

为了阐明苯丙氨酸解氨酶(PAL,EC4.3.1.5)基因在山药地下块茎酚类物质积累过程中的分子机理,本研究运用普通PCR、RACE和TAIL-PCR技术从大薯(Dioscorea alataL.)’Zixiao’地下块茎中克隆到同一个PAL基因的3个片段,即长度分别为1 145bp、1 151bp和424bp的中间片段、3’端和5’端的cDNA序列;将3段cDNA序列拼接后获得大小为2 376bp的PAL基因全长cDNA序列,该序列含有一个1986bp的最大开放阅读框(ORF),一个28bp的5’端非翻译区,一个362bp含25 nt的Poly(A+)尾的3’端非翻译区,最大ORF可推测编码一个包括PAL酶活性中心的特征序列(GTITASGDLVPLSYIA)在内的661个氨基酸的多肽,分子量为71.974kDa,等电点6.310;大薯地下块茎的PAL基因分别在核苷酸与氨基酸水平上和GenBank中所选已知其他物种的同源性为73%~77%和76%~82%,说明PAL基因在系统进化上相对保守;RT-PCR分析表明该基因仅在地下块茎中表达,而且表达丰度在收获前逐渐降低。     

桃脂氧合酶基因(LOX)家族cDNA全长克隆与序列分析

根据脂氧合酶保守序列设计的简并引物,从瑞蟠5号桃(Prunus persica cv ‘Rui pan 5')果肉总RNA中扩增出795 bp的脂氧合酶(lipoxygenase,LOX)基因的保守序列,并结合GenBank中公开的LOX基因的EST序列经Blast比对分析、序列组装之后设计基因特异引物(GSP).利用RACE技术共获得3条不同的桃LOX基因cDNA全长序列,分别命名为PpLox1～3(GenBank登录号:EU883638、FJ029110和FJ032015).序列分析结果表明,这3个桃LOX基因家族成员与其它植物的LOX基因尽管在核酸水平上的差异比较大.但在蛋白水平上却有较高的同源性.通过对桃LOX基因蛋白序列和其它植物LOX进行系统进化树分析,发现PpLox1属于13-LOX,PpLox2-3属于9-LOX.     

Intraradical hyphae phosphatase of the arbuscular mycorrhizal fungus, Gigaspora margarita

An alkaline phosphatase in the intraradical hyphae of arbuscular mycorrhizal fungi was found to be closely related to an improvement of plant growth. To detect the phosphatase activity in a crude extract of mycorrhizal roots, phosphatase isozymes in mycorrhizal and non-mycorrhizal onion roots were compared with those in Gigaspora margarita by electrophoresis. A mycorrhiza-specific band was found when the phosphatase was stained under alkaline conditions. To clarify the origin of this phosphatase, the phosphatase extracted from intraradical hyphae was also compared with the phosphatase from mycorrhizal roots by electrophoresis. The intraradical hyphae was isolated from mycorrhizal roots by enzyme digestion followed by Percoll gradient centrifugation. The soluble protein was extracted from the hyphae by ultra-sonication after treatment with chitinase. A phosphatase in the hyphal soluble protein showed a similar, but slightly higher, relative mobility on the gel, compared with the mycorrhiza-specific phosphatase from roots. By adding the hyphal extract to the root extract, the relative mobility of the mycorrhiza-specific phosphatase was slightly changed and became identical to that of the phosphatase in the hyphae. This indicated that the specific band of phosphatase found in the crude extract from mycorrhizal roots was of intraradical hyphal origin. Received: 16 April 1997     

缓控释掺混尿素对章丘大葱—小麦产量、效益及土壤氮素的影响

为了筛选出适合章丘大葱—小麦的缓控释尿素(CRU)与普通尿素(U)掺混比例,实现缓控释肥的一次性施用增产增效。采用田间定位试验方法,探讨CRU与U不同掺混比例对章丘大葱—小麦产量、氮肥表观利用率、经济效益和土壤氮素等指标的影响。结果表明,与习惯施肥相比,50%CRU+50%U、70%CRU+30%U处理两季大葱总产量提高2.2%~6.0%,两季小麦总产量提高4.3%~5.2%;大葱季50%CRU+50%U、70%CRU+30%U氮肥表观利用率分别提高3.44~8.48,2.74~3.77个百分点,小麦季50%CRU+50%U、100%CRU氮肥表观利用率分别提高6.41~6.96,3.00~6.98个百分点;大葱季50%CRU+50%U、70%CRU+30%U效益分别增加10783.93,5823.04元/hm^2;小麦季50%CRU+50%U、70%CRU+30%U效益分别增加2035.33,1448.24元/hm^2;0—20cm100%CRU、70%CRU+30%U土壤硝态氮含量高于习惯施肥,20—100cm土层含有缓控释肥处理的土壤硝态氮的累积高于习惯施肥,而且呈现缓控释肥掺混比例越高,保留的养分量越高。综合各项指标,50%CRU+50%U是应用在章丘大葱—小麦上的最佳配比,其次为70%CRU+30%U,这2个配比能够实现缓控释肥一次性施用,同时提高氮肥表观利用率,增加经济效益,延长土壤供氮能力。     

Relationship between Selenium and Sulfur Assimilation and Resultant Interaction on Quality Parameters in Onion

The relationship between selenium (Se) and sulfur (S) uptake and their interaction on the pungency and quercetin contents of onion was investigated in a sand culture trial under polyhouse conditions. The results indicated that application of Se with increasing rates produced an antagonistic effect on S assimilation. An amount of 20 kg Se ha^–1 drastically reduced the S content in onion bulbs. Further, the pungency and quercetin concentration also declined. Foliar application of Se at 1.0 ppm resulted in production of bulbs with lower levels of pungency and quercetin. Though Se is essential from a health point, its application up to 10 kg ha^–1 was sufficient for enriching onions without much effect on the other essential bulb quality parameters.     

套作对黄瓜根际土壤细菌群落结构的多样性影响

以设施蔬菜中的主要栽培种类黄瓜为研究对象,以毛葱、蒜为套作作物,利用T-RFLP(末端限制性片段长度多态性,Terminal Restriction Fragment Length Polymorphism)技术对套作黄瓜根际土壤细菌群落结构多样性进行了研究。结果表明:套作改变了黄瓜根际土壤细菌群落结构的多样性和优势菌群结构。套种毛葱的黄瓜根际土壤细菌群落结构多样性高于套种蒜的黄瓜根际土壤细菌群落结构多样性;在黄瓜定植前和拉秧期,套作处理的土壤细菌群落结构多样性有比对照高的趋势,而在根瓜期和盛瓜期套作处理的土壤细菌群落结构多样性有比对照低的趋势;毛葱的套作效果最佳,蒜套作次之。套作提高了黄瓜产量。     

3种大蒜中洋葱黄矮病毒的RT-PCR分子鉴定

洋葱黄矮病毒（Onion yellow dwarf virus,OYDV）是危害大蒜产量和品质的主要病毒之一。快速有效的病毒检测方法可为大蒜病毒病的研究和有效防御提供理论与技术资料。本研究利用反转录-聚合酶链式反应（RT-PCR）技术对甘肃＂成县迟蒜＂和山东＂鲁蒜王2号＂中OYDV外壳蛋白基因进行特异性扩增,并克隆到载体PMD18-TEasy Vector上进行核苷酸序列测定及分析。成功分离得到OYDV的两个DNA片段——GSCCS和SDLSW2,与GenBank中已报道的AB000837.1、AB000838.1和AJ409311.1等22个OYDV DNA片段的核苷酸相似性分别为81%～98%和81%～84%,氨基酸相似性分别为85%～99%和89%～94%,二者之间核苷酸相似性为84%,氨基酸相似性为89%。系统进化树显示不同DNA片段可聚为3个组群,GSCCS与中国山东金乡OYDV DNA片段同属一组,SDLSW2与其它16个OYDV DNA片段同属一组,表明OYDV在甘肃＂成县迟蒜＂和山东＂鲁蒜王2号＂中均存在,但具有一定差异。本实验确定了OYDV的基因变异程度,为进一步研究病毒进化和变异提供了有利条件。     

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,