不同农作方式红壤坡耕地土壤氮素流失特征

采用径流小区法研究了6种不同农作方式土壤N素的流失特征。结果表明,同顺坡农作方式相比,其它农作方式均有明显控制土壤N素流失的作用,水平草带、水平沟、等高耕种、休闲、等高土埂等农作方式分别减少土壤N素流失量43．46％、46．55％、71．36％、77．05％和87．92％,等高耕种、等高土埂、休闲等农作方式控制土壤N素流失优于水平沟和水平草带农作方式,坡耕地土壤N素的流失途径主要为径流流失,约占土壤N素流失量81．9％－93．4％,径流流失的N素中又以水溶态N素为主,约占径流流失N素的78％－87．6％,坡耕地土壤N素流失主要集中在5－8月份,占全年流失量的85％－100％。     

麻竹EST-SSR标记开发及其对慈竹变异类型的分析研究

利用麻竹(Dendrocalamus latiflorus)已有的EST序列,开发了一批EST-SSR分子标记,并用于慈竹(Bambusa emeiensis)栽培变异类型的多态性研究。结果表明,在麻竹9574个EST中找到了331个EST,含有381个SSR位点,SSR出现的频率为3.98%。EST-SSR的重复类型共有59个,其中2个核苷酸的重复最多,占63.8%,其次是3个核苷酸的重复序列。根据含有SSR的EST序列设计出了44对引物,对慈竹及其变异类型进行了扩增效率、多态性及通用性检测,其中37对引物能够扩增出稳定且清晰的条带,且扩增具有多态性,扩增片段长度主要集中在100～1000 bp,引物有效率达84.1%。遗传相似性分析结果显示,所检测样品间遗传距离为0.263～0.840,平均为0.552,其中‘黑笋慈竹’与‘琴丝慈竹’‘、蛇头慈竹’与‘龙头慈竹’之间的遗传距离较近,而‘罗汉慈竹’与其他样品的遗传距离最远。     

紧紧围绕教学内容,培养学生的创造性思维

现代教育对教学提出了新的要求,我们以引导学生掌握知识为"落脚点",培养学生的求异性思维;以引导学生巩固知识为"辐射点",培养学生的"放射性"思维;以引导学生开拓知识为"出发点",培养学生的"前瞻性"思维,从而培养学生的科学思维方式和开拓创新能力。     

巴西橡胶树栽培种质基因组C值测定和变异分析

为了解巴西橡胶树(Hevea brasiliensis)栽培种质的变异情况,以53份在云南植胶区综合性状表现较好的巴西橡胶树栽培种质为材料,采用流式细胞术测定了基因组C值,并进行了变异分析。结果表明,浅绿色嫩叶是巴西橡胶树流式细胞术测定的最适样品。53份巴西橡胶树栽培种质的细胞核DNA含量和基因组C值存在一定差异,基因组的平均C值是1.531 696×109 bp,最小的是CRTG-272种质(1.465 908×10~9 bp),最大的是CRTG-83种质(1.600 381×10~9 bp),变异系数较小(CV=0.035 5)。53份巴西橡胶树栽培种质中有47份为二倍体,6份为三倍体。在已测定基因组大小的40种大戟科(Euphorbiaceae)植物中,基因组大小变异较大(CV=1.248 6),与"C值悖论"观点相一致。因此,应用流式细胞术能快速、准确地测定巴西橡胶树细胞核DNA含量、基因组C值和染色体倍性。     

上海和雅安两地不同育幼方式大熊猫幼仔生长发育的初步研究

上海作为典型的低海拔地区,气候、环境等条件均与大熊猫Ailuropoda melanoleuca栖息地存在很大差异。为了研究在上海出生并生活的大熊猫幼仔的生长发育情况,以及与四川雅安的大熊猫幼仔生长发育是否存在差异,本文比较分析了上海、雅安两地大熊猫幼仔在母兽哺育、人工辅助育幼2种育幼方式下的体质量、体尺和其他器官的生长发育情况,并采用Chapman生长模型模拟了两地大熊猫幼仔的生长曲线。研究发现:上海大熊猫幼仔40 d、60 d和70 d的体质量显著大于四川雅安大熊猫幼仔(P <0. 05);母兽哺育的大熊猫幼仔40 d、60 d和70 d的体质量显著大于人工辅助育幼的大熊猫幼仔(P <0. 05);雄性大熊猫幼仔40 d、60 d、70 d和100 d的体质量显著大于雌性大熊猫幼仔(P <0. 05)。整体而言,大熊猫幼仔的体长增长最快,其次为腹围,尾长最慢。母兽哺育大熊猫幼仔的体尺数据稍高于人工辅助育幼,与海拔无关;而相同育幼方式下,高、低海拔组幼仔体尺之间的差异无明显规律。Chapman生长模型很好地模拟了上海和雅安两地大熊猫幼仔0～120 d的生长曲线,但2条曲线在拐点日龄、拐点体质量、最大生长率均存在一些差异。通过对两地大熊猫幼仔生长发育的差异研究,为上海地区繁育大熊猫提供了科学依据。     

Characterization of a novel <Emphasis Type="Italic">Stenotrophomonas</Emphasis> isolate with high keratinase activity and purification of the enzyme

A feather-degrading bacterium was isolated from poultry decomposition feathers in China. The strain, named L1, showed significant feather-degrading activity because it grew and reproduced quickly on basal medium containing 10 g/L of native feather as the source of energy, carbon, and nitrogen. According to the phenotypic characteristics and 16S rRNA profile, the isolate belongs to Stenotrophomonas maltophilia. Keratinase activity of the isolate was determined during cultivation on raw feathers at different temperatures and initial pH. Maximum growth and feather-degrading activity of the bacterium were observed at 40°C and initial pH ranging from 7.5 to 8.0. The crude enzyme was purified by ammonium sulphate precipitation, Sephadex G-100 chromatographic and ceramic hydroxyapatite (CHT) chromatographic. Its molecular mass estimated as 35.2 kDa in SDS-PAGE. The enzyme had an optimum activity at the pH was 7.8 and the temperature was 40°C. The keratinase was wholly inhibited by a serine protease inhibitor, PMSF. Its activity was activated or inhibited by different metal ions. The keratinase activity of enzyme from strain L1 functioned on different keratins, such as feather, hair, wool, horn, and so on.     

荧假单胞杆菌化感作用的初步研究

1　引　　言化感作用 (Allelopathy)是指一种植物或微生物通过产生化学物质而对其它生物产生的直接或间接的刺激或抑制作用[7] .虽然有关高等植物之间化感作用的研究已有大量报道 ,但微生物对高等植物的化感作用研究报道却较少 ,尤其是细菌在生态系统中的化感作用往往被忽视[1] .荧光假单胞杆菌 (P .fluorescens)是定殖于植物根际的优势细菌种群 ,此类细菌以其分布广、适应能力强、繁殖速度快、易于人工培养等特点 ,成为最具生防潜力和应用价值的生防菌[5] .对陕西农田土壤有益微生物的筛选研究中发现 ,一株荧光假单胞杆菌培养液对番茄灰霉…     

微生物异化硝酸盐和亚硝酸盐产铵研究进展

异化硝酸盐和亚硝酸盐还原产铵是氮转化附属途径,为生态系统中氮的重复利用提供了依据,已成为近年来的研究热点。据报道,氮源的种类及浓度不同异化还原产铵的发生机制及强度具有差异性,决定着微生物产铵的效率,因此,有必要明确不同氮源异化还原产铵的代谢机制。本文详细论述了参与硝酸盐和亚硝酸盐异化还原产铵过程的相关微生物种类、产铵途径及其机理;系统分析了单一氮源和混合氮源对不同微生物产铵的影响和差异,比较了放线菌与其他微生物产铵的优势,并对未来的研究方向进行了展望,旨在为微生物异化硝酸盐和亚硝酸盐还原产铵提供理论基础。     

Controlling for false discoveries subsequently to large scale one-way ANOVA testing in proteomics: Practical considerations

In discovery proteomics, as well as many other “omic” approaches, the possibility to test for the differential abundance of hundreds (or of thousands) of features simultaneously is appealing, despite requiring specific statistical safeguards, among which controlling for the false discovery rate (FDR) has become standard. Moreover, when more than two biological conditions or group treatments are considered, it has become customary to rely on the one-way analysis of variance (ANOVA) framework, where a first global differential abundance landscape provided by an omnibus test can be subsequently refined using various post-hoc tests (PHTs). However, the interactions between the FDR control procedures and the PHTs are complex, because both correspond to different types of multiple test corrections (MTCs). This article surveys various ways to orchestrate them in a data processing workflow and discusses their pros and cons.     

Distribution and organization of a tandemly repeated 352-bp sequence in the oryzae family

Summary A 352-bp EcoRI fragment from rice DNA was cloned and shown to be a member of a tandem repeat. Sequence determination revealed homologies with human alpha satellite DNA and maize knob heterochromatin specific repeat. This 352-bp sequence is highly specific for the AA genome of rice. However, copy number and sequence organization are variable, depending on the accession analyzed. Several examples of amplification were observed in O. rufipogon and O. longistaminata. Use of resolutive polyacrylamide gel electrophoresis and 4-bp cutter enzymes allowed one to distinguish between the Indica and Japonica subtypes of O. sativa. The same method also discriminates between two groups of O. rufipogon, the presumed ancestor of O. sativa, suggesting that the present day Indica and Japonica subtypes originated independently from two O. rufipogon distinct populations.