The effects of soil structure on protozoa in a clay-loam soil   总被引：2，自引：0，他引：2  

R.S. GRIFFITHS  I.M. YOUNG 《European Journal of Soil Science》1994,45(3):285-292

Physical disruption of a clay-loam soil by slaking, grinding and compaction was used to determine the specific effects of soil structure on soil protozoa. Individual air-dry aggregates (1–2 cm diameter) were wetted slowly, or had their structure disrupted by slaking or grinding. They were then moistened with nutrient solution and incubated, at a matric potential of ?10 kPa. The nutrient solution had to supply at least 400 μg C g^?1 dry soil before protozoan populations increased measurably. Numbers of ciliate protozoa were enhanced by grinding, regardless of the amount of nutrient added. The moisture content and, therefore, the final nutrient concentration of the disrupted aggregates, changed markedly and could account for the observed increase in protozoan biomass from slowly wet to slaked to ground aggregates. There were no differences in protozoan biomass when the applied nutrient concentration was adjusted so that all treatments contained the same amount of nutrient. Soil cores were prepared from sieved (2–4 mm diameter), ground and ground/compacted soil. Thin sections revealed that the pore space accessible to protozoa decreased in these three treatments from 24% to 13% to 9%, respectively. Protozoan biomass was unaffected by grinding but showed a greater than 30-fold decrease following compaction that could not be accounted for solely by the reduced pore space. Grinding and compacting could have favoured anaerobic conditions in the core which would have reduced protozoan activity. Soil structure had no measurable direct effect on protozoan populations, but it had a much greater indirect effect through its influence on moisture content and aeration status.  相似文献   

Humic acid–proton equilibria: A comparison of two models and assessment of titration error     

S.J. MARSHALL  S.D. YOUNG  K. GREGSON 《European Journal of Soil Science》1995,46(3):471-480

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蜂王浆的抗菌活性研究   总被引：7，自引：2，他引：5  

刘克武  杨守忠  葛绍荣  刘晓雯  闵丽娥  张斌  喻东  刘鑫 《蜜蜂杂志》2001,(2):5-6

本文采用平板培养法研究蜂王浆的抗菌活性 ,发现新鲜蜂王浆对10种试验菌均有不同程度的抑制作用。根据抑菌斑的大小判断 ,蜂王浆对各种试验菌株的抑制程度为 :枯草杆菌>威克氏酵母>蜡状芽孢杆菌>隐球酵母>鼠伤寒沙门氏菌>大肠杆菌O111>福氏志贺氏2型菌>假单孢杆菌>N1 米曲霉>霉菌W15。  相似文献   

创建学习型图书馆的实践与思考     

王洪娴  束春德  闵繁贵 《农业图书情报学刊》2005,17(2):100-102

文章分析了创建学习型图书馆的意义 ,论述了创建学习型图书馆的途径 ,提出了创建学习型图书馆中应注意的几个问题  相似文献   

利用PCR介导的基因置换技术构建阿维链霉菌bkdF-突变株   总被引：3，自引：1，他引：2  

熊伟  梁运祥  朱浩君  闵勇  吕和平  郑应华 《农业生物技术学报》2005,13(5):672-678

PCR介导的基因置换技术是一种利用λ噬菌体Red重组系统在微生物中进行基因中断的新方法。实验利用该方法快速构建基因中断载体，并成功地置换了阿维链霉菌（Streptomyces avermitilis）bkdF基因。先合成1对长度分别为58和59nt的引物，其5’端的39nt序列分别与bkdF基因两侧同源，3’端则分别与安普霉素抗性标记盒（aac（3）Ⅳ＋onT）两侧序列一致。以该引物扩增的PCR产物电转化能表达λRed重组酶且含有目标质粒的大肠杆菌（Eschcrichia．coli）菌株BW25113／pU790／pXW1224，获得了阳性重组质粒pXW1230。将该质粒中的大小为4．0kbBglⅡ目的片段插入基因置换载体pHZl35l，再接合转移至阿维链霉菌BJBM9903，筛选得到表型为Apma^RThio^S的接合子。PCR验证并对发酵产物进行HPLC和MS分析，证实该接合子为敞dkdF^-突变株。  相似文献   

小麦品种产量改良的限制因素分析     

孙道杰  王辉  闵东红  李学军  冯毅 《扬州大学学报(农业与生命科学版)》2001,22(3):18-21

通过对关中地区 5 0年来不同时期小麦品种在目前栽培条件下产量性状变化与当前推广品种源库关系的研究 ,初步探明 :①在以往品种改良中 ,收获指数的提高起了重要作用 ;②当前种植的品种中 ,源是产量进一步提高的制约因素 ;③引入新的种质 ,以改善源的功效为基础提高生物学产量 ,且不降低收获指数 ,是超高产育种的根本方法。  相似文献   

Two cases of intrascrotal torsion of a normal testicle     

A. C. B. YOUNG 《The Journal of small animal practice》1979,20(4):229-231

This paper reports two cases of torsion of a normal fully descended testicle in the dog, reviews the literature and discusses the pathogenesis of the condition.  相似文献   

Methylmalonate excretion in vitamin B12 deficiency     

BARNESS LA  YOUNG DG  NOCHO R 《Science (New York, N.Y.)》1963,140(3562):76-77

Urinary methylmalonate excretion is increased in rats with an insufficiency of vitamin B(12). Excretion of methylmalonate is not affected by folic acid, vitamin E, or selenium, but is markedly decreased by small amounts of vitamin B(12) added to the diet.  相似文献   

Record maintenance for a long-term monkey colony     

FREMMING BD  BENSON RE  YOUNG RJ  HARRIS MD  NACHTWEY DS 《American journal of veterinary research》1955,16(60):470-471

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Monitoring furosemide in racehorses participating in an EIPH program   总被引：1，自引：0，他引：1  

A. J. STEVENSON  M. P. WEBER  R. TRUDEL  R. LEAVITT‡  D. WOODARD‡  F. TODI  M. MENDONCA  V. ROBILLO  L. YOUNG  S. KACEW 《Journal of veterinary pharmacology and therapeutics》1994,17(3):163-168

Analytical procedures were developed to monitor furosemide concentrations in post-race serum and urine samples obtained from horses participating in an exercise-induced pulmonary haemorrhage (EIPH) program. High performance liquid chromatography with ultraviolet light detection proved a reliable, sensitive method for measuring urinary furosemide concentrations up to 12 h after administration of either 150 or 250 mg of the drug to race horses. However, this method was unreliable for determination of serum furosemide concentration. High performance liquid chromatography with fluorescence detection proved a reliable, sensitive method for measuring serum furosemide concentrations in horses administered 250 mg of the diuretic, permitting detection approximately 5–10 ng/ml 6 h after treatment. This method was applied field conditions where furosemide was administered to horses (between 150 and 250 mg intravenously) 4 h prior to the race. Analytical results assisted establishing a threshold concentration of 85 ng/ml for serum furosemide. was found that serum furosemide concentrations are a valid measure of compliance with furosemide administration in the EIPH program.  相似文献