边缘效应对棉田害虫和天敌种群的影响

比较了棉田中间棉株与边缘棉株上害虫、天敌的种群动态,分析了边缘效应对棉株-害虫-天敌能量动态的影响。结果表明,棉田边缘棉株上第2代棉铃虫幼虫发生量比其中间棉株高出1．94倍;第3代棉铃虫发生量比棉田中间要低62．12％;第4代棉铃虫比中间棉株高12．5％。棉田边缘棉株上苗蚜发生量比棉田中间要高出1．09倍,伏蚜和秋蚜的数量比棉田中间分别低97．73％和37．70％。棉田边缘棉株上捕食性瓢虫、蝽类、蜘蛛和寄生性天敌的种群数量低于棉田中间的数量,分别为棉田中间的73．81％、35．79％、52．90％和39．11％;棉田边缘棉株上害虫群落多样性高于棉田中间,而天敌群落的多样性低于棉田中间;棉田边缘的光能利用率和生产力比棉田中间的值要高。     

麦套春棉对棉花生态环境及生长影响的研究

对麦套春棉环境和棉株生长发育进行研究,结果表明：热、光、水资源的竞争是造成棉花苗弱、迟发的主要原因,其中热量尤为主要。因此,麦套春棉应采用地膜覆盖,增另有效地积温,以补偿作物层和耕层土壤热量亏缺。麦人生期,套种棉行生态环境和棉株生长发育显著受到小麦的遮荫和蔼和遮荫时间的影响。此种遮荫程度,随着小麦株高的增加而加重,随着麦棉间距的加大而减轻。遮荫时间也随着小麦成熟期的推迟而延长。因此,麦套春棉棉间距     

多样化的棉田生态系统控害保益功能特征研究

应用数量分析与能量测定相结合的方法 ,定量地分析和比较了华北棉区多样化的套间作棉田生态系统与单作棉田生态系统中主要害虫、天敌的种群动态及其天敌对害虫的控制作用 .结果表明 ,多样化的套间作系统中苗蚜与 2代棉铃虫发生轻 ,而伏蚜与 3代棉铃虫发生重 ;套间作系统有利于天敌群落能量的生产 ,尤其是利于捕食性蜘蛛类群的能量生产 ;从棉田生态系统棉株 害虫 天敌相互作用关系来看 ,尽管间套作系统内天敌群落生产力增加 ,保护益虫 (天敌 )作用好 ,同时也增加了害虫群落生产力 ,其控害功能较差 .     

麦田套种玉米共生期农田生态环境特征及对夏玉米苗期生长的影响

以登海661、郑单958为试验材料,设置麦田套种和麦收后接茬直播两种不同种植方式对比试验,研究了麦田套种玉米共生期的农田生态环境特征及对玉米苗期生长的影响.结果表明： 麦田套种玉米与直播玉米相比,土壤含水量差异较小;麦田套种玉米耕层（0～5 cm）土壤的种际最高温度比直播玉米低4.8～5.2 ℃,最低温度相近,日平均温度低1.4～1.7 ℃,日变化较小,但均达到种子萌发要求;麦田套种玉米苗期冠层光照强度比直播显著减少,套种玉米地表光强为自然光强的4.4%～10.6%,光照不足是玉米苗弱、迟发的主要原因.与直播相比,套种玉米种子萌发出苗速度和干物质积累速度较慢,叶龄较小,叶片瘦长,株高较矮,玉米苗健壮度下降,单株叶面积较小且叶绿素含量较低;随共生期延长,玉米苗生长受抑制程度增加.在大田生产中,直播可促进种子萌发出苗,有利于夏玉米幼苗的生长发育,形成壮苗.     

警惕紫云英茬棉苗被小地老虎危害

紫云英(红花草子)是我区重要的冬绿肥和饲料作物,近年来逐步推广。在棉区,常采用紫云英埋青种植棉花或紫云英条播留种套种棉花的种植方式。据我们调查,这类田块的棉苗遭受小地老虎危害极其严重。1975年5月15—25日在建湖县近湖公社和地区粮、棉原种场调查,一般田块如白茬棉田,麦套棉田,蚕豆茬棉田,每亩有小地老虎60—100条左右,棉苗断茎率0.1—1.5％;苕子茬棉田,每亩有小地老虎80—150条,棉苗断茎率0.6—3.4％;紫云英茬棉田,无论新翻埋青田块或留种套种田块,每亩有小地老虎幼虫3,500—     

小麦间作大蒜或油菜对麦长管蚜及其主要天敌种群动态的影响

麦长管蚜是我国冬小麦产区的重要害虫.试验探索了不同间作方式对麦长管蚜及其主要天敌的影响.结果表明,在调查期内,麦-油(油菜)间作田和麦-蒜(大蒜)间作田中麦长管蚜无翅蚜的种群密度多显著低于单作田;麦-油间作田中有较高的瓢虫种群密度和瓢蚜比;5月2日前,麦-油间作田中蚜茧蜂的种群密度高于单作田和麦-蒜间作田;5月5日后,麦-油间作田的僵蚜率和蜂/蚜比也显著高于单作田和麦-蒜间作田;麦-蒜间作田有翅蚜的种群数量较高,但瓢虫和蚜茧蜂的种群数量无明显变化.麦-油间作和麦-蒜间作均能对麦田中麦长管蚜起到较好的控制作用.     

免耕法对棉田生态系统能流功能的影响

比较了常规与免耕法对棉田生态系统中土壤微生物、害虫、天敌、棉株及其整个棉田生态系统能流功能的影响 .结果表明 ,免耕棉田土壤微生物量与年呼吸耗氧量均明显高于常规棉田 ,分别为常规棉田的 1 .32倍和 1 .63倍 ;免耕棉田的苗蚜与秋蚜、2代与 4代棉铃虫种群生产力下降 ,而伏蚜与 3代棉铃虫种群生产力增加 ;免耕棉田内天敌种群生产力及其捕食利用效率下降 ;免耕可提高棉田系统的光能利用率和总生产力 ,减少辅助能的投入 ,具有低耗、高效的特点 .     

绿盲蝽及其天敌在不同生态条件下的发生动态研究

2005年～2007年,在山东省德州市农科院良种场棉田内系统研究了不同生境对抗虫棉绿盲蝽及其天敌发生动态的影响。试验设5个试验10种处理：即远离果园棉、紧靠果园棉,亩株数3600株均行、亩株数3000株并大小行种植棉,合理化控棉、不化控棉,纯作棉田和插种葵花棉田,双基因抗虫棉和单基因抗虫棉。在棉花的整个生育期系统调查不同生境棉田主要害虫及其天敌的种群数量。结果表明,不同生境抗虫棉田内绿盲蝽天敌的种类基本相同,主要为龟纹瓢虫、七星瓢虫、中华草蛉、大草蛉、华姬蝽、小花蝽、T-纹豹蛛、三突花蛛、草间小黑蛛等。不同生境抗虫棉田内绿盲蝽及其天敌种群数量差异明显。远离果园棉、低密度亩株数3000株并大小行种植棉、合理化控棉能减轻绿盲蝽的发生,但不利于绿盲蝽天敌的发生;种植双基因抗虫棉能减轻绿盲蝽的发生且对绿盲蝽天敌影响不大;插种葵花的棉田即能增加绿盲蝽天敌的数量,又能减轻绿盲蝽的发生。研究还表明绿盲蝽及其天敌在远离果园棉、紧靠果园棉下发生趋势基本一致,仅是发生量存在明显差异,远离果园棉田的绿盲蝽及其天敌百株发生量显著低于紧靠果园棉田（P〈0.05）;合理化控棉田、亩株数3000株大小行棉田内的绿盲蝽及其天敌发生数量显著低于不化控棉田、亩株数3600株均行棉田内的发生数量（P〈0.05）;双基因抗虫棉田内的绿盲蝽百株发生量显著低于单基因抗虫棉田发生数量（P〈0.05）;插种葵花棉田内的绿盲蝽百株发生量极显著低于纯作棉田（P〈0.01）、插种葵花棉田内的绿盲蝽天敌百株发生量显著高于纯作棉田（P〈0.05）,葵花对绿盲蝽及其天敌的诱集效果非常显著,在转基因棉田插种葵花是保益灭害控制绿盲蝽的有效方法之一。     

谈谈七星瓢虫的滞育问题

自从1970年以来,我国黄河流域棉区利用七星瓢虫Coccinella septempunctata L.防治棉苗期棉蚜,取得了比较满意的结果。数年的实践证明:五月中、下旬当麦田瓢虫大量发生时,是人工助迁到棉田的有利时机,如棉株上瓢虫与棉蚜的比例为1:200(百株蚜数500以下)到1:100(百株蚜数1,000以上)时,则不需     

人工释放赤眼蜂对棉铃虫的防治作用及相关生态效应

1998～2000年在河北省南皮县棉区转Bt基因棉田及常规棉田中设置4种不同的组合处理,通过释放螟黄赤眼蜂控制棉铃虫的方法,减少化学农药的使用,达到提升和增强自然生物控制力的生态效应;并以不采取任何防治措施的常规棉田为常规棉对照田。研究表明：（1）转基因棉和常规棉棉田中自然寄生率随棉铃虫世代的增加而逐渐升高,2、3和4代棉铃虫卵被寄生率范围分别为13.3%～14.3%、26.7%～28.2%和60.8%～61.4%。（2）棉铃虫2代期,在常规棉综防田释放赤眼蜂2次,其寄生率为46.4%, 比未释放赤眼蜂的转基因棉棉田和常规棉对照田提高33.1%和32.1%; 3代期,转基因棉棉田释放赤眼蜂1次,其寄生率与常规棉综防田释放4次的效果相当,分别为73.7%和68.1%;但与转基因棉不放蜂田、常规棉化防田及对照田相比,分别提高45.5%、61. 8%和47.0%;4代期,无论放蜂与否,各处理棉田中的寄生率除化防田外（52.1%）均在60%以上。（3）常规棉化防田棉铃虫2代和3代期,分别使用农药2和3次,其自然寄生率分别为5.5%和11.9%,与对照田相比,分别降低8.8%和14.8%;与常规棉综防田相比,分别降低40.9%和56.2%;释放赤眼蜂的效果与施药时间有关,放蜂后1天内施药,寄生率仅为12.5%,施药后2天放蜂,寄生率达45.6%。（4）转基因棉棉田棉铃虫累计数和百株蕾铃被害数比常规棉综防田分别减少74.8%和73.8%,捕食性天敌增加63.0%;放蜂Bt棉田比不放蜂Bt棉田棉铃虫累计数、百株蕾铃被害数分别减少61.8%和33.3%;常规棉综防田棉铃虫累计数、百株蕾铃被害数、农药使用量比化防棉田分别减少29.7%、43.4%和60.0%,捕食性天敌数量增加63.0%。（5）转基因棉田和综防棉田的益害比（捕食性天敌/植食性害虫）分别为0.47∶1和0.30∶1, 而化防棉田为0.24∶1。上述结果表明释放赤眼蜂可弥补抗虫棉后期抗性减弱的不足,增加田间自然天敌的数量,提高对棉田害虫的自然控害功能。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.