黄瓜幼苗子叶在低温下的光抑制及其恢复

用ＰＡＭ脉冲调制荧光仪测定叶绿素荧光的变化研究了黄瓜幼苗子叶在ＰＦＤ为５０和１００μｍｏｌｍ＾－２Ｓ＾－１,温度为４、７、１０、１５℃下 挑抑制及其恢复。结果表明,黄瓜幼苗子叶Ｆｖ／Ｆｍ随着温度的下降和ＰＦＤ的增加而下降,并且增加等量的ＰＦＤ在４℃下比在１０℃下引起更大的Ｆｖ／Ｆｍ下降。在黑暗条件下光抑制有轻微恢复,但完全发电和需光照,且恢复起始时的光照十分重要。     

黄瓜幼苗的冷锻炼与低温引起的光抑制

黄瓜幼苗的冷锻炼与低温引起的光抑制李晓萍,陈贻竹,李平,郭俊彦（中国科学院华南植物研究所,广州５１０６５０）关键词：低温引起的光抑制,荧光猝灭,冷锻炼,黄瓜幼苗低温使植物利用光能的能力降低从而引起或加剧光抑制（ｈａｓ等１９８３）。在光抑制中常以叶绿素...     

夜间低温对2种热带雨林树种幼苗叶绿素荧光的影响

研究了夜间低温(5℃±1℃,12h,连续3个晚上)对生长于3种光照条件下(100%、25%和8%光照)的热带雨林冠层树种绒毛番龙眼(Pometiatomentosa)和中层树种滇南风吹楠(Horsfieldiatetratepala)幼苗叶绿素荧光的影响。结果表明:低温处理使生长于全光下的绒毛番龙眼幼苗的Fv/Fm(PSII最大光化学量子产量)急剧降低,中午发生了强烈的光抑制,但随着低温胁迫的解除Fv/Fm能很快恢复,表明没有发生不可逆的光氧化损伤。低温使生长于全光和25%光照条件下2个树种幼苗的NPQ(非光化学猝灭,热耗散)受到抑制,但没有引起2个树种幼苗Fo(初始荧光)的升高,不会导致幼苗PSII反应中心的失活。2种热带雨林植物对低温的抗性可能与这些植物的地理分布和历史渊源有关。     

夜间低温对生长在两种光强下两个芒果品种的气体交换和叶绿素荧光的影响

研究了夜间低温对两个芒果(Mangifera indica)品种翡翠芒(Khieo Sawoei)和四季芒(Choke Anand)光合生理的影响.两个芒果品种的幼茼盆栽于全光和50%相对光强下一年.在第二年的冬季,连续7天晚上将芒果幼苗移到4℃的冷库中,白大保持原条件.于低温处理前、处理期间和结束低温处理后10天中测定芒果幼苗的光合生理特征.结果表明,夜间低温导致两个芒果品种的净光合速率、气孔导度和光系统Ⅱ的最大光化学效率(Fv/Fm)降低、非光化学猝灭(NPQ)上升.夜间低温对生长在全光下的芒果幼苗光合作用的抑制比50%光下的更重.翡翠芒的Fv/Fm比四季芒下降的更多,但后者的NPQ上升更多.夜间低温还导致两种光下芒果幼苗叶片的叶绿素含量下降,类胡萝卜素/叶绿素比值、丙二醛含量、膜的透性和可溶性化合物(可溶性总糖和脯氨酸)上升.解除低温胁迫后,四季芒Fv/Fm的恢复比翡翠芒的快.解除低温胁迫7天后二者的F发、Fv/Fm能完全恢复.上述结果表明,翡翠芒对低温更敏感,遮荫可以明显缓解两个芒果品种低温引起的光抑制.     

水杨酸对高温胁迫下黄瓜幼苗叶绿素荧光参数的影响

以津春3号黄瓜为试材,对其喷施0.05、0.1和0.5 mmol/L的水杨酸(SA)溶液,并进行了昼(40±1)℃/夜(30±1)℃高温胁迫处理,研究了黄瓜幼苗四叶期叶片叶绿素荧光参数变化.结果表明,高温胁迫下幼苗叶绿素荧光参数Fo、NPQ等显著升高,Fv/Fm、Fv′/Fm′等明显降低,嫁接苗的变化趋势弱于自根苗;不同浓度的SA溶液可缓解高温胁迫对黄瓜幼苗叶绿素荧光参数的影响,且以0.1 mmol/L的SA处理效果最优.     

氯化胆碱对低温弱光下黄瓜幼苗叶片细胞膜和光合机构的保护作用

1.07mmol／L氯化胆碱处理降低了低温弱光（6℃．PFD100μmol m^-2s^-1）下黄瓜幼苗叶片膜脂组分中主要是磷脂酰甘油（PG）的饱和脂肪酸含量,增加了膜脂不饱和度：减缓了膜透性的下降、MDA的产生速率、叶绿素的降解及PSII最大量子效率（Fv/Fm）、捕光效率（Fv＇／Fm＇）、光化学猝灭系数（qp）、实际光化学效率（ФPSII）和抗氧化酶POD、APX及CAT活性的下降;提高了非光化学猝灭系数（NPQ）和脯氨酸的含量。以上结果表明氯化胆碱处理保护了低温弱光对黄瓜叶片细胞膜和光合机构的伤害。     

低温弱光胁迫及恢复对切花菊光合作用和叶绿素荧光参数的影响

以切花菊品种‘神马’为试材,在偏低温弱光(16℃/12℃,PFD100μmol.m-2.s-1)和临界低温弱光(12℃/8℃,PFD60μmol.m-2.s-1)下分别胁迫11d,然后转入正常条件(22℃/18℃,PFD450μmol.m-2.s-1)恢复11d,研究不同低温弱光强度及恢复对菊花光合作用和叶绿素荧光参数的影响.结果表明:低温弱光导致菊花叶片的净光合速率(Pn)和气孔限制值(Ls)下降,而胞间CO2浓度(Ci)上升.偏低温弱光胁迫下菊花叶片暗适应下最大光化学效率(Fv/Fm)和初始荧光(Fo)无明显变化,但光适应下最大光化学效率(Fv′/Fm′)在处理前期略有下降,后期则有所回升;而临界低温弱光处理的Fo明显升高,Fv/Fm和Fv′/Fm′显著降低.PSⅡ光合电子传递量子效率(ΦPSⅡ)、光化学猝灭系数(qP)和表观光合电子传递速率(ETR)均随着低温弱光胁迫程度的增加和时间的延长而降低;偏低温弱光处理植株在解除胁迫后能迅速恢复到对照水平,而临界低温弱光处理植株回升速度较慢;同时,低温弱光胁迫下吸收光强用于分配光化学反应部分(Prate)的比例减少,而天线热耗散(Drate)和反应中心的能量耗散(Ex)比例上升,但天线热耗散为过剩光能的主要分配途径.     

冷锻炼对甜椒叶片光合作用及其低温光抑制的影响

以冷敏感植物甜椒 (CapsicumannuumL .)抗冷性不同的两个品种为试材 ,利用CIRAS 1光合测定系统和FMS2调制式荧光仪 ,在控温控光条件下分析比较了冷锻炼苗与未经锻炼苗的叶片光合特性、叶绿素荧光参数对温度的响应。结果表明 ,随着温度的降低 ,无论是否经过锻炼 ,低温主要通过抑制碳同化能力来影响光合作用 ,并使光能过剩 ,导致低温光抑制。提高环境CO2 浓度以增强暗反应对光能的利用 ,低温光抑制减轻。 5d的亚适温锻炼过程中甜椒叶片已发生一定程度的光抑制 ,但锻炼苗叶片能在低温下维持较高的光系统II光化学效率(ФPSII)、光化学猝灭系数 (qP)和光适应下光系统II最大光化学效率 (Fv′/Fm)值 ;冷锻炼提高了两品种低温下对光抑制的抗性 ,而且对抗冷品种的作用效果更明显     

温州蜜柑叶片气体交换和叶绿素荧光对低温的响应

研究了低温对温州蜜柑叶片气体交换和叶绿素荧光的影响 ,结果表明 :(1) 8℃低温处理 18h对气体交换和叶绿素荧光影响不大。 (2 ) 2℃低温处理 15h后 ,净光合速率 (Pn)、气孔导度 (Gs)、羧化效率 (CE)下降 ,胞间CO2 浓度 (Ci)升高 ,表观量子效率 (AQY)和叶绿素荧光参数F0 及Fv/Fm没有显著变化。 (3)室外自然低温处理 2和 7d ,Pn、Gs、CE、饱和CO2 光合速率、AQY及Fv/Fm显著下降 ,Ci及F0 显著升高 ;在 2 0℃室内 ,Fv/Fm、F0 和AQY比CE和Pn恢复快。 (4 )低温胁迫使Jf(依据叶绿素荧光参数计算所得的电子传递速率 )和Jc(依据CO2 同化测定所得的电子传递速率 )下降 ,Jf/Jc 值升高。 (5 )低温处理降低了Pn和光呼吸速率 (Pr) ,但Pr下降的速率小于Pn下降的速率     

光和暗条件下低温对黄瓜和水稻叶绿素蛋白质复合体的影响

本试验以黄瓜和水稻幼苗为材料,研究了光照和黑暗条件下低温对植物叶绿素蛋白质复合体的影响。SDS—PAGE电泳结果表明:5℃及12h 280μmol m~(-2)S~(-1)处理2d,Chl-蛋白质复合体的降解明显大于5℃暗低温处理;低温与光照对P700-CPa_1的影响大于LHCP。叶绿素荧光测定表明;5℃及12h 280μmol m~(-2)s~(-1)的处理对PSⅡ的影响亦大于暗低温处理。由此认为:低温与光对植物叶绿体的PSⅠ和PSⅡ都有明显的影响,其机理可能与常温下高光强引起的光抑制相类似;不同的是低温下中等光强就能引起光抑制。因此,在光照低温下往往加剧植物冷害的发生。     

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.