五种紫萁属植物的核型分析

研究了5种紫萁属Osmunda植物的核形态学特征, 其间期核属于复杂染色中心型, 有丝分裂前期染色体为中间型, 对有丝分裂前期染色体的动态变化过程和在细胞核内的自然排布情况进行了观察。核型公式为: 粗齿紫萁O. banksiifolia (Presl) Kuhn, 2n=4sm+10st+26t+4T; 紫萁O. japonica Thunb., 2n=2sm+8st+32t(2SAT)+2T;华南紫萁O. vachellii Hook., 2n=4sm+8st+28t+4T; 狭叶紫萁O. angustifolia Ching ex Ching &; Ch. H. Wang, 2n=2sm+4st+34t+4T; 粤紫萁O. mildei C. Chr., 2n=2sm+6st+33t+3T。所有染色体臂比均大于2, 核型类型均为4A, 后3种染色体为首次报道, 且对5种紫萁属植物的核型变异及演化关系进行了讨论, 推测Plenasium亚属3种紫萁属植物中粗齿紫萁核型类型最原始, 狭叶紫萁最进化, 其地理分布与核型不对称性有关联, 粤紫萁可能为一自然种间杂种。     

华南紫萁和粗齿紫萁的配子体发育研究

以腐叶土为基质 ,对华南紫萁和粗齿紫萁进行了孢子繁殖 ;利用Olympus显微镜观察和记录了它们的孢子萌发和配子体发育过程。结果表明 ,两者的孢子及配子体性状极为相似 :孢子同型 ,三裂缝 ,壁厚 ,含叶绿体 ,萌发快 ;在常温下 ,孢子的存活期短 ;孢子萌发需要光 ,萌发类型为紫萁型 ;丝状体阶段不发达 ,仅 2～ 3个细胞 ;原叶体无毛状体 ,中脉厚 ,精子器和颈卵器较大 ;由原叶体发育成幼孢子体所需时间极长。不同之处 :粗齿紫萁的孢子和精子器大些、颈卵器成对着生、成熟配子体多数为雌雄异株、受精率极低。华南紫萁和粗齿紫萁的孢子及配子体发育特点与紫萁、分株紫萁、绒紫萁、桂皮紫萁的极为相似 ,它们既具有大量的原始性状 ,也具有少数进化性状 ,支持把紫萁科列入原始薄囊蕨纲的观点。此外 ,也从孢子和配子体性状方面说明了紫萁属是一个自然的分类群     

基于rbcL和trnL-trnF序列探讨粤紫萁的系统位置及遗传关系

通过对粤紫萁(Osmunda mildei C.Chr.)及紫萁属(Osmunda L.)植物的rbcL和trnL-trnF(包括trnL内含子和trnL-F间隔区)序列进行了测定,并结合部分已发表的紫萁科(Osmundaceae)植物的相关序列进行系统发育分析。结果表明:(1)所分析的紫萁属植物构成一个单系群;(2)粤紫萁与紫萁属中Sect.Plenasium组亲缘关系相近,聚成一支系,支持率为100%;(3)粤紫萁与Sect.Plenasium组的华南紫萁(O.vachellii Hook.)在碱基变异位点上高度一致,达94%,而与Sect.Osmunda组的紫萁(O.japonica Thunb)在变异位点上仅有2%的一致性。因此,根据叶绿体基因母系遗传的特性,推测华南紫萁为粤紫萁的母本,紫萁为其父本。     

聚合草的小孢子发生

本文研究了聚合草(Symphytum officinale L.)花粉母细胞减数分裂时染色体的行为。双线期和终变期染色体完全不形成交叉,中期I的染色体大部分以单价体形式存在,少数染色体次级联会。在减数分裂过程中有落后染色体,单价体提早分离,染色体桥,多极分裂与不均等分裂,形成单分体到十分体等不正常的小孢子,作者认为聚合草是一个远缘杂种,减数分裂染色体行为不正常是其不结实的重要原因。并且,观察到两种类型的减数分裂再组,认为聚合草的部分能育性是由于减数分裂再组时产生的不减数配子引起的。     

水稻亚种间杂种F1半不育小孢子发生的细胞学观察

利用石蜡切片和染色体压片法对水稻亚种间半不育杂种F1及其亲本的小孢子母细胞减数分裂过程进行细胞学观察.结果显示:亲本及杂种F1的花药壁发育正常,但部分F1的小孢子母细胞减数分裂异常,形成不均等的二分体和异常的四分体;其染色体在中期Ⅰ分散在赤道板两旁或远离赤道板,形成单价体;在后期Ⅰ和后期Ⅱ产生大量落后染色体或染色体桥.研究表明,部分花粉母细胞减数分裂中期和后期染色体行为异常可能是造成杂种F1花粉半不育的主要原因.     

枣胚乳三倍体的细胞学－中国果树资源细胞学研究之六

枣属植物经过染色体鉴定的5个种,未发现奇数倍性;中国枣为二倍体,未见自然多倍体类型。1978年通过胚乳培养,已首次诱导出三倍体植株。1983年三倍体始花结果,其细胞学特点如下: 1.胚乳二倍体胚乳二倍体的染色体数2n=24。小孢子母细胞减数分裂染色体行为正常。前期Ⅰ和中期Ⅰ,形成12个二阶体。减数分裂结束,形成正常的四分体,小孢子大小整齐。花粉粒属于正常的三孔沟型。2.胚乳三倍体胚乳三倍体的染色体数2n=36。小孢子母细胞较二倍体大。减数分裂染色体行为不正常。前期Ⅰ和中期Ⅰ有数目不等的单价体、二价体和多价体,染色体群数变动于14—20之间。后期Ⅰ、Ⅱ染色体分离不规则,数目不均衡,有落后染色体,多极分裂,并带有微核。减数分裂结束时,部分小孢子母细胞形成一分体、二分体、不等四分体、五分体和六分体等,小孢子大小不一致。正常花粉比二倍体大,有三孔沟和四孔沟两种类型,还有部分小花粉粒和败育花粉。     

广东万年青的细胞遗传学研究

采用常规压片法和去壁低渗法,以生长于广西凭祥和广东深圳的广东万年青（Aglaonema modestumSchott ex Engl.）为材料,对二者的体细胞染色体、花粉母细胞减数分裂染色体配对行为和花粉发育过程进行了观察。结果表明：（1）野生植株为二倍体2n=40,栽培植株为三倍体2n=60;（2）野生种的小孢子母细胞减数分裂前期I终变期均为二价联会,栽培种偶见三价联会;（3）中期I,野生种为20个二价体排列在赤道板上,未见单价体,栽培种的20个二价体排列于赤道板上,20个单价体随机分布于两极,证实其为三倍体;（4）后期I,野生种二价体分离,出现单染色单体桥和断片,几率为10%,栽培种几率为3%,还存在落后染色体,部分不能进入两极的落后染色体和染色体断片在末期I形成微核;（5）四分体时期,野生种未观察到异常孢子,栽培种出现大量败育的四分体或多分体;（6）小孢子进入正常的发育分化,通过两次有丝分裂形成三细胞型花粉。野生种成熟花粉败育率为2.18%,栽培种为88.29%;（7）野生种正常结实,栽培种果实中未发现种子,为高度不育。     

香港蕨类植物分布新记录和名称修订(一)

记载香港地区蕨类植物9种,其中分布新记录2种,即粗齿紫萁和铁芒萁;名称修订5种,即粗叶卷柏、福建莲座蕨、华南紫萁、阔边假脉蕨和华南膜蕨;报道珍稀濒危蕨类2种,即广东小石松和粤紫萁．     

蕨类植物配子体发育的研究

研究了福建观音座莲、华南紫萁、粗齿紫萁、粗齿桫椤、溪边凤尾蕨、娱蚣草、狭翅铁角蕨、乌毛蕨等21种庆类植物的配子体发育过程。结果如下：(1)对孢子和配子体性状的UPG—MA法聚类分析结果表明,秦仁昌分类系统中亲缘关系近的种类在孢子和配子体性状方面相似性也高,但也有少数例外的情况;(2)蕨类植物的配子体发育有许多共性,但也存在许多不同点;(3)配子体发育中出现的某些性状是稳定的,可以作为分类的依据。     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅲ .母株减数分裂前期Ⅰ染色体配对的光镜观察

首次报道在光镜下观察美味猕猴桃 (品种 :No.2 6原生质体植株的母株 )花粉母细胞( PMC)染色体在减数分裂前期的配对 ,发现其配对和凝缩有明显不同步性。不同细胞间染色体配对形式变化较大 ,一般以二价联会为主 ,其次由其它多种配对方式 (包括有复合配对、重复配对、着丝点或端粒处联合和多价联会 )形成多价体 ,还有少数未配对或发生内配对 (偶见 )的单价体和几条二价体之间的次级配对。粗线期观察到少数染色体有缺失 (或重复 )、倒位、易位和疏松配对等结构性改变。表明该植株是一个复杂的区段异源六位体 ,少数染色体在结构上累积有变异。还认为该植株是研究减数分裂染色体配对和联会机制的好材料。     

Meiotic mutants of rye Secale cereale L.

Summary A mutant form of weedy rye characterized by male and female sterility and having a hereditary block in the chromosome synapsis has been found and described. Genetic analysis has shown the synapsis block to be determined by the recessive allele of a gene designated as sy-1. Electron microscopy of surface-spread microsporocyte nuclei revealed the complete absence of the synaptonemal complex over the whole meiotic prophase I, although the axial cores were perfectly formed by each chromosome. Only univalents were observed at metaphase I, their average number ranging from 13.1 to 14.0 per cell. A precocious distribution of univalents at the poles is observed at metaphase I. All of the later stages of meiosis were irregular and resulted in the formation of abnormal microspores. Thus, the mutant proves to be asynaptic because of the blocked initiation of synapses at prophase I.     

Genetic collection of meiotic mutants of rye Secale cereale L

Genetic collection of meiotic mutants of winter rye Secale cereale L. (2n = 14) was created. Mutations were detected in inbred F2 generations after self-fertilization of the F1 hybrids, obtained by individual crossing of rye plants (cultivar Vyatka) or weedy rye with plants from autofertile lines. The mutations cause partial or complete plant sterility and are maintained in collection in a heterozygous state. Genetic analysis accompanied by cytogenetic study of meiosis has revealed six mutation types. (1) Nonallelic asynaptic mutations sy1 and sy9 caused the formation of only axial chromosome elements in prophase and anaphase. The synaptonemal complexes (SCs) were absent, the formation of the chromosome "bouquet" was impaired, and all chromosomes were univalent in meiotic metaphase I in 96% (sy1) and 67% (sy2) of cells. (2) Weak asynaptic mutation sy3, which hindered complete termination of synapsis in prophase II. Subterminal asynaptic segments were always observed in the SC, and at least one pair of univalents was present in metaphase I, but the number of cells with univalents did not exceed 2%. (3) Mutations sy2, sy6, sy7, sy8, sy10, and sy19, which caused partially nonhomologous synapsis: change in pairing partners and fold-back chromosome synapsis in prophase I. In metaphase I, the number of univalents varied and multivalents were observed. (4) Mutation mei6, which causes the formation of ultrastructural protrusions on the lateral SC elements, gaps and branching of these elements. (5) Allelic mutations mei8 and mei10, which caused irregular chromatin condensation along chromosomes in prophase I, sticking and fragmentation of chromosomes in metaphase I. (6) Allelic mutations mei5 and mei10, which caused chromosome hypercondensation, defects of the division spindle formation, and random arrest of cells at different meiotic stages. However, these mutations did not affect the formation of microspore envelopes even around the cells, whose development was blocked at prophase I. Analysis of cytological pictures of meiosis in double rye mutants reveled epistatic interaction in the mutation series sy9 > sy1 > sy3 > sy19, which reflects the order of switching these genes in the course of meiosis. The expression of genes sy2 and sy19 was shown to be controlled by modifier genes. Most meiotic mutations found in rye have analogs in other plant species.     

Deficiency of X and Y chromosomal pairing at meiotic prophase in spermatocytes of sterile interspecific hybrids between laboratory mice (Mus domesticus) and Mus spretus

The normal association between the X and Y chromosomes at metaphase I of meiosis, as seen in air-dried light microscope preparations of mouse spermatocytes, is frequently lacking in the spermatocytes of the sterile interspecific hybrid between the laboratory mouse strains C57BL/6 and Mus spretus. The purpose of this work is to determine whether the separate X and Y chromosomes in the hybrid are asynaptic, caused by failure to pair, or desynaptic, caused by precocious dissociation. Unpaired X-Y chromosomes were observed in air-dried preparations at diakinesis, just prior to metaphase I. Furthermore, immunocytology and electron microscopy studies of surface-spread pachytene spermatocytes indicate that the X and Y chromosomes frequently fail to initiate synapsis as judged by the failure to form a synaptonemal complex between the pairing regions of the X and Y Chromosomes. Several additional chromosomal abnormalities were observed in the hybrid. These include fold-backs of the unpaired X or Y cores, associations between the autosome and sex chromosome cores, and autosomal univalents. The occurrence of abnormal autosomal and XY-autosomal associations was also correlated with cell degeneration during meiotic prophase. The primary breakdown in hybrid spermatogenesis occurs at metaphase I (MI), with the appearance of degenerated cells at late MI. In those cells, the X and Y are decondensed rather than condensed as they are in normal mouse MI spermatocytes. These results, in combination with the previous genetic analysis of spermatogenesis in hybrids and backcrosses with fertile female hybrids, suggest that the spermatogenic breakdown in the interspecific hybrid is primarily correlated with the failure of XY pairing at meiotic prophase, asynapsis, followed by the degeneration of spermatocytes at metaphase I. Secondarily, the failure of XY pairing can be accompanied by failure of autosomal pairing, which appears to involve an abnormal sex vesicle and degeneration at pachytene or diplotene.by C. Heyting     

小麦ph1b突变体与小黑麦杂交的细胞遗传学研究

本文利用普通小麦品系"中国春"(对照)、中国春ph1b突变体分别与八倍体小黑麦、六倍体小黑麦杂交,杂种F1的减数分裂前期Ⅰ染色体行为表现异常,中期Ⅰ出现较多的单价体、棒状二价体和多价体,在后期和末期出现落后染色体、染色体片断和微核。原因是ph1b基因的存在造成染色体联会机制紊乱,致使一些部分同源染色体配对并发生互换,有可能在以后的世代产生染色体易位与基因重组。     

Role of the pseudoautosomal region in sex-chromosome pairing during male meiosis: meiotic studies in a man with a deletion of distal Xp.

Meiotic studies were undertaken in a 24-year-old male patient with short stature, chondrodysplasia punctata, ichthyosis, steroid sulfatase deficiency, and mild mental retardation with an inherited cytologically visible deletion of distal Xp. Molecular investigations showed that the pseudoautosomal region as well as the steroid sulfatase gene were deleted, but telomeric sequences were present at the pter on the deleted X chromosome. A complete failure of sex-chromosome pairing was observed in the primary spermatocytes of the patient. Telomeric approaches between the sex chromosomes were made at zygotene in some cells, but no XY synaptonemal complex was formed. The sex chromosomes were present as univalents at metaphase I, and germ-cell development was arrested between metaphase I and metaphase II in the vast majority of cells, consistent with the azoospermia observed in the patient. The failure of XY pairing in this individual indicates that the pseudoautosomal sequences play an important role in initiating XY pairing and formation of synaptonemal complex at meiosis.     

Chromosome numbers, meiotic behavior, and pollen viability of species of Vriesea and Aechmea genera (Bromeliaceae) native to Rio Grande do Sul, Brazil

Chromosome number, meiotic behavior, and pollen viability were analyzed in 15 species of two genera, Vriesea and Aechmea, native to Rio Grande do Sul, Brazil. This study is the first cytogenetic analysis of these taxa. The chromosome numbers are all n = 25, consistent with the proposed base number of x = 25 for Bromeliaceae. All examined taxa displayed regular bivalent pairing and chromosome segregation at meiosis. Observed meiotic abnormalities include univalents in metaphase I; missing or extra chromosomes and precocious division of centromeres in metaphase II; laggards in telophase I and anaphase II/telophase II. The high pollen viability (>88%) reflects a regular meiosis.     

Interaction of B chromosomes with A or B chromosomes in segregation in insects

Additional or B chromosomes not belonging to the regular karyotype of a species are found in many animal and plant groups. They form a highly heterogeneous group with respect to their morphology and behaviour both in mitosis and meiosis. Achiasmatic mechanisms that ensure the segregation of a B chromosome from another B chromosome or from an A chromosome are reviewed. An achiasmatic mechanism characterized by the "distance pairing" of segregating univalents at metaphase I was found to be responsible for the preferential segregation of B chromosome univalents in Hemerobius marginatus L. (Neuroptera), and a mechanism characterized by the "touch and go pairing" of segregating univalents was responsible for the highly regular segregation of a B chromosome and the X chromosome in Rhinocola aceris (L.) (Psylloidea, Homoptera). The latter mechanism resulted in the integration of a B chromosome to the A chromosome set as a Y chromosome in a psyllid species Cacopsylla peregrina (Frst.). Furthermore, B chromosomes can disturb the regular segregation of the achiasmatic X and Y chromosomes resulting in the formation of X0/XY polymorphism in a population, which might precede the loss of the Y chromosome. The absence of observations on accurately functioning achiasmatic segregation mechanisms in grasshoppers (Orthoptera) was attributed to the X and B chromosomes, which re-orient one or several times during metaphase I. Apparently, these re-orientations mask any achiasmatic segregation mechanism that might operate during meiotic prophase in these insects.     

Semisterile meiotic mutant <Emphasis Type="Italic">sy11</Emphasis> with heterologous chromosome synapsis in rye <Emphasis Type="Italic">Secale cereale</Emphasis> L.

A study was made of the expression and inheritance of the sy11 mutation, which alters homologous chromosome synapsis in meiotic prophase I of rye. The abnormal phenotype proved to be determined by a recessive allele of a single sy11 gene. Univalents and multivalents were observed in homozygotes for the mutant allele. Analysis of the synaptonemal complex revealed a combination of homologous and nonhomologous synapsis in the mutant. The nonhomologous synapsis frequency significantly decreased in the course of meiotic prophase I in the mutant. The number of chiasmata per bivalent in metaphase I was 1.1 ± 0.01 versus 1.8 ± 0.01 in wild-type plants, and the number of univalents was 2.7 ± 0.06 versus 0.5 ± 0.05 in wild-type plants. As a result, a broad range of abnormalities was observed at subsequent stages of meiosis and led to the formation of defective microspores. Mutant plants were semisterile.