兰州百合小孢子母细胞减数分裂异常现象的观察

对兰州百合(Lilium davidii var.unicolor)小孢子母细胞减数分裂异常进行了研究,发现存在不等二价体、同源染色体早分离、染色体桥、不均等分离、滞后染色体、核外染色体、微核等。分析了这些异常形成的可能机制及对正常小孢子形成的影响。人工花粉萌发实验表明：小孢子母细胞减数分裂异常是导致花粉败育的主要原因。认为兰州百合长期行无性繁殖引起染色体结构变异,导致减数分裂异常。     

百合花粉母细胞减数分裂及其雄配子体发育观测

以百合“Siberia”品种为材料,采用染色压片法对花粉母细胞减数分裂和雄配子体形成进行了系统的细胞学观察,结果表明：百合花药6枚,花药4室,胞质分裂方式为连续型,四分体小孢子排列方式为四面体型和十字型,成熟花粉为二细胞型,具1个萌发沟。百合同一植株、同一花蕾乃至同一花药,能观察到2～4个分裂相,减数分裂具不同步性,这是适应环境的一种进化表现,对其种群繁殖具有重要意义。     

矮牡丹小孢子母细胞减数分裂异常现象的观察

矮牡丹(Paeonia suffruticosa subsp. spontanea)(永济居群)存在多种结构杂合现象,减数分裂存在一些异常:如单价体、异形二价体、互锁四价体、六价体、后期I倒位桥、落后单价体、不均等分离、后期Ⅱ桥和微核等。统计了这些异常现象出现的频率,并对其形成的机制和对正常小孢子形成的影响进行了讨论。从细胞学水平上探讨了矮牡丹可能的濒危机制。同时结合前人的研究,对芍药属内3个组的结构杂合程度进行了比较。     

兰州百合花粉母细胞的减数分裂--植物学彩色显微摄影系列之六

植物细胞的减数分裂（成熟分裂）是植物生物学教学中的重要内容之一,但如何使学生能自己动手操作,观察到这种复杂而特殊的细胞分裂过程,却难度较大,障碍因素很多。因此我们一直关注供试材料的筛选,希望获得在我国原产或在我国覆盖地区面积大、又便于大家取材和操作的减数分裂实验的供试材料,要求它们的染色体个体较大、数目较少,以利观察和计数。此外还要选择着色最好、染色深而背景清晰、还能制成永久涂片而长久不褪色的染剂。     

花粉母细胞减数分裂观察技术

介绍了常见大田作物、蔬菜和花卉植物的花粉母细胞减数分裂自制涂片 的观察技术要点,为进一步提高花粉母细胞减裂分裂的观察效果提供参考。     

麦蓝菜的花粉母细胞减数分裂及核型分析

采用压片法,对麦蓝菜的花粉母细胞减数分裂及体细胞核型进行了研究。结果表明,麦蓝菜的绝大多数花粉母细胞减数分裂中染色体的行为正常,在终变期同源染色体配对后可形成15个二价体;在少数花粉母细胞减数分裂中观察到落后染色体、染色体桥等异常行为;其减数分裂为同时型,其花粉粒育性为88.04%。麦蓝菜的染色体数目为2n=2X=30,核型公式为K(2n)=2X=30=22m(2SAT)+8 sm,染色体相对长度组成为2n=16M2+14M1,其核型为"1A"型。     

黄瓜花粉母细胞减数分裂行为的研究

研究了华北型、华南型和西南型黄瓜花粉母细胞的减数分裂行为,发现黄瓜细胞核减数分裂的同步性较高,细胞质是同时型分裂。在细胞核分裂的过程中,核仁在前期Ⅰ到中期Ⅰ逐渐消失,在前期Ⅰ再次出现,随后消失;染色体在前期Ⅰ到中期Ⅰ逐渐收缩,变得清晰,至末期Ⅰ解螺旋,变得模糊,在前期I再次清晰。不同生态型黄瓜终变期的染色体构型均以环状二价体为主。在前期Ⅰ和前期Ⅰ,西双版纳黄瓜的核仁都相应地比另外两种生态型黄瓜品种的多,在后期Ⅰ还偶尔出现染色体桥,显示了西双版纳黄瓜变种的特殊性。研究还发现寒冷的气候条件下栽培黄瓜都能够形成高频率的多分体,推测其形成很可能与低温逆境有关。     

黄芩的花粉母细胞减数分裂及核型分析

采用压片法,对黄芩花粉母细胞减数分裂及核型进行了研究。结果表明:黄芩的大多数花粉母细胞减数分裂中染色体的行为正常,在终变期同源染色体配对后可形成9个二价体,后期Ⅰ染色体以9∶9的方式向细胞两极分离,其减数分裂为同时型;在少数花粉母细胞减数分裂中观察到落后染色体、染色体桥等异常行为;其花粉粒育性为76.49%。黄芩的染色体数目为2n=2X=18,核型公式为K(2n)=2X=18=16m+2 sm,染色体相对长度组成为2n=1 s+4M1+3M2+1L,其核型为"1A"型。     

紫露草花粉母细胞减数分裂的研究

以鸭跖草科植物紫露草(Tradescantia paludosa)为材料,采用花粉母细胞压制法和改良苯酚品红染色法,将临时制片和永久制片方法同步化,并在油镜下拍摄了紫露草花粉母细胞减数分裂各时期的照片。实验结果应用于医学细胞生物学和遗传学的实验教学,收到了较好的教学效果。     

鱼腥草花粉母细胞减数分裂特征及其育性研究

为深入了解鱼腥草花粉母细胞的减数分裂特征与花粉育性的关系,该研究采用卡宝品红染色法对2个鱼腥草居群花粉母细胞的减数分裂过程进行观察,并采用氯化三苯基四氮唑(TTC)染色法、I2-KI染色法、B-K培养基培养法及荧光显微镜观察法来检测鱼腥草花粉的活力及萌发率。结果发现:(1)鱼腥草减数分裂的进程与花序大小、花药颜色、花药长度均有密切的关系。(2)2个居群的鱼腥草中花粉母细胞减数分裂过程正常占88.2%,有11.8%的花粉母细胞减数分裂异常。(3)减数分裂异常表现在减数分裂过程中出现微核、落后染色体、染色体桥、不均等分离、多分体等现象,并发现在二分体阶段及单核花粉发育过程中存在细胞融合。(4)2个居群的鱼腥草花粉活力均不超过1.5%,花粉几乎不萌发。研究认为,鱼腥草花粉育性低的主要原因是单核花粉的发育过程异常,而非鱼腥草花粉母细胞减数分裂异常所致。     

Abnormalities in synaptonemal complexes in pollen mother cells of a lily hybrid

Two abnormalities, one in lateral elements of synaptonemal complexes the other involving whole complexes, have been studied with the electron microscope in pollen mother cells of the lily hybrid, Lilium aureliensis × L. henryi, which with the light microscope showed almost complete bivalent formation at metaphase. Brief water treatment of pollen mother cells prior to fixation, revealed that the aberrant configurations in lateral elements arose by breakage and subsequent folding of severed fragments up to about 0.8 m long. The abnormality ocurred at recognisable heterologous regions, apparently immediately after pairing. The folded fragments were eliminated from the chromosomes at some time during pachytene. Pseudo pairing was observed after synapsis between either more than one pair of homologues or one pair bent back on themselves, so as to produce polycomplexes. Seemingly, central elements could develop between lateral elements on their outer face under these conditions.     

小麦花粉母细胞减数分裂与旗叶距的关系

减数分裂是形成性细胞时所进行的一种细胞分裂,染色体经过一次复制,细胞连续两次分裂．结果形成的子细胞的染色体数为母细胞的一半,由2n变为n。通过配子结合,染色体又恢复到2n。这样保证了有性生殖时染色体的恒定性,从而保证了生物上下代之间遗传物质的稳定性和连续性,也保证了物种的稳定     

Membranes in the spindle of Iris pollen mother cells during the second division of meiosis

Summary Spindle membrane in the second division of meiosis inIris comprises endoplasmic reticulum (ER) and small spherical vesicles (40–80 nm diameter). The vesicles are in all respects similar to those of dictyosomes and it is proposed that they originate in the Golgi system. ER on the other hand is generated from the nuclear envelope (NE). Invaginations and evaginations of the inner and outer membranes of the NE are present at interphase and they enlarge during prophase II and break to form spindle ER elements at the beginning of prometaphase II. The area enclosed by this ER continues to increase until the entire spindle is filled with irregular profiles at mid-prometaphase II. During late-prometaphase II the quantity of ER decreases and, concurrent with an increase in the number of microtubules (MTs), the cisternae align alongside MT bundles and accumulate at the poles. It is suggested that ER increases in quantity by growth of NE membranes. Furthermore, the alignment of ER along the interpolar axis and its transport polewardsprior to anaphase suggest the action of a force on each ER element.     

华北落叶松小孢子母细胞(PMC)减数分裂和花粉的发育

采用染色体压片法系统地观察了华北落叶松Larix principis-rupprechtii小孢子母细胞(PMC)减数分裂的细胞学特征和花粉发育过程。结果表明:华北落叶松PMC减数分裂始于当年秋季,以弥散双线期的特殊状态休眠越冬,次年春天又重新恢复其后续的减数分裂过程。主要特点是在同一花药中,减数分裂不同步,且各阶段分裂速度较快,3天内全部停留在四分体阶段;二价体构型主要为两臂共发生过两次以上交换的环形二价体,少数细胞中偶见一臂发生交换的棒状二价体;其平均构型为10.62II 1.38II;中期II核分裂相既有平行式样,又有互为垂直式样,形成左右对称型和四面体型四分体,兼具单、双子叶植物四分体主要类型特点。四分体持续一周后,细胞壁开始溶解,4个小孢子分离并游离在药室中,成为独立的单核花粉。其后细胞核开始有丝分裂,最后形成由2个原叶细胞、1个管细胞、1个柄细胞和1个体细胞共5个细胞组成的成熟花粉。此外,还观察到成熟花粉当中有13.6%是由4个细胞组成的。     

Binding form of pollen mother cell protein in the nucleosomes of lily

We have previously reported the existence of pollen mother cell nuclear protein (PMCP) which appears during microsporogenesis in lily (Lilium spesiosum). It is very similar to mammalian testis specific H1 histone, H1t. In this paper, we describe the PMCP distribution in lily nucleosomes. Isolated nuclei were treated with micrococcal nuclease, and template active and inactive chromatin fractions were prepared. The nucleosome repeat length of pollen mother cells was determined to be 210 base pairs. The majority of the PMCP was found in the template inactive chromatin fraction, similar to other histones. PMCP was contained in the nucleosome monomer, but not in the core particle. However, PMCP was mainly found in the nucleosome dimer when slightly digested. Salt extraction from isolated nuclei indicated that PMCP and H1 histone share similar binding affinities to DNA. Judging from our results, it seems probable that PMCP links two core particles more strongly than H1 histone does. Since it is known that meiotic chromatin includes nick transferase and nuclease activity, one possible role of PMCP is the protection of its own chromatin. Other possible functions of PMCP are also discussed.     

Isolation and characterization of a novel nuclear protein from pollen mother cells of lily

Pollen mother cells of the lily (Lilium speciosum) were found to have a histone-H1-like protein (PMCP) not detected in other tissues. The PMCP appears from the late S-G₂ period of premeiosis and is present in mature pollen. PMCP and H1 were extracted from pollen mother cells with 5% perchloric acid and isolated by reverse-phase high-performance liquid chromatography. The amino acid composition of PMCP differs from that of somatic H1. However, PMCP is similar to H1t in mammalian testis with regard to amino acid composition.     

Developmental changes in DNA methylation of pollen mother cells of David lily during meiotic prophase I

Epigenetic marks in the form of DNA methylation are involved in the development of germ cells and are important in the maintenance of fertility. However, the controlling system of the on-off switch for DNA methylation largely remains unclear. In this study, the extent of cytosine methylation during the meiotic prophase I in David lily is assessed using high pressure liquid chromatography to evaluate the DNA methylation rates. Comparing the degree of DNA methylation before, during, and after synizesis, both de novo methylation and demethylation occurred. Mainly the methylation level decreased by 21.3% (from 54.8 to 33.5%) during synizesis in the pollen mother cells. The developmental timing of genome-wide DNA methylation acquisition during pollen mother cell development is clarified in this paper. The relative amounts of 5-methyl-deoxycytidine of global methylation in leaf DNA in David lily were also higher than in other species reported.     

An ultrastructural study of cytomixis in tobacco pollen mother cells

Intercellular chromatin migration (cytomixis) in the pollen mother cells of two tobacco (Nicotiana tabacum L.) lines was analyzed by electron microscopy during the first meiotic prophase. The maximal manifestation of cytomixis was observed in the pachytene. As a rule, several cells connected with one another by cytomictic channels wherein the nuclei migrated were observable at this stage. In the majority of cases, nuclei passed from cell to cell concurrently through several closely located cytomictic channels. Chromatin migrated between cells within the nuclear envelope, and its disintegration was unobservable. The nucleus, after passing through cytomictic channels into another cell, can be divided into individual micronuclei or, in the case of a direct contact with another nucleus, can form a nuclear bridge. It has been demonstrated that the chromatin structure after intracellular migration visually matches the chromatin structure before it passed through the cytomictic channel. No signs of pyknosis were observable in the chromatin of the micronuclei formed after cytomixis, and the synaptonemal complex was distinctly seen. The dynamics of changes in the nucleoli during cytomixis was for the first time monitored on an ultrastructural level. Possible mechanisms determining cytomixis are discussed and the significance of this process in plant development is considered.