黑节草双受精过程及胚胎发育的研究

黑节草从传粉到受精约需１３０ｄ,精子在花粉管中形成,胚囊发育属蓼型胚囊,因反足细胞较早退化,故受精前胚囊多只由卵器和中央细胞组成。精卵核融合时,精核染色质进入卵核后凝集成颗粒状,并在原位与卵核的染色质融合,雌、雄性核仁一直维持至合子的第一次分裂期前。双受精作用正常,属于有丝分裂前配子融合类型,初生胚乳核发生２－３次分裂后逐渐退化消失,胚的发育局限于球形胚阶段。     

Observations on Fertilization in Sugar Beet

The whole process of double fertilization in sugar beet has been observed, the main results are as follows: About 2 hours after pollination, the pollen grains germinate, the sperms in the pollen tube are long-oval. 15 hours after pollination, the pollen tube destroys a synergid and releases two sperms on one side or at the chalazal end of the egg cell. The sperms are spherical each having a cytoplasmic sheath. 17 hours after pollination, one sperm enters the egg cell, and the sperm nucleus fuses with the egg nucleus rapidly. 21 hours after pollination, the zygote is formed. In the meantime, the primary endosperm nucleus has divided into two free endosperm nuclei. 25 hours after pollination, the zygote begins to divide, forming a two-celled proembryo. The dormancy stage of the zygote is about 4 hours. In the meantime the endosperm is at the stage of four free nuclei. 17 hours after pollination, the sperm nucleus comes into contact and fuses with the secondary nucleus. The sperm nucleus fuses with the secondary nucleus, faster than the sperm with the egg. he first division of the primary endosperm nucleus is earlier than that of the zygote, it takes place about 20 hours after pollination, the dormancy stage of the primary endosperm is about 2 hours. The endosperm is free nuclear. The fertilization of sugar beet belongs to premitotic type of syngamy. From the stage of zygote to the two-celled proembryo, it can be seen that addition- al sperms enter the embryo sac, but polyspermy has not been observed yet.     

侧金盏胚和胚乳发育的细胞胚胎学研究

利用石蜡切片技术对毛茛科植物侧金盏胚及胚乳发育进行了研究,以明确其胚胎发育的特征,为毛茛科植物的系统研究提供资料。结果表明:(1)侧金盏胚的发育属于柳叶菜型,胚乳发育为核型;初生胚乳核的分裂早于合子的第一次分裂。(2)种子成熟时,种胚尚未分化完全,尚处于球形胚后期或心形胚早期阶段,整个胚发育大约需要50~60d。(3)侧金盏种子存在明显的形态生理休眠现象,经后熟作用逐渐完成种胚的分化与生长,形成子叶形胚;侧金盏种子在相同处理条件下胚分化和发育的速度存在差异。     

羊草受精作用及其胚与胚乳早期发育的观察

利用常规石蜡制片方法研究了羊草受精过程及胚与胚乳的早期发育,其主要结果为：(1)授粉后1h,花粉管破坏1助细胞,释放2精子。精子为眼眉状,难以区分其细胞质鞘;(2)授粉后1～2h,2个精子分别移向卵细胞与极核;(3)授粉后2～3h,精核分别贴附于卵细胞与极核核膜上;(4)授粉后3～10h,精核与卵核融合,并出现雄性核仁,形成合子;(5)授粉后3～4h,精核与极核融合,并出现雄性核仁,形成初生胚乳核,精核与极核的融合比与卵核融合快;(6)传粉后20h,合子分裂,合子的休眠期为10h左右;(7)传粉4h,初生胚乳核分裂,初生胚乳核没有休眠期;(8)羊草双受精作用属于有丝分裂前配子融合类型;(9)胚胎发育属于紫菀型,胚乳发育属于核型胚乳。     

番茄受精作用及其间隔期的研究

利用常规石蜡切片法研究了番茄受精作用的全过程,具体研究结果为:(1)授粉后2 h,花粉粒在柱头上萌发;约2~4 h,花粉管长入柱头,且末端膨大;约8 h后,生殖细胞进入分裂期;并于约两小时后,分裂为两个精细胞。(2)约14 h,花粉管进入子房腔;约18~24 h,花粉管进入胚囊,破坏一个助细胞,并在其珠孔端释放两个精子;随后被释放的精子移到卵细胞与次生核附近。(3)授粉后约30 h精核进入卵细胞;约34 h,精核与卵核融合,并在卵核内出现分散的雄性染色质,进而出现雄性核仁;44~50 h,雌、雄性核仁融合,形成合子;合子的休眠期为10 h左右。60 h之后,合子分裂形成二细胞原胚。(4)约26 h,另一个精子的精核与次生核核膜相贴伏,随后与之融合;约30~34 h,次生核内出现分散的雄性染色质,随之出现雄性核仁;约38~42 h,雌、雄性核仁融合,形成初生胚乳核。约44 h后,初生胚乳核进行有丝分裂,形成两个胚乳细胞。番茄胚乳发育属于细胞型。初生胚乳核无休眠期。(5)精子与次生核的融合比与卵核的融合快。(6)番茄的受精作用属于有丝分裂前配子融合类型。     

The Fertilization and Early Development of Embryo and Endosperm in Stevia rebaudiana Bertani

The mature embryo sac is surrounded by endothelium tapetum. It is composed or an egg apparatus, one central cell with secondary nucleus, and 1–6 antipodal cells. About the 6th hour after pollination, female and male nuclei fuse with each other. The syngamy occurred almost simultaneously with the fusion of an other sperm nucleus and the secondary nucleus, but the velocity of the latter is faster than that of the syngamy. The fertilization of Stevia rebaudiana Bertani belongs to the premitotic type. About the 8th hour after pollination, primary endosperm nucleus is in mitosis, its dividing orientation may parallel or at right angle to the long axis of the embryo sac, and gives rise to two initial endosperm cells. The first five divisions of the endosperm cells are of synchronism. At the stage of heart-shaped embryo, the endosperm cells show the signs of digestion and absorbed. The endosperm development is of the cellular type. About the 10th hour after pollination, zygote divides for the first time. The division of the zygote is always transverse. The embryo development conforms to the Asterad type.     

侧金盏花双受精进程研究

应用荧光显微镜和常规石蜡切片观察侧金盏花(Adonis amurensis)花粉管生长和受精作用的全过程。结果表明,侧金盏花为湿型柱头,授粉后1–2小时,花粉粒与柱头识别;授粉后2–4小时,花粉粒萌发;授粉后4–6小时,花粉管进入柱头。侧金盏花的受精模式为珠孔受精,授粉后10小时,精子被释放;授粉后30小时,精核与卵核融合;授粉后7天合子形成;授粉后15天合子进入分裂期,合子休眠期为8天。2个极核在受精前不融合,授粉后14–16小时,精核与1个极核融合;授粉后20–22小时,受精极核与另1个极核融合形成初生胚乳核。双受精作用属于有丝分裂前配子融合型。通过实验确定了侧金盏花受精过程的雌雄性细胞融合形态变化与相应经历的时间及其合子休眠期。研究结果丰富了侧金盏花胚胎学资料,对其今后的育种及转基因研究具有重要意义。     

北柴胡胚和胚乳的发育及对其种子萌发的影响

利用常规石蜡制片技术对北柴胡胚和胚乳的发育及对其种子萌发的影响进行了观察。结果表明北柴胡胚的发育属于茄型,基细胞进行一次横分裂后不再分裂,因而胚柄不发达,且很早解体。胚乳的发育属于核型,初生胚孔核的分裂远远早于受精卵的分裂。对果实采收时期胚发育状况进行统计发现,在被测采收期果实中有20%的果实的胚处于球形胚阶段,70%处于心形胚,只有10% 处于鱼雷胚,说明北柴胡种子采收时胚处于不同的发育阶段,存在形态后熟现象,这是北柴胡种子萌发难、萌发率低且出苗不整齐的主要因素。     

Cytologic Observations on the Double Fertilization in Maize

1.The double fertilization is the type of the premitotic syngamy. 2. In 21 to 24 hours after pollination, most of the female nuclei fuse with the male nuclei. When the female nucleus fuses with the male nucleus, there are two situations in the appearance of the male nucleolus: one is that while the chromatin of the sperm nucleus relaxes gradually, a male nucleolus appears; the other is that after the chromatin of the sperm nucleus relaxes gradually, the male nucleus just appears in about 2 to 4 hours. 3. Generally, the fusion of the female nucleolus with the male nucleolus takes place before the division of the nygote. The nygote enters the stage of division when it has a jarge nucieojus; the zygote, in which the female nucleoius does not fuse with the male nucleolus, also can enter the stage of division. In 30 to 33 hours after pollination, the first division of the zygote occurs. The resting period of the zygote is about 9 hours 4. In the primary endosperm nucleus, the female nucleolus does not fuse with the male nucleolus. 24 to 26 hours after pollination, the primary endosperm nucleus begins the first division. The resting period of the primary endosperm nucleus is 2 to 4 hours. 5. Under the condition of artificial pollination, the fertilization of the fruit ears of maize proceeds sequencely, i.e. from the upper of the fruit ears to the lower the fertilization is fulfilled gradually.     

FERTILIZATION IN BARLEY

The mature embryo sac of barley consists of an egg, two synergids, a central cell, and up to 100 antipodal cells. At shedding the male gametophyte is 3-celled, consisting of a vegetative cell with a large amount of starch and two sperms having PAS+ boundaries. Before pollination the nucleus and cytoplasm of each synergid appear normal. After pollination the nucleus and cytoplasm of one synergid undergo degeneration. The pollen tube grows along the surface of the integument of the ovule, passes through the micropyle, and enters the degenerate synergid through the filiform apparatus. The pollen tube discharges the vegetative nucleus, two cellular sperms, and a variable amount of starch into the degenerate synergid. Soon after deposition the sperms migrate by an unknown mechanism to the chalazal end of the degenerate synergid. Sperm nuclei then enter the cytoplasm of the egg and central cell, ultimately resulting in the formation of the zygote and primary endosperm nucleus, respectively. Sperm boundaries do not enter egg or central cell, but it was not possible to determine the fate of other sperm components. Degenerate vegetative and synergid nuclei remain in the synergid after fertilization, constituting what are considered to be X-bodies in barley. The second synergid degenerates during early embryogeny.     

Ultrastructural Changes of the Egg Apparatus Associated with Fertilization and Proembryo Development of Soybean, Glycine max (Fabaceae)

As part of a study involving pod retention in soybean, Glycinemax (L.) Merr., we investigated changes occurring in the eggapparatus of non-abscised flowers from the time immediatelypreceding fertilization through early embryogeny. Prior to theentry of the pollen tube into the embryo sac, one of the synergidsbegins to degenerate as evidenced by increased electron densityand a loss of volume. This cell serves as the site of entryfor the pollen tube. The cytoplasm of the second, or persistentsynergid, remains unaltered until after fertilization. Bothsynergids contain, in addition to a filiform apparatus, a singleunidentified inclusion of flocculent material located in thechalazal portion of each cell. The zygote can be distinguishedfrom the egg by its consistently narrow wall; and it dividesto form a proembryo, a mass of cells not yet differentiatedinto embryo proper and suspensor. The basal cells of the proembryoare more vacuolate than the apical ones, characteristic of thebasal vacuolation of both egg and zygote. Cells of the proembryoare connected to one another via plasmodesmata, and with theexception of the basal-most cell, are isolated symplasticallyfrom the surrounding endosperm. Wall ingrowths frequently occurin certain cells of the proembryo, notably those cells in contactwith the degenerate synergid and embryo sac wall. At a laterstage of ontogeny, by which time the globular embryo properhas become distinct from the suspensor, the wall ingrowths areconcentrated in the suspensor. Glycine max, soybean, embryogeny, synergids     

獐牙菜的胚胎发生

对獐牙菜大孢子发生、雌配子体形成、受精、胚及胚乳发育过程进行了研究。主要结果如下：子房2心皮,1室,4列胚珠,侧膜胎座;薄珠心,单珠被,倒弯生胚珠。大孢子母细胞减数分裂形成4个大孢子直线形排列,合点端的大孢子具功能,胚囊发育为蓼型。3个反足细胞宿存,每个细胞均多核和异常膨大,反足吸器明显,并在胚乳之外形成染色较深的类似“外胚乳”的结构。珠孔受精,受精作用属于有丝分裂前类型。胚乳发育为核型;胚胎发育为茄型。果实成熟时,种子发育至球形胚阶段。反足细胞在龙胆科一些短命植物中的宿存与分裂具有重要的生殖适应与进化意义。     

Fertilization and Embryo Development of Populus lasiocarpa Oliv

The double fertilization and embryo development of P. lasiocarpa were studied using cytochemical method for DNA, RNA, polysaccharides and proteins. Stigmas were covered by secretion stained positively with PAS and mercuric bromphenol blue at receptive stage. The pollen grains germinated on the stigma in large quantities 6 hours after pollination. Fertilization started at the 6th days after pollination. The sperm nucleus fused with the secondary nucleus faster than the sperm nucleus with the egg nucleus. The syngamy belonged to peremitotic type. A great deal of starch grains in the embryo sac disappeared during fertilization. The endosperm was nuclear type and becomed a cel 31 days after pollination. The endosperm was characterized by a dense cytoplasm rich in protein. No discrete starch grains were observed in endosperm. Afterwards, the endosperm was consumed by the developing embryo, thus the mature seeds were non-endospermous. The zygote was dormant for 6–8 days. During the dormency, many striking changes took place, and then, the zygotes showed more pronounced polarity. These changes included the shinkage of the large vacuole, the reduced size, the reappearance of large vacuole, the enlarging of the size. The embryogenesis conformed to the Solanad type. The ovules matured into seeds successively 44 days after pollination. The mature embryo was straight. Two cotyledons folded each other.     

玉米双受精过程的细胞学观察

1.玉米双受精属于有丝分裂前配子融合的类型。2.授粉后21至24小时,大部分雌、雄性核发生融合。雌、雄性核融合时,雄性核仁的出现存在两种情况,其一是精核染色质逐渐分散的同时出现雄性核仁,其二是精核染色质逐渐分散后,约经2至4小时才出现雄性核仁。3.合子内的雌、雄性核仁若发生融合,一般在合子分裂前进行。合子以一个大核仁的形式进入分裂期;雌、雄性核仁不融合的合子同样可以进入分裂期。授粉后30至33小时,合子进行第一次分裂。合子静止期大约为9小时左右。4.初生胚乳核内的雌、雄性核仁不发生融合。授粉后24至26小时,初生胚乳核进行第一次分裂。初生胚乳核的静止期为2—4小时。5.人工授粉条件下,玉米果穗受精过程的进行有一定的顺序;即自果穗上部逐渐向下部完成受精作用。     

A study on the development of stigma and megagametophyte,and embryogeny in Cimicifuga simplex Wormsk

This is one of a series of studies on the reproductive features in Cimicifuga nanchuanensis Hsiao, an endangered plant endemic to China, and C. simplex Wormsk, a closely related and widely spread species as a control. The present paper deals with the results of cyto-morphological observations on the megasporogenesis, the development of female gametophytes, and the embryogeny in C. simplex. Its anatropous ovules are bitegminous and crassinucellate. A megaspore mother cell undergoes meiosis to form a linear or T-shaped megaspore tetrad. The embryo sac is of Polygonum type. The three antipodal cells persist up to the globular stage of embryo development.Two polar nuclei fuse to form a secondary nucleus close to the chalazal end of the embryo sac and connect with antipodal cells before fertilization. The development of endosperm is of Nuclear type. Cellularization of nuclear endosperm initiates since early globular stage of the embryo development. Development of the embryo in C. simplex is of Onagrad type. C. simplex is dichogamous. Stigmatic papillae emerge on the 1st∽2nd day and they elongate into stigmatic hairs on the 3rd∽5th day after stamens withering. The great impact of the differences of the receptible period of stigmas and pollen viabilitybetween the two species on effective pollination and seed-setting rate is discussed.     

ADVENTIVE EMBRYOGENESIS IN CITRUS AND ITS RELATION TO POLLINATION AND FERTILIZATION

Cytological and histological studies of seeds from three facultative apomictic Citrus cultivars show that adventive embryos develop, as a rule, from the first few cell layers of the nucellus adjacent to the embryo sac in the micropylar half and occasionally from the chalazal end. The adventive embryos initiated in nucellar tissue away from the embryo sac and most of those initiated from the chalazal end of the nucellus do not develop beyond the one-celled stage. When two or more embryos are developing in the same seed, the successful development of a given embryo depends on its location in relation to access to nutrients from the endosperm. The presence of a zygote and triploid endosperm in seeds with adventive embryos, the abortion of seed when endosperm degenerates, and the lack of seed set without pollination indicate that pollination and fertilization are essential for in vivo adventive embryogenesis.     

The modified ABC model explains the development of the petaloid perianth of <Emphasis Type="Italic">Agapanthus praecox</Emphasis> ssp. <Emphasis Type="Italic">orientalis</Emphasis> (Agapanthaceae) flowers

The class B genes, which belong to the MADS-box gene family, play important roles in regulating the development of petals and stamens in flowering plants. To understand the molecular mechanisms of floral development in Agapanthus praecox ssp. orientalis (Agapanthaceae), we isolated and characterized the homologs of the Antirrhinum majus genes GLOBOSA and DEFICIENS in this plant. These were designated as ApGLO and ApDEF, respectively. ApGLO and ApDEF contain open reading frames that encode deduced protein with 210 and 214 amino acid residues, respectively. Phylogenetic analysis indicated that ApGLO and ApDEF belong to the monocot class B gene family. In situ hybridization experiments revealed that hybridization signals of ApGLO and ApDEF were observed in whorl 1 as well as in whorls 2 and 3. Moreover, the flowers of transgenic Arabidopsis plants that ectopically expressed ApGLO formed petal-like organs in whorl 1. These observations indicate that the flower developmental mechanism of Agapanthus follows the modified ABC model.     

ADVENTIVE EMBRYOGENESIS IN CITRUS I. THE OCCURRENCE OF ADVENTIVE EMBRYOS WITHOUT POLLINATION OR FERTILIZATION

Anatomical studies of unfertilized undeveloped seeds from open- and control-pollinated fruits of ten facultative apomictic Citrus cultivars were carried out with the aid of light and epifluorescence microscopes. With or without pollination, adventive embryos autonomously developed at all positions in the nucellus in all cultivars. The adventive embryos initiated at the chalazal end of the nucellus were more vigorous than those initiated at the micropylar end. Because of the lack of endosperm and poor seed development, however, all adventive embryos within the unfertilized seeds terminated their development at the globular or early cotyledonary stages and were unable to germinate under natural conditions. The capability of unfertilized seeds to develop varied from species to species. Growth of the adventive embryos was dependent on nucellus size, but the growth rate of adventive embryos relative to nucellus size was different in different species. Neither pollination, fertilization nor subsequent zygote and endosperm development further stimulated adventive embryo initiation. Conversely, pollination and subsequent fertilization of other seeds in the same fruit slightly, but significantly, suppressed adventive embryo growth in the unfertilized seeds. These facts concerning adventive embryogenesis in unfertilized seeds indicate that neither pollination nor fertilization is essential for in vivo adventive embryogenesis and that normal endosperm is necessary for perfect development of adventive embryos initiated only in the micropylar half of the nucellus.     

香果树花及胚胎发育的细胞学研究

香果树为茜草科香果树属单种属植物,是我国特种古老珍稀濒危树种。对香果树大小孢子发生及胚胎发育过程进行了细胞学观察,观察结果表明：香果树子房两室,中轴胎座,胚珠多数,倒生,单珠被,厚珠心。大孢子四分体排列成线性,靠近合点端的大孢子发育成功能大孢子,珠孔端的3个退化,胚囊发育为蓼型,典型的七胞八核胚囊。雄蕊浅黄色,蝶形花粉囊,小孢子四分体成四面体型,成熟的花粉为二胞花粉。胚胎发育过程经历了合子、原胚、球形胚、心形胚、鱼雷胚5个阶段,种子成熟时,胚发育未完全成熟。本文在香果树大小孢子发生发育切片的观察中未发现异常现象,胚胎发育停留在鱼雷胚时期。