Double fertilization in ephedra, a nonflowering seed plant: its bearing on the origin of angiosperms

Double fertilization and the associated formation of endosperm have long been considered unique and defining characters (autapomorphies) of the angiosperms. During normal fertilization in Ephedra nevadensis, a nonflowering seed plant, fusion of a second sperm nucleus with the ventral canal nucleus occurs regularly within the egg cytoplasm. The occurrence of double fertilization in Ephedra assumes added significance in light of its critical phylogenetic position as a basal member of the most closely related extant group of seed plants (Gnetales) to angiosperms. Thus, double fertilization in angiosperms and Ephedra may represent an evolutionary homology.     

糜子的受精过程和胚的发育

本文应用光学显微镜和石蜡制片法,对糜子的受精过程与胚的发育进行研究,结论如下:开花2h 后后,精核进入卵细胞;开花4h 后,精核的染色质逐渐分散,并出现核仁,受精卵内有一大而明显的雌性核仁和一较小的雄性核仁,此时合子形成,开花10h 后,合子进行1次分裂,糜子合子静止期长达4h 左右。2细胞原胚时,胚乳处于6个游离核时期。糜子的胚胎发育为紫菀型。合子无极性,第1次分裂为横分裂。胚发育经过原胚、椭圆形胚再经胚分化期和成熟期发育为成熟胚。受精前,两极核紧贴,不合并,位于卵细胞的合点端。受粉2h 后,精子进入一个极核,精核与极核融合过程同精核与卵核的融合过程相同;开花4h 后,形成初生胚乳核;开花5h 后初生胚乳核进行第1次分裂;胚乳发育为核型,游离核分裂为有丝分裂,球形胚期胚乳开始细胞化。     

大麦双受精过程研究初报

通过光学显微观察,大麦双受精过程如下:授粉后35分钟,花粉管进入胚囊;45分钟释放出两个精子;50分钟,一精子先与卵细胞融合,另一精子移向中央细胞的二极核;55分钟,精子附卵核上,另一精子附于一极核上,同时还观察到一精子附于两极核上的现象;60分钟,精子仍贴附在卵核上,另一精子与二极核之一融合;90分钟,精子开始与卵核融合,初生胚乳核形成,其核中的三个核仁未融合;120分钟,精子与卵核融合,初生胚乳核分裂,但未见核仁融合。     

葡萄双受精过程的形态学观察

观察了葡萄双受精过程中雌雄性核的融合。结果表明:花粉管通过珠孔穿入退化助细胞,释放出二精子;精子核接近并贴附在卵核和次生核上,二者核膜融合,精核沉入卵核及次生核,染色质松解,并与雌性核染色质融合,出现雄性核仁,两性核仁融合,形成合子及初生胚乳核。卵核完成受精较次生核晚。受精属有丝分裂前型。精核进入卵核前看到了它的核仁。少数胚囊具有两套卵器。     

激光扫描共聚焦显微镜观察水稻双受精过程

利用激光扫描共聚焦显微镜对水稻双受精过程进行了观察。结果表明:开花后0.5 h可见花粉粒在柱头上萌发,形成一定长度的花粉管,但仍未进入胚囊;开花后1~2 h花粉管进入胚囊,但尚未释放精细胞,此时,在卵器内有两条肌动蛋白冠的形成,肌动蛋白冠起始于助细胞的基部,1条终止于卵细胞核的位置,另一条终止于极核附近;开花后2~3 h花粉管释放精细胞,精细胞在肌动蛋白冠的作用下分别进入极核及卵细胞;开花后3~4 h,精核的染色质向卵核扩散,极核内的雄性核仁逐渐变大,最后增大至与极核的核仁差不多大小;开花后4~5 h,精核与极核完成受精作用,形成初生胚乳核,而此时在卵核内出现1个雄性核仁;开花后6 h左右,卵核核仁仍未完成与精核核仁的融合,此时初生胚乳核已分裂1~2次;开花后12 h,精核核仁与卵核核仁融合形成1个较大的核仁,至此合子形成;开花后24 h,合子有丝分裂1次,形成2个细胞的原胚,此时初生胚乳核已分裂形成8~16个游离核,绕胚囊周缘分布。水稻双受精作用属于有丝分裂前配子融合类型。     

Fertilization in Brassica campestris ssp. pekinensis and its duration of each stage

This paper reports the process of fertilization in Brassica campestris ssp. pekinensis and the duration of each stage. The results are as follows: (1) Pollen germinates on stigma 2–3 h after pollination. (2) 4–8 h after pollination, pollen tube grows in the style. (3) 8–14 h after pollination, pollen tube grows in the ovary and gets into the ovule via the micropyle. (4) 16 h after pollination, one sperm nucleus moves to the egg and enters it. (5) The sperm nucleus adheres to the nuclear membrane of the egg 18 h after pollination. (6) 20 h after pollination, it enters the egg nucleus and male chromatin gradually disperses and 24 h after pollination, a male nucleolus appears. A large female nucleolus and a small male nucleolus occur in the nucleus of the fertilized egg, and zygote formed. The dispersing of sperm chromatin in the egg nucleus takes about 4 h. (7) 32–34 h after pollination, the division of zygote begins. The dormancy stage of the zygote lasts for about 8–10 h. (8) The pair polar nuclei lie in the chalazal end of the egg before fertilization, which may fuse into a secondary nucleus or not. (9) 16–18 h after pollination, the sperm nucleus moves to the polar nuclei or the secondary nucleus. 18 h after pollination, the sperm nucleus adheres to the nuclear membrane of the polar nuclei or that of the secondary nucleus. (10) 20 h after pollination, the sperm nucleus enters one of the polar nuclei or the secondary nucleus and a triple fusion takes place. The process of fusion is similar to the karyogamy but faster. The dispersing of the sperm chromatin in the polar nucleus or secondary nucleus takes about 2 h. (11) 22 h after pollination, the primary endosperm nucleus formed. The female and male nucleoli cannot fuse with each other before mitotic division of the primary endosperm nucleus. (12) 24 h after pollination, the division of the primary endosperm nucleus actually takes place. __________ Translated from Acta Horticulturae Sinica, 2005, 32(5): 812–817 [译自: 园艺学报]     

花生的双受精作用

本文观察了花生受精作用的全过程。开花前２－４ｈ散粉。花粉在柱头上萌发后，花粉管进入花柱，没中空的花柱道向子房室生长。在子房室内，沿珠柄侧的子房内壁生长至与胚珠珠孔相当部位时，花粉管离开子房壁进入珠孔，经珠心冠细胞之间隙抵达胚囊。开花后９ｈ，花粉管通过一个助细胞的丝状器进入助细胞而释放精子和内容物。     

Requirement of phospholipase Cdelta4 for the zona pellucida-induced acrosome reaction

Several phospholipase C (PLC) isoforms have been found in male and female mammalian gametes, and splicing isoforms of PLCdelta4 are predominantly expressed in testis. Here we report that male mice in which the PLCdelta4 gene had been disrupted either produced few small litters or were sterile. In vitro fertilization studies showed that insemination with PLCdelta4-/- sperm resulted in significantly fewer eggs becoming activated and that the calcium transients associated with fertilization were absent or delayed. PLCdelta4-/- sperm were unable to initiate the acrosome reaction, an exocytotic event required for fertilization and induced by interaction with the egg coat, the zona pellucida. These data demonstrate that PLCdelta4 functions in the acrosome reaction that is induced by the zona pellucida during mammalian fertilization.     

TAM诱导水稻无融合生殖的胚胎学研究

为探明TAM诱导剂诱导水稻无融合生殖所形成的籽实的胚和胚乳起源，对其进行了胚胎学研究，结果表明，胚可能起源于卵细胞和一个助细胞融合所形成的细胞，两极核融合成次生核，由次生核分裂形成胚乳核，最终形成正常胚乳。     

太和樱桃胚胎发育的研究

研究了太和樱桃大鹰紫甘桃品种雌雄配子体、授粉受精和胚的发育阶段及时间。结果表明,３月初花粉粒发育成熟,３月１３日开花时胚囊发育成熟,授粉后２６ｈ花粉管进入子房,然后进行双受精作用,形成初生胚乳核和合子。至４月初合子发育成原胚,原胚经分裂与分化,形成幼胚,４月中旬胚发育完全。胚胎发育与樱桃结果关系密切,树体营养和外界气候条件对胚胎发育过程有重要影响。     

核桃无融合生殖的细胞胚胎学研究

以40%～70%饱和度硫酸铵分级沉淀、DEAESepharoseiCL-6B、SephadexG-100、羟基磷灰石、PhenylSepharoseCL-4B和制备电泳分离纯化了小麦的尿卟啉原合酶(UROS)。酶的亚基分子质量为54ku,全酶分子质量为66ku,酶的等电点6.3,在pH8.2时比活为257μmol/(mg·min),最适反应温度40℃,5mmol/L的巯基乙醇和Mg2+促进酶活,纯化的小麦UROS在-20℃下0.1mol/L,pH8.5的Tris-HCl,内含质量分数为50%的甘油,5mmol/L的巯基乙醇和MgCl2中贮藏7d酶活损失90%。     

草莓胚和胚乳发育的研究

以哈尔滨地区推广的“戈雪拉”和“小实”草莓品种为材料,采用常规石蜡切片法,荧光技术和透射电镜技术,对草莓受精、胚和胚乳的发育过程进行观察,其结果如下：１．草莓属于多心皮离生单雌蕊,柱头较小,表面有栅状排列的乳突细胞,花柱细长,中央可见有较发达的引导组织,子房内１枚横生胚珠,单珠被,厚珠心,蓼型胚囊,利用荧光法可清楚看到落在柱头上的花粉萌发,花粉管的延伸途径,即由柱头一花柱引导组织—子房内壁—胎座—胚珠表面—进入珠孔。２．胚的发育过程与大多数双子叶植物基本一致,先后经历了合子—二细胞原胚—球形原胚—心形胚—鱼雷形胚—成熟胚等阶段,胚发育属紫菀型,胚的形态呈直立型。３．草莓属核型胚乳,先后经历初生胚乳核—胚乳游离核—胚乳细胞—胚乳逐渐被胚吸收等过程,戈雪拉品种幼胚发育中,在其周围具有一个特殊的结构     

异属花粉诱导小麦孤雌生殖的假受精研究

采用延迟授粉和胚胎学显微观察的方法,研究了黑麦和六倍体小黑麦花粉诱导小麦孤雌生殖的假受精特性。结果表明：①用六倍体小黑麦花粉授粉,精子进入胚囊的频率高于黑麦花粉;②受粉后２ｈ,一个精核已进入卵细胞质中,极少数精核能够刺激卵细胞单性分裂形成胚;③极核正常受精后形成胚乳。     

索氏六须鲶受精细胞学研究

采用连续切片显微观察的方法对索氏六须鲶成熟卵的受精细胞进行了研究。结果显示，精子入卵刺激卵细胞形成胚盘，精子头部在胚盘中逐渐核化，形成雄性原核；卵母细胞放出第二极体，完成第二次成熟分裂，形成雌性原核，两性原核结合成合子核；合子核膜消失，产生第一次卵裂，受精全过程历时50min。     

Electrical responses of eggs to acrosomal protein similar to those induced by sperm

The earliest known response of eggs to sperm in many species is a change in egg membrane potential. However, for no species is it known what components of the sperm cause the opening of the egg plasma membrane channels. Protein isolated from sperm acrosomal granules of the marine worm Urechis caused electrical responses in oocytes with the same form, amplitude, and ion dependence as the fertilization potentials induced by living sperm. Sperm initiated fertilization potentials in oocytes when sperm-oocyte fusion, but not binding, was inhibited by clamping oocyte membrane potentials to positive values. Acrosomal protein also initiated electrical responses in clamped oocytes. These results support the hypothesis that it is the sperm acrosomal protein that opens ion channels in the oocyte membrane.     

大鳞副泥鳅卵和泥鳅精子杂交受精细胞的观察

大鳞副泥鳅和泥鳅杂交的受精细胞学过程,证实异源的泥鳅精子能够进入大鳞副泥鳅的卵子中,诱导星光并形成雄性原核。雌雄原核相互接触并融合形成合子核。全部过程有正常的受精细胞学程序和卵裂方式,由此产生的后代兼具父,母本双方的遗传性状。     

黑麦花粉诱导小麦孤雌生殖的细胞学研究

观察ＡＲ７７黑麦花粉诱导［８４Ｇ６×７９（ｌＢ）８－８］Ｆ１植株的假受精行为，结果表明：①大量花粉管物质及精子停留在卵细胞外，不能诱发卵细胞单性分裂；②较大的精子进入卵核，靠近或接触核仁且不与核仁融合，对卵细胞单性分裂有明显的诱发作用；③当卵核被诱发启动分裂，其极核中的精子可能与其融合形成初生胚乳核并继续分裂，也可能以雄性核仁的状态继续停留在极核中。     

女贞的胚胎学及其在木犀科中的系统地位

 应用光学显微镜对女贞的传粉和受精、胚乳和胚胎的发育、果皮和种皮的发育等胚胎学特征进行了研究,对木犀科六属的胚胎学特征进行了比较.虫媒传粉,珠孔受精,花粉管通过一助细胞进入胚囊;初生胚乳核先于合子分裂,核型胚乳发育;胚胎发育属茄型,种子具丰富的油质胚乳和匙形稍弯的双子叶的胚;果皮分3层:外果皮细胞厚壁,中果皮细胞薄壁,内果皮细胞厚壁且木栓化;种皮也分3层.胚胎学特征显示女贞属与茉莉属有较近的亲缘关系,支持木犀科分成3亚科的分类.     

Use of cryopreserved rooster sperm in breeding

The use of frozen sperm of elite roosters for inseminating hens reduces egg fertilization rate, but increases livability, live weight, average daily gain of offspring, dressing percentage, and European efficiency index. A cryopreserved rooster sperm bank has been created.