金线莲花药发育中的钙离子分布特征

该研究以金线莲不同发育时期的花药为材料,采用电子显微镜观察花粉块中的钙离子分布,以揭示钙离子在金线莲花药发育中的相关生理功能。结果发现:(1)在造孢细胞时期,较多的钙沉淀颗粒出现在花药表皮和药室内壁细胞的液泡中,暗示钙离子与植物细胞的液泡发生和形成有关。(2)在减数分裂前期,小孢子母细胞核中聚集了较多的钙沉淀颗粒,当小孢子母细胞分裂时,在二组染色体之间有大量的钙沉淀颗粒,显示钙离子与细胞分裂有关。(3)在合成淀粉的质体表面覆盖了较多的钙沉淀颗粒,显示钙离子与质体中的糖代谢有关。研究表明,开花时在花粉块表面的花粉外壁上和成熟花粉中仍保持有大量的钙沉淀颗粒,为花粉萌发所需钙离子做好了储备。     

烟草花粉萌发和花粉管生长期间柱头和花柱中的钙分布

烟草柱头表面有两层覆盖物,其中含有少量细小的钙颗粒.花粉落到柱头上后,储存在花粉外壁中的钙被释放到覆盖层中.当花粉管穿过覆盖层长入柱头细胞之间时,花粉管顶端的细胞壁中出现了大量的细小钙颗粒.开花后22 h观察时,在花柱引导组织中形成了钙的梯度分布:花柱上部引导组织中的钙较少,而下部连接子房处的花柱引导组织中含有较多的钙颗粒.去雄花开花后1 d时,花柱上部引导组织中的钙明显增多;3 d时,连柱头细胞中也出现了较多的钙颗粒.讨论了烟草花柱引导组织中钙梯度分布和花粉管生长的关系.     

猕猴桃花粉原位生长过程中Ca2+的超微细胞化学定位

应用扫描电镜和荧光显微镜对软枣猕猴桃同种花粉在柱头上原位萌发及花粉管生长情况进行了观察,并用焦锑酸盐沉淀法对其授粉前后柱头及花柱中Ca2+进行超微细胞化学定位.结果显示:(1)猕猴桃柱头属于干性柱头,具有一道裂沟,乳突呈长圆柱形,授粉前后形态差异不明显.(2)授粉后3 h,花粉管生长穿过柱头表面,授粉后7 h,花粉管生长到达花柱底部;(3)授粉前后,柱头接受面靠近柱头外围细胞的角质层一侧细胞器内含有丰富的钙,而柱头非接受表面钙颗粒分布很少;(4)授粉前和授粉后3 h,花柱顶端钙颗粒较少,基部钙颗粒较多;授粉后7 h,花柱顶端和基部钙分布密度无明显差别;(5)授粉前后花柱顶端钙主要均匀分布在细胞质膜位置;在花柱基部授粉前钙主要分布在引导组织胞间隙中,授粉后3 h主要分布在细胞质内,授粉后7 h主要存在于细胞质、内质网上.研究表明,猕猴桃授粉前后,柱头和花柱组织中均含有钙,授粉前和授粉后3 h花柱中的钙呈现出梯度分布,授粉后7 h钙的梯度分布现象减弱甚至消失.     

枸杞花药发育过程中钙的分布

在枸杞花药发育过程中,用焦锑酸钾沉淀的钙颗粒显示出了一个与花药发育事件有关的分布特征：在孢原细胞时期的花药中钙颗粒很少。在造孢细胞到小孢子母细胞时期,花药中钙颗粒增加。当花粉母细胞进行减数分裂时,花药中的钙颗粒进一步增加,尤其是在小孢子母细胞的胼胝质壁中。在小孢子发育早期,花药药隔部位的绒毡层细胞质中钙颗粒也明显增加并特异性地分布在其内切向壁上。当小孢子被释放出后,钙颗粒开始特异性积累在正在形成的花粉外壁中,尤其在萌发孔的部位聚集了大量的钙颗粒。当小孢子形成大液泡时,其细胞质中的钙颗粒明显减少。在小孢子分裂形成二胞花粉后,在二胞花粉的大液泡中又特异性地出现许多细小钙颗粒。随着二胞花粉的大液泡完全消失,其细胞质中又出现了许多钙颗粒。接近开花时的成熟花粉粒细胞质中,细小的钙颗粒主要分布在营养细胞和生殖细胞中。枸杞花药发育过程中钙的分布特征反映了其参与调控花粉发育过程。     

洋葱花药发育中钙离子分布特征

采用焦锑酸钾沉淀钙离子技术,对洋葱（Alliumcepa）花药发育中Ca^2＋分布进行了研究。在小孢子母细胞时期,小孢子母细胞中的钙沉淀颗粒很少,但绒毡层细胞的内切向壁已出现明显的钙沉淀颗粒。在四分体时期,四分体小孢子的胼胝质壁中出现较多的钙沉淀颗粒;绒毡层细胞内切向壁的钙沉淀颗粒消失,而在外切向壁和径向壁部位的钙沉淀颗粒增加。在小孢子早期,小孢子中也出现了钙沉淀颗粒,而绒毡层细胞内切向壁表面出现了很多絮状物,其上附有细小钙沉淀颗粒。到小孢子晚期,小孢子中出现一些小液泡,细胞质中的钙沉淀颗粒有所下降。此时绒毡层细胞已明显退化,但在绒毡层膜上仍有一些乌氏体和钙沉淀颗粒。在二胞花粉早期,营养细胞中的液泡收缩、消失,细胞质中又出现了较多的钙沉淀颗粒,在质体和其内部的淀粉粒表面上附有较多的钙沉淀颗粒。到二胞花粉晚期,花粉中的钙沉淀颗粒已明显下降,仅在花粉外壁中还有一地钙沉淀颗粒．     

水芹花药发育中Ca~(2+)分布特征研究

应用焦锑酸钾沉淀技术对水芹发育花药中的Ca~(2+)分布特征和生理功能进行分析。在小孢子母细胞的胼胝质壁中聚集了较多的钙沉淀颗粒,其他部位较少。小孢子母细胞减数分裂后,花药药壁和药隔组织中的钙沉淀颗粒明显增加。早期小孢子先在花粉外壁基柱层中聚集了较多的钙沉淀颗粒,在小孢子质膜与花粉外壁之间也特异性聚集了许多钙沉淀颗粒。在小孢子形成大液泡过程中,小孢子质膜内陷形成小液泡,钙沉淀颗粒被包裹到小液泡中,并被转移到大液泡中,显示Ca~(2+)参与了液泡的构建。小孢子不等分裂后,二胞花粉中的大液泡分解,细胞质内含物增加,积累营养储存物——淀粉和脂滴。花粉中的钙沉淀颗粒明显减少,而药壁的表皮和药室内壁细胞中的则增加。成熟花粉中钙沉淀颗粒很少,但在花粉外壁的基柱层空隙中仍有许多钙沉淀颗粒分布。水芹花粉中的Ca~(2+)分布的特点显示其在小孢子发育的液泡代谢过程具有重要的生理功能。     

莴苣花药发育过程中钙的分布特征

减数分裂前,莴苣花药中的钙颗粒很少。减数分裂后,花药绒毡层细胞中的钙颗粒明显增加。同时在花药药室基质中也出现许多细小的钙颗粒。刚从四分体中释放出的小孢子内钙颗粒很少。伴随着花粉外壁物质在小孢子表面的沉积,钙颗粒开始积累在花粉壁部位。随后。小孢子中开始出现钙颗粒。当小孢子开始形成液泡后,钙颗粒向其中聚集,伴随着小液泡融合成大液泡。体积较大的钙颗粒主要集中在液泡中,而细胞质基质中的钙颗粒很少。随着二胞花粉中的大液泡消失,花粉细胞质中的钙颗粒变得很少。在以后的发育中,只有花粉壁中积累较多的钙颗粒。在莴苣花药发育过程中,钙与绒毡层细胞的退化和小孢子液泡形成以及二胞花粉中大液泡的消失有关。而花粉外壁表面积累丰富的钙与以后花粉的萌发有关。     

莴苣花药发育过程中钙的分布特征

减数分裂前,莴苣花药中的钙颗粒很少。减数分裂后,花药绒毡层细胞中的钙颗粒明显增加, 同时在花药药室基质中也出现许多细小的钙颗粒。刚从四分体中释放出的小孢子内钙颗粒很少,伴随着花粉外壁物质在小孢子表面的沉积,钙颗粒开始积累在花粉壁部位。随后,小孢子中开始出现钙颗粒。当小孢子开始形成液泡后,钙颗粒向其中聚集,伴随着小液泡融合成大液泡,体积较大的钙颗粒主要集中在液泡中,而细胞质基质中的钙颗粒很少。随着二胞花粉中的大液泡消失,花粉细胞质中的钙颗粒变得很少。在以后的发育中,只有花粉壁中积累较多的钙颗粒。在莴苣花药发育过程中,钙与绒毡层细胞的退化和小孢子液泡形成以及二胞花粉中大波泡的消失有关。而花粉外壁表面积累丰富的钙与以后花粉的萌发有关。     

拟南芥授粉前后花粉与乳突细胞的超微结构

利用透射电子显微镜技术,对自交亲和植物拟南芥授粉前后花粉和乳突细胞的超微结构进行了观察。发现花粉和柱头乳突细胞一些未经报道的超微结构特征,可能与拟南芥花粉和乳突细胞的识别及花粉管生长相关:(1)成熟花粉中,电子透明的、体积较大的小液泡(直径200～1000nm)呈均匀分布。部分小液泡内含有多层膜状结构物质,推测可能是膜的一种储存形式,与花粉萌发时大量出现的小囊泡有关。(2)花粉萌发时,小液泡由均匀分布变为不均匀分布。(3)授粉前后的乳突细胞顶端和侧端的内壁上有明显的壁内突结构,粘附的花粉开始萌发时的乳突细胞壁内突处可观察到直径50～100nm的小泡存在,表明拟南芥乳突细胞具有一定的分泌功能。     

蛋白酶体抑制剂MG132对青扦花粉萌发和花粉管生长的影响

泛素/蛋白酶体系统(UPP)是真核细胞内蛋白质选择性降解的主要途径,而蛋白酶体是UPP中蛋白质降解的场所。本文应用细胞学、统计学方法以及FTIR技术研究了蛋白酶体抑制剂MG132对青扦(Peceawilsonii)花粉萌发、花粉管生长的影响。结果表明:MG132显著抑制青扦花粉萌发和花粉管生长,并导致花粉管形态异常,主要表现为花粉管亚顶端出现液泡化,并且液泡随着培养时间的延长而扩大到整个花粉管,花粉管濒临死亡;而DMSO以及非蛋白酶体抑制剂E-64不产生类似结果;半薄切片结果表明,MG132处理后不仅花粉管细胞质发生液泡化,生殖细胞也发生液泡化;FTIR分析进一步表明,MG132处理后,花粉管顶端的细胞壁蛋白和果胶质含量大幅度下降。上述结果表明:MG132通过抑制蛋白酶体活性显著影响青扦花粉萌发及花粉管生长;UPP在青扦花粉萌发、花粉管极性生长模式的建立和维持过程中起重要作用;抑制蛋白酶体活性将导致青扦花粉管的程序性死亡。     

Calcium snapshots in the stigma and style of medlar (Lycium barbarum L.) during pollen germination and pollen tube growth suggest active calcium oscilations

Abstract

The stigma (tip of the pistil) of medlar is wet and covered with stigmatic exudate at anthesis. The exudate contains many vesicles with abundant calcium precipitates. After deposition on the stigma, the pollen grain undergoes hydration, displaying signs of calcium ion (Ca²⁺) transfer from the exudate vesicles into the pollen grains. Calcium precipitates in the pollen cytoplasm are concentrated into small vacuoles that fuse to form large vacuoles, which provide turgor pressure to push the cytoplasm to the apical region of the growing pollen tube. Many calcium precipitates are present in the stylar transmitting tract, which displays a calcium gradient: fewer precipitates are localised in the distal (upper) transmitting tissue below the stigma, and more precipitates are present in the transmitting tract at the style base. The emporal and spatial distribution of calcium in the stigma and style of medlar suggests that it satisfies the demand for calcium in vivo and played some functional significance.     

Distribution of calcium in the stigma and style of tobacco during pollen germination and tube elongation

Potassium antimonate was used to locate loosely bound calcium in the stigma and style of tobacco. The tobacco stigma is wet and covered by a thick layer of glycoprotein exudate at anthesis. The exudate contains abundant vesicles, which are densely labeled with calcium precipitates. When pollen grains arrive at the stigma, become hydrated, and as the pollen swells, Ca²⁺ precipitates accumulate at the aperture. Calcium precipitates that accumulate in pollen cytoplasm are initially concentrated within small vacuoles, but as germination proceeds these appear to fuse, forming prominent, densely labeled vesicles that preferentially accumulate near the proximal region of the growing tube. Although the stigma has abundant particles, few calcium precipitates are observed in the transmitting tissue from anthesis to 11 h after pollination. However, at 22 h after pollination, accumulation of calcium increases distally from the stigmatic interface with the transmitting tissue through the length of the style to the ovary. An examination of flowering plants with differing floral biology will be needed to understand the role of loosely bound calcium accumulation and its relationship to tissue-level changes in calcium uptake, maintenance of other calcium pools, including [Ca²⁺]_cyt, and in pollen and style maturation during the progamic phase.     

荞麦水合花粉和花粉管中的被膜小泡

荞麦水合花粉粒和生长中的花粉管中内质网潴泡形成的囊袋状结构较少见,但内质网囊袋中含有丰富的被膜小泡,直径约为100－150nm。刚刚形成的花粉管中,被膜小泡主要来自于花粉粒营养细胞的细胞质。生长中的花粉管的被膜小泡可由高尔基体分泌形成。另外还观察到内质网的碎裂也是荞麦花粉管中产生被膜小泡的一种机制。花粉管的被膜小泡中含有花粉管壁的前体物质,与花粉管的壁融合参与花粉管的生长。被膜小泡可能含有与脂体和造粉质体水解有关的酶,参与此类物质的降解。荞麦花柱和柱头细胞内含物的解体物质参与花粉管的生长。     

Cotton embryogenesis: The pollen tube in the stigma and style

Summary The ultrastructure and composition of the pollen tube of cotton (Gossypium hirsutum) growing in the tissues of the stigma and style of the flower were examined. The distal portion of the tube is densely cytoplasmic and contains the vegetative nucleus and the two sperms. The vegetative nucleus is highly convoluted and the membrane contains many pores and connections with the ER. No organized nucleolus is present but 4–6 membrane-bound, protein containing bodies are found in the nucleus. Mitochondria containing numerous cristae are abundant in the cytoplasm. Dictyosomes are also plentiful and are engaged in the production of many large vesicles. Rough ER is conspicuous and polysomes are found in the cytoplasm. Plastids are few in number, poorly developed, and contain little starch. Many uniform, small vesicles are found throughout the cytoplasm. Lipid bodies frequently with small vesicles associated with them are found in the tube. In the proximal region vacuoles form and the cytoplasm becomes pressed against the wall. In the transition zone the ER frequently becomes distended and filled with protein. The wall has two distinct layers: one strongly PAS positive, the other faintly PAS positive. The inner wall is apparently formed by the deposition of large dictyosome vesicles. Plug structure and development were studied.     

钙在被子植物受精过程中的作用

近年来,花粉管中的钙信号和生理功能的研究取得了明显的进展,同时在雌蕊系统中有关钙分布的研究也初步显示了其时、空特征与被子植物的受精作用密切相关。该文总结了花粉萌发和花粉管生长过程中外源钙和内源钙的作用机制,结合雌蕊组织中钙分布的特征,进一步探讨了钙在被子植物受精过程中的功能。     

Fast pollen tube growth in Conospermum species

BACKGROUND AND AIMS: An unusual form of pollen tube growth was observed for several Conospermum species (family Proteaceae). The rate of pollen tube growth, the number of tubes to emerge and the ultrastructure of these tubes are given here. METHODS: Pollen was germinated in vitro in different sucrose concentrations and in the presence of calcium channel blockers, and tube emergence and growth were recorded on a VCR. Measurements were taken of the number of tubes to emerge and rate of tube emergence. Pollen behaviour in vivo was also observed. The ultrastructure of germinated and ungerminated pollen was observed using TEM. RESULTS: After 10 s to 3 min in germination medium, up to three pollen tubes emerged and grew at rates of up to 55 micro m s(-1); the rate then slowed to around 2 micro m s(-1), 30 s after the initial growth spurt. Tubes were observed to grow in pulses, and the pulsed growth continued in the presence of calcium channel blockers. Optimal sugar concentration for pollen germination was 300 g L(-1), in which up to 81 % of pollen grains showed fast germination. Germination and emergence of multiple tubes were observed in sucrose concentrations of 100-800 g L(-1). The vegetative and generative nuclei moved into one of the tubes. Multiple tubes from a single grain were observed on the stigma. Under light microscopy, the cytoplasm in the tube showed a clear region at the tip. The ultrastructure of C. amoenum pollen showed a bilayered exine, with the intine being very thick at the pores, and elsewhere having large intrusions into the plasma membrane. The cytoplasm was dense with vesicles packed with inner tube cell wall material. Golgi apparatus producing secretory vesicles, and mitochondria were found throughout the tube. The tube wall was bilayered; both layers being fibrous and loosely packed. CONCLUSIONS: It is proposed that, for Conospermum, initial pollen tube wall constituents are manufactured and stored prior to pollen germination, and that tube extension occurs as described in the literature for other species, but at an exceptionally fast rate.     

Cotton embryogenesis: The tissues of the stigma and style and their relation to the pollen tube

Summary The stigma of cotton (Gossypium hirsutum) is covered by unicellular hairs. The cytoplasm of these hairs degenerates before the stigma becomes receptive. The vacuole remains intact, but the hair cytoplasm becomes a mass of dark, amorphous material with only a few organelles still being visible. The rest of the stigma consists of thin-walled parenchyma cells with large vacuoles and large amounts of starch. The cells of the style are differentiated into a uniseriate epidermis, vascular tissue, a cortex of thin-walled, vacuolate parenchyma cells, and the transmitting tissue. This latter tissue occupies the center of the style and consists of thick-walled cells with few vacuoles. The cells are rich in starch, ribosomes, endoplasmic reticulum and dictyosomes. They also contain deposits of calcium salts in the form of druses. The pollen germinates on the stigmatic hairs, grows down the outside of the hair and between the cells of the stigma to the transmitting tissue of the style. There the tubes grow between the walls of the cells but do not enter the cells themselves. Some transmitting cells adjacent to the pollen tube degenerate after the tip of the pollen tube has grown past them. However, not all degenerate, and those that do show no fixed spatial relationship to one another. The cells which do degenerate follow a characteristic pattern of breakdown. No ultrastructural evidence was found for the secretion of hydrolytic enzymes by the pollen tube.