Pollen structure and germination of Crocus thomasii Ten. (Iridaceae)

Abstract

Mature pollen of C. thomasii Ten. (Iridaceae) has been studied from a morphological and physiological point of view and compared to that of C. sativus L., C. thomasii pollen is roundish, with a 83 μm diameter and a 14% of anomalous grains. Percentage of the positive alcoholdehydrogenase (ADH +) pollen grains is about 90% whereas the in vitro germinated rate reaches 55%. Exine is homogeneously thickened (2.5 μm) with randomly distributed thinner zones and 5 μm thick intine. Cytoplasm of vegetative and generative cells is very rich of small and large smooth vesicles and vesicles coated by ribosomes. The generative cell shows a thin ondulated pectocellulosic wall. Its nucleus is intensely fluorescent after treatment with the 4,6-diamidino-2-phenylindole (DAPI) fluorochrome. Although many ultrastructural aspects of the C. thomasii pollen are common in C. sativus. L., C. thomasii pollen is smaller, more regularly structured and germinates in vivo and in vitro in higher percentage than that of C. sativus.     

Ultrastructure of chromoplasts and other plastids in Crocus sativus L. (Iridaceae)

Saffron (Crocus sativus L. Iridaceae) chromoplasts and other plastids were studied by electron microscope to determine their structure, origin and pigment localization. Plastids from pistils of floral buds and flowers at anthesis, dried and decoloured stigmas, and green and senescent leaves were examined. Results indicated that mature saffron chromoplasts occur in the red parts of stigmas and have a reticulo-tubular structure. They contain a reticulum of tubules and plastoglobules. Tubules formed dilated vesicles mainly while plastoglobules appeared numerous and scattered on the whole chromoplast. Chromoplasts appeared in red stigma of very young floral buds. They originated from amyloplasts, the only plastids occurring in the colourless basal portion of style, as well as in the parenchyma of ovary and corm. Transition forms of plastid as amylo-chromoplast, occur in the yellow parts of stigma and style. Senescent leaves did not show plastids with structure similar to the chromoplast of red stigma. Red pigmented and scented stigmas might cooperate in saffron reproduction by attracting pollinator.     

Chromosome numbers of Turkish Crocus (Liliiflorae,Iridaceae) and their geographical distribution

The genus Crocus is known for its widely varying chromosome numbers (from 2n = 6 to 2n = 70) with varying numbers occurring even within species, as it is the case for Crocus biflorus Miller (2n = 8, 10, 12, 14, 16, 18, 20, 22, 24). After we found morphological diverse C. biflorus populations in Turkey doubts arose about their rank of being subspecies of the Italian C. biflorus (2n = 8). Here we publish the chromosome numbers for 76 populations of C. biflorus sensu lato distributed all over Turkey. The chromosome numbers ranged from 2n = 8 to 2n = 36, with the higher numbers occurring in the mountain ranges of the Anatolian Diagonal and east of it, while lower numbers were found only southwest of these mountains. Closely related taxa with similar distribution mostly differ in their chromosome numbers. This led us to assume that chromosomal changes influence speciation processes in the genus. Therefore, chromosome numbers may represent an important character for the establishment of a new taxonomic treatment of the Crocus species, especially within section Nudiscapus. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A study on pollen grains ofCrocus cartwrightianus (Iridaceae)

Crocus cartwrightianus andC. cartwrightianus cv.albus pollen have been studied from structural and ultrastructural points of view and the germination assayed in vivo and in vitro.C. cartwrightianus pollen is regularly shaped and sized, has a low percentage of anomalous grains and has a high germination rate in vitro, whileC. cartwrightianus cv.albus is less regularly shaped with some variation in size and has a high percentage of anomalous grains and a low germination percentage in vitro. Ultrastructural observations have revealed, in the pollen of both the taxa, the presence of a thin elongated vegetative nucleus and a generative cell surrounded by a thin membrane. However,C. cartwrightianus pollen shows a thicker intine, andC. cartwrightianus cv.albus shows numerous pollen germination anomalies which are in common withC. sativus.     

Self-incompatibility inCrocus vernus subsp.vernus (Iridaceae)

Outcross, self- and mixed pollinations were performed inCrocus vernus subsp.vernus, a species with bicellular pollen, dry stigmas and hollow style. No differences were noted among the above pollinations concerning the germination of pollen and the growth of pollen tubes until the top of ovary. Within 45 min after pollinations 62% of pollen grains germinated. Pollen tubes penetrated the papilla cuticle extending along the papilla wall; on entry into stigmatic lobes they continued growth in the stylar secretion to ovarian locules. Here, however, self-pollen tubes failed to reach or to enter the ovule micropyle; while pollen tubes from either outcross- or mixed pollinations grew until fertilizing ovules. These observations gave evidence of a self-incompatibility system inCrocus, which appeared to be neutralized by mentor effect. The ovary as site of incompatibility response is discussed.     

Reversible inhibition of the pollen germination and the stigma penetration in Crocus vernus ssp. vernus (Iridaceae) following fumigations with NO2, CO, and O3 Gases

We assessed the pollen hydration, the pollen germination, and the stigma papilla penetration of CROCUS VERNUS subsp. VERNUS (Iridaceae) after 2 h fumigations with O (3), NO (2), and CO gases within humidified (90 - 100 % RH) box experiments. When the pollen and the pistil were separately fumigated, the pollen retained the capacity to emit a tube which penetrated papilla, and the stigma papillae retained the receptivity; when the pistils were first pollinated and then fumigated, the capacity of pollen to hydrate was not affected, but the germination was significantly reduced. The vulnerability to gases became evident at 0.3 ppm O (3), 0.2 ppm NO (2), and 0.5 ppm CO. The inhibition curves as a function of the gas concentrations were of an exponential type, and they saturated at 2 ppm NO (2), 25 ppm CO, and 0.5 ppm O (3), with germination percentages of 17 %, 27 %, and 60 %, respectively. Both the pollen germination and the papilla penetration were fully restored by prolonging for 60 - 90 min the incubation at 90 - 100 % RH, after the cessation of fumigations. The vulnerability of the pollen-papilla system is discussed.     

凯特杏花粉的离体培养及影响因子分析

采用离体培养法,在不同培养基组分含量、pH值、温度及植物生长调节物质的培养条件下,对凯特杏(Prunus armeniacaL.cv Katy)花粉的离体萌发和花粉管生长状况进行观察研究。结果表明:(1)凯特杏花粉离体萌发及花粉管生长的适宜培养基为20%蔗糖 0.04%硼酸 0.01?Cl2,最适pH为6.0,最适温度为20℃,培养20 h后,花粉的萌发率达68.76%,花粉管长度达1 083.53μm。(2)不同植物生长调节物质对花粉萌发和花粉管生长作用不同,赤霉素浓度为5~8 mg/L、矮壮素浓度为10~150 mg/L、多效唑浓度为5~10 mg/L时对凯特杏花粉萌发和花粉管生长都有促进作用,但国光丁酰肼对凯特杏花粉萌发和花粉管生长均有抑制作用。     

Crocus antalyensis subsp. striatus subsp. nov. (Iridaceae) from southwest Anatolia

A new subspecies Crocus antalyensis subsp. striatus subsp. nov. from western Turkey is described. It is characterized by rough papery, light brown corm tunics, leaves that exceed the flower at anthesis and are recurved, distinctly striped inner perianth segments and deeply branched pale yellow or white style. The karyotype of the new subspecies is presented.     

Ovary-ovule transmitting tract in Crocus (Iridaceae), structure and calcium distribution

 The structure of and the calcium distribution in the ovary-ovule transmitting tracts of Crocus were examined by using conventional and antimonate fixation methods for electron microscopy, and fluorescence microscopy as well. The ovarian locules are bordered with epidermal cells and transmitting cells. The epidermal cells are extensively cutinized, and the cytoplasm is rich in the organelles and vesicles prevalently engaged in thickening the exposed wall. The transmitting cells have uncutinized walls with numerous labyrinthine ingrowths, and the cytoplasm is rich in organelles and vesicles engaged in the secretion of the extracellular matrix (e.m.). The micropylar tissue of the ovule consists of largely vacuolated cells with scarcely structured cytoplasm, the e.m. appears to be of gametophytic origin. Both the ovary and ovule e.m. have a glycosidic and proteinic nature, and are rich in loosely bound Ca²⁺ ions. In the embryo sac, Ca²⁺ ions are concentrated in one synergid. The results are discussed in relation to the guided growth of pollen tubes. Received April 9, 2002; accepted July 9, 2002 Published online: November 28, 2002 Addresses of the authors: Giuseppe Chichiriccò (e-mail: Chichiri@univaq.it), Dipartimento di Scienze Ambientali, University of L'Aquila, Via Vetoio, I-67100 L'Aquila, Italy. Anna Maria Ragnelli, Pierpaolo Aimola, Dipartimento di Biologia di Base ed Applicata, University of L'Aquila, Via Vetoio, I-67100 L'Aquila, Italy.     

淫羊藿花粉萌发及花粉管生长研究

运用方差分析、多重比较和正交实验方法对淫羊藿花粉的萌发和花粉管生长进行了研究.结果表明:培养基内硼酸、硝酸钙、蔗糖在一定浓度范围内,对花粉萌发及花粉管生长起促进作用,但超过一定浓度时则起抑制作用;镁和钾对花粉萌发及花粉管生长影响不显著.在正交实验中蔗糖和H3BO3对淫羊藿花粉萌发有显著影响,而培养基组分间没有明显的交互作用.淫羊藿最适花粉液体培养基为15%蔗糖 40 mg/L H3BO3 40 mg/LCa(NO3)2·4H2O;在pH值为5.0、25℃和600 lx光照时淫羊藿花粉萌发和花粉管生长最好.     

桔梗花粉萌发与花粉管生长研究

以2年生桔梗植株为材料,采用液体培养法研究了培养基种类、PEG、蔗糖、pH以及培养温度、培养时间对桔梗花粉离体萌发生长的影响,结果表明:(1)浓度为100~150 g.L-1的PEG可显著促进桔梗花粉萌发和花粉管的生长;200~250 g.L-1PEG显著促进花粉萌发,但对花粉管生长的作用不显著。(2)100 g.L-1的蔗糖有利于花粉萌发和花粉管生长,高浓度蔗糖(200 g.L-1)有明显抑制作用;(3)桔梗花粉离体萌发和花粉管生长的适宜培养基为ME3+BK+10%蔗糖+150 g.L-1PEG(pH5.8);(4)25~40℃条件下桔梗花粉均可较好萌发,以30℃培养1.5 h为最佳培养条件。     

Isolation and Artificial Germination of De-exined Pollen in Brassica

In view of the fact that pollen deprived of exine has been shown by electroporation to be a superior receptor of foreign genes in tobacco, the authors developed a technique to isolate and artificially germinate the de-exined pollen in Brassica. Pollen grains of B. chinens/s and B. campestris var. purpurea were first hydrated at 4 ℃ in a medium containing Roberts' salts, 24% sucrose, 7.3% mannitol, 0.05% lactoalbumin hydrolysate (pH 8.5) for 18 h, followed by heat shock at 34 ℃ for 40～60 min and osmotic shock for 20 min subsequently. Through this three-step procedure the exine could dehisce along the germination furrows and completely detached off, resulting in the release of pollen coated with naked intine with an isolation rate as high, as over 60%. The de-exined pollen were germinated in a modified medium containing 15%～20% polyethylene glycol (MW 6000), 5% sucrose, 0.05% lactoalbumin hydrolysate and Roberts' salts (pH 8.5) with a rate of 41% in B. chinensis and 33% in the other species. However, in sharp contrast with the behavior of the intact pollen, the de-exined pollen did not germinate in the carbon and nitrogen sources free media. Scanning electron microscopic and light microscopic observations on the processes of isolation and germination of de-exined pollen were carried out. The phenomenon of exine detachment in a few plant species is reviewed. There might be some corresponding association between pollen wall characteristics and methods of isolation. The de-exined pollen may be a useful experimental system not only for introducing and transferring foreign genes, but also for investigating the role of exine in pollen germination and in sporophytic self-incom- patibility.     

扇脉杓兰花粉超微结构及花粉管生长的观察

为明确扇脉杓兰花粉形态结构及雄性生殖特性,利用扫描电镜、透射电镜和荧光显微镜对花粉形态和超微结构及花粉管生长过程进行观察。结果表明:(1)扇脉杓兰单粒花粉长球形,表面光滑无特征纹饰,有少量胶黏物质,一些表面有2个或以上的深凹陷,凹陷内有球形突起的内容物。(2)花粉壁分为由棒状的基柱小单元组成的外壁和纤维素果胶组成的内壁,有覆盖层;生殖细胞近圆形,细胞核大而致密;营养细胞多弧形,核质分散;花粉粒细胞质含有大量的线粒体、质体和小泡等细胞器,淀粉、蛋白质和多糖含量丰富。(3)花粉管萌发后沿子房壁方向伸长,授粉20d花粉管伸长生长并不明显,授粉30d伸长的花粉管中出现大量胼胝质塞,并且伸长方向转为胚珠中间,花粉管逐渐接近胚珠,在授粉后50d基本完成受精作用。研究认为,扇脉杓兰花粉发育正常,不阻碍有性生殖过程。     

The avoidance of self-interference in the Tuscan endemic spring geophyte Crocus etruscus Parl. (Iridaceae)

Spatial separation between sexes within hermaphrodite flowers (herkogamy) is widespread among angiosperms and is traditionally viewed as an adaptation that reduces the likelihood of self-pollination. While different degrees of herkogamy have been reported for Crocus, the relationship between sexual organ positions and reproductive fitness has not been explored yet, and studies of the breeding system within natural populations remain scarce within the genus. We analyzed the effects of different breeding systems (spontaneous self-pollination, facilitated self-pollination and cross-pollination) and of herkogamy degree on female reproductive success of the Tuscan endemic Crocus etruscus. Results showed that C. etruscus is monomorphic for style length and self-incompatible (SCI = 0.29). We also detected a significant negative effect of herkogamy on seed set of open-pollinated flowers. Thus, we conclude that the species avoids self-fertilization by self-incompatibility, but interestingly shows also a certain degree of spatial separation of male and female reproductive structures within the same flower. This floral trait could be useful to avoid self-interference thus reducing ovule discounting and pollen loss on its own stigma.     

桃花粉离体萌发和花粉管生长特性研究

采用花粉离体萌发法研究不同培养基组分和培养条件对桃花粉萌发和花粉管生长的影响,同时对不同贮藏温度下的桃花粉寿命进行研究.结果表明:固体培养基与液体培养基对桃的花粉萌发率和花粉管长度影响差异不显著;10%蔗糖是大多数桃品种花粉的最适萌发条件;硼能提高桃花粉的萌发率,但对花粉管的生长没有促进作用;桃花粉在20℃～25℃的培养温度下萌发率最高,花粉管最长;桃花粉萌发率和花粉管长度在培养前3 h内上升最快,3～5 h上升趋势减弱,5 h后基本停止;随着贮藏温度的升高和贮藏时间的延长,花粉生活力呈降低的趋势.     

地下结实植物白番红花的繁育系统与传粉生物学

地下结实是植物用来防御不利环境的一种策略, 研究地下结实植物的繁殖特性, 可以揭示它们的繁殖对策多样性, 对于探讨环境选择压力对其繁育系统及后代适合度的影响具有重要意义。白番红花(Crocus alatavicus)是一种分布在天山西部亚高山带、具地下芽和地下结实特性的早春短命植物。我们采用野外观测和统计分析方法, 对该物种的繁育系统与传粉生物学及其对亚高山环境的适应进行了研究。研究结果表明: 白番红花具有先花后叶的特性, 于4月上中旬始花, 呈爆发式开花式样; 花白色, 无花蜜无气味; 开花时, 下位子房位于地下, 花蕾在地上开放并随光照变化而开闭; 单花花期为6–9 d, 花萎蔫时花粉活性仍保持在75.39±5.69%, 柱头可授期为8 d。人工授粉实验结果显示, 该物种属于兼性异交繁育系统, 且具有自主自花授粉能力。白番红花属于泛化传粉系统, 鲁熊蜂 (Bombus lucorum)、老条蜂 (Anthophora senilis)和黄腹地花蜂 (Andrena capillosa)是有效传粉昆虫, 通过采食花粉进行传粉, 访花频率分别为0.50±0.27次•花–1•h–1、0.18±0.08次•花–1•h–1和0.13±0.05次•花–1•h–1。在天山西部亚高山早春环境中, 白番红花不仅利用其开花式样、泛化传粉系统及早春空白生态位来提高传粉效率, 而且通过自交亲和及主动自花授粉等繁育系统特征来弥补传粉昆虫少及访花频率低的不足, 从而保障繁殖成功。     

果梅花粉离体萌发及花粉管生长特性研究

研究了果梅(Prunus mumeSieb.1et Zucc.)花粉在不同培养基组分、花粉不同培养密度和不同温度及培养时间的离体萌发和花粉管生长特性.结果表明:细叶青花粉萌发及花粉管生长最适宜的液体培养基为30mmol/L MES(pH 6.5)缓冲液中含20%蔗糖,0.01%硼酸,20%PEG-4000,0.03?(NO3)2?4H2O,0.02%Mg-SO4?7H2O;萌发率达45.03%,花粉管长度达597.2μm.适宜于果梅花粉萌发和花粉管生长的花粉粒密度为20~80粒/μL.培养温度过高或过低都不利于果梅花粉的萌发和生长,25℃时花粉萌发和花粉管生长最好.细叶青"、月世界"、莺宿"3个品种的平均萌发率为48.6%,平均花粉管长度为762.3μm.果梅花粉在不同培养温度下,萌发及生长不同,在25℃条件下花粉管生长速度最快,集中在0~12 h内,3个品种花粉管平均生长速度为58.5μm/h.     

花粉萌发和花粉管生长发育的信号转导

显花植物授粉是一个复杂的发育过程。从花粉落在柱头上开始,经过粘附、识别、水合、萌发,花粉管在花柱内生长,直至到达子房发生双受精作用,整个过程发生在雌、雄两性细胞和组织之间,受到严格的遗传控制和细胞控制。一方面雌雄配子的基因型决定两者是否亲和,另一方面雌雄两性细胞间发生复杂的相互作用,细胞外信号分子是这些过程的主要调控因子。当花粉或花粉管细胞感知外部信号后,必然通过信号转导级联反应,达到控制萌发、调整花粉管生长方向等目的。这一系列动力学的细胞事件,关系到受精的成败。因此研究此过程中的信号及其转换机…     

钙调素对花粉萌发和花粉管生长的效应

牛脑和玉米胚ＣａＭ能显著促进花粉萌发和花粉管生长（图１）,而ＣａＭ抑制剂ＴＦＰ、ＣＰＺ及另外两个专一性更强的抑制剂Ｃｏｍｐｏｕｎｄ４８／８０和Ｗ７均严重抑制甚至阻止花粉的萌发（图２,３）。用对ＣａＭ亲和性较低的Ｗ７同系物Ｗ５,在与Ｗ７同样浓度下,对花粉萌发和花粉管生长无明显影响。此外,Ｗ７对花粉萌发和花粉管生长的抑制效应可被外源ＣａＭ所消除（图４）。在花粉萌发过程中,其内源ＣａＭ含量显著上升,在花粉萌发率接近最大值时,花粉ＣａＭ含量达最高水平（图５）。上述结果表明ＣａＭ对花粉萌发和花粉管生长的调控起重要作用。     

木立芦荟小孢子母细胞减数分裂与花粉育性关系的初步研究

文章从减数分裂过程、小孢子发育两方面,探讨了木立芦荟（Aloe arboresens Mill.）花粉败育的原因。木立芦荟花粉母细胞染色体数目为2n=14,由四对长染色体和三对短染色体组成,属二型性核型。其减数分裂异常,发现存在单价体和多价体、染色体桥、落后染色体、不均等分离、微核等。同时观察到木立芦荟染色体具有极度的粘质性,使减数分裂各阶段的染色体不易散开。统计各种异常现象出现的频率并分析了这些异常现象形成的可能机制及对正常小孢子形成的影响,推测染色体间的丝状粘连可能是木立芦荟小孢子母细胞减数分裂异常并导致败育花粉产生的主要因素。成熟花粉粒中90%以上为败育花粉,属碘败型。