12种鹅绒藤属（萝藦科）植物花粉器形态学研究

用光学显微镜对萝藦科（Asclepiadaceae）鹅绒藤属（Cynanchum）12种植物花粉器形态进行了观察。结果表明：花粉块的形态有3种类型：球形、长球形和超长球形。着粉腺的形态有6种类型：长圆形、方形、近方形、三角形、正三角形和近三角形。花粉器形态学结果对青羊参（Cynanchum otophyllum）在鹅绒藤属中的分类具有较大意义;支持《中国植物志》第63卷中对催吐白前组（Sect. Vincetoxicum）的分组处理;结合鹅绒藤属花粉块下垂,娃儿藤属（Tylophora）花粉块平展的特点,支持将娃儿藤属作为一个独特类群的观点。     

17种1亚种鹅绒藤属植物花粉器形态学研究

利用光学显微镜对萝藦科鹅绒藤属17种1亚种植物花粉器的形态特征进行观察。结果表明:(1)该属植物花粉器形状大小在各个种间差异较大:花粉块下垂,通常呈球形、长球形和超长球形,平均大小为327.2μm×183.9μm;着粉腺呈长圆形、近圆形、近方形和近三角形,平均大小为406.1μm×231.4μm。(2)翅果杯冠藤的花粉块柄最不发达,豹药藤的花粉块柄最发达。(3)白薇与朱砂藤、刺瓜与轮叶白前的花粉器特征均较相近。研究结果支持《中国植物志(第63卷)》中对催吐白前组(Sect.Vincetoxicum)的分组处理;支持将娃儿藤属(Tylophora)作为一个独特类群的观点;因国内翅果杯冠藤和美翼杯冠藤的花粉器形态存在差别,故不支持Flora of China(Vol.16)中认为翅果杯冠藤是美翼杯冠藤的错误鉴定与处理。     

牛奶菜族7属11种植物的花粉器形态

在光学显微镜和扫描电子显微镜下观察了萝藦科（Asclepiadaceae R.Br.）牛奶菜族（MarsdenieaeBenth.）7属11种植物花粉器的形态特征。该族植物花粉块直立或平展,通常呈椭圆形、长圆形、肾形或球形;花粉块膜表面平滑、波浪状、脊状或粒状;娃儿藤属（TylophoraR.Br.）的花粉块膜具独特的表面纹饰,与其它属植物差异较大;匙羹藤属和娃儿藤属的花粉块柄不发达,眼树莲属（Dischidia）和纤冠藤属（Gongronema）的花粉块柄发达。     

蜘蛛抱蛋属植物花粉形态及系统学意义

用扫描电子显微镜对国产 1 4种蜘蛛抱蛋属植物的花粉形态进行了观察 ,该属植物的花粉形态有长球形和球形 2种 ;外壁纹饰可分为 3大类型 :( 1 )皱波状纹饰 ;( 2 )小芽孢状纹饰 ;( 3)瘤棒状纹饰。它们的演化趋势是 :皱波状纹饰→芽孢状纹饰→瘤棒状纹饰     

马尾树科及其近缘科花粉形态研究

本文观察了马尾树科(Rhoipteleaceae)、胡桃科(Juglandaceae)以及桦木科(Be-tulaceae)、9属9种植物花粉形态。马尾树科与桦木科桦木属(Betula L.)花粉粒均为扁球形,极面观呈钝三角形,萌发孔类型均为多孔类型,孔之间均有弓形加厚,而且外表面均具细颗粒状雕纹。而胡桃科大多为多边形、散孔类型。根据花粉形态资料,探讨了马尾树科的系统位置。     

中国天南星科花粉形态的研究

利用扫描电镜对天南星科Araceae22属28种(除Arum maculatum产自德国外,其余均产自中国) 及菖蒲科Acoraceae 1属2种植物的花粉形态进行了观察。结果显示天南星科花粉形态在科内变异很 大。花粉粒形状从球形、近球形、椭球形到扁球形和橄榄形;萌发孔类型有散孔型、具薄壁区型、环沟型 或无萌发孔;外壁纹饰为小穴状、网状、肋条状、条纹状、疣状、具刺或光滑。主要依据花粉形态方面的证 据探讨了崖角藤属Rhaphidophora、麒麟叶属Epipremnam 、龟背竹属Monstera 3属的属间关系以及犁头尖属Typhonium属下分类中存在的一些问题。     

中国无患子科的花粉形态及其系统学意义

利用扫描电镜对国产无患子科(狭义,Sapindaceae)23属30种1变种植物的花粉形态进行了观察。结果显示,该科花粉粒多为扁球形,部分为长球形,少数为球形或近球形,极面观多为三角形;从花粉萌发孔类型看,大多数种类具三沟孔,有的形成合沟,少数仅具三孔而无沟;从花粉外壁纹饰看,多数花粉外壁具网状或条纹状雕纹,少数花粉的外壁具刺状或颗粒状纹饰。花粉形态特征支持文冠果亚科(Xanthoceroideae)以及广义鳞花木属(Lepisanthes)概念,并支持仍将茶条木属(Delavaya)置于车桑子亚科(Dodonaeoideae)。观察发现黄梨木(Boniodendron minus)与栾树属(Koelreuteria),龙眼属(Dimocarpus)、荔枝属(Litchi)与韶子属(Nephelium)从花粉形态上表现出较近的亲缘关系。基于花粉形态特征编制了国产无患子科分属检索表。     

12种十字花科植物花粉形态研究

采用扫描电子显微镜对十字花科8属12种植物的花粉形态特征进行了观察分析.其中8种为首次报道.观察结果表明:4族8属12种十字花科植物花粉形态的一般特征为:花粉粒长球形至超长球形;极面观三裂圆形,少数四裂圆形;外壁纹饰为网状或细网状纹饰;三沟,偶四沟.12种植物的花粉可划分为5种类型:(1)花粉粒长球形,网状纹饰,三沟;(2)花粉粒超长球形,网状纹饰,三沟;(3)花粉粒长球形,细网状纹饰,三沟;(4)花粉粒超长球形,细网状纹饰,三沟;(5)花粉粒长球形,三或四沟,网状纹饰.十字花科花粉形态特征在不同族间、不同属间以及同属不同种间均没有明显规律,在十字花科分类过程中,不宜单独以花粉形态特征作为依据.     

国产省藤属植物的花粉形态学

对国产棕榈科省藤属(Calamius L.)15种植物的花粉进行了光学和扫描电镜观察,其中12种为首次报道。省藤属的花粉均为两沟型花粉,外壁覆盖层多为网状纹饰(大喙省藤C．macrorrhynchus)或具穿孔(华南省藤C.rhabdocladus)。首次发现省藤属花粉的外壁纹饰存在穿孔和外壁疣状突起的类型(阔叶鸡藤C.pulchellus)以及皱波状突起的类型(长鞭省藤C.flagellum)。花粉的大小、形状、外壁纹饰、外壁是否有突起,外壁厚度和网状纹饰网眼的大小,对于省藤属的种级分类有较大的意义。     

我国椴树科花粉形态的研究

本文对分布于我国的椴树科(Tiliaceae)9属44种植物的花粉形态进行了光学显微镜 的系统观察,并对其中10种花粉的外壁细微结构进行了扫描电镜观察。本科花粉为长球形、 扁球形和球形,萌发孔为长3孔沟、短3孔沟和3(一4)孔三种类型,外壁主要为网状纹饰,个 别属为刺状纹饰。根据花粉资料,本文还探讨了该科植物分类中的某些问题。     

14种石斛属(兰科)植物的花粉团形态及分类学意义

利用体式显微镜和扫描电镜观察了14种石斛的花粉团形态及其表面纹饰超微特征,为该属的物种划分和系统演化提供花粉形态证据。解剖镜下,14种石斛的花药里有4枚花粉团,表面金黄油亮呈蜡质,质地坚硬。根据每种石斛的4枚花粉团的总体轮廓形态和大小,可分为3种形态(心形、近心形和长心形)和4种类型(极小花粉团,小花粉团,大花粉团和超大花粉团)。根据单个花粉团边界轮廓的曲直,可将其分为4种类型(月牙型、弓型、棍状和米粒型)。扫描电镜下,14种石斛的花粉团表面纹饰类型有5种(光滑平整型、光滑带丝状突起型、光滑不平整型、粗网纹状型和皱波状型),在广东石斛和球花石斛的花粉团表面观察到晶体的存在。花粉团的形态大小和外壁纹饰特征在种间变化明显,对澄清石斛属的分类学问题有一定意义。     

Pollination genetics of hybridization in sympatric populations of asclepias exaltata and a. syriaca (asclepiadaceae)

Enzyme electrophoresis of pollinia and seeds was used to identify pollinia on pollinators, interspecific pollinations, and hybrid seed production in sympatric populations of Asclepias exaltata and A. syriaca. The frequency of mixed pollinia loads on pollinators was low. Only 4.1% (N= 169 pollinia) and 8% (N= 244 pollinia) of the pollinia collected from pollinators of A. syriaca and A. exaltata, respectively, were identified as pollinia from the other species. Natural levels of interspecific pollination, 3.6% (N = 166 pollinia) on A. syriaca and 3.1% (N = 228 pollinia) on A. exaltata, were typically lower than the number of foreign pollinia carried by pollinators. Hybrid seeds were identified in only two of 208 A. syriaca fruits and one of 178 A. exaltata fruits. Hybrid seeds were largely underdeveloped in the single A. exaltata fruit. High fruit set (34.7%) and near normal seed set following hand-pollination of A. syriaca with A. exaltata pollinia suggest that hybridization is more likely between these taxa when A. syriaca is the maternal parent. Our findings indicate that the likelihood of hybridization between A. exaltata and A. syriaca is remote. Nevertheless, introgressive hybridization has been documented in these species, which suggests that hybridization remains a strong evolutionary force even for species that infrequently interbreed.     

Pollination ecology of Ecuadorian Asclepiadoideae (Apocynaceae): How generalized are morphologically specialized flowers?

This paper studies phenology and pollination ecology of an assemblage of nine small-flowered species of Asclepiadoideae–Asclepiadeae in a southern Ecuadorian mountain forest. These observations were augmented by laboratory studies of floral traits including scanning electron microscopy. Supported by multidimensional scaling analysis, three distinct pollination systems were identified: (a) pollination by small flies (Orthosia, Scyphostelma), (b) pollination by small bees and flies (Ditassa), and (c) pollination unspecialized (“Cynanchum”, Jobinia, Oxypetalum). Although numerous floral visitors were observed in the field, pollinaria were carried by only seven insect species. The average pollinaria removal rate of all species was low with 0.32±0.13%, and still lower for the pollinia insertion rate with 0.13±0.07%. The ratio of inserted pollinia to removed pollinaria was comparatively high with an average of 42.7±22.3%. If an insect achieved pollinia transfer, it did so very effectively. The complex floral morphology of the Asclepiadoideae has often been interpreted as a general trend toward specialization, but our observations indicate that the flowers are specialized functionally rather than ecologically.     

Mast fruiting in a hawkmoth-pollinated orchid Habenaria glaucifolia: an 8-year survey

Aims The hypothesis of predator satiation has been proposed to explain mast fruiting in various flowering plants. It considers that the simultaneous production of large numbers of seeds by a plant population reduces the risk of seed predation for each individual. Orchids produce huge numbers of seeds per fruit and rarely experience seed predation. It remains unclear which factors may affect fluctuating fruit production in orchids, which generally suffer a widespread pollen limitation. To explore the temporal pattern of fruiting and potential factors related to fluctuation in fruit production, we investigated reproductive success of a long-spurred orchid (Habenaria glaucifolia) in an alpine meadow with thousands of individuals over 8 years.Methods To estimate reproductive success, pollinator observation was conducted by day and at night, and pollinia removal and receipt were recorded in the field population for 8 years. To examine whether fruit set and seed set are pollen limited, we conducted supplementary pollination experiments and compared fruit set, seed set and pollinia movement of open-pollinated flowers from 2011 to 2013. We measured lengths of spurs and pollinator proboscises, and nectar volume and concentration, to identify potential pollinators.Important findings Hawkmoths were seen to be effective pollinators for H. glaucifolia in 3 years, whereas in the remaining 5 years no pollinators were observed, and consequently pollinia were rarely transferred. Numerous pollinia movements were observed in 2012, 2013 and 2014 (pollinia removal: 48, 59 and 85%; pollinia receipt 51, 70 and 80%), and correspondingly fruit set was significantly higher in 2012 and 2013 (59 and 46%) than in 2011 (25%). It was fruit set, rather than seed set, that was pollen limited in this orchid in the 3 years, in that supplementary pollination increased fruit set but did not increase seed set per fruit compared to natural. Three species of hawkmoths had proboscis lengths that matched the spur length of H. glaucifolia. Fruit set in this long spurred orchid depends on the activity of long-tongued hawkmoths, resulting in significant temporal variation in fruit production. Mast fruiting in this alpine orchid could be attributed to a 'sit and wait' strategy, awaiting an abundance of effective pollinators.     

The turnover of milkweed pollinia on bumble bees,and implications for outcrossing

Summary Bumble bees (Bombus spp.) picked up a pollen packet (pollinium) of milkweed (Asclepias syriaca L.) every 2–5 h, usually more rapidly on their feet than on their mouthparts. Pollinia were retained an average of slightly over one day on the mouthparts and one-quarter day on the feet. This long retention period enhances the possibility of outcrossing in this largely or completely self-incompatible species. Although many more pollinia were carried on the feet, the longer retention of those on the mouthparts resulted in their collective outcrossing potential exceeding that of pollinia on the feet. Once pollinia became attached to the bees (via their attachment mechanisms, the corpuscula), others often attached to the translator arms (connecting corpusculum with pollinia) of the first pollinia. Long strings of pollinia and corpuscula often resulted, but they frequently were shed down to a single corpusculum, which was usually retained for long periods (estimated retention time=12–43 days). During the middle and latter part of the flowering period about two-thirds of the bees' feet carried only a single corpusculum. Feet in this condition picked up extremely few pollinia and thus were largely unavailable as sites for pollen transfer. Having several single corpuscula on the feet greatly lowered the number of pollinia carried by a bee over the season. Single corpuscula occurred much less frequently on the mouthparts and were shed over 25 times as rapidly as those on the feet. Many more bumble bees moved between clones than did other possible diurnal pollinators, largely a result of being several times more abundant than all other visitors combined. This factor, plus their heavy pollinia load, suggests that they were the most important diurnal pollinators of these clones.     

Molecular phylogeny of Vincetoxicum (Apocynaceae-Asclepiadoideae) based on the nucleotide sequences of cpDNA and nrDNA

Molecular phylogenetic analyses of Vincetoxicum and Tylophora (Apocynaceae-Asclepiadoideae) were conducted based on the nucleotide sequences of cpDNA (two intergenic spacers of trnL (UAA)-trnF (GAA) and psbA-trnH and three introns, i.e., atpF, trnG (UCC) and trnL (UAA)), and nrDNA (ITS and ETS regions). Our phylogenetic analysis revealed two monophyletic groups; one consisted of seven taxa of Tylophora and Vincetoxicum inamoenum, Vincetoxicum magnificum and Vincetoxicum macrophyllum (Clade I) and the other consisted of 17 accessions of Vincetoxicum (Clade II). The monophyly of the genus Vincetoxicum was not supported. Although many nucleotide substitutions were observed in Clade I, the genetic differentiation within Clade II was small. Low genetic diversification but considerable morphological divergence suggests that the species in Clade II had undergone rapid diversification. Although most species in Clade I have tiny flowers, those in Clade II have larger and more nectariferous ones. Thus, we hypothesized that the rapid morphological radiation in Clade II may have been due to the gaining of floral characters such as large flowers and large amounts of nectar corresponding to diverse pollinators.     

Breeding system and factors limiting fruit production in the nectarless orchid Broughtonia lindenii

Low fruit set values in most orchids (especially epiphytic and tropical species) are normally thought to be the consequence of pollination constraints and limited resources. In particular, pollination constraints are modulated by pollinator visitation rates, pollinator visitation behaviour (promoting crossing or selfing), the type and number of pollinia deposited on stigmas (in the case of orchids with subequal pollinia) and the amount of pollen loaded per inflorescence. In order to assess to what extent these factors can affect fruit set in specific orchid-pollinator systems, the repercussions of some of these aspects on reproduction of Broughtonia lindenii were examined in a coastal population in western Cuba. The study focused on plant breeding system, importance of pollen load and type of pollinia on subsequent fruit and seed, limiting factors of seed production and interaction with pollinators. This species presents long-lasting flowers that senesce after all forms of effective visit. Pollinator dependence for fruit production was demonstrated, while hand-pollination experiments revealed self-compatibility and inbreeding depression at seed level. More pollinia on stigmas enhance the proportion of well-developed seeds. In contrast, the pollinia type used in pollination is not important for seed quality of fruits, suggesting that small pollinia are not rudimentary. Natural fruit set in two consecutive years was substantially affected by pollinator activity, and also by systematic depredatory activity of ants and a caterpillar. Considering that this orchid completely lacks nectar and that the local assemblage of pollinators and predators influenced its reproduction, a minor importance of resource constraints in this epiphyte (with long-lasting reserve structures) is confirmed at least for a short time.     

On the mechanism of floral shifts in speciation: gained pollination efficiency from tongue- to eye-attachment of pollinia in Platanthera (Orchidaceae)

This work explores the mechanism of floral shifts that may result in speciation. The model organisms chosen were the moth-pollinated pollinator-limited orchid species Platanthera bifolia and P. chlorantha . P. bifolia exhibits tongue-attachment of pollinia on pollinators, a character state that has been found previously to be ancestral. The close relative P. chlorantha exhibits the derived state of eye-attachment of pollinia on pollinators. We reasoned that differences between the species in pollination efficiency could give insights into the mechanism of floral shifts and thus cladogenesis. Four populations per species were investigated. In three populations, where the species were growing intermixed and were sharing pollinators, there was significant difference in the pollen export and import efficiency per visit-night (night with pollen export and/or import) between the two species. P. bifolia exported pollinia more efficiently but imported pollen less efficiently than did P. chlorantha . Pollen import was 1.7–4 times faster in P. chlorantha (eye-attachment) than it was in P. bifolia (tongue-attachment). P. chlorantha had a lower risk of interference between pollen import and export. An increase in fitness through greater speed and efficiency of pollen import due to an enlargement of the stigmatic surface and a reduction in the risk of sexual interference may therefore be mechanisms of the floral shift from tongue- to eye-attachment of pollinia on pollinators.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 481–495.