Pollen morphology of the tribe Cynoglosseae of Boraginoideae (Boraginaceae) in China

Pollen morphology of 16 Chinese species representing 7 genera in the tribe Cynoglosseae of Boraginoideae(Boraginaceae) was examined under LM and SEM, and 5 species under TEM. Pollen grains are cocoon-shaped, rarely subprolate, prolate or ovoid, very small, 7～ 15.7μm× 3.5 ~ 13.9 μm in size, P/E = 1.6～2.02; 3-colporate apertures alternate with 3-pseudocolpi, with equatorial endocingulus except those in Bothriospermum; exine surface is usually smooth, with or without perforations in two poles, rarely with tuberculate ornamentation; exine is rather thin and includes ectexine and endexine, while ectexine consists of imperforate tectum, columellae and foot-layer. The tribe Cynoglosseae has many common characters of pollen grains, but there are some differences among genera. A key to the genera is given based on pollen morphology. Bothriospermum, without endocingulus, may be a primitive genus in this tribe, and its pollen morphology is more similar to that of Eritrichieae than to Cynoglosseae, thus it seems more reasonable to put it into Eritrichieae. Solenanthus may be the most advanced genus in the tribe Cynoglosseae for its pollen grains of sub-isopolar and ovoid shape.     

中国木犀属花粉形态研究及其系统学意义

观察了中国木犀属4组21种植物的花粉形态。花粉为圆球形或近长球形,外壁表面均具网状纹饰。大多数种类都具有三孔沟的萌发孔,极少四孔沟,或六萌发孔。内孔明显或不明显,有9种植物同时存在具三孔沟和具三沟二种类型的花粉及中间过渡类型(显脉木犀同时存在具三拟孔沟和具四拟孔沟)。很多特点表明,木犀属花粉的萌发孔在木犀科中处于由简单萌发孔向复合萌发孔过渡的阶段。根据网眼从沟间区中央到沟边是否变细,可将本属花粉分为两大类型,与分组有一定的对应关系。综合一些花粉特征,可发现本属花粉形态差异较明显,与一般形态差异有一定的相关性。花粉形态在木犀属具有一定的系统学意义。     

APERTURE EVOLUTION IN THE GENUS PTYCHOPETALUM BENTH. (OLACACEAE)

The genus Ptychopetulum (Olacaceae), disjunct between South America (2 spp.) and Africa (2 spp. West Africa; I sp. Rhodesia), exhibits predominantly diploporate pollen among the West African species and predominantly triporate pollen among the South American taxa. An analysis of aperture evolution suggests two possible schemes of aperture evolution for the genus. Scheme I avers the independent origin of both triporate and diploporate apertures from a basic brevicolpate condition while scheme II proposes a basic diploporate condition in which the diploporate apertures have migrated to the equator, fused to form brevicolpi and have ultimately become reduced to pores. Pollen evidence in support of both schemes is discussed. The distribution of aperture types within the genus also suggests West Africa as the original site of aperture evolution and South America as the second area of aperture development with types traceable to West African stock.     

Morphology of pollen and orbicules in some Dioscorea species and its systematic implications

Pollen and orbicule morphology of 35 Dioscorea L. species is described based on observations with light microscopy, and scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly bisulcate (sometimes monosulcate) with a perforate, microreticulate or striate sexine. Our results indicate that pollen data may be significant at sectional rank. The close relationship between sections Asterotricha and Enantiophyllum proposed by Burkill and Ayensu is supported by pollen morphology as all species investigated share bisulcate, perforate pollen with small perforations and a high perforation density. Macromorphological differences between the two compound-leaved sections Botryosicyos and Lasiophyton are also supported by pollen morphology; pollens of these two sections have very different perforation patterns. Orbicules in Dioscorea are mostly spherical and possess a smooth or spinulose surface. The latter is often correlated with a striate sexine.     

Die pollenmorphologie der afrikanischen buxus- und notobuxus-arten (buxaceae) und ihre systematische bedeutung

Pollen grains of 8 African species of Buxus and Notobuxus were examined by light and scanning electron microscopy. Three pollen types are recognized based on the exine sculpture and the evolutionary trends of the pollen characters are discussed. Pollen morphology shows the existence of three major systematic groups. These results support the previous classification of an African section Probuxus with two subsections and speak in favor of the generic rank of the Notobuxus species. Together with anatomical and taxonomical data pollen morphology and its evolutionary trends lend support to the suggestions that the centre of origin of the genus Buxus might have been in Africa, while secondary centres of evolution have developed in the neotropical and Eastasian region.     

Pollen morphology of the genus <Emphasis Type="Italic">Skimmia</Emphasis> (Rutaceae) and its taxonomic implications

Pollen morphology of the genus Skimmia was studied. Of six species of the genus, five species were investigated by light microscopy and scanning electron microscopy. Pollen grains of Skimmia had striate to striate-reticulate sculpture and variable aperture number (3-7), and these characters differed from even the phylogenetically closest relatives such as Dictamnus and Casimiroa which have 3-colporate pollen grains with reticulate exine. In Skimmia laureola, pollen dimorphism is suggested in the aperture number in accordance with the floral system. Pollen grains of Skimmia japonica, a morphologically very variable species, were extensively surveyed covering its whole distribution area. The grains were also striate to striate-reticulate, and the exine sculpture was not different between varieties. However, the aperture number of S. japonica showed a geographical variation ranging from 4 to 6; in Sakhalin, Hokkaido, most part of Honshu and Taiwan, grains with 4-5 apertures were dominant, while in the southern part of Japan, including the Ryukyu Islands and the Izu Islands, those with 5-6 apertures were common.     

Variation of pollen morphology, and its implications in the phylogeny of Clematis (Ranunculaceae)

Clematis s.l. (including Archiclematis and Naravelia) is a genus of approximately 300 species with cosmopolitan distribution. The diversity of its pollen was surveyed in 162 taxa belonging to all infrageneric groups of Clematis s.l. Pollen morphology was investigated by use of scanning electron microscopy to identify useful characters, test taxonomic and systematic hypotheses, and elucidate pollen character evolution on the basis of the molecular phylogeny. Clematis pollen is small to medium (14.8–32.1?μm?×?14.2–28.7?μm), oblate to prolate (P/E?=?0.9–1.4) in shape. The apertures may be tricolpate and pantoporate sometimes with 4-zonocolpate and pantocolpate pollen grains as transitional forms. The tricolpate pollen grains are predominant and occur in all the sections of the genus, whereas pantoporate pollen grains can be found in sect. Tubulosae, sect. Viorna, sect. Viticella, and Naravelia only. Phylogenetic mapping of aperture types reveals that the pantoporate pollen type may be the apomorphy in the genus and evolved several times. The surface ornamentation in all taxa studied is similar and characterized by microechinae evenly distributed on the microperforate tectum. The size and density of spinules on the tectum vary greatly but successive in the whole genus. According to the character syndromes of the ornamentation, separating sect. Brachiata from sect. Meclatis is supported. Though pollen morphology may contribute to investigation of problematic taxa, the taxonomic value of pollen morphology is limited at the species level.     

Systematic relevance of pollen and orbicule characters in the tribe Hillieae (Rubiaceae)

Pollen and orbicule morphology of 26 species in the tribe Hillieae is described based on observations by light, scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the tribe. Pollen is 3-zonocolporate with a perforate, microreticulate, reticulate or eutectate sexine. In the two species of Blepharidium , however, the pollen has one, four or five apertures. These pollen morphological data were incorporated into an existing macromorphological matrix of the group and cladistically analysed. The resulting phylogenies indicate that it may be appropriate to reduce Cosmibuena to a subgenus of the genus Hillia , while Blepharidium should be removed from Hillieae because of the deviating pollen type that is unique to the Rubiaceae. All species investigated produce orbicules, which are mostly spherical and possess an electron-lucent core that is sometimes characteristically flattened.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 303−321.     

亚洲茜草科粗叶木属及其相关属植物花粉形态研究

利用光学显微镜和扫描电镜研究了茜草科粗叶木属Lasianthus 16种2亚种、1变种及相关的5属5种的花粉形态。粗叶木属的花粉属于广孢型, 单粒。一般中等大小, 绝大多数为圆球形, 少数为近长球形或长球形。花粉形态特征, 特别是在萌发孔和外壁纹饰上表现出多样化。根据孔沟的数目或是否具有内孔, 可以将萌发孔分为(3-)4-(-5)孔沟和3孔。在所观察的这些种中, 萌发孔以3-4孔沟为主要类型, 比例为62.4%。外壁纹饰可分为细网状、粗网状和穴状。有部分种的花粉极面有穴状纹饰, 其余均为网状纹饰。网眼一般椭圆形、近圆形、三角形或者不规则形。少数外壁纹饰网脊上有颗粒状雕纹或模糊的颗粒, 网脊轮廓线呈波浪形, 一般凸出且平滑。大部分种的花粉具有沟膜, 沟膜上具有瘤状突起或小颗粒状, 沟边缘一般较平滑, 或粗糙, 有的种具有沟桥。     

Pollen Morphology of Microula Benth. and Allied Genera (Boraginaceae)

Pollen grains of 16 species of Microula Benth. and six species of three related genera were examined under LM and SEM, and four of them also under TEM. Pollen grains of Microula and three related genera are dumb-bell-shaped, 3-colporate apertures alternate with three pseudocolpi. Pollen grains are very small,ranging from 12.18 x 7.13 μm to 6.36 x 3.66μm. In general, colpi with os are wider and shorter, rhomboid, but sometimes they are equal to pseudocolpi in length. Colpus margins are regularly or irregularly tooth-like. The surface of colpi is psilate or processed. Ora are circular or lalongated in outline, protruded or not; surface of os membrane is smooth or scabrid. The exine is usually indistinctly layered under LM. The exine surface is psilate, and more or less perforate. TEM examination shows that the pollen wall is differentiated into exine and intine: the exine includes ectexine and endexine, while the ectexine consists of tectum, columellae and foot-layer. However, there are differences in constriction of equatorial area, apertural characters, ornamentation and exinous ultrastructure between these genera. Pollen morphology indicates that the genus Microula Benth. is primitive, directly related to the genus Actinocarya Benth .; the genus Asperugo L. Is more advanced. The genus Eritrichium Schrad. which has two ora or one os and is anisopolar, represents the most advanced group among them. Noteworthily, the diorate phenomenon is found for the first time not onlyin the genus but in the family Boraginaceae.     

甘薯属10种植物花粉形态扫描电镜观察

对用于育种研究的甘薯属(Ipomoea)10种植物花粉形态进行扫描电镜观察研究,以补充该属植物花粉形态学信息. 结果表明,甘薯属植物花粉粒的形状均为近球形,体积较大;花粉萌发孔多为散孔,少数萌发孔不明显;表面纹饰有3种:刺状类型、网状带刺类型和网状类型.根据花粉粒大小、刺的长短、萌发孔特征和表面纹饰类型等可以把这10种植物区分开来,同时发现I.wrightii与已有报道存在较大差异.     

我国罂粟科(Papaveraceae)植物的花粉形态

本文用光学显微镜对我国16属60种5变种罂粟科植物花粉形态进行了系统地观察研究。其中对15属27种进行了扫描观察。本科花粉形态为多类型。3沟为原始的、基本的花粉类型。根据萌发孔的形状、数目和特征,将罂粟科的花粉分为2沟,3沟,4-6沟、散沟、散孔和无萌发孔6个花粉类型。根据孢粉学资料,本文对绿绒蒿属(Meconopsis Vig.)花粉粒和其它器官的进化趋势,罂粟科在进化上的亲缘关系和本科花粉萌发孔的演化趋向等问题进行了讨论。     

猕猴桃属花粉形态及其系统学意义

由于天然种间杂交,猕猴桃属Actinidia Lindl.的分类存在着组间界限不清、近缘种之间很难区分的问题。本文试图通过对该属不同组、系的植物花粉及种间杂交后代花粉的扫描电镜观察,探讨该属物种的系统学关系。在扫描电镜下观察了猕猴桃属植物21种、 6变种和4个不同种间杂交F1代植株的花粉,描述了它们的花粉形态,并根据花粉形态特征建立了相应的检索表。研究结果表明：（1）猕猴桃属的花粉形状主要以长球形至近球形为主,变异较小,而花粉粒大小和外壁纹饰的种间差异较大。（2）多数迁地保护物种的花粉粒以三孔沟为主,不同于以前报道的以三拟孔沟为主,原因可能是花粉样本采集地的环境不一样,以及野外的广泛杂交造成的。（3）种间杂交后代花粉空瘪,无授粉能力,是由于所采用亲本植株染色体的倍性不同,后代不能产生正常花粉所致。（4）人工选育雄株花粉外壁纹饰较野生雄株花粉的精细,这种花粉外壁纹饰变小的特征可能有利于雌雄异株植物的授粉受精。这一现象值得进一步探讨。（5）雄株花粉大小与其雌株果实大小之间有一定相关性,这一现象有助于杂交后代的早期筛选。     

Pollen morphology of Adenandra (Rutaceae: Diosminae) and its taxonomic implications

The pollen morphology of Adenandra Willd. (Rutaceae: Diosminae) was investigated to determine its taxonomic significance. Pollen of 27 of the 30 infrageneric taxa (representing 16 of the 18 species) was investigated by LM, SEM and TEM. Adenandra differs from all other Diosminae in having 4-colporate rather than 3-colporate pollen grains. This supports the alleged monophyletic status of the genus. Exine morphology and structure, however, is extremely diverse considering the size of the genus, with eight distinct pollen types and four subtypes being discerned. In some members the grains have uniform macroreticulate, striate or striato-reticulate sculpturing, whereas in others the poles have striate, striato-reticulate or reticulate-perforate sculpturing with various types of reticulate or rugulate sculpturing at the mesocolpia. Taxonomic groupings revealed by the pollen characters suggest elationships between taxa that were not previously apparent. It is suggested that evolutionary diversification among species of Adenandra is often more strikingly reflected by pollen morphology than by macromorphology, hence the eurypalynous state of the genus.     

Pollen morphology and infra-generic evolutionary relationships in some Chinese species of Pedicularis (Scrophulariaceae)

 The pollen grains of 32 Chinese species of Pedicularis representing 13 groups within the genus were investigated using light microscopy and scanning electron microscopy. The genus is eurypalynous, the apertures may be tricolpate, trisyncolpate, or bisyncolpate and five types of surface ornamentation (microscabrate, microrugulate, retipilate, microreticulate and microfoveolate) were observed. Comparison of the different aperture types using light microscopy allows three pollen types to be distinguished. Examination of exine ornamentation with scanning electron microscopy enabled each pollen type to be divided into two or three sub-types (giving a total of seven sub-types). Pollen morphology within the genus is discussed in relation to infrageneric relationships, evolutionary and pollination biology. There is little correlation with the existing infrageneric taxonomy (some taxonomic groups have more than one pollen type, while the same pollen type may be found in several different species-groups), but greater correlation with the corolla morphology. Received January 10, 2002; accepted March 5, 2002 Published online: March 10, 2003     

Studies on Pollen Morphology of the Genus Corylopsis

The present paper describes the pollen morphology of 11 species of thc genus Corylopsis (Hamamelidaceae). The pollen grains were all examined with light microscope and scanning electron microscope. Pollen grains of the genus are prolate, spheroidal or subprolate. Three size types are recognized: (l) 18-23 μm, found in Corylopsis omeiensis Yang, C.gotoana Makino, C. himalayana Griff and C.platypetala Rehd. et Wils. (2) 24-32μm, found in C. sinensis Hemsl., C.willmottiae Rehd. et Wils., C.veitchiana Bean, C. brevistyla H.T.Chang, C.multiflora Hance, C.pauciflora Sieb. et Zucc. and C.spicata Sieb. Zucc. (3) 34-39μm, found in C. wilsonii Hemsl. and C. cordata Merrill. Pollen grains are 3-colpate and 4-colpate (only infrequently found in Corylopsis sinensis Hemsl.); the exine is 2-layered, 1.25-2.50μm thick, distinctly reticulate, sexine almost equal to nexine in thickness. From the pollen morphology the genus is considered as a natu-ral group.     

Pollen morphology of Astragalus section Hymenostegis (Fabaceae) and evaluation of its systematic implications

Astragalus is with nearly 3000 described species the largest genus of flowering plants. So far analyses of pollen characters have only been conducted for a few species of the groups within the genus. Here we analyse pollen grains of 22 species representative for Astragalus section Hymenostegis using scanning electron microscopy. We found the basic shape of the pollen grains to be oblate-spheroidal and apertures to be tricolpate as for other eudicots. The sculpturing pattern of the exine is micro-reticulate. Pollen grains show low morphological variation among different species of this section, but differences occur between sections of the genus. We conclude that the vast morphological differentiation that occurred during the rapid radiation of section Hymenostegis was not accompanied by comparable differentiation in pollen morphology.     

Distyly in Polygonum jucundum Meisn. (Polygonaceae)

Pollen grains of tribe Sanguisorbeae (Rosaceae, Rosoideae) were examined using scanning electron microscopy to identify useful characters, test taxonomic and phylogenetic hypotheses among genera, and elucidate pollen character evolution based on a molecular phylogeny. Aperture number, aperture structure, pollen shape, and exine sculpturing were variable within Sanguisorbeae and were used to delineate six pollen types. Four types (I–IV) were observed only in subtribe Sanguisorbinae whereas two types (V–VI) were found only in subtribe Agrimoniinae. Pollen grains of tribe Sanguisorbeae were generally subprolate to spheroidal in shape, had operculate or pontoperculate apertures, and had three apertures, except for Margyricarpus (tetraperturate). Exine sculpturing within Sanguisorbinae represented variations of striate, verrucate, rugulate, and perforate patterns often with microechinate sculpturing. Striate exine patterns and prolate shapes characterized the pollen of the Agrimoniinae, except for the microechinate-verrucate pattern and subprolate to spheroidal shapes observed in Hagenia. Pollen characters are most useful at the generic level and, when mapped on to a molecular phylogenetic tree of the tribe, are concordant with a monophyletic Agrimoniinae and a clade comprising Margyricarpus + Acaena + Polylepis + Cliffortia + Sanguisorba in the Sanguisorbinae. Outgroup comparison indicated that operculate colpi, three apertures, and polymorphism for striate or microverrucate exines represented primitive states for tribe Sanguisorbeae.     

FINE STRUCTURE OF MISTLETOE POLLEN. V. MADAGASCAN AND CONTINENTAL AFRICAN VISCUM L. (VISCACEAE)

Pollen characters of Madagascan and continental African Viscum are described and compared to those in Asia and Australia. The subprolate, tricolporate, nonuniformly sculptured pollen of Madagascan taxa is most similar to that of Asian species. Ultrastructurally, however, the completely granular equatorial ektexine of Madagascan Viscum is most similar to that of continental African taxa. Continental African Viscum, in contrast to Madagascan and Asian species, display a wide variation in pollen shape and apertures. Pollen shape ranges from subprolate to oblate, the latter unique to Africa. The most striking feature of continental Viscum is their variability in aperture number and aperture type. Aperture number varies at both the intra- and interpopulational levels with such variation resolvable to the individual flower—a condition unique to the continent. The only simple (colpate) aperture type in the genus is restricted to Africa. The continental species can be divided into two species groups based on pollen characters: Group I (4 spp.) characterized by strictly tricolporate rounded convex pollen with a rodlet/granular equatorial ektexine structure and Group II (most continental species) possessing multiapertures, concave lobate shape, uniform sculpturing and granular equatorial ektexine. The African V. menyharthii, V. fischeri, V. rotundifolium and V. minimum exhibit no clear Group I or II affinities. An analysis of overall pollen characters in Viscum indicates a trend towards spheroidal shape, multiapertures and uniform sculpturing and ektexine organization. Though pollen characters suggest ties between Australia, Asia and Madagascar, they indicate an even stronger relationship between Madagascar and continental Africa, particularly eastern Africa. The relationship of the majority of African Viscum, excluding those with obvious Madagascan affinities, remains obscure. The unique palynological features of Group II species coupled with their inflorescence structure suggest an independently evolving group.     

Pollen morphology of Strobilanthes Blume (Acanthaceae) in China and its taxonomic implications

The pollen morphology of 37 Chinese species of Strobilanthes Blume (Acanthaceae), a large and taxonomically problematic genus, was investigated by LM and SEM. Two distinct pollen shape classes, ellipsoid and spheroidal, recognised by earlier workers were found. Eight pollen types could be distinguished on the basis of variation in ornamentation, and the number, distribution and type of apertures. Five of these fall within twenty two pollen types reported from Strobilanthes in southern India and Sri Lanka. Three new pollen types are also described, further extending the palynological diversity of the genus. From the results presented, the characters of palynological diversity and the related taxonomic implications are discussed.