POLLEN MORPHOLOGY OF THE DILLENIACEAE AND ACTINIDIACEAE

Pollen of 53 species of Dilleniaceae and Actinidiaceae was examined by light microscopy, scanning electron microscopy, and a selected group in transmission electron microscopy. Dilleniaceae pollen ranges from tricolpate, tricolporate, tetracolpate, and incipiently inaperturate. Tricolpate types occur only among the Old World subfamily Dillenioideae and the compound aperturate (3-colporate) condition is restricted to the subfamily Tetraceroideae. Within the Dilleniaceae the tricolpate pollen type with elongated apertures is considered primitive, having given rise to the 3-colporate and 4-colpate conditions. The striking pollen dimorphism in the Neotropical species of Tetracera, all of which are androdioecious, is documented; however, in contrast to previous reports, pollen from bisexual flowers appears to be incipiently inaperturate and not pantoporate. The inaperturate condition is interpretated as an early stage in the evolution of outcrossing. Pollen morphology does not support a close relationship between Dilleniaceae and Actinidiaceae. Pollen morphological differences that can be noted between these families are: tectum complete and predominantly psilate or psilate-granular in Actinidiaceae, tectum incomplete, punctate to reticulate in Dilleniaceae; an equatorial bridge of ektexine over the endoaperture usually present in Actinidiaceae, absent in Dilleniaceae; columellae reduced in Actinidiaceae, columellae usually well-developed in Dilleniaceae. Pollen morphology does not argue against a close relationship between Actinidiaceae and Theaceae.     

FINE STRUCTURE OF MISTLETOE POLLEN. IV. EURASIAN AND AUSTRALIAN VISCUM L. (VISCACEAE)

Fifteen Eurasian and Australian species of Viscum L. were examined by light, scanning, and transmission electron microscopy. Pollen characters divide the species into two groups, each correlated with differences in habit and inflorescence structure: Group I (12 spp.) characterized by psilate or slightly sculptured exines and a non-uniform ektexine pattern and Group II (3 spp.) possessing highly sculptured (echinate, rodlet) surfaces and uniform ektexine patterns. Within each of the groups, pollen characters divide the species into several subgroups. Among Group I, species V. nepalense, V. heyneanum and V. ovalifolium are particularly close. The Group I species, V. trilobatum, is placed in its own subgroup primarily because of its uniform ektexine pattern—a unique feature among Asian and Australian Viscum. Of the three Group II species, V. album and V. alniformosanae are palynologically almost indistinguishable. Pollen of the Group II V. cruciatum, though exomorphologically similar to V. album, is closest ultrastructurally to the Indian V. trilobatum. Overall, the most common and probably basic pollen characters among the Eurasian and Australian species include: subprolate, rounded convex almost spherical shapes; tricolporate apertures, and non-uniform sculpturing and ektexine patterns. Oblate-spheroidal or prolate-spheroidal shapes, prominent sculpturing, and a uniform ektexine pattern are derived characters largely restricted to the Eurasian and Asian Group II species (V. album, V. alniformosanae, V. cruciatum).     

国产爵床科山牵牛属6种、叉柱花属和老鼠簕属各1种植物的花粉形态

报道了国产爵床科Acanthaceae山牵牛属Thunbergia(山牵牛亚科Thunbergioideae)6种、叉柱花属Staurogyne(瘤子草亚科Nelsonioideae)和老鼠簕属Acanthus(老鼠簕亚科Acanthoideae)各1种植物在扫描电镜下的花粉形态。山牵牛属植物的花粉粒为圆球形,均具螺旋状萌发孔,外壁纹饰以光滑或颗粒状为主,偶具棒状突起。具螺旋状萌发孔被认为是该科独特而较原始的花粉特征。叉柱花属的花粉粒为圆球形,具3孔沟,外壁平滑。老鼠簕属的花粉粒为长球形,具3沟,外壁具细网状纹饰或具小穿孔。花粉形态特征支持传统上将上述3属置于3个不同亚科的处理。     

Pollen morphology in <Emphasis Type="Italic">Lysipomia</Emphasis> (Campanulaceae: Lobelioideae) and interpretation of shape artifacts

The pollen of 32 species of Lysipomia was examined by light, scanning, and transmission electron microscopy. Two pollen types occur in the genus: 3-colporate and 6-colporate. The 3-colporate condition occurs in only two species, L. laciniata and L. pumila. The remaining 30 species are 6-colporate, a condition known from only one other genus in the Campanulaceae. Surface sculpturing among the species is uniformly striate. Pollen shape was highly variable within a single individual in comparisons of pollen gathered from herbarium specimens, FAA preserved material collected in the field, and fresh pollen from cultivated individuals grown from seed. Shape may change from oblate spheroidal to subprolate as a result of drying time and temperature, and should not be used as a morphological character in systematic studies if infraspecific variation is seen. When fresh or preserved pollen is not available, rehydrated pollen should be compared to reduce the possibility of inadvertent artifact production confounding the analysis of morphological data.     

Pollen morphology of the subtribe Cuspariinae (Rutaceae)

The neotropical subtribe Cuspariinae (Rutaceae) comprises as many as 26 genera and over 125 species. Pollen grains from 111 collections representing 71 species and 24 genera were examined by LM, SEM, and TEM. The pollen morphology of this subtribe is very diverse. Grains are mostly 3–6-aperturate and colporate, rarely porate (Spiranthera) or pantocolporate (Almeidea). Exine sculpturing is most commonly reticulate, sometimes perforate, foveolate-perforate, foveolate, foveolate-reticulate, reticulate, striate-reticulate, echinate, clavate, or baculate. The exine structure is columellate and tectate-perforate, columellate and semitectate, or intectate and is stratified into ektexine and endexine. The exine ofLeptothyrsa is distinctive in that the ektexine of the mesocolpium is longitudinally deeply ridged. The pollen ofHortia, characterized by a psilate exine with rare perforations, a very thick foot-layer, and reduced columellae, is unlike that of any member of the Cuspariinae and offers no support for the transfer of this genus from the Toddalioideae. The pollen data correlate with macromorphological characters and are taxonomically useful.     

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。     

POLLEN ULTRASTRUCTURE OF THE TRIBE INGEAE (MIMOSOIDEAE: LEGUMINOSAE)

All genera within the Ingeae, excluding Wallaceodendron, were examined with the transmission electron microscope. Thin sections reveal two pollen types (Types I and II) distinguished primarily by differences in polyad cohesion and ektexine organization. Type I polyads (only eight-grained species of Calliandra) are calymmate and the ektexine of individual cells is continuous around the grain, organized into a thin, foraminate tectum, irregularly shaped, often basally flared, foraminate columellae and thin, discontinuous foot layer. Type II polyads (16-grained species of Calliandra and remaining Ingeae) are predominantly acalymmate with individual grains typically free from one another or rarely, partially calymmate, i.e., individual grains show limited forms of attachment through small endexinous bridges (Pithecellobium latifolium [Zygia], Lysiloma) or localized appression of adjacent endexines (Pithecellobium daulense [Cathormion]). The adhesion of individual grains through localized fusion of lateral-distal and proximal ektexine in Enterolobium is unique among the partially calymmate Type II polyads. Ektexine in Type II polyads, largely restricted to the distal face, is composed of a thick, channeled tectum, granular interstitium and when present, thin discontinuous foot layer. Lateral-distal and proximal areas exhibit only endexine and, occasionally, a foot layer. The occurrence of nondistal ektexine is restricted to Enterolobium. The pollen data suggest that the acalymmate Ingeae polyads composed of grains with porate apertures, thick, highly channeled tectum, granular interstitium and lack of, or greatly reduced foot layer, are clearly derived within the Mimosoideae. Type I calymmate polyads appear to be independently derived. Ultrastructural data suggest that the Ingeae, excluding the eight-grained Calliandra species, represent a natural grouping with a close affinity to the Acacieae.     

POLLEN MORPHOLOGY AND DETAILED STRUCTURE OF FAMILY COMPOSITAE,TRIBE CICHORIEAE. I. SUBTRIBE STEPHANOMERIINAE

A survey of pollen morphology in 20 species representing the 11 genera of the North American subtribe Stephanomeriinae by light, scanning electron, and transmission electron microscopy revealed 10 of the 11 genera to have echinate, tricolporate pollen grains, Lygodesmia being the only genus with echinolophate pollen. Sectioned exines of most of the species examined are similar, being composed of ektexine and endexine. The ektexine surface is composed of spines which typically have globose perforate bases. A cavus occurs as a separation between the basis (foot layer) and the columellae in all of the genera examined except Chaetadelpha. Pollen of the two species of Glyptopleura were found to be strikingly different in exomorphology. Pollen of the putatively self-fertile G. marginata has much shorter spines than the closely related G. setulosa. Atrichoseris, Anisocoma, Calycoseris, Glyptopleura, Pinaropappus, Prenanthella, and most species of Malacothrix have pollen which lack paraporal ridges. The remaining genera, Chaetadelpha, Lygodesmia, Rafinesquia, and Stephanomeria have well-developed ridges of fused spine bases around the apertures. Pollen characters, particularly those of the aperture region, have been found to be systematically useful in the subtribe, therefore acetolyzed material gives more useful information than untreated pollen.     

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.     

横断山区高山豆属的花粉形态及凉山高山豆的分类学地位

为澄清我国西南横断山区特有属高山豆属（Tibetia）中凉山高山豆（T.liangshanensis）的花粉粒形态及其分类学地位,用电子显微镜重新扫描了本属的花粉粒。报道了除一个可疑种中甸高山豆（T.forrestii）外所有5个种的花粉形态,即高山豆（T.himalaica）,云南高山豆（T.yunnanensis）,凉山高山豆（T.liangshanensis）,黄花高山豆（T.tongolensis）和亚东高山豆（T.yadongensis）。结果纠正了凉山高山豆的花粉粒形态,而另外4个种的花粉粒与之前的研究基本一致,仅在形状和大小上稍有差别。本属的花粉粒呈圆球形或近长球形,表面有穿孔凹陷,3 孔沟和4 孔沟两种花粉类型与高山豆属分为两个组相吻合。但我们发现凉山高山豆的花粉是4 孔沟类型,而不是之前报道的3 孔沟类型。另外,凉山高山豆与中甸高山豆的形态差异明显,凉山高山豆茎长,小叶13~17片,托叶分离,花冠紫色;而中甸高山豆茎短,小叶7~9片,托叶基部合生,花冠黄色,叶片下表皮细胞形态差异明显,因此我们认为应该将凉山高山豆独立作为一个种,而不是作为中甸高山豆的异名。     

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.     

中国紫草科厚壳树亚科的花粉形态及其系统学意义

为探讨厚壳树亚科在紫草科中的系统位置,用扫描电子显微镜研究了国产厚壳树亚科Ehretioideae的厚壳树属Ehretia、轮冠木属Rotula和基及树属 Carmona 3属12种植物的花粉形态,其扫描电镜资料属首次报道。从本文并结合文献报道的双柱紫草属 Coldenia的花粉资料,可得知该亚科花粉为长球形 、近球形,稀球形,赤道部位具有不同程度的膨大;萌发孔类型为三孔沟和三拟假沟二者交替排列,稀具三孔;外壁表面具微弱的小穿孔,稀光滑或皱波状纹饰。厚壳树亚科Ehretioideae与破布木亚科     

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.     

Pollen morphology and its taxonomic significance of the monotropoideae (Ericaceae)

A palynological survey, including LM, SEM and TEM is presented for eight genera, nine species and 76 samples of the Monotropoideae which is composed of 10 genera and 13 species. On the basis of the aperture number and shape, the following six pollen types are recognized: 1) 3-colp(oroid) ate—Allotropa, 2) 2-colpor(oid)ate—Monotropsis andHemitomes, 3) 4-colpor(oid)ate—Pterospora, Sarcodes andPleuricospora, 4) 2- and 3-colpor(oid)ate—Monotropa hypopitys, 5) 3-colporate and-porate —Monotropa uniflora, 6) 3- to 4- porate—Monotropastrum humile. Relationships among taxa within the Monotropoideae are illustrated on the palynological characters including the aperture type, exine sculpture and structure. Both pollen grains with two and four apertures have evolved independently from pollen grains with three apertures, according to the infraspecific variation of aperture numbers and the usual occurrence of three-aperturate pollen grains in the Ericaceae. 3-colp(oroid)ate pollen ofAllotropa is the most primitive and occupies an isolated position in the subfamily, on the other hand 3- to 4-porate pollen ofMonotropastrum humile is most advanced in the subfamily, probably even in the Ericaceae. A reduced sexine inMonotropastrum humile appears to be a specialized pollen character. Infraspecific geographical difference in palynological characters is revealed in two species ofMonotropa for the first time.M. hypopitys is basically characterized by pollen grains with two apertures in the New World vs. three apertures in the Old World.M. uniflora is basically characterized by 3-porate pollen in the New World vs. 3-colporate in the Old World. In both species pollen grains with more primitive characters usually occur in the Old World.     

Pollen morphology of the genus Paliurus (Rhamnaceae)

The pollen morphology of the genus Paliurus and the 5 species it comprises is described. Consistent with the general morphological pattern of the family Rhamnaceae, the pollen grains of Paliurus are uniformly isopolar, radially symmetrical, 3-(zono)-colporate and angulaperturate. Despite this general infrageneric uniformity, certain differences and trends can be recognized with respect to pollen size, shape, and tectum architecture.     

Pollen wall development in Vigna vexillata I. Characterization of wall layers

Light and electron microscope observations characterized the layers that comprise Vigna vexillata L. pollen walls, and identified the timing of their development. Exine sculpturings form an unusually coarse ektexinous reticulum. The structure of the ektexine is granular; this differs from the columellate/tectate type of structure typical of most angiosperm pollen. The ektexine overlies a homogeneous-to-lamellar, electron-dense endexine, which in turn surrounds a thick, microfibrillar intine. Pollen grains are triporate and operculate, with Zwischenkörper and thickened intine underlying the apertures. The ektexine forms during the tetrad period of microspore development, the endexine and Zwischenkörper during the free microspore stage, and the intine during the bicelled (pollen) stage. Coarsely reticulate exine sculpturings and the granular structure of the patterned exine wall of the pollen grains are features that make this species suitable for detailed studies of pollen wall pattern formation.     

Beschorneria yuccoides and Asimina triloba (L.) Dun: Examples for proximal polar germinating pollen in angiosperms

Beschorneria yuccoides (Agavaceae) microspores are arranged mostly in planar tetrads. Later on, the pollen grains of the tetrad usually fall apart, but sometimes remain loosely connected by ektexine elements. The ektexine consists of a tectum, of short columellae, and of a thin, discontinuous foot layer. An endexine is absent. The bilayered intine is without any additional thickening that would usually indicate an aperture region. From this point of view the pollen grain might be considered as omniaperturate. The pollen ornamentation is reticulate with wide lumina and robust, smooth muri.

The pollen grains show an indistinct sulcus characterised by a loose reticulate ornamentation. The sulcus is not exactly at the distal pole, but shifted towards the equator. No pollen tubes are formed regularly at the sulcus. Instead, pollen tubes are normally formed at the proximal pollen face. The proximal area, indicating a large germination field, is morphologically and functionally clearly an aperture (a germination zone); however, it does not represent a sulcus. The proximal face of all pollen grains appears as ornamented, with some exine lumps.

Asimina triloba (Annonaceae) pollen is shed in permanent planar or decussate tetrads. The distal sides are microreticulate to foveolate, and do not show an aperture; the psilate proximal sides are the germination areas of A. triloba.

The presence of apertures placed at the proximal pole was reported for distinct taxa of several angiosperm families. For Drosera, Dionaea (Droseraceae) and most probably for the diaperturate Cuphea species (Lythraceae) the existence of polar germination areas can be excluded. However, in some Annonaceae taxa with permanent tetrads (Annona cherimola, Asimina triloba) a situation similar to Beschorneria might be present, and indeed a proximal polar pollen tube is formed. Beschorneria yuccoides, Annona cherimola and Asimina triloba are unequivocal examples of angiosperm pollen with an exactly proximal aperture (germination area).     

Evolution of pollen,stigmas and ovule numbers at the caesalpinioid–mimosoid interface (Fabaceae)

In this study we examine the pollen, stigmas and ovaries from 62 collections of herbarium material representing 16 genera, using light and scanning electron microscopy. The caesalpinioid Dimorphandra group (Burkea, Dimorphandra, Erythrophleum, Mora, Pachyelasma, Stachyothyrsus and Sympetalandra) pollen grains are small, tricolporate monads, with perforate or psilate ornamentation. Dinizia, Pentaclethra and Aubrevillea have morphological characters that have suggested either a mimosoid or caesalpinioid placement. Dinizia pollen is in permanent tetrads with clavate ornamentation. Pentaclethra pollen grains are monads, two species have tricolporate pollen and the third is porate. Aubrevillea has tricolporate, finely reticulate monads. All ten genera have variable, non‐predictable stigma type and ovule number. The mimosoid Adenanthera group (Adenanthera, Tetrapleura, Amblygonocarpus, Pseudoprosopis, Calpocalyx and Xylia) pollen grains are in 8‐ to 16‐grain polyads. In all Adenanthera group species, the stigmatic cavity is only large enough to accommodate one polyad. In addition, the number of ovules present matches the number of pollen units in one polyad. Polyads have porate, operculate apertures that differ in layout, aperture morphology and development when compared with caesalpinioid and other eudicot pollen. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 594–615.     

Pollen morphology of some selected plant species from Horton Plains,Sri Lanka

The pollen morphology of four species: Gaultheria leschenaultii (Ericaceae), Psychotria zeylanica (Rubiaceae), Rubus leucocarpus (Rosaceae) and Symplocos bractealis (Symplocaceae) from Horton Plains, Sri Lanka was investigated using LM and SEM. Psychotria zeylanica is endemic to Sri Lanka and the other three taxa are common in Horton Plains. Gaultheria leschenaultii has tetrads with 3-colporate, coarsely granular to granulo-rugulate pollen grains; in the polar region and at the colpus margin the exine is smooth with micro-rugulate structure. Psychotria zeylanica has 3- (or 4-) colporate, reticulate-spinulose to granular pollen grains. Rubus leucocarpus has 3-colporate, striate-perforate pollen grains and Symplocos bractealis has 3- (or 4-) colporate pollen grains with a verrucate-perforate exine. Pollen grains of these four species are very indicative of human impact and palaeoclimate.