POLLEN MORPHOLOGY AND SYSTEMATICS OF SIPHONOGLOSSA SENSU LATO (ACANTHACEAE)

Pollen morphology of 15 species of Siphonoglossa and of two closely related groups was investigated. Two tribal-specific pollen types are found within Siphonoglossa sensu lato suggesting that the genus is artificial, composed of taxa belonging in several genera among two tribes (subtribes sensu Bremekamp) of Acanthaceae. Five taxa currently included in an informal subgeneric category of Siphonoglossa have tricolporate, prolate pollen (termed Type I) that is characteristic of Odontonemeae (= Odontoneminae, Justicieae). Pollen of the remaining taxa, belonging in two formal sections of the genus, are mostly 2-porate, bilateral (Type II) with a sexine sculpturing characteristic of Justicieae (= Justiciinae). Pollen of section Siphonoglossa is rather uniform, 2-porate, bilateral with lolongate pores, and seem to delimit a natural group. Taxa of section Pentaloba have a more heterogeneous pollen morphology, mostly 2-porate, bilateral with lalongate pores. Controversial aspects of the interpretation of pollen morphology in Justiciinae are presented and their relevance to this study are examined. Hypothetical trends in the evolution of pollen of Justiciinae are discussed and the application of pollen morphology to taxonomy of the genus is presented, including a recommendation for narrowing the generic concept of Siphonoglossa to the taxa of the type section.     

Pollen morphology of endemic species of the Gonospermum Less., Lugoa DC. and Tanacetum L. complex (Asteraceae: Anthemideae) in the Canary Islands (Spain), and its taxonomical implications

The pollen of nine endemic taxa of the Gonospermum Less., Lugoa DC. and Tanacetum L. complex and of T. parthenium L. (introduced species from the Canary Islands) was studied using light and scanning electron microscopy with the aim of extending the knowledge of their morphology and to investigate whether pollen morphology may help clarifying the controversial taxonomy of these taxa. Twenty six populations in the Canary Islands (Spain) were studied and the following parameters were measured: polar axis (P), equatorial diameter (E), polar exine thickness (Ex1), length (L) and thickness (A) of the spines in the meridional optical section, exine thickness at the centre of the mesocolpium in the interapertural area (Ex2) and distance between spines (De) in the equatorial optical section. The studies show that the pollen of the three genera is very similar regarding shape, apertures, and ornamentation, but may be distinguished by size and exine thickness.     

Pollen exine ornamentation in the F2 generation of an interspecific hybrid of Chorisia (Bombacoideae,Malvaceae) in relation to inheritance pattern

Pollen morphology in ten plants of F₂ progeny of an interspecific tree hybrid, Chorisia insignis H. B.& K.×C. speciosa St. Hil (Bombacoideae, Malvaceae) has been studied with a view to have an insight in to the effect of hybridization on the pollen morphological features in F₂ generation. The study is a sequel to an earlier study on the pollen morphology of Chorisia species and their F₁ hybrid, in which case the hybrid pollen uniformly exhibited the apertural features of the male parent and exine features of the female parent. In the F₂ progeny the pollen grains display the apertural feature of the male parent in all the plants. However, with regard to exine ornamentation, variability has been observed. Of the ten plants, two plants exhibit the exine features of the male parent showing empty lumina (without bacula), five plants have their pollen exactly like that of the F₁ plant (showing prominent columellar heads in the lumina of the apocolpium region) and the remaining three plants showing columellae in lumina of both apocolpium and mesocolpium region being different from the above types. It has been inferred that the variability in the exine pattern in F₂ pollen indicates that the pollen exine pattern in hybrids, perhaps, is not unequivocally controlled by sporophytic or gametophytic genomes.     

Pollen morphology inParis and its related genera

Pollen grains ofParis, Medeola, andScoliopus have been examined with light, scanning electron, and transmission electron microscopies.P. quadrifolia L.,P. verticillata Bieb.,P. delavayi Franch. andP. polyphylla Smith have monosulcate pollen characterized by psilate, foveolate or reticulate exine sculpture. In contrast to the former species,P. japonica (Fr. et Sav.) Franch. andP. tetraphylla A. Gray have monosulcate pollen with gemmate (rarely rugulate) exine.Medeola has monosulcate pollen with reticulate exine that is distinct from that ofParis. Scoliopus has monosulcate pollen characterized by a peculiar reticulate exine pattern. The palynological evidence suggests thatParis andTrillium are closely related to each other, andMedeola andScoliopus should be separated fromParis andTrillium.     

何首乌不同种质花粉形态及进化趋势研究

采用电镜扫描法,对48份何首乌种质的花粉形态进行了观察和分析。结果表明:何首乌花粉形状主要为椭球形,少量为长椭球形和近球形,部分种质花粉形状正处于椭球形向长椭球形进化的阶段;极面观主要为三裂圆形,部分种质的变异为半球状、四边形、凹陷状或平三角形;赤道面观主要为椭圆形,部分种质为三角形或四边形;萌发沟3条,狭长,几达两极,部分种质的1条或2条萌发沟中部或近极端处隆起,2条或3条萌发沟在极端处相交;表面纹饰为穴状,部分种质的穴中出现小孔。研究结果表明,何首乌物种正处于活跃进化阶段且因区域及生境的差异其进化速度不一致,低纬度地区的种质进化程度较高纬度地区的高,其最初的起源中心可能位于高纬度地区,在向低纬度地区迁移过程中其花粉形态发生了不同程度的变异。     

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.     

Morphology and variability of pollen of the genus <Emphasis Type="Italic">Spiraea</Emphasis> L. (Rosaceae) in Siberia and the Far East

Pollen of 12 species of the genus Spirea L. growing in different regions of Siberia and the Far East was investigated. The ultrasculpture of pollen grains is described. On the basis of aperture morphology and exine sculpture, pollen grains are typified, with key indices given for their identification. The species of the Spiraria section are distinguished by large grains. Pollen grains of S. media and S. alpina considerably vary in size. The level of natural polymorphism of palynological indices has been established.     

CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

The tubular exine ofLauraceae andHernandiaceae,a novel type of exine structure in seed plants

The pollen grains ofLauraceae andHernandiaceae are characteristic in having a tubular exine of ± microfibrillar structure. This is coated with a layer of medium electron-dense globules and very peculiar spines, made up of a substance differing from that of the exine. Such a pollen wall structure is otherwise unknown in seed plants and thus adds to the list of odd features erratically present in various taxa of the Ranalean complex.     

Dimorphic exine sculpturing in two distylous species ofDyerophytum (Plumbaginaceae)

Light and SEM observations on the pollen ofDyerophytum africanum andD. indicum have revealed marked differences in exine features. These distylous species also have dimorphic pollen. In the short-styled individuals of both species, the sexine and nexine are of equal thickness, and the clava-like sexinous processes are short without marked projections. In the long-styled individuals, the sexine is thicker than the nexine, the clavae are higher than broad with an apical spinule. Pollen size and apertures are identical in both morphs. — Palynological evidence is presented for relationships betweenDyerophytum andCeratostigma, Plumbago andAegialitis. Moreover, the genusDyerophytum exhibits pollen morphological similarities with some species ofLinum (Linaceae).     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Sippen derOleaceae,Scrophulariaceae, Plantaginaceae undAsteraceae

Different members of the Angiosperm familiesOleaceae, Scrophulariaceae, Plantaginaceae andAsteraceae with variable modes of pollination were studied in relation to ultrastructure of pollenkitt and exine. In entomophilous representatives the mostly electron-dense and homogeneous pollenkitt is located on the outside layer of the exine, making the pollen sticky. In related anemophilous taxa the pollenkitt mostly is electrontransparent and inhomogeneous; it becomes inactive by remaining in the loculus or sinking to the bottom of the exine caves; this makes the pollen powdery. According to such criteria,Fraxinus ornus andRhinanthus serotinus are entomophilous, whileFraxinus excelsior is anemophilous. The pollen ofLathraea squamaria eventually becomes powdery and suited for wind dispersal. The broad transition field between entomo- and anemophily is demonstrated byPlantago andArtemisia. Plantago lanceolata is anemophilous, whilePl. serpentina andPl. media are amphiphilous.Artemisia nitida andA. mutellina are entomophilous,A. absinthium, A. pedemontana andA. gabriellae are amphiphilous, but tend towards entomo- (A. absinthium) or anemophily (A. gabriellae), whileA. chamaemelifolia and especiallyA. vulgaris are anemophilous.

     

Polarity, aperture condition and germination in pollen grains ofEphedra (Gnetales)

Pollen grain polarity, aperture condition and pollen tube formation were examined inEphedra americana, E. foliata, E. rupestris, E. distachya, andE. fragilis using LM, SEM and TEM. In the characteristic oblate pollen, as seen in situ in the tetrad configuration, the polar axis is the minor one and the equatorial plane runs between the two narrow ends of the microspore. The intine is thick in fresh fixed mature pollen but we have seen no indication of regions having an exceptionally thick intine that could be considered associated with an aperture or apertures. About three minutes after transferring fresh pollen to the germinating medium the ridged exine splits and twists away from the intine and its enclosed protoplast. The shed exine spreads out and curls into a scroll-like configuration that is as distinctive as that of the pollen shape had been but now having the ridges and valleys perpendicular to the long axis. The pollen tube develops, in our experience with more than a hundred germinating pollen grains, near one of the narrow tips of the pollen grain's equatorial plane. The location of the pollen tube initiation probably is related to the position of the tube cell nucleus. The pollen tube starts to grow about one hour after the exine was shed. The pollen tube emerges close to the narrow end (equator) of the gametophyte. This end emerged first as the exine is shed and is opposite to the prothallial cells. The stout pollen tube is c. 10µm in diameter grown in vitro on agar. In our germination medium the stout tube continued to elongate for about 24 hours reaching a length of c. 100 µm. With respect to exine morphology the aperture condition could be considered as inaperturate. The pollen tube, however, is formed in a germination area near one end of the exineless gametophyte.     

Systematic significance of tepal surface morphology in tribes Persicarieae and Polygoneae (Polygonaceae)

In order to improve understanding of the systematic relationships between taxa and of tepal-pollinator and tepal-habitat relationships, a detailed scanning electron microscopy (SEW study of the adaxial tepal surface of 135 taxa belonging to c. 14 genera in the tribes Persicarieae and Polygoneae (Polygonoideae-Polygonaceae) was carried out. The tepal surfaces have revealed some striking differences among the genera studied. Three main patterns of sculpturing and cell shape can be recognized. Type I: mostly rectangular to elongate cells with straight or undulating anticlinal walls; the cuticles smooth or striate in longitudinal direction and often continuous (Persicaria, Bistortu, Aconogonon, Koenigia and some species of Fagopyrum). Type II: irregular tesselated to elongated cells, rarely rectangular with mostly sinuate anticlinal walls; the cuticles rarely with longitudinal striation, but with strong orthogonal to reticulate ridges or striae, often without correlation between cells (Polygonum s.s., Polygonella, Fallopia, Parapteropyrum, Pteropyrum, Atraphaxis and Calligonum). Type III: mostly irregular, mammilliform, papillose cells with either longitudinal tightly pressed or randomly ridged cuticles (some species of Fagotyrum and Oxygonum). The present data generally support the division of Polygoneae and Persicarieae by Ronse Decraene & Akeroyd. The mammilliform, papillate epidermis of tepals in Oxygonum and some Fagopyrum is probably well-adapted to entomophily either as a foothold or even as a light-trap, and also shows some correlation with heterostyly. It is noteworthy that the tepal structure of Polygonella (tesselated form) is highly similar to that of Polygonum s. s. (especially P. sect. Duravia). Cuticular striation alone does not appear to have much systematic value, but has a mechanical function in affording extra strength to the cell walls. Some correlations between the degree/shape of cuticles and the pollination mechanisms or the habitat of each taxon are also briefly discussed. It is concluded that the studied tepal characters can be useful in improving the classification of tribes Persicarieae and Polygoneae, arid give additional support at the infrageneric level.     

Relationships of pollen size,pistil length and pollen tube growth rates in Rhododendron and their influence on hybridization

Summary Pollen size and pistil length data have been collected for 93 species of Rhododendron (Ericaceae) belonging to a number of different subgeneric taxa. For a sample of eight species in section Vireya, pollen tube growth in the style after selfor interspecific pollination has been quantified. Pollen volume and the time taken for pollen tubes to reach the ovary were both related to pistil length. Pollen-tube growth rates were generally greater for species with longer pistils and larger pollen. Increasing temperature increased the rate of pollen-tube growth. There was no detectable effect of pollen tube density on tube growth rate in the style. After interspecific pollinations tube growth rates in foreign styles could be faster or slower than in self styles. A semisterile individual with two viable pollen grains per tetrad and a plant grafted as scion to a longer-styled stock both showed more rapid pollen-tube growth than expected on the basis of pistil size. Data collected for 26 species in section Vireya showed that where extreme disparity of pollen/pistil size causes failure of interspecific crosses, one or more bridging species with intermediate pollen/pistil size can generally be selected.     

Pollen morphology and localization of Ni in some Ni-hyperaccumulator taxa of Alyssum L. (Brassicaceae)

Pollen morphology of seven Alyssum L. taxa growing on serpentine soils in different places in the European Mediterranean macrobioclimate territory were studied, described and compared. Cluster analysis was performed to show similarity between species and their populations. The shape of the pollen grains varies among the species and among the grains within the same anther. The pollen grains are 3-colpate, prolate, with long and narrow colpi reaching the poles. The ornamentation of the exine varies from micro-reticulate to reticulate between the species. Pollen sterility/fertility was also calculated. The highest percentage of sterile pollen (73.76%) was calculated for Alyssum murale subsp. murale and the lowest (9.54%) for A. bertolonii subsp. bertolonii. All species are representatives of sect. Odontarrhena (C.A. Meyer) Koch well known as Ni-hyperaccumulators. Nickel and other elements present in pollen and stamen were studied by inductively coupled plasma-mass spectrometry. The stamen parts of all species were micromorphologically analyzed by scanning electron microscopy coupled to an energy-dispersive X-ray probe. Accumulation of Ni was detected in the stamens of all studied species and rarely in the pollen grains. The distribution patterns of Ni were similar among the species examined.     

Embryology ofCrocus thomasii (Iridaceae)

The embryology ofCrocus thomasii is described. Male meiosis is of simultaneous type, and gives rise to starchy microspores which develop into lipoid pollen grains; these are two-celled and show a spinulate acolpate, abaculate exine lacking apertures. The tapetum is glandular and its cells become bi- or sometimes multinucleate. The ovule is anatropous and bitegmic; the inner integument forms the micropyle. Megasporogenesis is heteropolar with starch accumulation in the functional chalazal megaspore. Embryo sac development conforms to thePolygonum type. The endosperm development is nuclear. The embryo develops according to the Caryophyllad type. In the ripe seed it is differentiated and enveloped by a starchy cellular endosperm. The embryological characters observed strongly favour a close relation betweenC. thomasii andC. sativus.     

Pollen morphology in Asiatic species ofTrillium

Pollen grains of five species and two interspecific hybrids ofTrillium from eastern Asia have been examined with scanning electron and transmission electron microscopy. All species from eastern Asia, excludingT. govanianum, are characterized by inaperturate pollen and an unstratified and granulated exine structure. Pollen of the Himalayan species,T. govanianum, is, however, monocolpate and intectate. The palynological evidence suggests that the Asiatic species, excludingT. govanianum, are closely related to each other and toT. erectum in North America, andT. govanianum is independent of the other species in the genus.     

两栖蓼的分子系统学研究

两栖蓼是一种水陆两栖植物,植株在不同生态环境下外部形态差异较大,同时两栖蓼的系统位置存在争议,被归入春蓼组(sect.Persicaria)或提升为两栖蓼组(sect.Amphibium)。该文选取两栖蓼及春蓼组植物12种,以及刺蓼组、头状蓼组、神血宁组、拳参组、萹蓄组和外类群掌叶大黄共23种植物进行研究。植物总DNA的提取采用改进的CTAB法,所测序列以及从Genbank数据库下载的序列,以掌叶大黄为外类群,采用最大简约法和贝叶斯法对核糖体ITS序列和叶绿体trn L-F序列进行了系统发育分析。ITS序列对位排列的长度为735 bp,包括489个可变位点,272个位点是信息位点。简约法得到9个简约树,步长为1 084,CI指数为0.680,RI指数为0.614。trn L-F序列对位排列的长度为1 121 bp,包括427个可变位点,239个位点是信息位点。简约法寻找到9个简约树,步长为551(CI=0.911,RI=0.910)。贝叶斯法和简约法得到的树基本一致。分子序列分析结果显示,trn L-F序列树类似于ITS序列树。ITS序列构建的发育树上,两栖蓼与刺蓼组植物、春蓼组其他植物形成3个并列的分支;在trn L-F序列树上,两栖蓼则与其他春蓼组植物形成两个并列的分支。由此可见,两栖蓼与春蓼组其他植物的亲缘关系较远,成一独立的分支。两个分子证据支持将两栖蓼提升为两栖蓼组的处理意见。此外,两栖蓼的花粉具散沟,与典型的春蓼组的具散孔花粉不一致。再加上两栖蓼水陆两栖的特性,因此支持把两栖蓼提升为两栖蓼组的观点。两栖蓼组的界定为多年生草本,水陆两栖,根状茎横生,生于水中茎漂浮,叶长圆形或椭圆形,生于陆地茎直立,叶披针形或长圆状披针形,托叶鞘为筒状、薄膜质,总状花序穗状,瘦果近圆形,花粉具散沟。     

COMPARATIVE POLLEN MORPHOLOGY AND TAXONOMIC AFFINITIES IN CYCADALES

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat-shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro- and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity between Encephalartos, Lepidozamia, and Macrozamia is recognized. Pollen characteristics of the genus Bowenia show some similarity with those of the latter group. Except for two species of Macrozamia which are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genus Dioon exhibit a unique morphology but are more similar to Stangeria than they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguish Dioon from Stangeria. Ceratozamia and Zamia share a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ from Microcycas in sexine thickness, gross morphology and chromosome numbers. The pollen grains of Cycas circinalis and C. revoluta differ in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.     

绣球属(Hydrangea L.)及近缘属花粉形态的研究

为深入研究绣球属植物花粉形态的分类学价值和系统学意义,厘清绣球属与近缘属之间的系统发育关系,该文利用扫描电子显微镜(SEM,scanning electron microscope)对国产绣球属及其近缘属41种绣球花科(Hydrangeaceae)植物的花粉形态以及表面纹饰进行了观察。结果表明:绣球属及其近缘属的花粉为三孔沟;形状多数为长圆体形或近球体形;赤道面观为椭圆形或圆形;极面观多为圆形,少数为三角形或圆三角形。花粉外壁纹饰可分为网状和孔穴状。网眼内的三级纹饰可分为光滑和具颗粒状突起。根据花粉形状和外壁纹饰类型将上述物种划分为4个组,即花粉的形状为长圆体形,表面纹饰为孔穴纹饰;花粉的形状为长圆体形,表面纹饰为网状纹饰;花粉的形状为近球体形,表面纹饰为孔穴纹饰;花粉的形状为近球体形,表面纹饰为网状纹饰。以上可进一步细分为8个类型。上述表明花粉形态证据可为绣球属及其近缘属的属下分类和种间界定提供重要佐证;但结合前人的系统发育重建分析该属植物花粉形态的系统学意义相对有限,如花粉形态证据对于该属及其近缘种属系统发育树上大支的界定难以提供有力的证据。