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 Dioscorea (Dioscoreaceae) and its relation to systematics

This paper adds new data on the pollen and orbicule morphology of 61 Dioscorea L. (Dioscoreaceae) species to the survey of Schols et al . (2001). The results indicate that pollen characters may be significant in infrageneric systematics in Dioscorea . Pollen and orbicule characters are described based on observations with light microscopy, and scanning and transmission electron microscopy, and are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly disulculate (sometimes monosulcate) with a perforate, microreticulate, striate, gemmate, rugulate, or cerebroid perforate sexine. The basal section Stenophora is one of the few sections with monosulcate pollen. Brachyandra , Cardiocapsa , and Seriflorae , three Malagasy sections, are characterized by striate pollen. Pollen morphology strongly supports section Enantiophyllum as a monophyletic group. The correlation between pollen size and tuber type, as suggested previously by P. Su (1987), is confirmed by our data. As found in our earlier survey, orbicules in Dioscorea are mostly spherical with a smooth or spinulose surface.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 375–390.     

EXPERIMENTAL HYBRIDIZATION,CHROMOSOMAL DIVERSITY,AND PHYLOGENY WITHIN GAURA (ONAGRACEAE)

Patterns of interfertility for intersectional hybridizations in Gaura are generally consistent with current taxonomic hypotheses regarding the sectional division of the genus. Crossability is generally lower for intersectional crosses than for intrasectional, interspecific crosses. Average intersectional cross-success ranged from 0–14% among the eight sections, and a total of 54 intersectional hybrids were produced from 1,872 intersectional pollinations. Low rates of capsule-set and no intersectional hybrids were produced by G. mutabilis (section Gauridium), an early offshoot of a primitive ancestor of Gaura. Two species of section Xerogaura that are regarded as relicts of the primitive ancestor of all other Gaura showed low averages for cross-success, but did produce hybrids in combination with three relatively advanced sections (Campogaura, Stipogaura, Pterogaura). Low capsule-set and no intersectional hybrids were produced by G. parviflora (section Schizocarya). Extreme morphological specialization for autogamous reproduction has been accompanied by reproductive isolation of G. parviflora. Only three hybrids resulted from crosses using G. coccinea (section Campogaura), a polyploid complex. Each successful cross paired G. coccinea with a putative progenitor, either a species of section Xerogaura or G. villosa of section Stipogaura. Hybrids of G. coccinea with odd ploidy number showed reduced pollen staining. Species of Stipogaura produced only three hybrids, one each in combination with species of sections Xerogaura, Campogaura, and Pterogaura. Gaura drummondii (section Xenogaura) registered the highest average cross-success despite being a tetraploid. All 25 hybrids of G. drummondii resulted from crosses with G. suffulta, and were triploids that showed reduced pollen staining. Intersectional crosses fail to support the hypothesized relationships of G. drummondii either to G. coccinea or to species of section Stipogaura. Section Gaura produced moderate averages of cross-success, but all 20 hybrids resulted from crosses with G. suffulta. Fifty of the 54 intersectional hybrids were descended from a species of section Pterogaura. Crosses that used G. suffulta as one parent produced 49 of these hybrids. Four hybrids were from crosses with G. macrocarpa (section Xerogaura), and the remaining 45 were due to the recurrent success of crosses that paired G. suffulta as maternal parent with either G. drummondii or a species of section Gaura.     

The Restoration of the Genus Cyclocodon ( Campanulaceae) and Its Evidence from Pollen and Seed-coat

The genus Cyclocodon Griff. was reduced by C. B. Clarke in 1881 into a section of the genus Campanumoea. Our LM and SEM observations on pollen morphology show that the pollen of all the three species in the former is 3-colporate with the exine sparsely high-spinulose, whereas that of the two species in the latter is 5～8-colpate with the exine relatively densely short-spinulose. SEM observations on seed-coat indicate that the primary ornamentation of the seed-coat of the two species in Campanumoea (s. str. ) is characterized by regular and polygonal areoles which are much larger than the radial walls in diameter and by the bead-like secondary ornamentation on the radial walls, while that of the three species in Cyclocodon is characterized by irregular-shaped areoles which are nearly equal to the radial walls in diameter and by the rope-like secondary ornamentation on the radial walls. Thus, the pollen morphology is closely correlated with the seed-coat morphology. Taking the characteristics of pollen, seed-coat and gross morphology into consideration, the genus Cyclocodon is restored, separate from Campanumoea (s. str. ). One new combination, Cyclocodon celebicus (B1.)Hong, is made in the present paper. The genus Cyclocodon is con-sidered closely related to Platycodon rather than to Campanumoa.     

Characteristics of pollen from natural triploid Betula hybrids

Birch has a key role in the Holocene vegetation history of northern Europe and in sub‐arctic climates dwarf birch and tree birch co‐exist. In Iceland, triploid hybrids between diploid Betula nana (dwarf birch) and tetraploid B. pubescens (downy birch) are common and therefore likely to contribute to pollen deposition. Pollen from 22 triploid trees/shrubs from ten woodlands in Iceland was examined and its size and shape compared with pollen from the parental species. The mean diameter of pollen grains from the triploid hybrids was not statistically different from that of B. nana pollen, but was significantly smaller than the mean value of B. pubescens pollen. On the contrary, the size of the vestibulum was similar to that of B. pubescens, which was significantly greater than that of B. nana, and therefore the diameter‐pore depth ratio was lower than the values from either species. The pattern of size distribution within plants indicated that triploid hybrids might have produced two sizes of triporate pollen grains, but the small B. nana size was far more prevalent than the larger B. pubescens size. Several anomalies in pollen morphology were common among the hybrid pollen grains: four or more pores were the most frequent type of abnormality. Characteristics of the pollen of triploid Betula hybrids, especially structural anomalies, may provide a means to reveal periods of interspecific hybridisation in the analysis of sub‐fossil pollen.     

The evolution of pollen heteromorphism inViola: A phylogenetic approach

Pollen heteromorphism, defined here as the production within all flowers of a plant of several pollen morphs differing in aperture number, is common in angiosperms. We have focused on the evolution of pollen heteromorphism in the genusViola, in which about 1/3 of the species are pollen-heteromorphic. We have studied the distribution of pollen heteromorphism in the genusViola using a molecular phylogeny based on ITS sequence data. We show that pollen heteromorphism has evolved independently at least six times inViola. A comparative analysis shows that the occurrence of pollen heteromorphism is correlated with sporophytic polyploidy in all sections of the genus apart from sectionMelanium. This section differs from all other sections on several aspects such as flower morphology, absence of cleistogamous flowers, and a high proportion of heteromorphic species. We discuss the possible adaptiveness of pollen heteromorphism in this section.     

国产黄耆属簇毛黄耆亚属花粉形态及其系统学意义

观察了国产黄耆属簇毛黄耆亚属6组12种植物的花粉形态。这些花粉的外壁表面纹饰可分为网状纹饰,穿孔或小沟渠状,以及穴网状纹饰3种类型。所有种类都具三孔沟的萌发孔,根据内孔明显与否可分为两类。虽然萌发孔类型与分组并没有严格的对应关系,但综合一些花粉特征,仍然发现6个组间花粉形态差异较为明显,与一般的形态差异有一定的对应性。特别是Sect．Robusti比较特殊,根据花粉大小等特征,推测它和Sect.Phyllolobium等有可能是本亚属的原始类群。Sect.Sesbanella的两个近缘种Astragalus heydei和A.hendersonii,花粉形态却很有区别。Sect.Bibacteola种类较多,有24种,花粉形态呈多样性。总之,花粉形态在簇毛亚属中具有一定的系统学意义。     

Pollen morphology of Euphorbia caputmedusae

A particular pollen type is observed in the species Euphorbia caputmedusae which is distributed in South Africa. The exine of this pollen is clearly rugulose and beset with coarse granules. In addition 10 to 25% of the pollen grains are heteropolar and have a characteristic aperture type which is something between tricolporate and parasyncolpate. The pollen morphology of this species gives grounds for suggesting its removal from the section Euphorbium to a separate section, as suggested by Carter (1988).     

ARTIFICIAL INTERSPECIFIC HYBRIDIZATION IN RUELLIA (ACANTHACEAE)

Observations were made on the morphology, seed fertility, pollen viability and meiotic configurations of 22 different interspecific hybrids of 12 North American taxa representative of 3 sections of Ruellia. The hybrids were classified as (1) fully vigorous and fertile; (2) vigorous but with reduced fertility; (3) reduced vigor and fertility; (4) weak and sterile. Hybrids showed meiotic irregularities in microsporogenesis: univalents, chains, precocious separation of bivalents, nondisjunction, and micronuclei were commonly observed. Interspecific pollinations within sect. Dipteracanthus resulted in fertile or partially sterile F₁ hybrids. Intersectional crosses produced partially or completely sterile hybrids or failed. Assuming that crossability is correlated with degree of evolutionary relationship, the parental species are interpreted in genecological terms to be grouped in polytypic ecospecies. Hybridization experiments doubtless would be of value in clarifying relationships in tropical and subtropical species of Ruellia.     

Pollen discounting and the evolution of selfing in Arenaria uniflora (caryophyllaceae)

Although most models of mating system evolution assign a central role to the male transmission advantage of selfing genotypes, empirical data on the male fitness consequences of increased self-pollination are still uncommon. Here, I use measures of pollen import and export by focal plants in genotyped arrays to investigate the effects of floral morphology and pollination environment on self and outcross male function. Plants from an autogamous population of Arenaria uniflora (Caryophyllaceae) exhibit complete pollen discounting relative to closely related outcrossers, as do morphologically intermediate F1 hybrids between the two populations. However, the low cumulative male fitness of hybrids probably results from reduced pollen number or competitive ability, rather than a nonlinear relationship with floral morphology. When surrounded by selfers, plants from the outcrosser population self-fertilize at nearly the same rate as selfers (>80%), but have much lower self male fitness due to reduced fruit set. Because outcross siring success is also extremely low (<8%) in this treatment, these mate-limited outcrossers are at male fitness disadvantage to both pseudocleistogamous selfers and nonlimited outcrossers. The relative male fitness of plants with different mating systems appears dependent on the ecological context, as well as on morphological trade-offs.     

Variation inHieracium subgen.Pilosella (Asteraceae): What do we know about its sources?

The present paper reviews mechanisms producing complicated patterns of variation withinHieracium subgen.Pilosella. The taxonomic complexity of this subgenus is due to highly variable basic species and intermediate (hybridogenous) species. The most important sources of variation are polyploidy, hybridization and (mostly) facultative apomixis of the aposporous type. The combination of hybridization, apomixis and clonal growth leads to the maintenance of various hybrids having originated from backcrossing and hybridization among more than two species, which is possible because of the fertile pollen of apomictic hybrids. Ever since Mendel’s experiments, some of F₁ hybrids have been found to be highly variable, probably reflecting the high heterozygosity of some of the basic species. Variable progeny can also result from unreduced gametes, or the rare parthenogenetic development of reduced gametes. While these processes were detected in experiments, their role within field populations remains unknown. However, multiple origins of intermediate species, and introgression within basic species are highly likely to result in high levels of variation. While few population level studies have been undertaken in Europe, several such studies have been carried out on adventive populations in New Zealand, and these show a different pattern. Aneuploid plants, rare in Europe, are common in New Zealand, and there is frequently more than one ploidy level within a population.     

厚朴基原植物及其4个近缘种的花粉鉴定

采用扫描电镜对2种厚朴基原植物(厚朴Magnolia officinalis Rehd.et Wils.、凹叶厚朴M.officinalis Rehd.et Wils.var.biloba Rehd.et Wils.)及4种近缘植物(玉兰M.denudata Desr.、紫玉兰M.liliiflora Desr.、望春玉兰M.biondii Pampan.、荷花玉兰M.grandiflora L.)的花粉形态、表面纹饰和大小进行了观察研究。结果显示:(1)6种植物的花粉粒均为单粒,具远极单萌发沟,沟长,直达两端,左右对称,异极;侧面观均为舟形,两端较尖,赤道面观为椭圆形或近椭圆形,极面观均为近圆形;外壁均具小穴状或网状纹饰。(2)厚朴的小穴状纹饰小而浅,不明显;凹叶厚朴的小穴状纹饰小但较深,也不甚明显;相比之下,紫玉兰、玉兰、望春玉兰和荷花玉兰的花粉粒表面密布不规则隆起及深穴点,明显。(3)6种植物花粉粒由大至小依次为:荷花玉兰凹叶厚朴厚朴玉兰紫玉兰望春玉兰。3种不同的花粉处理方法中,自然干燥法能清晰地观察到花粉的扫描电镜特征,此方法优于戊二醛固定法和叔丁醇真空冷冻干燥法。本研究结果为厚朴中药资源的基原植物及其近缘种鉴定提供了新的证据,也为现代植物从种及亚种级水平分类提供了参考。     

Pollen Morphology of the Genus Malus and Its Taxonomic and Evolutionary Significance

The pollen morphology of 26 species and 5 hybrids of the genus Malus was investigated with aid of SEM. It is found that the pollen morphology of Malus is rather similar in shape, size, position and number of aperture and exine sculpture. The characters of polle morphology of sections and series are as follows: Sect. Malus Ser. Baccatae: Striae regular, parallel to colpi, and conjunct at pole; Ser. Pumilae: the same as in Ser. Baccatae, but more or less curved near pole. Sect. Docyniopes: Striae regular and parallel to colpi, but bent near pole. Sect. Chloromeles: Striae irregular, dense and interlock. Sect. Sorbormalus: Striae irregular, sparse and not interlock. Ser. Sieboldiance: pollen grains prolate, with perforation among striae, colpi narrow; Ser. Kansuenses: Pollen grains spheroidal, colpi wide in the middle but narrow at both ends, striae relatively dense and regular, mostly dichotomous, perforation present; Ser. Yunnanenses; Pollen grain spheroidae, colpi wide in the middle but narrow at both ends, striae obviously irregular, less dichotomous, perforation absent. The major evolutionary trend of exine sculpture of pollen may be from densely thin-striate to sparsely striate with perforation. Characters of the exine sculpture of hybrids can be used to recognize the rela-tionship between the parental species.     

Pollen morphology in Primula sect. Carolinella (Primulaceae) and its taxonomic implications

Pollen morphology in Primula section Carolinella has been investigated for the first time. Seven of the nine species constituting the section were available for study, i. e., P. cardioeides, P. chapaensis, P. intanoensis, P. kwangtungensis, P. kweichouensis, P. partschiana , and P. rugosa, A considerable variation in pollen morphology was found among the investigated species, particularly in number and arrangement of the apertures. Pollen of different species were either tricolpate, tricolporate, trisyncolpate, or polycolpate. Within Primula , the section Carolinella is diagnosed by having calyptrate capsules and leaves with revolute vernation, but the variation in pollen morphology indicates that this group is heterogeneous, and that either polycolpate pollen or a capsular lid has evolved more than once in the genus Primula.     

Predicting patterns of mating and potential hybridization from pollinator behavior

Hybridization in flowering plants is determined in part by the rate at which animal pollinators move between species and by the effectiveness of such movements in transferring pollen. Pollinator behavior can also influence hybrid fitness by determining receipt and export of pollen. We incorporated information on pollinator effectiveness and visitation behavior into a simulation model that predicts pollen transfer between Ipomopsis aggregata, Ipomopsis tenuituba, and hybrids. These predictions were compared with estimates of pollen transfer derived from movement of fluorescent dyes in experimental plant arrays. Interspecific pollen transfer was relatively uncommon in these arrays, whereas transfer between hybrids and the parental species was at least as common as conspecific transfer. Backcrossing was asymmetrical; I. aggregata flowers frequently received mixed loads of hybrid and conspecific pollen. The simulation suggests that these patterns of pollen transfer are largely explained by the visitation sequences of hummingbird and insect pollinators, with little contribution from mechanical isolation. Pollen receipt by hybrids exceeded that of both parental species in a year when pollinators preferred to visit F(1) and F(2) hybrids and was intermediate in another year when they preferred to visit I. aggregata. This suggests that natural variation in pollination may produce spatiotemporal variation in hybridization and hybrid fitness.     

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.     

Comparison of Nicotiana tabacum and Nicotiana nesophila hybrids produced by ovule culture and protoplast fusion

Summary Somatic hybrids were produced between Nicotiana tabacum and N. nesophila, two species incapable of conventional sexual hybridization. Sexual hybrids, though, could be produced between these two species by using ovule culture only when N. nesophila was female. Clones of somatic hybrids were compared with sexual hybrids. Statistically significant variation was observed between clones, but not between sexual hybrids, for pollen viability, flower morphology, leaf morphology, and trichome density. As all clones of somatic hybrids have 96 chromosomes, the variability could not be explained by interclonal variation in chromosome number. Variation between somatic hybrids could be the result of cytoplasmic segregation or recombination, mitotic recombination or small chromosomal rearrangements prior to plant regeneration. Variation between clones could be exploited as these interspecies hybrids are now being used to incorporate disease resistance into cultivated tobacco.     

POLLEN TUBE GROWTH AND INCOMPATIBILITY FOLLOWING INTRA- AND INTER-SPECIFIC POLLINATIONS IN LILIUM LONGIFLORUM

The growth of pollen tubes of a sampling of Lilium species in styles of L. longiflorum incubated at 24 C for 48 hr after pollination indicated two types of interspecific incompatibility. Pollen tubes of two self-compatible species of section Leucolirion, the section including L. longiflorum, stopped growth abruptly upon reaching the stylar canal, were of abnormal morphology, and were incapable of continued growth with longer incubation. Pollen tubes of self-compatible or self-incompatible species of sections Sinomartagon, Pseudolirium, Liriotypus, and Daurolirion approached but did not exceed the length of intraspecific incompatible pollen tubes in styles of L. longiflorum. Pollen tube morphology was normal and tubes were capable of continued growth with additional incubation. Unilateral interspecific incompatibility occurred in reciprocal crosses between self-incompatible L. longiflorum and self-compatible L. regale and L. formosanum, but exceptions occurred in Aurelian hybrids. Incubation of interspecifically pollinated L. longiflorum styles at 39 C, which removes the self-incompatibility reaction, had no effect on interspecific incompatibility.     

Studies on the Pollen Morphology and Seed Coat of the Genus Cistanche (Orobanchaceae) in China

In the present paper pollen grains of 5 species and seed coat of 4 species of the genus Cistanche (Orobanchaceae) from China were examined by scanning electron microscope As a result, two types of the pollen exine sculpture are distinguished: (1) tuberculate, C. salsa and C. lanzhouensis; (2) rugulate or fine reticulation formed by the fusion of rugae, C. sinensis, C. deserticola and C. tubulosa. Chinese Cistanche was classified into two sections based on the gross morphology by the present author (Zhang, 1984). C. lanzhouensis and C. sinensis were included in one section. This classification is in conflict with the pollen type, which indicates that the characters of pollen grains and external morphology in this genus have evolved at different rates. The differences in pollen morphology of Chinese Cistanche can serve as characters for delimitating species. According to our abservation, C. lanzhouenis Z. Y. Zhang differs from the other members of Cistanche not only in external morphology but also in pollen morphology. Pollen grains are subprolate in this species, while prolate in the other four species, and exine sculpture is tuberculate. The present study provides the establishment of this new species (Zhang, 1984) with palynological evidence. The seed coat sculpture in Chinese Cistanche are constantly alveolate, but there are some slight differences, by which the sculpture can be divided into two types: (1) testa cells have or have not thickenings on the inner anticlinal walls; cavernulous sculpture is present on outer periclinal wall of some cells: C. sinensis; (2) testa cells have striate thickenings on the inner anticlinal walls: C. salsa, C. deserticola and C. tubulosa. The characters of seed coatof some significance for the delimitation of species.     

Pollen morphology and phylogenetic relationships in neotropical Phyllanthus (Euphorbiaceae)

In order to provide new insights into phylogenetic relationships among the neotropical taxa of Phyllanthus , 28 illustrations are provided of the pollen grains of 22 selected species studied from 11 sections of the subgenera represented in the neotropics. Special attention has been given to subgenus Conami because of its variability in pollen morphology: of eight species illustrated, the apertures are diploporate colpi in three species and pores in five species; exine ornamentation is vermiculate in two species and pilate in the other six species. The six species in the neotropical sections Pityrocladus and Microglochidion (subgenus Emblica ) are characterized by prolate grains with an increased number of colpi (4–8). Of particular interest are species in which the pollen exine is clypeate (with exine shields); clypeate pollen grains are illustrated in two species of subgenus Xylophylla and in one species of section Cyclanthera that has unique exine shields with single central pila. The pollen of the one Brazilian phylloclade-bearing species illustrated (in section Choretropsis ) has 3-colporate grains with reticulate exine, typical for subgenus Phyllanthus , and very different from the clypeate grains of the West Indian phylloclade-bearing species in section Xylophylla . This pollen evidence clearly demonstrates homoplasy in the origin of phylloclades in Phyllanthus . Pollen morphological data suggest that the neotropical taxa of Phyllanthus have arisen following colonization from Africa (subgenus Kirganelia ) and Asia (subgenus Emblica ). © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 325–338.