The pollen morphology ofOdontites (Scrophulariaceae) and its taxonomic significance

The pollen morphology of 29 species ofOdontites and related genera was examined by light and scanning electron microscopy. Three major pollen types differing fundamentally in exine sculpturing were found. In the parasitic tribePedicularieae retipilate sculpturing is the most widespread type representing a plesiomorphic character state from which the two other types are derived. Of these, reticulate sculpturing is confined toOdontites, whereas a complex retirugulate pattern was found only in the monotypic Near East genusBornmuellerantha. Within the retipilate and the reticulate major types eight minor types were distinguished based on the differential correlation of exine surface morphology, size, shape and amb form. The pollen data are generally well correlated with macromorphological features and furnish important taxonomic characters at the genus—as well as at the specieslevel.     

Polyploid origins in a circumpolar complex in Draba (Brassicaceae) inferred from cloned nuclear DNA sequences and fingerprints

Polyploid evolution has been of major importance in the arctic flora, but rarely addressed on the full circumpolar scale. Herein we study the allopolyploid Draba lactea and its close allies, which form a taxonomically intricate arctic-alpine complex including diploids, tetraploids, and hexaploids. Based on samples from the entire circumpolar area, we inferred the origins of polyploids in this complex using cloned DNA sequences from two nuclear regions (one intron from a gene encoding a second largest subunit in the RNA polymerase family, RPD2, and the ribosomal internal transcribed spacer region, ITS) and DNA fingerprints (random amplified polymorphic DNAs, RAPDs). Although D. lactea and all other polyploids examined in Draba are genetic alloploids showing fixed heterozygosity, the data obtained in the present study suggest that each of the polyploids analyzed here may have originated from a single diploid lineage: hexaploid D. lactea via tetraploid D. lactea from the D. palanderiana lineage (not from the D. fladnizensis and D. nivalis lineages as previously hypothesized), the tetraploid D. turczaninovii from the D. fladnizensis lineage, the tetraploid D. porsildii from the D. lonchocarpa lineage, and a tetraploid here named Draba spB from the D. nivalis lineage. Draba lactea has probably originated several times in the Beringian area, and it is not necessary to invoke complex origins based on a combination of different species lineages as previously suggested.     

THE EFFECTS OF GENOTYPE AND PLOIDY LEVEL ON POLLEN SURFACE SCULPTURING IN MAIZE (ZEA MAYS L.)

Pollen exine sculpturing is a consistent feature of seed plant taxa, yet no mechanism for control of sculpturing pattern has been found. On grass pollen, exine sculpturing takes the form of closely packed spinules. Exine spinules on pollen grains from six maize populations representing all combinations of three genetic backgrounds (single cross hybrids W22 W23, N6 W23, R75 W23) and two ploidy levels (2x, 4x) were examined by scanning electron microscopy. Doubling ploidy levels from 2x to 4x increased pollen diameter (minor axis) with the magnitude of increase related to genetic background. For spinule density, only the effect of genetic background was statistically significant. Spinule density was altered by the genotype of the plant on which the pollen was produced but not by the ploidy level, including genome number and difference in surface area and cytoplasmic volume resulting from chromosome doubling.     

The relation between pollen exine sculpturing and self-incompatibility mechanisms

In angiosperm pollen the reticulate-perforate exine sculpturing is associated with sporophytic self-incompatibility (S.S.I.) and imperforate and microperforate exine sculpturing is associated with gametophytic self-incompatibility. The earliest unequivocal angiosperm pollen conforms to exine morphology of pollen from plants with S.S.I. The orgin of S.S.I. is hypothesized to have coincided with the appearance of what is now the earliest recognizable angiosperm pollen. Other angiosperm characteristics correlated with S.I., functional stigmatic areas, large showy flowers (or aggregated inflorescences), and passive seed dispersal, provide some insight into the biological aspects of the earliest angiosperms.     

Taxonomy of the Genus Oreocharis (Gesneriaceae)

The genus Oreocharis as circumscribed here consists of 27 species including 5 varieties, of which 5 species and 4 varieties are described as new in the present paper. In the work analysed were the external morphology and geographic distribution and examined under SEM were pollen exine of 22 species and seed coat of 16 species. As a result, three types of the corolla, two types of the anther, three types of the pollen exine and three types of the seed coat are distinguished here in the paper. It is discovered that the corolla in the genus is relatively stable, though diverse, and highly correlated with the characters of pollen grains and seeds. The corolla clearly bilabiate but constricted at the throat, occurring in O. auricula, O. cordatula, O. aurantiaca, etc., for an example, is correlated with smooth, reticulate pollen exine and partial tectum and the reticulate and smooth seed coat. For this reason the subdivision of the genus in the paper is mainly based on the characters of the corolla, but combined with those of the anther, pollen and seed coat. The genus is divided into four sections in the present classification. Dasydesmus Craib, based on a single species. O. bodinieri, is reduced here, and the reasons are given. The genus is distributed mainly in the subtropics, and less frequently in the tropics, of China south of 32.5°N and east of 98.5°E, with only two species beyond the border, O. hirsuta in Thailand (only a single locality in Chiengmai) and O. aurea also found in north Vietnam (see Fig. 1, Table 3). Sect. 1. Stomactin (Clarke) Fritsch. Corolla urceolate-tubular, constricted at the throat, with limb distinctly bilabiate; anthers broad-oblong; seed coat reticulate, smooth, rarely minutely tuberculate; pollen exine fine-reticulate, tectum partial and smooth, luminae slightly unequal in size. Sect. 2. Orthanthera K. Y. Pan Corolla campanulate or campanulate-tubular; anthers broad-oblong; seed coat reticulate, muri smooth, rarely spiny-processed; pollen exine fine-reticulate, with partial and smooth tectum and luminae slightly unequal in size, rarely exine insular and fine-tuberculate, tectum perforate. Setc. 3. Oreocharis Corolla thin-tubular; anthers broad-oblong; seed coat densely spinyprocessed, rarely fine-tuberculate; pollen exine insular, densely spiny-processed, rarely finereticulate and smooth, luminae unequal in size. Sect. 4. Platyanthera K. Y. Pan Corolla campanulate; anthers hippocrepiform; seed coat densely spiny-processed; pollen exine fine-reticulate, tectum perforate, luminae small, nearly equal in size. In the section Stomactin, although the constriction of corolla at its throat is a specialized character, the characters of seed coat, pollen grains and anthers are apparently primitive. Therefore it may be said at least that more primitive characters are preserved in the section. In the section Oreocharis, on the contrary, the characters of corolla, seed coat and pollen exine are all advanced. And in the section Platyanthera, the seed coat, pollen (with perforate tectum) and anthers have developed rather specialized characters.     

Pollen morphology of the genus Gagea (Liliaceae) in Iran

Pollen grains of 26 species of the genus Gagea distributed in Iran were examined by light and scanning electron microscopy. Detailed pollen morphological characteristics are given for these species. Among the studied species, the newly described G. iranica together with G. olgae and G. graminifolia possess the smallest pollen grains, and the widely distributed G. lutea the largest ones. Our studies show that the sculpturing of exine provides valuable characters for separating the species, sometimes even for closely related ones, and delimitation of natural groups within the genus. The exine of the genus Gagea is in most cases perforated upon tectum or rarely tectate-columellate. The muri are solid or structured, compound, simpli-, dupli- or pluricolumellate. It seems that the structure of muri is very important in recognizing natural groups within the genus. Tectal perforations vary from <0.2 to 2.0 μm in diameter among the studied species. Regarding sculpturing of the exine in proximal face, four basic types of pollen grains can be distinguished: reticulate, microreticulate, foveolate and perforate. Within the reticulate type there is sufficient variation in exine structure at distal face to describe three subtypes: reticulate, microreticulate and perforate. A diagnostic key is given for all studied taxa based on palynomorphological characters. For a limited number of populations of selected Iranian species of Gagea, further aspects of pollen biology were studied. It seems that populations with ploidy levels other than diploidy, show a low percentage of pollen fertility. Moreover, the rate of pollen fertility is correlated with the manner of the reproduction in certain species.     

Multiple origins of the octoploid Scandinavian endemic Draba cacu minum: electrophoretic and morphological evidence

The octoploid Draba cacuminum (Brassicaceae) is one of the few endemic species in Scandinavia and has frequently been considered an example supporting the glacial survival theory. Two subspecies, ssp. cacuminum in southern Norway and ssp. angusticarpa in northern Scandinavia, have been described and suggested to be geographically diverged remnants of a more continuously distributed ancestor. To test an alternative hypothesis of independent origins of similar octoploids in different areas, we investigated populations of D. cacuminum and its possible progenitors using enzyme electrophoresis and morphological analysis. Electrophoretic analysis of progeny of D. cacuminum revealed high levels of fixed heterozygosity, suggesting that the species is a genetic alloploid. Fixed electrophoretic differences among the populations and additivity of electrophoretic phenotypes indicate that the octoploid D. cacuminum has originated at least three times by alloploidizations involving different populations of the hexaploid D. norvegica and a diploid species, possibly D. fladnizensis. Electrophoretic and morphometric data suggest that populations of D. cacuminum with broad siliculae have originated from populations of D. norvegica that had broad siliculae, and that populations of D. cacuminum with narrow siliculae have originated from populations of D. norvegica that had narrow siliculae. However, the electrophoretic and morphometric variation within D. cacuminum did not correspond to the geographic origin of the populations, and the previously described subspecies could not be recognized. Draba cacuminum gives no relevant information on the glacial survival theory; the polyploidizations may have occurred in postglacial time as well as in pre-Weichselian periods.     

Proteome analysis of diploid,tetraploid and hexaploid wheat: towards understanding genome interaction in protein expression

Hexaploid wheat (Triticum aestivum L.) is derived from a complex hybridization procedure involving three diploid species carrying the A, B and D genomes. The proteome patterns of diploid, tetraploid and hexaploid wheat were analyzed to explore the genome interaction in protein expression. At least two species from each of the diploid and tetraploid were used to compare their proteome maps with a hexaploid wheat cv. Chinese Spring. The ancestral cultivars were selected based on their history of closeness with the cultivated wheat. Proteins were extracted from seed flour and separated by two-dimensional electrophoresis (2-DE) with isoelectric focusing of pH range from 4-10. 2-DE maps of cultivated and ancestral species were analyzed by computer assisted image analyzer. The region of high molecular weight glutenin subunits of hexaploid wheat showed similarity with those of the diploid donors, BB and DD genomes. The omega gliadin, which is controlled by B genome in common wheat, was assumed to have evolved as a result of interaction between AA and BB genomes. The low molecular weight glutenins and alpha and beta gliadin regions were contributed by the three genomes. This result suggests that the function of donor genomes particularly in the expression of proteins in hexaploid wheat is not totally independent; rather it is the product of interactions among the diploid genomes in the hexaploid nuclear constitutions. The expression of nonstorage proteins was affected substantially due to the removal of the D genome from hexaploid constitution. Location of the structural gene controlling one of the alpha amylase inhibitor proteins in the nonstorage protein region was identified in the short arm of chromosome 3D.     

Crossing relationships and chromosome numbers of Nordic populations of Draba (Brassicaceae), with emphasis on the D. alpina complex

101 populations of Nordic Draba were investigated for chromosome numbers and crossing relationships. The populations were referred to 16 currently recognized species of Sect. Draba, Sect. Chrysodraba (including the D. alpina complex with D. alpina, D. oxycarpa, and D. corymbosa), and Sect. Drabella. The chromosome data suggest that all populations and species are homoploid. Three species are diploid, and 13 species are polyploids ranging from tetraploid to 16-ploid. Draba alpina is decaploid, D. oxycarpa is octoploid, and D. corymbosa is 16-ploid. The chromosome numbers of D. micropetala (n = 16,4x) and D. adamsii (n = 24,2n = 48, 6x) of Sect. Chrysodraba and D. cinerea (n = 24, 6x) of Sect. Draba were determined for the first time based on Nordic material. The relationships inferred from the crossing data largely agree with those inferred from previously published molecular data, but correspond poorly to relationships inferred from morphology. Inter-populational F₁ hybrids in D. fladnizensis were entirely sterile, suggesting that this predominantly inbreeding diploid species comprises at least two sibling species, possibly isolated by genic barriers. Sterile to semifertile F₁ hybrids with intermediate chromosome numbers were obtained in 19 interspecific combinations. F₂ hybrids were obtained in seven of these combinations. Both Sect. Chrysodraba and the D. alpina complex are probably polyphyletic. The crossing data suggest that the morphologically very similar polyploids D. alpina (10x) and D. oxycarpa (8x) do not have any diploid progenitors in common, and that Sect. Draba forms an intricate allopolyploid complex that also includes D. alpina and D. corymbosa of Sect. Chrysodraba. Draba corymbosa (16x) is probably an intersectional, polyphyletic alloploid derived from D. alpina (10x) and various hexaploids of Sect. Draba. Crossing data also suggest that D. norvegica (6x) is one of the progenitors of the Nordic endemic D. cacuminum (8x). The phenotypic expression of genes encoding taxonomically important indument characters did not follow consistent patterns in interspecific hybrids. This result may explain the discrepancy between genetic and taxonomic relationships in Nordic Draba, and supports the use of wide taxonomic concepts in this highly reticulate genus.     

Pollen morphology of Solanurn L. section Solanum

J. M. EDMONDS, 1984. Pollen morphology of Solanum L. section Solnnum . The pollen morphology of both dried and fresh, fixed material was examined using SEM. The work confirmed thc spheroidal to sub-prolate shape, the tricolporate nature and the granular surface sculpturing, typical of Solanurn pollen, but failed to demonstrate the occurrence of exine patterns which could bc of practical taxonomic use is differentiating the species belonging to the section Solanurn . Quantification of the exine sculpturing, by means of granule density counts, indicated a possible relationship between this feature and the morpho-genetic diversity of certain species.     

Ploidal levels in the arctic-alpine polyploid Draba lactea (Brassicaceae) and its low-ploid relatives

Ploidal level information is of particular importance in intricate polyploid complexes such as in arctic-alpine Draba . Relative DNA content is reported for the tetra- and hexaploid D. lactea and seven of its low-ploid relatives. Flow cytometry was used to study 200 plants from 93 populations, the screening based on relative fluorescence. Absolute DNA content was determined by Feulgen densitometry for 13 plants from seven species, and reference chromosome numbers were determined in 12 plants (1–3 per species) representing six species. The plants grouped into diploids (2 n  = 16), tetraploids (2 n  = 32), hexaploids (2 n  = 48), and two triploids. Each ploidal level showed a linear increase in relative DNA content, pointing to a relatively recent polyploid origin. The diploid level was confirmed in D. nivalis, D. subcapitata, D. fladnizensis , and D. lonchocarpa. Draba palanderiana , reported previously as di-, tetra- and octoploid, was diploid in all investigated accessions. Hexa- and tetraploids were observed in D. lactea , in approximately the same ratio (8 : 1) as reported previously. The ploidal levels of the Central Asian D. altaica and D. turczaninovii are reported here for the first time as diploid and tetraploid, respectively.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 333–347.     

A Contribution to the Pollen Morphology of Camellia (Theaceae)

The pollen morphology and ultrastructure of 20 species of Camellia (Theaceae) representing the four subgenera were examined. The pollen is tricolporate, spherical to slightly oblate or prolate, with scabrate to rugulate exine sculpturing. The tectum is traversed by perforations that vary in diameter. Pollen wall structure is tectate-columellate, the columellae fused to a footlayer. Endexine is present in all of the taxa examined. The greatest variation was observed in pollen size.     

Evolution of parental ITS regions of nuclear rDNA in allopolyploid Aegilops (Poaceae) species

The genus Aegilops comprises approximately 25 diploid, tetraploid and hexaploid species, in which the genome types of all allopolyploids involve either U or D genome, or both of them. The internal transcribed spacer (ITS) region of 18S-26S nuclear ribosomal DNA (rDNA) from 11 allopolyploid species and 7 related diploid species in the genus were directly sequenced by pooled PCR products. Phylogenetic analyses for tracing evolutionary patterns of parental rDNA in allopolyploid species were performed using the neighbor-joining method. The D genome involved tree included three clades (CC-DDCC, DDMM-DDMMSS-DDMMUU, and MM-MhMh-DDNN), but did not include Ae. squarrosa (DD). It indicated that the rDNA of ancestral D genome had been somewhat differentiated in allopolyploids. The U genome involved tree showed that the allopolyploids and their common ancestor, Ae. umbellulata, formed a clade, suggesting that rDNA in UUMM and UUSS genomes has been homogenizing toward that of ancestral U genome. The phylogenetic pattern of U genome based on ITS sequences also supported the "pivotal-differential" hypothesis.     

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

The pollen morphology of Diosma and Coleonema of the taxonomically problematic subtribe Diosminae (Rutaceae) was investigated to determine its taxonomic relevance. Pollen of 26 of the 28 species of Diosma and of each of the eight species of Coleonema was investigated by LM, SEM and TEM. In pollen of Diosma the exine sculpturing is uniform, and only one pollen type, reticulate, could be distinguished. In contrast, exine sculpturing shows interspecific variation in Coleonema and three distinct types, striate, reticulate and perforate, could be discerned. Species groupings indicated by the pollen types suggest possible relationships between species within Coleonema and with other genera that were not previously apparent. Pollen data support macromorphological evidence that suggests the generic re-classification of the Diosminae.     

The allopolyploid origin of kiwifruit,Actinidia deliciosa (Actinidiaceae)

The genetic origin of kiwifruit (Actinidia deliciosa var.deliciosa) was studied using phylogenetic analysis of DNA sequences derived from the polygalacturonase gene. Results indicate that hexaploid kiwifruit had an allopolyploid origin with the diploidA. chinensis contributing one genome (genome A) and another (as yet unidentified) diploid species contributing a second genome (genome B). The results leave open the question of whether a third, distinct species contributed to the hexaploid kiwifruit genome. A tetraploid race ofA. chinensis is also suggested to be allopolyploid containing genomes A and B.     

茨藻科、角果藻科植物花粉形态的研究

在水生植物茨藻目中,茨藻科Najadaceae和角果藻科Zannichelliaceae植物由于其结构、尤其是花部结构的极度简化和趋同适应,系统关系仍不清楚。本文应用光学显微镜、扫描电镜和透射电镜对上述2科4属的10种代表植物的花粉形态进行了观察,系统描述了各属、种的花粉形态。结果表明角果藻科植物花粉均无萌发孔,外壁纹饰通常为拟网状至浅网状。花粉形态的研究结果支持将Vleisia作为角果藻属Zannichellia的近缘属处理的观点。茨藻科植物花粉外壁光滑、稍皱波状或为疣状,具颗粒状纹饰,萌发孔的有无在种间存在变异。花粉形态的研究结果表明角果藻科与眼子菜科Potamogetonaceae近缘,茨藻科可能与水蕹科Aponogetonaceae或水鳖科Hydrocharitaceae中具单沟花粉的类群有一定联系,而与角果藻科和眼子菜科则相去甚远。     

POLLEN MORPHOLOGY OF THE EUCHARIDEAE (AMARYLLIDACEAE)

Eucharis, Caliphruria, and Urceolina form a monophyletic group of petiolate-leaved, Neotropical Amaryllidaceae ecologically specialized to the understory of primary tropical rain forest below 2,000 m elevation. Pollen morphology of the three genera is surveyed. Pollen grains of all species of Eucharis, Caliphruria, and Urceolina are boat-shaped elliptic, monosulcate, heteropolar, and bilateral in symmetry. Exine sculpturing is semitectate-columellate and reticulate in all species examined. A transformation series in reticulum coarseness and pollen grain size is described. The large pollen grain with coarse reticulum of most Eucharis species is considered ancestral. The fine reticulation of Caliphruria is considered derived and the exine morphology of Urceolina is intermediate. Both of these genera have medium-sized pollen grains. Exine dimorphism common to all Urceolina, but rare in Eucharis and Caliphruria, may be symplesiomorphous among those taxa exhibiting this morphology. The three genera are largely uniform in pollen grain ultrastructure, with completely ektexinous exines. Pollen grain size in Eucharis is not closely correlated with style length. Several wide-ranging species show considerable intraspecific variation in pollen size. Parallelisms in pollen grain evolution among related tribes of Neotropical Amaryllidaceae are discussed.     

FINE STRUCTURE OF MISTLETOE POLLEN. III. LARGE-FLOWERED NEOTROPICAL LORANTHACEAE AND THEIR AUSTRALIAN RELATIVES

Pollen of all large-flowered neotropical loranthaceous genera and related Australian taxa (Nuytsia, Atkinsonia) were examined in the light, scanning, and transmission electron microscopes. Trilobate, deeply concave, peroblate or oblate pollen shapes are basic within the complex; triangular, slight convex, suboblate shapes are more derived features. The non-fixiform pollen of Atkinsonia is unique within the family. Most of the large-flowered genera possess exclusively syncolpate aperture types. However, among Psittacanthus species tricolpate, diplosynrugate and diplorugate apertures are also present, representing derived types for the complex. The inaperturate pollen of Atkinsonia appears to have developed independently within the family. Pollen sculpturing is typically non-uniform, i.e., there are pronounced sculpturing differences in polar and equatorial regions. Uniformly sculptured pollen is restricted to Atkinsonia, Ligaria and some species of Psittacanthus. Ultrastructurally, most exine modifications have occurred in the equatoral ektexine. Here the basic organization ranges from essentially columellaless to columellate, the latter the more derived condition. Endexine is typically thick and stratified in polar areas, thin and lamellate in peripheral and apertural regions. Similar pollen morphologies of Nuytsia and Gaiadendron support the idea of a transoceanic evolutionary connection between the Old and New Worlds. Pollen characters show Gaiadendron to be the most primitive and Psittacanthus the most advanced among the large-flowered neotropical genera.     

Genetics of intrinsic postzygotic isolation in a circumpolar plant species, Draba nivalis (Brassicaceae)

Sterility barriers, ranging from incomplete to fully developed, were recently demonstrated within taxonomic species of the genus Draba, suggesting the existence of numerous, cryptic biological species. Because these taxa are predominately selfers and of Pleistocene origin, it was concluded that hybrid sterility evolved quickly and possibly by genetic drift. Here we used genetic mapping and QTL analyses to determine the genetic basis of hybrid sterility between geographically distant populations of one of these taxonomic species, Draba nivalis. Fifty microsatellite loci were mapped, and QTL analyses identified five loci underlying seed fertility and two underlying pollen fertility. Four of five seed fertility QTLs reduced fertility in heterozygotes, an observation most consistent with drift-based fixation of underdominant sterility loci. However, several nuclear-nuclear interactions were also found, including two that acted like reciprocal translocations with lowest fitness in double heterozygotes, and two that had a pattern of fitness consistent with Bateson-Dobzhansky-Muller incompatibilities. In contrast, pollen fertility QTLs exhibited additive inheritance, with lowest fertility associated with the paternal allele, a pattern of inheritance suggestive of cytonuclear incompatibilities. The results imply that multiple genetic mechanisms underlie the rapid evolution of reproductive barriers in Draba.     

水雍科植物的花粉形态研究

应用光学显微镜、扫描电镜和透射电镜对世界水雍科6种植物的花粉形态进行了观察。水雍科植物花粉为舟形或船形,具远极单沟萌发孔类型,外壁纹饰通常为浅网状至网状,稀为小刺状纹饰,外壁外层由覆盖层、柱状层和基层组成,覆盖层厚。水雍科植物花粉外壁纹饰表现了从小刺状向网状的过渡。该科花粉为远极单沟,覆盖层厚,具小刺等特征反映了其与水鳖科和泽泻目花蔺科的密切联系,而该科花粉外壁纹饰多为网状则与茨藻目植物接近。这一结果支持将水雍科从茨藻目中分出作为一个独立的目处理的观点。此外,水雍科植物的花粉大小、纹饰类型、网眼大小与深浅等方面的差异对种级分类有一定意义。